Account for type alias projections in E0308 "expected/found" shortening logic - #159189

Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom
estebank:issue-159043
Jul 20, 2026
Merged

Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom
estebank:issue-159043

Conversation

@estebank

@estebankestebank commented Jul 12, 2026•
edited by rustbot
Loading

Copy link
Copy Markdown
Contributor

View all comments

When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:

error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:

error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang

@rustbotrustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank marked this pull request as ready for review July 12, 2026 20:29
@rustbotrustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 12, 2026
chenyukang
chenyukang reviewed Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs Outdated
chenyukang
chenyukang reviewed Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang reviewed Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs Outdated
@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot

rustbot commented Jul 17, 2026

Copy link
Copy Markdown
Collaborator

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

chenyukang
chenyukang reviewed Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs Outdated
chenyukang
chenyukang reviewed Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs Outdated
@chenyukang

chenyukang commented Jul 18, 2026

Copy link
Copy Markdown
Member

No other issues except two trivial one.
r=me after resolve it.

@estebank

estebank commented Jul 18, 2026

Copy link
Copy Markdown
ContributorAuthor

@bors r=chenyukang

@rust-bors

rust-borsBot commented Jul 18, 2026

Copy link
Copy Markdown
Contributor

📌 Commit 068c52f has been approved by chenyukang

It is now in the queue for this repository.

@rust-borsrust-borsBot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 18, 2026
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer mentioned this pull request Jul 18, 2026
Closed
rust-borsBot pushed a commit that referenced this pull request Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot pushed a commit that referenced this pull request Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 18, 2026
@rust-bors

rust-borsBot commented Jul 18, 2026

Copy link
Copy Markdown
Contributor

💔 Test for b356d7c failed: CI. Failed job:

@JonathanBrouwer

JonathanBrouwer commented Jul 18, 2026

Copy link
Copy Markdown
Member

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #159501 (comment)

@rust-borsrust-borsBot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 18, 2026
@rust-bors

rust-borsBot commented Jul 18, 2026

Copy link
Copy Markdown
Contributor

This PR was contained in a rollup (#159501), which was unapproved.

View changes since this unapproval

@chenyukang

chenyukang commented Jul 19, 2026

Copy link
Copy Markdown
Member

ah, I got it, you need add these files for windows:

long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅

@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank

estebank commented Jul 20, 2026

Copy link
Copy Markdown
ContributorAuthor

@bors r=chenyukang

Restricted the color tests to linux-only. The textual ones still happen everywhere.

@rust-bors

rust-borsBot commented Jul 20, 2026

Copy link
Copy Markdown
Contributor

📌 Commit d0cfd66 has been approved by chenyukang

It is now in the queue for this repository.

@rust-borsrust-borsBot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 20, 2026
@JonathanBrouwerJonathanBrouwer mentioned this pull request Jul 20, 2026
Merged
rust-borsBot pushed a commit that referenced this pull request Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot merged commit a0b1444 into rust-lang:mainJul 20, 2026
13 checks passed
@rustbotrustbot added this to the 1.99.0 milestone Jul 20, 2026
rust-timer added a commit that referenced this pull request Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit to lnicola/rust-analyzer that referenced this pull request Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas mentioned this pull request Aug 28, 2026
Open
Sign up for freeto join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note

5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
Account for type alias projections in E0308 "expected/found" shortening logic - #159189
Merged
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Jul 20, 2026
Merged
Account for type alias projections in E0308 "expected/found" shortening logic#159189
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom 
estebank:issue-159043
Conversation
@estebank
@estebankestebank
commented
Jul 12, 2026•

edited by rustbot

Loading

Copy link


Copy Markdown

Contributor
View all comments
When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console

Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console

r? @chenyukang
@rustbotrustbot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
labels
Jul 12, 2026
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@estebank
estebank
marked this pull request as ready for review
July 12, 2026 20:29
@rustbotrustbot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 12, 2026
chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 13, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@rustbot

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-log-analyzer

This comment was marked as resolved.

