Propagate expected type hints through struct literals. by eddyb · Pull Request #40398 · rust-lang/rust

eddyb · 2017-03-09T19:50:26Z

Partial fix for #31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to.

The added test works because {...; x} with a hint of T coerces x to T, and the reasoning why that is slightly different has to do with DSTs: &Struct { tail: [x] }: &Struct<[T]> has a hint of [T] for [x], but the inferred type should be [T; 1] to succeed later, so [x] shouldn't be forced to be [T].

However, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixes#40355 and can be backported.

r? @nikomatsakis

…put.

nikomatsakis · 2017-03-09T21:40:54Z

r=me pending crater.

nikomatsakis · 2017-03-09T21:41:50Z

We discussed this in the @rust-lang/compiler meeting. It's a tough call regarding the backport. On the one hand, we definitely want to fix the bug, and it affects anybody using the phf crate to some degree. On the other hand, changes to inference are notoriously sensitive, and so we risk unintended side-effects.

Let's see what crater has to say (a clean run would help allay fears) before reaching a final decision.

eddyb · 2017-03-09T21:54:56Z

Crater report only contains false positives (network errors, I think)!

nikomatsakis · 2017-03-09T22:01:42Z

OK, we're marking as beta-accepted. Live on the edge!

cc @rust-lang/compiler

@alexcrichton

Beta next - #40285 - #40272 - #40064 - #39835 - #40398 r? @alexcrichton

nikomatsakis · 2017-03-16T16:52:41Z

@bors r+

bors · 2017-03-16T16:52:42Z

📌 Commit 50aee36 has been approved by nikomatsakis

nikomatsakis · 2017-03-16T16:52:52Z

Looks like this was never formally r+'d?

@nikomatsakis

Propagate expected type hints through struct literals. Partial fix for rust-lang#31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to. The added test works because `{...; x}` with a hint of `T` coerces `x` to `T`, and the reasoning why that is slightly different has to do with DSTs: `&Struct { tail: [x] }: &Struct<[T]>` has a hint of `[T]` for `[x]`, but the inferred type should be `[T; 1]` to succeed later, so `[x]` shouldn't be *forced* to be `[T]`. *However*, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixesrust-lang#40355 and can be backported. r? @nikomatsakis

@nikomatsakis

Propagate expected type hints through struct literals. Partial fix for rust-lang#31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to. The added test works because `{...; x}` with a hint of `T` coerces `x` to `T`, and the reasoning why that is slightly different has to do with DSTs: `&Struct { tail: [x] }: &Struct<[T]>` has a hint of `[T]` for `[x]`, but the inferred type should be `[T; 1]` to succeed later, so `[x]` shouldn't be *forced* to be `[T]`. *However*, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixesrust-lang#40355 and can be backported. r? @nikomatsakis

@nikomatsakis

Propagate expected type hints through struct literals. Partial fix for rust-lang#31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to. The added test works because `{...; x}` with a hint of `T` coerces `x` to `T`, and the reasoning why that is slightly different has to do with DSTs: `&Struct { tail: [x] }: &Struct<[T]>` has a hint of `[T]` for `[x]`, but the inferred type should be `[T; 1]` to succeed later, so `[x]` shouldn't be *forced* to be `[T]`. *However*, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixesrust-lang#40355 and can be backported. r? @nikomatsakis

@nikomatsakis

Propagate expected type hints through struct literals. Partial fix for rust-lang#31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to. The added test works because `{...; x}` with a hint of `T` coerces `x` to `T`, and the reasoning why that is slightly different has to do with DSTs: `&Struct { tail: [x] }: &Struct<[T]>` has a hint of `[T]` for `[x]`, but the inferred type should be `[T; 1]` to succeed later, so `[x]` shouldn't be *forced* to be `[T]`. *However*, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixesrust-lang#40355 and can be backported. r? @nikomatsakis

