async/await: improve not-send errors #64895

davidtwco · 2019-09-29T13:40:40Z

note: future does not implement `std::marker::Send` because this value is used across an await
  --> $DIR/issue-64130-non-send-future-diags.rs:15:5
   |
LL |     let g = x.lock().unwrap();
   |         - has type `std::sync::MutexGuard<'_, u32>`
LL |     baz().await;
   |     ^^^^^^^^^^^ await occurs here, with `g` maybe used later
LL | }
   | - `g` is later dropped here

r? @nikomatsakis

Centril

Just some nits.

src/librustc/traits/error_reporting.rs

davidtwco · 2019-09-29T19:20:15Z

I'm not sure where the duplicate diagnostic item error is coming from, a quick glance only found the rustc_diagnostic_item attribute that I added.

Centril · 2019-09-29T19:21:35Z

cc @oli-obk ^---

src/libstd/future.rs

src/librustc/traits/error_reporting.rs

oli-obk · 2019-09-30T19:32:15Z

@bors r+

bors · 2019-09-30T19:32:17Z

📌 Commit 28be5ae8c558613e59a56eb83f069da47eda56ed has been approved by oli-obk

nikomatsakis

This is awesome. Beautiful work. My one concern is that I think we can do better still with the error, but I'm sort of inclined to land this PR and continue that work afterwards.

src/test/ui/async-await/issue-64130-non-send-future-diags.stderr

src/librustc/traits/error_reporting.rs

src/librustc_typeck/check/generator_interior.rs

src/librustc/ty/context.rs

This commit improves obligation errors for async/await: ``` note: future does not implement `std::marker::Send` because this value is used across an await --> $DIR/issue-64130-non-send-future-diags.rs:15:5 | LL | let g = x.lock().unwrap(); | - has type `std::sync::MutexGuard<'_, u32>` LL | baz().await; | ^^^^^^^^^^^ await occurs here, with `g` maybe used later LL | } | - `g` is later dropped here ``` Signed-off-by: David Wood <david@davidtw.co>

nikomatsakis · 2019-09-30T23:22:56Z

@bors r+

bors · 2019-09-30T23:22:58Z

📌 Commit 04fa9b1 has been approved by nikomatsakis

@nikomatsakis

…efinition, r=nikomatsakis async/await: improve not-send errors cc rust-lang#64130. ``` note: future does not implement `std::marker::Send` because this value is used across an await --> $DIR/issue-64130-non-send-future-diags.rs:15:5 | LL | let g = x.lock().unwrap(); | - has type `std::sync::MutexGuard<'_, u32>` LL | baz().await; | ^^^^^^^^^^^ await occurs here, with `g` maybe used later LL | } | - `g` is later dropped here ``` r? @nikomatsakis

@ghost

Rollup of 10 pull requests Successful merges: - #63674 (syntax: Support modern attribute syntax in the `meta` matcher) - #63931 (Stabilize macros in some more positions) - #64887 (syntax: recover trailing `|` in or-patterns) - #64895 (async/await: improve not-send errors) - #64896 (Remove legacy grammar) - #64907 (A small amount of tidying-up factored out from PR #64648) - #64928 (Add tests for some issues) - #64930 (Silence unreachable code lint from await desugaring) - #64935 (Improve code clarity) - #64937 (Deduplicate closure type errors) Failed merges: r? @ghost

bors · 2019-10-01T11:53:15Z

☔ The latest upstream changes (presumably #64946) made this pull request unmergeable. Please resolve the merge conflicts.

ghost · 2019-10-02T08:26:01Z

~~It appears that~~ this causes ICE #64964 (comment)

~~I'm currently retesting that by applying this PR on top of the rust compilation that succeeded without it.~~confirmed

nikomatsakis · 2019-10-03T08:36:21Z

I'd like to nominate this PR (and the follow-up #64989) for inclusion in beta. It's not the sort of thing I would normally include, but this error is (a) one of the most common problems I hear people complaining about with async-await and (b) particularly opaque without this fix. Moreover, it is early in the cycle, so it will presumably get a reasonable amount of testing before landing. The change is relatively low risk, in that it is confined to error reporting.

pnkfelix · 2019-10-03T18:37:53Z

discussed at rustc meeting. accepted for beta backport in tandem with PR #64989 (since that fixes an ICE this injected).

