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Add comments explaining inherited references

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This adds explanation of inherited references and how they relate to the default binding mode.

Co-authored-by: Nadrieril <Nadrieril@users.noreply.github.com>
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dianne 2025-01-19 15:26:14 -08:00 committed by GitHub
parent 562c522b94
commit 48e023a56f
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6
compiler/rustc_hir_typeck/src/pat.rs
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@ -215,6 +215,10 @@ impl MutblCap {
}
/// Variations on RFC 3627's Rule 4: when do reference patterns match against inherited references?
///
/// "Inherited reference" designates the `&`/`&mut` types that arise from using match ergonomics, i.e.
/// from matching a reference type with a non-reference pattern. E.g. when `Some(x)` matches on
/// `&mut Option<&T>`, `x` gets type `&mut &T` and the outer `&mut` is considered "inherited".
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum InheritedRefMatchRule {
/// Reference patterns try to consume the inherited reference first.
@ -223,7 +227,7 @@ enum InheritedRefMatchRule {
/// Reference patterns consume inherited references if matching against a non-reference type.
/// This assumes reference patterns can always match against an inherited reference.
EatInner,
/// Reference patterns consume both layers of reference.
/// Reference patterns consume both layers of reference, i.e. reset the binding mode when consuming a reference type.
/// Currently, this assumes the stable Rust behavior of not allowing reference patterns to eat
/// an inherited reference alone. This will need an additional field or variant to represent the
/// planned edition <= 2021 behavior of experimental match ergonomics, which does allow that.