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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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11
compiler/rustc_middle/src/thir.rs
View file

@ -635,7 +635,12 @@ impl<'tcx> Pat<'tcx> {
use PatKind::*;
match &self.kind {
Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } | Error(_) => {}
Wild
| Never
| Range(..)
| Binding { subpattern: None, .. }
| Constant { .. }
| Error(_) => {}
AscribeUserType { subpattern, .. }
| Binding { subpattern: Some(subpattern), .. }
| Deref { subpattern }
@ -809,6 +814,9 @@ pub enum PatKind<'tcx> {
pats: Box<[Box<Pat<'tcx>>]>,
},
/// A never pattern `!`.
Never,
/// An error has been encountered during lowering. We probably shouldn't report more lints
/// related to this pattern.
Error(ErrorGuaranteed),
@ -1069,6 +1077,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
match self.kind {
PatKind::Wild => write!(f, "_"),
PatKind::Never => write!(f, "!"),
PatKind::AscribeUserType { ref subpattern, .. } => write!(f, "{subpattern}: _"),
PatKind::Binding { mutability, name, mode, ref subpattern, .. } => {
let is_mut = match mode {

2
compiler/rustc_middle/src/thir/visit.rs
View file

@ -227,7 +227,7 @@ pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'
is_primary: _,
name: _,
} => visitor.visit_pat(subpattern),
Binding { .. } | Wild | Error(_) => {}
Binding { .. } | Wild | Never | Error(_) => {}
Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {
for subpattern in subpatterns {
visitor.visit_pat(&subpattern.pattern);