Rollup of 22 pull requests - Successful merges: #40241, #40346, #40348, #40377, #40398, #40409, #40441, #40445, #40509, #40521, #40523, #40532, #40538, #40564, #40581, #40583, #40588, #40589, #40590, #40603, #40611, #40621 - Failed merges: #40501, #40541

@nikomatsakis

Propagate expected type hints through struct literals. Partial fix for rust-lang#31260 to maximize backwards-compatibility, i.e. the hint is provided but not coerced to. The added test works because `{...; x}` with a hint of `T` coerces `x` to `T`, and the reasoning why that is slightly different has to do with DSTs: `&Struct { tail: [x] }: &Struct<[T]>` has a hint of `[T]` for `[x]`, but the inferred type should be `[T; 1]` to succeed later, so `[x]` shouldn't be *forced* to be `[T]`. *However*, implementing that complete behavior in a backwards-compatible way may be non-trivial, and has not yet been fully investigated, while this PR fixesrust-lang#40355 and can be backported. r? @nikomatsakis

Rollup of 9 pull requests - Successful merges: #40241, #40281, #40398, #40521, #40532, #40554, #40566, #40581, #40587 - Failed merges:

eddyb · 2017-03-20T11:23:23Z

@nikomatsakis @brson If this made it into the stable release but wasn't merged on nightly, it might be missing from beta. I'll re-nominate it to make sure we don't forget to check (and backport if needed).

[beta] Backports and version bump This PR backports these PRs to beta: * #40583 * #40398 * #40542 and it also includes a version bump to push out a beta with all recent backports.

eddyb added 2 commits March 9, 2017 21:05

Rename expected_types_for_fn_args to expected_inputs_for_expected_out…
c7db40f
…put.

Propagate expected type hints through struct literals.
50aee36

eddyb added beta-nominated Nominated for backporting to the compiler in the beta channel. S-waiting-on-crater Status: Waiting on a crater run to be completed. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 9, 2017

nrc assigned nikomatsakis Mar 9, 2017

nikomatsakis removed the S-waiting-on-crater Status: Waiting on a crater run to be completed. label Mar 9, 2017

nikomatsakis added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Mar 9, 2017

brson mentioned this pull request Mar 9, 2017
[beta] Beta next #40401
Merged

alexcrichton removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Mar 9, 2017

bors added a commit that referenced this pull request Mar 9, 2017
Auto merge of#40401- brson:beta-next, r=alexcrichton
94dca9a
Beta next - #40285 - #40272 - #40064 - #39835 - #40398 r? @alexcrichton

frewsxcv mentioned this pull request Mar 17, 2017
Rollup of 15 pull requests #40615
Closed

frewsxcv mentioned this pull request Mar 17, 2017
Rollup of 16 pull requests #40616
Closed

frewsxcv mentioned this pull request Mar 18, 2017
Rollup of 20 pull requests #40643
Closed

arielb1 mentioned this pull request Mar 18, 2017
Rollup of 22 pull requests #40644
Closed

frewsxcv mentioned this pull request Mar 20, 2017
Rollup of 9 pull requests #40659
Merged

bors added a commit that referenced this pull request Mar 20, 2017
Auto merge of#40659- frewsxcv:rollup, r=frewsxcv
244f893
Rollup of 9 pull requests - Successful merges: #40241, #40281, #40398, #40521, #40532, #40554, #40566, #40581, #40587 - Failed merges:

bors merged commit 50aee36 into rust-lang:masterMar 20, 2017

eddyb deleted the struct-hint branch March 20, 2017 11:22

eddyb added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Mar 20, 2017

alexcrichton mentioned this pull request Mar 20, 2017
[beta] Backports and version bump #40675
Merged

brson added beta-accepted Accepted for backporting to the compiler in the beta channel. and removed beta-accepted Accepted for backporting to the compiler in the beta channel. beta-nominated Nominated for backporting to the compiler in the beta channel. labels Mar 20, 2017

nikomatsakis mentioned this pull request May 4, 2017
Coercion sites are not consistent between struct tuples and structs #31260
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Propagate expected type hints through struct literals. - #40398

Propagate expected type hints through struct literals.#40398
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