bjoernager/rust
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Statically enforce revealing of opaques

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This commit is contained in:
Nadrieril 2023-12-26 13:21:35 +01:00
parent e51e98dde6
commit c35272058d
5 changed files with 132 additions and 94 deletions
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17
compiler/rustc_pattern_analysis/src/usefulness.rs
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@ -847,8 +847,11 @@ impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
self.pats.len()
}
fn head_opt(&self) -> Option<&'p DeconstructedPat<'p, Cx>> {
self.pats.first().copied()
}
fn head(&self) -> &'p DeconstructedPat<'p, Cx> {
self.pats[0]
self.head_opt().unwrap()
}
fn iter(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
@ -1028,14 +1031,8 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
matrix
}
fn head_ty(&self, mcx: MatchCtxt<'_, 'p, Cx>) -> Option<Cx::Ty> {
if self.column_count() == 0 {
return None;
}
let ty = self.wildcard_row.head().ty();
// FIXME(Nadrieril): `Cx` should only give us revealed types.
Some(mcx.tycx.reveal_opaque_ty(ty))
fn head_ty(&self) -> Option<Cx::Ty> {
self.wildcard_row.head_opt().map(|pat| pat.ty())
}
fn column_count(&self) -> usize {
self.wildcard_row.len()
@ -1345,7 +1342,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
return WitnessMatrix::empty();
}
let Some(ty) = matrix.head_ty(mcx) else {
let Some(ty) = matrix.head_ty() else {
// The base case: there are no columns in the matrix. We are morally pattern-matching on ().
// A row is useful iff it has no (unguarded) rows above it.
for row in matrix.rows_mut() {