deref patterns: impl DerefPure for more std types
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…iaskrgr Rollup of 10 pull requests Successful merges: - rust-lang#123480 (deref patterns: impl `DerefPure` for more std types) - rust-lang#124412 (io safety: update Unix explanation to use `Arc`) - rust-lang#124441 (String.truncate comment microfix (greater or equal)) - rust-lang#124594 (run-make-support: preserve tooks.mk behavior for EXTRACXXFLAGS) - rust-lang#124604 (library/std: Remove unused `gimli-symbolize` feature) - rust-lang#124607 (`rustc_expand` cleanups) - rust-lang#124609 (variable-precision float operations can differ depending on optimization levels) - rust-lang#124610 (Tweak `consts_may_unify`) - rust-lang#124626 (const_eval_select: add tracking issue) - rust-lang#124637 (AST pretty: Use `builtin_syntax` for type ascription) Failed merges: - rust-lang#124638 (Move some tests from `rustc_expand` to `rustc_parse`.) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#123480 - Nadrieril:impl-all-derefpures, r=compiler-errors deref patterns: impl `DerefPure` for more std types Context: [deref patterns](rust-lang#87121). The requirements of `DerefPure` aren't precise yet, but these types unambiguously satisfy them. Interestingly, a hypothetical `impl DerefMut for Cow` that does a `Clone` would *not* be eligible for `DerefPure` if we allow mixing deref patterns with normal patterns. If the following is exhaustive then the `DerefMut` would cause UB: ```rust match &mut Cow::Borrowed(&()) { Cow::Owned(_) => ..., // Doesn't match deref!(_x) if false => ..., // Causes the variant to switch to `Owned` Cow::Borrowed(_) => ..., // Doesn't match // We reach unreachable } ```
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Context: deref patterns. The requirements of
DerefPurearen't precise yet, but these types unambiguously satisfy them.Interestingly, a hypothetical
impl DerefMut for Cowthat does aClonewould not be eligible forDerefPureif we allow mixing deref patterns with normal patterns. If the following is exhaustive then theDerefMutwould cause UB: