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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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4
compiler/rustc_ast/src/ast.rs
View file

@ -645,6 +645,7 @@ impl Pat {
// These patterns do not contain subpatterns, skip.
PatKind::Wild
| PatKind::Rest
| PatKind::Never
| PatKind::Lit(_)
| PatKind::Range(..)
| PatKind::Ident(..)
@ -795,6 +796,9 @@ pub enum PatKind {
/// only one rest pattern may occur in the pattern sequences.
Rest,
// A never pattern `!`
Never,
/// Parentheses in patterns used for grouping (i.e., `(PAT)`).
Paren(P<Pat>),

2
compiler/rustc_ast/src/mut_visit.rs
View file

@ -1249,7 +1249,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
let Pat { id, kind, span, tokens } = pat.deref_mut();
vis.visit_id(id);
match kind {
PatKind::Wild | PatKind::Rest => {}
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
PatKind::Ident(_binding_mode, ident, sub) => {
vis.visit_ident(ident);
visit_opt(sub, |sub| vis.visit_pat(sub));

2
compiler/rustc_ast/src/visit.rs
View file

@ -559,7 +559,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
walk_list!(visitor, visit_expr, lower_bound);
walk_list!(visitor, visit_expr, upper_bound);
}
PatKind::Wild | PatKind::Rest => {}
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
walk_list!(visitor, visit_pat, elems);
}