bjoernager/rust
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Don't build the same matrix twice

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The exact same logic was used in check_arms and check_match to build the
matrix of relevant patterns. It would actually probably have been a bug
if it was not the case, since exhaustiveness checking should be the same
as checking reachability of an additional `_ => ...` match branch.
This commit is contained in:
Nadrieril 2019-11-03 17:10:33 +00:00
parent 2da942f328
commit fe67196679
1 changed files with 5 additions and 10 deletions
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15
src/librustc_mir/hair/pattern/check_match.rs
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@ -181,7 +181,7 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {
} }
// Fourth, check for unreachable arms. // Fourth, check for unreachable arms.
check_arms(cx, &inlined_arms, source); let matrix = check_arms(cx, &inlined_arms, source);
// Then, if the match has no arms, check whether the scrutinee // Then, if the match has no arms, check whether the scrutinee
// is uninhabited. // is uninhabited.
@ -248,12 +248,6 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {
return; return;
} }
let matrix: Matrix<'_, '_> = inlined_arms
.iter()
.filter(|&&(_, guard)| guard.is_none())
.flat_map(|arm| &arm.0)
.map(|pat| PatStack::from_pattern(pat.0))
.collect();
let scrut_ty = self.tables.node_type(scrut.hir_id); let scrut_ty = self.tables.node_type(scrut.hir_id);
check_exhaustive(cx, scrut_ty, scrut.span, &matrix, scrut.hir_id); check_exhaustive(cx, scrut_ty, scrut.span, &matrix, scrut.hir_id);
}) })
@ -403,11 +397,11 @@ fn pat_is_catchall(pat: &Pat) -> bool {
} }
// Check for unreachable patterns // Check for unreachable patterns
fn check_arms<'tcx>( fn check_arms<'p, 'tcx>(
cx: &mut MatchCheckCtxt<'_, 'tcx>, cx: &mut MatchCheckCtxt<'_, 'tcx>,
arms: &[(Vec<(&super::Pat<'tcx>, &hir::Pat)>, Option<&hir::Expr>)], arms: &[(Vec<(&'p super::Pat<'tcx>, &hir::Pat)>, Option<&hir::Expr>)],
source: hir::MatchSource, source: hir::MatchSource,
) { ) -> Matrix<'p, 'tcx> {
let mut seen = Matrix::empty(); let mut seen = Matrix::empty();
let mut catchall = None; let mut catchall = None;
for (arm_index, &(ref pats, guard)) in arms.iter().enumerate() { for (arm_index, &(ref pats, guard)) in arms.iter().enumerate() {
@ -485,6 +479,7 @@ fn check_arms<'tcx>(
} }
} }
} }
seen
} }
fn check_not_useful( fn check_not_useful(