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Extract helper, fix comment on DerefPure

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+37

-15

lines changed

compiler
- rustc_hir_typeck/src
  - pat.rs
- rustc_middle/src/ty
  - typeck_results.rs
library/core/src/ops
- deref.rs

+37

-15

lines changed

Lines changed: 3 additions & 14 deletions

Original file line number	Diff line number	Diff line change
`@@ -2020,20 +2020,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {`
`2020`	`2020`
`2021`	`2021`	// Check if the pattern has any `ref mut` bindings, which would require
`2022`	`2022`	// `DerefMut` to be emitted in MIR building instead of just `Deref`.
`2023`		`- let mut needs_mut = false;`
`2024`		`- inner.walk(\|pat\| {`
`2025`		`- if let hir::PatKind::Binding(_, id, _, _) = pat.kind`
`2026`		`- && let Some(ty::BindByReference(ty::Mutability::Mut)) =`
`2027`		`- self.typeck_results.borrow().pat_binding_modes().get(id)`
`2028`		`- {`
`2029`		`- needs_mut = true;`
`2030`		`- // No need to continue recursing`
`2031`		`- false`
`2032`		`- } else {`
`2033`		`- true`
`2034`		`- }`
`2035`		`- });`
`2036`		`- if needs_mut {`
	`2023`	`+ // We do this after checking the inner pattern, since we want to make`
	`2024`	`+ // sure to apply any match-ergonomics adjustments.`
	`2025`	`+ if self.typeck_results.borrow().pat_has_ref_mut_binding(inner) {`
`2037`	`2026`	`self.register_bound(`
`2038`	`2027`	`expected,`
`2039`	`2028`	`tcx.require_lang_item(hir::LangItem::DerefMut, Some(span)),`

Lines changed: 25 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -430,6 +430,31 @@ impl<'tcx> TypeckResults<'tcx> {`
`430`	`430`	`LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.pat_adjustments }`
`431`	`431`	`}`
`432`	`432`
	`433`	+ /// Does the pattern recursively contain a `ref mut` binding in it?
	`434`	`+ ///`
	`435`	+ /// This is used to determined whether a `deref` pattern should emit a `Deref`
	`436`	+ /// or `DerefMut` call for its pattern scrutinee.
	`437`	`+ ///`
	`438`	`+ /// This is computed from the typeck results since we want to make`
	`439`	`+ /// sure to apply any match-ergonomics adjustments, which we cannot`
	`440`	`+ /// determine from the HIR alone.`
	`441`	`+ pub fn pat_has_ref_mut_binding(&self, pat: &'tcx hir::Pat<'tcx>) -> bool {`
	`442`	`+ let mut has_ref_mut = false;`
	`443`	`+ pat.walk(\|pat\| {`
	`444`	`+ if let hir::PatKind::Binding(_, id, _, _) = pat.kind`
	`445`	`+ && let Some(ty::BindByReference(ty::Mutability::Mut)) =`
	`446`	`+ self.pat_binding_modes().get(id)`
	`447`	`+ {`
	`448`	`+ has_ref_mut = true;`
	`449`	`+ // No need to continue recursing`
	`450`	`+ false`
	`451`	`+ } else {`
	`452`	`+ true`
	`453`	`+ }`
	`454`	`+ });`
	`455`	`+ has_ref_mut`
	`456`	`+ }`
	`457`	`+`
`433`	`458`	/// For a given closure, returns the iterator of `ty::CapturedPlace`s that are captured
`434`	`459`	`/// by the closure.`
`435`	`460`	`pub fn closure_min_captures_flattened(`

Lines changed: 9 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -275,7 +275,15 @@ impl<T: ?Sized> DerefMut for &mut T {`
`275`	`275`	`}`
`276`	`276`	`}`
`277`	`277`
`278`		`-/// UwU`
	`278`	+/// Perma-unstable marker trait. Indicates that the type has a well-behaved [`Deref`]
	`279`	+/// (and, if applicable, [`DerefMut`]) implementation. This is relied on for soundness
	`280`	`+/// of deref patterns.`
	`281`	`+///`
	`282`	`+/// FIXME(deref_patterns): The precise semantics are undecided; the rough idea is that`
	`283`	+/// successive calls to `deref`/`deref_mut` without intermediate mutation should be
	`284`	`+/// idempotent, in the sense that they return the same value as far as pattern-matching`
	`285`	+/// is concerned. Calls to `deref`/`deref_mut`` must leave the pointer itself likewise
	`286`	`+/// unchanged.`
`279`	`287`	`#[unstable(feature = "deref_pure_trait", issue = "87121")]`
`280`	`288`	`#[cfg_attr(not(bootstrap), lang = "deref_pure")]`
`281`	`289`	`pub unsafe trait DerefPure {}`

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