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Rollup merge of #118157 - Nadrieril:never_pat-feature-gate, r=compiler-errors

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Add `never_patterns` feature gate

This PR adds the feature gate and most basic parsing for the experimental `never_patterns` feature. See the tracking issue (https://github.com/rust-lang/rust/issues/118155) for details on the experiment.

`@scottmcm` has agreed to be my lang-team liaison for this experiment.
This commit is contained in:
Matthias Krüger 2023-11-29 12:34:47 +01:00 • committed by GitHub
commit c03f8917ee
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40 changed files with 325 additions and 18 deletions
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7
compiler/rustc_hir/src/hir.rs
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@ -1002,7 +1002,7 @@ impl<'hir> Pat<'hir> {
use PatKind::*;
match self.kind {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
@ -1029,7 +1029,7 @@ impl<'hir> Pat<'hir> {
use PatKind::*;
match self.kind {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@ -1142,6 +1142,9 @@ pub enum PatKind<'hir> {
/// Invariant: `pats.len() >= 2`.
Or(&'hir [Pat<'hir>]),
/// A never pattern `!`.
Never,
/// A path pattern for a unit struct/variant or a (maybe-associated) constant.
Path(QPath<'hir>),

2
compiler/rustc_hir/src/intravisit.rs
View file

@ -660,7 +660,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
walk_list!(visitor, visit_expr, lower_bound);
walk_list!(visitor, visit_expr, upper_bound);
}
PatKind::Wild => (),
PatKind::Never | PatKind::Wild => (),
PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
walk_list!(visitor, visit_pat, prepatterns);
walk_list!(visitor, visit_pat, slice_pattern);