Choose predicates without inference variables over those with them by Aaron1011 · Pull Request #55453 · rust-lang/rust

Aaron1011 · 2018-10-28T19:40:57Z

When constructing synthetic auto trait impls, we may come across
multiple predicates involving the same type, trait, and substitutions.
Since we can only display one of these, we pick the one with the 'most
strict' lifetime paramters. This ensures that the impl we render the
user is actually valid (that is, a struct matching that impl will
actually implement the auto trait in question).

This commit exapnds the definition of 'more strict' to take into account
inference variables. We always choose a predicate without inference
variables over a predicate with inference variables.

Fixesrust-lang#54705 When constructing synthetic auto trait impls, we may come across multiple predicates involving the same type, trait, and substitutions. Since we can only display one of these, we pick the one with the 'most strict' lifetime paramters. This ensures that the impl we render the user is actually valid (that is, a struct matching that impl will actually implement the auto trait in question). This commit exapnds the definition of 'more strict' to take into account inference variables. We always choose a predicate without inference variables over a predicate with inference variables.

rust-highfive · 2018-10-28T19:41:07Z

r? @michaelwoerister

(rust_highfive has picked a reviewer for you, use r? to override)

michaelwoerister · 2018-11-01T10:39:12Z

Thanks for the PR, @Aaron1011!
I think I'll hand this off to @pnkfelix for re-assignment since I don't know the logic involved here very well.
r? @pnkfelix

pnkfelix · 2018-11-06T10:51:17Z

@Aaron1011 you said here #54705 (comment) that you had a minimal reproduction, and it does not appear to utilize rustdoc.

The test you have included on this PR does require using rustdoc ...

(Meanwhile the minimal "reproduction" does not cause an error in play, so maybe I've misunderstood how it works or what its reproducing...)

Update: Oh, the minimal reproduction must be something you are intending to be fed into rustdoc ...

Anyway: Can you provide a unit test that does not require rustdoc; i.e. one in either ui or run-pass? I know in my own workflow that i don't tend to run the rustdoc tests locally, but I always run the suite of ui+compile-fail+run-pass before I attempt to post a PR.

pnkfelix · 2018-11-06T12:05:16Z

Anyway this seems fine, apart from the question about the current test.

r=me once that question is answered.

Aaron1011 · 2018-11-06T15:59:11Z

@pnkfelix: I've only incliuded a rustdoc test because AutoTraitFinder is only used by rustdoc. A run-pass test wouldn't actually exercise any of the code I've changed, since AutoTraitFinder is only used to synthesize impls for rustdoc to render.

pnkfelix · 2018-11-07T09:54:07Z

@bors r+

bors · 2018-11-07T09:54:09Z

📌 Commit 20aa751 has been approved by pnkfelix

bors · 2018-11-07T09:54:22Z

💡 This pull request was already approved, no need to approve it again.

There's another pull request that is currently being tested, blocking this pull request: Value visitors for miri #55549

bors · 2018-11-07T09:54:23Z

📌 Commit 20aa751 has been approved by pnkfelix

pnkfelix · 2018-11-07T09:56:12Z

Accidentally did rollup originally and editing my comment didn’t undo it. Going to r- and then r+

pnkfelix · 2018-11-07T09:56:21Z

@bors r-

pnkfelix · 2018-11-07T09:56:35Z

@bors r+

bors · 2018-11-07T09:56:36Z

📌 Commit 20aa751 has been approved by pnkfelix

pnkfelix · 2018-11-07T09:57:16Z

Hmmm

pnkfelix · 2018-11-07T09:57:28Z

@bors rollup-

…nkfelix Choose predicates without inference variables over those with them Fixesrust-lang#54705 When constructing synthetic auto trait impls, we may come across multiple predicates involving the same type, trait, and substitutions. Since we can only display one of these, we pick the one with the 'most strict' lifetime paramters. This ensures that the impl we render the user is actually valid (that is, a struct matching that impl will actually implement the auto trait in question). This commit exapnds the definition of 'more strict' to take into account inference variables. We always choose a predicate without inference variables over a predicate with inference variables.

Rollup of 14 pull requests Successful merges: - #55377 (Slight copy-editing for `std::cell::Cell` docs) - #55441 (Remove unused re import in gdb_rust_pretty_printing) - #55453 (Choose predicates without inference variables over those with them) - #55495 (Don't print opt fuel messages to stdout because it breaks Rustbuild) - #55501 (Make `process_obligations`' computation of `completed` optional.) - #55510 (Fix feature gate only being checked on first repr attr.) - #55609 (Run name-anon-globals after LTO passes as well) - #55645 (do not print wrapping ranges like normal ranges in validity diagnostics) - #55688 (Standardised names and location of ui issue tests) - #55692 (-C remark: fix incorrect warning about requiring "--debuginfo" instead of "-C debuginfo=n") - #55702 (Add `aarch64-pc-windows-msvc` to deployed targets) - #55728 (Update lldb) - #55730 (Use trait impl method span when type param mismatch is due to impl Trait) - #55734 (refactor: use shorthand fields)

rust-highfive assigned michaelwoerister Oct 28, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 28, 2018

rust-highfive assigned pnkfelix and unassigned michaelwoerister Nov 1, 2018

pnkfelix 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 Nov 6, 2018

bors 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 Nov 7, 2018

bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 7, 2018

bors 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 Nov 7, 2018

kennytm mentioned this pull request Nov 7, 2018
Rollup of 14 pull requests #55746
Merged

bors merged commit 20aa751 into rust-lang:masterNov 7, 2018

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