bjoernager/rust
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Simplify for loop desugar

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This commit is contained in:
Cameron Steffen 2021-10-25 23:33:12 -05:00
parent 3bfde2f1f4
commit 9c83f8c4d1
26 changed files with 181 additions and 256 deletions
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21
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
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@ -74,19 +74,16 @@ impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, '_, 'tcx> {
let (msg, sp) = match loc.source {
hir::LocalSource::Normal => ("local binding", Some(loc.span)),
hir::LocalSource::ForLoopDesugar => ("`for` loop binding", None),
hir::LocalSource::AsyncFn => ("async fn binding", None),
hir::LocalSource::AwaitDesugar => ("`await` future binding", None),
hir::LocalSource::AssignDesugar(_) => ("destructuring assignment binding", None),
};
self.check_irrefutable(&loc.pat, msg, sp);
self.check_patterns(&loc.pat, Irrefutable);
}
fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
intravisit::walk_param(self, param);
self.check_irrefutable(&param.pat, "function argument", None);
self.check_patterns(&param.pat, Irrefutable);
}
}
@ -161,12 +158,12 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
fn check_match(
&mut self,
scrut: &hir::Expr<'_>,
arms: &'tcx [hir::Arm<'tcx>],
hir_arms: &'tcx [hir::Arm<'tcx>],
source: hir::MatchSource,
) {
let mut cx = self.new_cx(scrut.hir_id);
for arm in arms {
for arm in hir_arms {
// Check the arm for some things unrelated to exhaustiveness.
self.check_patterns(&arm.pat, Refutable);
if let Some(hir::Guard::IfLet(ref pat, _)) = arm.guard {
@ -178,7 +175,7 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let mut have_errors = false;
let arms: Vec<_> = arms
let arms: Vec<_> = hir_arms
.iter()
.map(|hir::Arm { pat, guard, .. }| MatchArm {
pat: self.lower_pattern(&mut cx, pat, &mut have_errors),
@ -196,6 +193,9 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let report = compute_match_usefulness(&cx, &arms, scrut.hir_id, scrut_ty);
match source {
// Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }`
// when the iterator is an uninhabited type. unreachable_code will trigger instead.
hir::MatchSource::ForLoopDesugar if arms.len() == 1 => {}
hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
report_arm_reachability(&cx, &report)
}
@ -208,7 +208,13 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let is_empty_match = arms.is_empty();
let witnesses = report.non_exhaustiveness_witnesses;
if !witnesses.is_empty() {
non_exhaustive_match(&cx, scrut_ty, scrut.span, witnesses, is_empty_match);
if source == hir::MatchSource::ForLoopDesugar && hir_arms.len() == 2 {
// the for loop pattern is not irrefutable
let pat = hir_arms[1].pat.for_loop_some().unwrap();
self.check_irrefutable(pat, "`for` loop binding", None);
} else {
non_exhaustive_match(&cx, scrut_ty, scrut.span, witnesses, is_empty_match);
}
}
}
@ -225,6 +231,7 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
let witnesses = report.non_exhaustiveness_witnesses;
if witnesses.is_empty() {
// The pattern is irrefutable.
self.check_patterns(pat, Irrefutable);
return;
}