Sign in to view
@rust-log-analyzer

This comment has been minimized.

Sign in to view
chenyukang
chenyukang
reviewed
Jul 15, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

@rustbot

This comment has been minimized.

Sign in to view
@estebank
Account for type alias projections in E0308 "expected/found" shorteni…
60bf4db
…ng logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Deduplicate param highlighting logic.
Account for type param difference in trait in E0308 highlighting.
@rustbot
rustbot
commented
Jul 17, 2026

Copy link


Copy Markdown

Collaborator
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.
Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.
chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
Outdated

chenyukang
chenyukang
reviewed
Jul 18, 2026
View reviewed changes
Comment threadcompiler/rustc_errors/src/diagnostic.rs
Outdated

@chenyukang
chenyukang
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
No other issues except two trivial one.

r=me after resolve it.
@estebank
estebank
commented
Jul 18, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
📌 Commit 068c52f has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
JonathanBrouwer added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 18, 2026
@JonathanBrouwer
Rollup merge ofrust-lang#159189- estebank:issue-159043, r=chenyukang
b395963
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fixrust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 18, 2026
 Closed

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159501- JonathanBrouwer:rollup-R9B6UYL, r=JonathanBro…
d1ac568
…uwer
Rollup of 5 pull requests
Successful merges:
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #158545 (Move `std::io::read_to_string` to `alloc::io`)
- #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test)
- #159470 (Fix string indexing in diagnostic format strings)
- #159500 (Move compiletest CLI parsing to `cli.rs`)
@rust-bors

This comment has been minimized.

Sign in to view
rust-borsBot
pushed a commit
that referenced
this pull request
Jul 18, 2026
@bors
Auto merge of#159189- estebank:issue-159043, r=chenyukang
b356d7c
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@rust-borsrust-borsBot
added

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
and removed

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
💔 Test for b356d7c failed: CI. Failed job:
@JonathanBrouwer
JonathanBrouwer
commented
Jul 18, 2026

Copy link


Copy Markdown

Member
💔 I suspect this PR failed tests as part of a rollup
@bors r-
After fixing the problem, consider running a try job for the failed job before re-approving.
Link to failure: #159501 (comment)
@rust-borsrust-borsBot
added

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
and removed

S-waiting-on-review
Status: Awaiting review from the assignee but also interested parties.
labels
Jul 18, 2026
@rust-bors
rust-borsBot
commented
Jul 18, 2026

Copy link


Copy Markdown

Contributor
This PR was contained in a rollup (#159501), which was unapproved.
View changes since this unapproval
@chenyukang
chenyukang
commented
Jul 19, 2026

Copy link


Copy Markdown

Member
ah, I got it, you need add these files for windows:
long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅
@estebank
When shortened type would look the same, use textual shortening on th…
d0cfd66
…e highlighted string instead
Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts.
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
@estebank
estebank
commented
Jul 20, 2026

Copy link


Copy Markdown

ContributorAuthor
@bors r=chenyukang
Restricted the color tests to linux-only. The textual ones still happen everywhere.
@rust-bors
rust-borsBot
commented
Jul 20, 2026

Copy link


Copy Markdown

Contributor
📌 Commit d0cfd66 has been approved by chenyukang
It is now in the queue for this repository.
@rust-borsrust-borsBot
added

S-waiting-on-bors
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed

S-waiting-on-author
Status: This is awaiting some action (such as code changes or more information) from the author.
labels
Jul 20, 2026
@JonathanBrouwerJonathanBrouwer
mentioned this pull request
Jul 20, 2026
 Merged

