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self-borrowing AsyncFnMut closures do not implement FnOnce #217

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lcnr opened this issue May 22, 2025 · 0 comments · Fixed by rust-lang/rust#141359
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self-borrowing AsyncFnMut closures do not implement FnOnce #217

lcnr opened this issue May 22, 2025 · 0 comments · Fixed by rust-lang/rust#141359
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from-crater A regression found via a crater run, not part of our test suite

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@lcnr
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lcnr commented May 22, 2025 

fn call_once<F>(_: impl FnOnce() -> F) {}

fn main() {
    let mut i = 0;
    let c = async || {
        i += 1;
    };
    call_once(c);
}
@lcnr lcnr self-assigned this May 22, 2025
@lcnr lcnr added the from-crater A regression found via a crater run, not part of our test suite label May 22, 2025
@lcnr lcnr assigned compiler-errors and unassigned lcnr May 22, 2025
@lcnr lcnr moved this from unknown to in progress in -Znext-solver=globally May 22, 2025
@lcnr lcnr mentioned this issue May 22, 2025
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rust-timer added a commit to rust-lang-ci/rust that referenced this issue May 22, 2025
@rust-timer
Unrolled build for rust-lang#141359
cfe9972 
Rollup merge of rust-lang#141359 - compiler-errors:async-fn-once, r=lcnr

Fix `FnOnce` impl for `AsyncFn`/`AsyncFnMut` self-borrowing closures in new solver

This only affects closures that are "`AsyncFn`/`AsyncFnMut`" in their calling capability that are being called with the `FnOnce` trait.

fixes rust-lang/trait-system-refactor-initiative#217

r? lcnr
@lcnr lcnr moved this from in progress to done in -Znext-solver=globally May 24, 2025
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from-crater A regression found via a crater run, not part of our test suite
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Fix FnOnce impl for AsyncFn/AsyncFnMut self-borrowing closures in new solver compiler-errors/rust
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@compiler-errors @lcnr