Tweak spans for trait bounds on associated types #85799

estebank · 2021-05-29T03:30:38Z

Provide more information on projection failure, by pointing at the associated type (the note on line 16 and the use of a note instead of a label on line 27 are new):

error[E0271]: type mismatch resolving `<ModelT as Vehicle>::Color == Blue`
  --> src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs:31:10
   |
31 | fn b() { blue_car(ModelT); } //~ ERROR type mismatch
   |          ^^^^^^^^ type mismatch resolving `<ModelT as Vehicle>::Color == Blue`
   |
note: expected this to be `Blue`
  --> src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs:16:40
   |
16 | impl Vehicle for ModelT { type Color = Black; }
   |                                        ^^^^^
note: required by a bound in `blue_car`
  --> src/test/ui/associated-types/associated-types-binding-to-type-defined-in-supertrait.rs:27:19
   |
27 | fn blue_car<C:Car<Color=Blue>>(c: C) {
   |                   ^^^^^^^^^^ required by this bound in `blue_car`

We are now pointing at the two places where the user can change things to make them compile: the trait bound and the associated type. We can't know for sure which of the two would be more appropriate on each case (although we already provide some suggestions when an extra trait bound would fix things), so instead we just put all the cards on the table and let the user decide for themselves with all the information at their disposal.

Reminded about this by the recent closing of #57663.

rust-highfive · 2021-05-29T03:30:41Z

r? @varkor

(rust-highfive has picked a reviewer for you, use r? to override)

src/test/ui/associated-types/issue-63593.stderr

src/test/ui/generic-associated-types/issue-47206-where-clause.stderr

estebank · 2021-05-30T02:33:28Z

src/test/ui/generic-associated-types/issue-68656-unsized-values.stderr

   |
 LL |     type Item<'a>: std::ops::Deref<Target = T>;
   |                                    ---------- required by this bound in `UnsafeCopy::Item`
 ...
 LL | impl<T: Copy + std::ops::Deref> UnsafeCopy<T> for T {
   |      - this type parameter
 LL |     type Item<'a> = T;
-   |     ^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found associated type
+   |                     ^ expected type parameter `T`, found associated type


This seems somewhat confusing, but thankfully we provide a structured suggestion.

estebank · 2021-05-30T02:34:33Z

src/test/ui/hrtb/issue-62203-hrtb-ice.stderr

 LL |     let v = Unit2.m(
-   |                   ^ expected struct `Unit4`, found associated type
+   |                   ^ type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:39]> as T0<'r, (<Unit2 as Ty<'r>>::V,)>>::O == <_ as Ty<'r>>::V`


That's quite a mouthful 😬

hellow554 · 2021-05-30T20:15:53Z

You are truly amazing. Thank you for making the suggestion even better! ❤️

compiler/rustc_infer/src/infer/error_reporting/mod.rs

varkor · 2021-06-30T21:45:13Z

I don't have time to review this right now. Going to reassign to r? @pnkfelix, as they've already taken a look at it. Apologies for taking so long to get around to this.

bors · 2021-12-14T01:13:27Z

☀️ Try build successful - checks-actions
Build commit: bcb46bf6598f6d916def946b3df130355704bfa0 (bcb46bf6598f6d916def946b3df130355704bfa0)

rust-timer · 2021-12-14T05:02:09Z

Finished benchmarking commit (76d48c2e95803f4154d13bfa62b71ed9ba7d2d1d): comparison url.

Summary: This change led to very large relevant regressions 😿 in compiler performance.

Very large regression in instruction counts (up to 12.3% on full builds of diesel)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

rust-timer · 2021-12-14T06:32:59Z

Finished benchmarking commit (76d48c2e95803f4154d13bfa62b71ed9ba7d2d1d): comparison url.

Summary: This change led to very large relevant regressions 😿 in compiler performance.

