Try to suggest dereferences on trait selection failed #72456

ldm0 · 2020-05-22T06:28:33Z

Fixes #39029 Fixes #62530
This PR consists of two parts:

Decouple Autoderef with FnCtxt and move Autoderef to librustc_trait_selection.
Try to suggest dereferences when trait selection failed.

The first is needed because:

For suggesting dereferences, the struct Autoderef should be used. But before this PR, it is placed in librustc_typeck, which depends on librustc_trait_selection. But trait selection error emitting happens in librustc_trait_selection, if we want to use Autoderef in it, dependency loop is inevitable. So I moved the Autoderef to librustc_trait_selection.
Before this PR, FnCtxt is coupled to Autoderef, and FnCtxt only exists in librustc_typeck. So decoupling is needed.

After this PR, we can get suggestion like this:

error[E0277]: the trait bound `&Baz: Happy` is not satisfied
  --> $DIR/trait-suggest-deferences-multiple.rs:34:9
   |
LL | fn foo<T>(_: T) where T: Happy {}
   |                          ----- required by this bound in `foo`
...
LL |     foo(&baz);
   |         ^^^^
   |         |
   |         the trait `Happy` is not implemented for `&Baz`
   |         help: consider adding dereference here: `&***baz`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.

r? @estebank

bors · 2020-05-23T07:38:55Z

☔ The latest upstream changes (presumably #72256) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2020-05-30T16:49:34Z

☔ The latest upstream changes (presumably #72778) made this pull request unmergeable. Please resolve the merge conflicts.

rust-highfive · 2020-05-30T19:03:07Z

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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Agent running as: 'vsts'
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Step 6/7 : ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
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Step 7/7 : ENV SCRIPT python3 ../x.py test src/tools/expand-yaml-anchors &&            python3 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu &&            python3 ../x.py build --stage 0 src/tools/build-manifest &&            python3 ../x.py test --stage 0 src/tools/compiletest &&            python3 ../x.py test src/tools/tidy &&            python3 ../x.py doc --stage 0 src/libstd &&            /scripts/validate-toolstate.sh
 ---> 537a01811900
Successfully built 537a01811900
Successfully tagged rust-ci:latest
Built container sha256:537a018119009dc218456238dec90b5530050db1e2a1e166550c218003f6159d
---
extracting /checkout/obj/build/cache/2020-04-22/rustfmt-nightly-x86_64-unknown-linux-gnu.tar.xz
error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`

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Build completed unsuccessfully in 0:00:20
== clock drift check ==
  local time: Sat May 30 19:02:45 UTC 2020
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  network time: Sat, 30 May 2020 19:02:45 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
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==============================================================================
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bors · 2020-06-19T16:14:56Z

☔ The latest upstream changes (presumably #73504) made this pull request unmergeable. Please resolve the merge conflicts.

estebank

Apologies for the delay on reviewing this. I have a couple of nitpicks. Could you address them as you rebase? Other than that, I'm happy with the changes!

src/librustc_trait_selection/traits/error_reporting/suggestions.rs

…trait_selection`.

ldm0 · 2020-06-20T14:18:41Z

Rebase done, nitpicks applied.

estebank · 2020-06-20T20:41:50Z

@bors r+

bors · 2020-06-20T20:41:51Z

📌 Commit f1e0710 has been approved by estebank

@ghost

…arth Rollup of 9 pull requests Successful merges: - rust-lang#72456 (Try to suggest dereferences on trait selection failed) - rust-lang#72788 (Projection bound validation) - rust-lang#72790 (core/time: Add Duration methods for zero) - rust-lang#73227 (Allow multiple `asm!` options groups and report an error on duplicate options) - rust-lang#73287 (lint: normalize projections using opaque types) - rust-lang#73291 (Pre-compute `LocalDefId` <-> `HirId` mappings and remove `NodeId` <-> `HirId` conversion APIs) - rust-lang#73378 (Remove use of specialization from librustc_arena) - rust-lang#73411 (Update bootstrap to rustc 1.45.0-beta.2 (1dc0f6d 2020-06-15)) - rust-lang#73443 (ci: allow gating GHA on everything but macOS) Failed merges: r? @ghost

rust-highfive assigned estebank May 22, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 22, 2020

ldm0 marked this pull request as draft May 23, 2020 10:32

ldm0 force-pushed the dereftrait branch 2 times, most recently from 8d3898b to e66f84e Compare May 23, 2020 10:40

ldm0 marked this pull request as ready for review May 23, 2020 11:13

ldm0 marked this pull request as draft May 30, 2020 16:55

ldm0 force-pushed the dereftrait branch 2 times, most recently from c3fb825 to 3fc1c11 Compare May 30, 2020 18:50

ldm0 marked this pull request as ready for review May 30, 2020 18:51

ldm0 force-pushed the dereftrait branch from 3fc1c11 to 9550a8e Compare May 30, 2020 18:59

ldm0 marked this pull request as draft May 30, 2020 19:00

ldm0 force-pushed the dereftrait branch 2 times, most recently from 79a33b0 to 0c0b32d Compare May 30, 2020 19:25

ldm0 marked this pull request as ready for review May 30, 2020 19:30

Elinvynia added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 10, 2020

estebank approved these changes Jun 19, 2020

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src/librustc_trait_selection/traits/error_reporting/suggestions.rs Outdated Show resolved Hide resolved

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ldm0 added 3 commits June 20, 2020 18:29

Decouple Autoderef with FnCtxt and move Autoderef to `librustc_…

5155518

…trait_selection`.

Try to suggest dereferences when trait selection failed.

ef68bf3

Prevent incorrect help message for dereference suggestion

f1e0710

ldm0 force-pushed the dereftrait branch from 0c0b32d to f1e0710 Compare June 20, 2020 12:02

ldm0 requested a review from estebank June 20, 2020 14:17

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-review Status: Awaiting review from the assignee but also interested parties. labels Jun 20, 2020

Manishearth mentioned this pull request Jun 20, 2020

Rollup of 9 pull requests #73563

Merged

bors merged commit a1404a9 into rust-lang:master Jun 21, 2020

ldm0 deleted the dereftrait branch June 21, 2020 03:32

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