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Reveal opaque types in exhaustiveness checking

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Nadrieril
2023-11-16 04:28:22 +01:00
parent 7e4924b55d
commit 2a87bae48d
7 changed files with 76 additions and 42 deletions
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20
compiler/rustc_pattern_analysis/src/usefulness.rs
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@@ -865,24 +865,14 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
matrix
}
fn head_ty(&self) -> Option<Cx::Ty> {
fn head_ty(&self, mcx: MatchCtxt<'a, 'p, Cx>) -> Option<Cx::Ty> {
if self.column_count() == 0 {
return None;
}
let mut ty = self.wildcard_row.head().ty();
// If the type is opaque and it is revealed anywhere in the column, we take the revealed
// version. Otherwise we could encounter constructors for the revealed type and crash.
if Cx::is_opaque_ty(ty) {
for pat in self.heads() {
let pat_ty = pat.ty();
if !Cx::is_opaque_ty(pat_ty) {
ty = pat_ty;
break;
}
}
}
Some(ty)
let ty = self.wildcard_row.head().ty();
// FIXME(Nadrieril): `Cx` should only give us revealed types.
Some(mcx.tycx.reveal_opaque_ty(ty))
}
fn column_count(&self) -> usize {
self.wildcard_row.len()
@@ -1181,7 +1171,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
) -> WitnessMatrix<Cx> {
debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));
let Some(ty) = matrix.head_ty() else {
let Some(ty) = matrix.head_ty(mcx) 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() {