[beta] backport rollup This includes a bunch of PRs: * Fix redundant semicolon lint interaction with proc macro attributes #64387 * Upgrade async/await to "used" keywords. #64875 * syntax: fix dropping of attribute on first param of non-method assocated fn #64894 * async/await: improve not-send errors #64895 * Silence unreachable code lint from await desugaring #64930 * Always mark rust and rust-call abi's as unwind #65020 * Account for macro invocation in `let mut $pat` diagnostic. #65123 * Ensure that associated `async fn`s have unique fresh param names #65142 * Add troubleshooting section to PGO chapter in rustc book. #65402 * Upgrade GCC to 8.3.0, glibc to 1.17.0 and crosstool-ng to 1.24.0 for dist-armv7-linux #65302 * Optimize `try_expand_impl_trait_type` #65293 * use precalculated dominators in explain_borrow #65172 * Fix ICE #64964 #64989

[beta] backport rollup This includes a bunch of PRs: * Fix redundant semicolon lint interaction with proc macro attributes #64387 * Upgrade async/await to "used" keywords. #64875 * syntax: fix dropping of attribute on first param of non-method assocated fn #64894 * async/await: improve not-send errors #64895 * Silence unreachable code lint from await desugaring #64930 * Always mark rust and rust-call abi's as unwind #65020 * Account for macro invocation in `let mut $pat` diagnostic. #65123 * Ensure that associated `async fn`s have unique fresh param names #65142 * Add troubleshooting section to PGO chapter in rustc book. #65402 * Upgrade GCC to 8.3.0, glibc to 1.17.0 and crosstool-ng to 1.24.0 for dist-armv7-linux #65302 * Optimize `try_expand_impl_trait_type` #65293 * use precalculated dominators in explain_borrow #65172 * Fix ICE #64964 #64989 * [beta] Revert "Auto merge of #62948 - matklad:failable-file-loading, r=petro… #65273 * save-analysis: Don't ICE when resolving qualified type paths in struct members #65353 * save-analysis: Nest tables when processing impl block definitions #65511 * Avoid ICE when checking `Destination` of `break` inside a closure #65518 * Avoid ICE when adjusting bad self ty #65755 * workaround msys2 bug #65762

@nikomatsakis

…provements, r=nikomatsakis async/await: improve not-send errors, part 2 Part of #64130. Fixes #65667. This PR improves the errors introduced in #64895 so that they have specialized messages for `Send` and `Sync`. r? @nikomatsakis

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Centril mentioned this pull request Oct 1, 2019

Rollup of 10 pull requests #64946

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bors merged commit 04fa9b1 into rust-lang:master Oct 1, 2019

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 Oct 1, 2019

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sinkuu mentioned this pull request Oct 2, 2019

ICE while compiling hyper (StableHasher: unexpected region '_#0r) #64964

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nikomatsakis added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 3, 2019

nikomatsakis mentioned this pull request Oct 3, 2019

Fix ICE #64964 #64989

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Centril added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Oct 3, 2019

pnkfelix added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Oct 3, 2019

davidtwco mentioned this pull request Oct 12, 2019

async/await: improve not-send errors, part 2 #65345

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Mark-Simulacrum mentioned this pull request Oct 22, 2019

[beta] backport rollup #65708

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tmandry mentioned this pull request Dec 17, 2019

non-send futures error at point of use, but could cite point of definition in some cases #64130

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eddyb mentioned this pull request Apr 6, 2020

note_obligation_cause reporting for non-async/await not optimal #70818

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async/await: improve not-send errors #64895

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