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Drop temporaries as early as possible in $:expr case #187

Merged
merged 2 commits into from
Nov 4, 2021
Merged

Drop temporaries as early as possible in $:expr case #187

merged 2 commits into from
Nov 4, 2021

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dtolnay
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@dtolnay dtolnay commented Nov 4, 2021

Fixes #186.

@dtolnay
Add regression test of issue 186
45f6545 
Currently fails to build without the fix:

    error: future cannot be shared between threads safely
      --> tests/test_macros.rs:64:5
       |
    64 |     require_send_sync(async {
       |     ^^^^^^^^^^^^^^^^^ future created by async block is not `Sync`
       |
       = help: within `impl Future`, the trait `Sync` is not implemented for `Cell<&str>`
    note: future is not `Sync` as this value is used across an await
      --> tests/test_macros.rs:65:9
       |
    65 |         future::ready(anyhow!(message(Cell::new("...")))).await;
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ first, await occurs here, with `Cell::new("...")` maybe used later...
    note: `Cell::new("...")` is later dropped here
      --> tests/test_macros.rs:65:64
       |
    65 |         future::ready(anyhow!(message(Cell::new("...")))).await;
       |                                       ----------------         ^
       |                                       |
       |                                       has type `Cell<&str>` which is not `Sync`
    note: required by a bound in `require_send_sync`
      --> tests/test_macros.rs:50:41
       |
    50 |     fn require_send_sync(_: impl Send + Sync) {}
       |                                         ^^^^ required by this bound in `require_send_sync`
@dtolnay
Drop temporaries as early as possible in $:expr case
38591a9
@dtolnay dtolnay merged commit a32c1d1 into master Nov 4, 2021
@dtolnay dtolnay deleted the temporaries branch November 4, 2021 12:36
@x-hgg-x x-hgg-x mentioned this pull request Jan 14, 2022
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Successfully merging this pull request may close these issues.

The $:expr case keeps temporaries alive longer than needed
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@dtolnay