rust-borsBot
pushed a commit
that referenced
this pull request
Jul 20, 2026
@bors
Auto merge of#159610- JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
87e5904
…uwer
Rollup of 18 pull requests
Successful merges:
- #159600 (`rust-analyzer` subtree update)
- #158046 (proc_macro: preserve file module spans for inner attrs)
- #159000 (Small cleanups to the incr comp session code)
- #159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- #159449 (Enable single Location to issue multiple borrows)
- #159544 (Suggest valid command-line crate names)
- #159587 (Improve `AttrItem::span`)
- #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- #159597 (std: use `arc4random_buf` from libc)
- #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- #158061 (Make `pin!()` more foolproof.)
- #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- #159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- #159571 (Remove unused bundled library lookup for the local crate)
- #159585 (Minor `TokenStream` improvements)
- #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- #159602 (Remove `ItemLike`)
- #159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- #159590 (Remove some dead code)
@rust-bors
rust-borsBot
merged commit a0b1444
into
rust-lang:mainJul 20, 2026

13 checks passed

@rustbotrustbot
added this to the 1.99.0 milestone
Jul 20, 2026
rust-timer added a commit
that referenced
this pull request
Jul 20, 2026
@rust-timer
Unrolled build for#159189
3bd9e19
Rollup merge of #159189 - estebank:issue-159043, r=chenyukang
Account for type alias projections in E0308 "expected/found" shortening logic
When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant:
```
error[E0308]: mismatched types
--> tests/ui/associated-types/long-type-E0308.rs:19:5
|
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
| ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Fix#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:
```
error[E0308]: mismatched types
--> $DIR/long-type-E0308.rs:30:5
|
LL | ) -> <
| ______-
LL | | <
LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | | >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
| |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL | value...oc())
| ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
|
= note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
= note: an associated type was expected, but a different one was found
= note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
= note: consider using `--verbose` to print the full type name to the console
```
r? @chenyukang
lnicola pushed a commit
to lnicola/rust-analyzer
that referenced
this pull request
Aug 17, 2026
@bors
Auto merge of #159610 - JonathanBrouwer:rollup-Wil0K5d, r=JonathanBro…
688993e
…uwer
Rollup of 18 pull requests
Successful merges:
- rust-lang/rust#159600 (`rust-analyzer` subtree update)
- rust-lang/rust#158046 (proc_macro: preserve file module spans for inner attrs)
- rust-lang/rust#159000 (Small cleanups to the incr comp session code)
- rust-lang/rust#159189 (Account for type alias projections in E0308 "expected/found" shortening logic)
- rust-lang/rust#159449 (Enable single Location to issue multiple borrows)
- rust-lang/rust#159544 (Suggest valid command-line crate names)
- rust-lang/rust#159587 (Improve `AttrItem::span`)
- rust-lang/rust#159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures)
- rust-lang/rust#159597 (std: use `arc4random_buf` from libc)
- rust-lang/rust#159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.)
- rust-lang/rust#158061 (Make `pin!()` more foolproof.)
- rust-lang/rust#159460 (Do not mark unnormalized const aliases as rigid when normalizing param env)
- rust-lang/rust#159529 (Add regression test for nested replacement ranges in `collect_tokens`)
- rust-lang/rust#159571 (Remove unused bundled library lookup for the local crate)
- rust-lang/rust#159585 (Minor `TokenStream` improvements)
- rust-lang/rust#159586 (Separate `InterpCx` usage by `ConstAnalysis` phases)
- rust-lang/rust#159602 (Remove `ItemLike`)
- rust-lang/rust#159603 (Clarify `push_stream`/`push_tree`)
Failed merges:
- rust-lang/rust#159590 (Remove some dead code)
@theemathastheemathas
mentioned this pull request
Aug 28, 2026

Open

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@chenyukangchenyukangchenyukang left review comments

Assignees

@chenyukangchenyukang

Labels

S-waiting-on-borsStatus: Waiting on bors to run and complete tests. Bors will change the label on completion.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Projects


None yet


Milestone

1.99.0

Development

Successfully merging this pull request may close these issues.

E0308 with complex types produces an unhelpful expected type vs found type note


5 participants

@estebank@rust-log-analyzer@rustbot@chenyukang@JonathanBrouwer