Very large regression in instruction counts (up to 12.3% on full builds of diesel)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

estebank · 2021-12-15T02:38:12Z

@bors try @rust-timer queue

rust-timer · 2021-12-15T02:38:13Z

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

bors · 2021-12-15T02:38:20Z

⌛ Trying commit 979937e with merge 041d85b0a9a7ac359e1292be7168d6b5c0508d26...

rust-log-analyzer · 2021-12-15T02:47:52Z

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

configure: rust.debug-assertions := True
configure: rust.overflow-checks := True
configure: llvm.assertions      := True
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
skip untracked path cpu-usage.csv during rustfmt invocations
skip untracked path src/doc/book/ during rustfmt invocations
skip untracked path src/doc/rust-by-example/ during rustfmt invocations
skip untracked path src/llvm-project/ during rustfmt invocations
Diff in /checkout/compiler/rustc_middle/src/ty/mod.rs at line 752:
     pub constness: BoundConstness,
 
     pub polarity: ImplPolarity,
-
     // pub implicit: ImplicitBound,
 
 
Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/compiler/rustc_middle/src/ty/consts/valtree.rs" "/checkout/compiler/rustc_middle/src/ty/consts/int.rs" "/checkout/compiler/rustc_middle/src/ty/consts/kind.rs" "/checkout/compiler/rustc_middle/src/ty/relate.rs" "/checkout/compiler/rustc_middle/src/ty/mod.rs" "/checkout/compiler/rustc_middle/src/ty/context.rs" "/checkout/compiler/rustc_middle/src/ty/vtable.rs" "/checkout/compiler/rustc_middle/src/ty/binding.rs"` failed.
If you're running `tidy`, try again with `--bless`. Or, if you just want to format code, run `./x.py fmt` instead.

bors · 2021-12-15T04:10:19Z

☀️ Try build successful - checks-actions
Build commit: 041d85b0a9a7ac359e1292be7168d6b5c0508d26 (041d85b0a9a7ac359e1292be7168d6b5c0508d26)

rust-timer · 2021-12-15T04:10:22Z

Queued 041d85b0a9a7ac359e1292be7168d6b5c0508d26 with parent 2f4da62, future comparison URL.

rust-timer · 2021-12-15T05:44:44Z

Finished benchmarking commit (041d85b0a9a7ac359e1292be7168d6b5c0508d26): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

jackh726 · 2022-01-06T21:14:19Z

Going to mark this as waiting on author. Seems like it needs a rebase and perf fix.

Dylan-DPC · 2022-05-31T16:43:41Z

Closing this as it has bitrotted

rust-highfive assigned varkor May 29, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 29, 2021

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estebank marked this pull request as ready for review May 30, 2021 02:27

estebank commented May 30, 2021

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estebank mentioned this pull request May 30, 2021

Poor error message with associated constrained trait type #57663

Closed

This was referenced Jun 2, 2021

Explain origin of implicit Sized obligations and provide suggestions when possible #85947

Closed

E0277: suggest ?Sized to relax implicit Sized bound on associated types #85378

Closed

pnkfelix reviewed Jun 4, 2021

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estebank force-pushed the type-trait-bound-span branch from 340972a to 3956224 Compare June 11, 2021 03:22

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rust-highfive assigned pnkfelix and unassigned varkor Jun 30, 2021

estebank force-pushed the type-trait-bound-span branch from 3de9f42 to 5d93231 Compare July 2, 2021 18:49

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estebank force-pushed the type-trait-bound-span branch from 5d93231 to 0cca15d Compare July 2, 2021 18:57

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bors mentioned this pull request Dec 14, 2021

Tweak errors coming from for-loop, ? and .await desugaring #90939

Merged

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 14, 2021

remove implicit field

979937e

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Dec 15, 2021

rustbot removed S-waiting-on-perf Status: Waiting on a perf run to be completed. perf-regression Performance regression. labels Dec 15, 2021

jackh726 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 Jan 6, 2022

joelpalmer 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 1, 2022

JohnCSimon 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 27, 2022

JohnCSimon 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 11, 2022

Dylan-DPC closed this May 31, 2022

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Tweak spans for trait bounds on associated types #85799

Tweak spans for trait bounds on associated types #85799

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Tweak spans for trait bounds on associated types #85799

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