From ff90c6353b1e78aee13acedbfd545b02bc9e830f Mon Sep 17 00:00:00 2001
From: Nadrieril <nadrieril+git@gmail.com>
Date: Mon, 13 Sep 2021 15:49:57 +0100
Subject: [PATCH] Cleanup the reporting of unreachable patterns
---
.../src/thir/pattern/check_match.rs | 34 ++++++++-----------
1 file changed, 14 insertions(+), 20 deletions(-)
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index d04d3261a26..42645fca3aa 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -190,20 +190,16 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {
let scrut_ty = self.typeck_results.expr_ty_adjusted(scrut);
let report = compute_match_usefulness(&cx, &arms, scrut.hir_id, scrut_ty);
- report_arm_reachability(&cx, &report, |arm_span, arm_hir_id, catchall| {
- match source {
- hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
- unreachable_pattern(cx.tcx, arm_span, arm_hir_id, catchall);
- }
- // Unreachable patterns in try and await expressions occur when one of
- // the arms are an uninhabited type. Which is OK.
- hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
+ match source {
+ hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
+ report_arm_reachability(&cx, &report)
}
- });
+ // Unreachable patterns in try and await expressions occur when one of
+ // the arms are an uninhabited type. Which is OK.
+ hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
+ }
// Check if the match is exhaustive.
- // Note: An empty match isn't the same as an empty matrix for diagnostics purposes,
- // since an empty matrix can occur when there are arms, if those arms all have guards.
let is_empty_match = arms.is_empty();
let witnesses = report.non_exhaustiveness_witnesses;
if !witnesses.is_empty() {
@@ -434,9 +430,10 @@ fn check_let_reachability<'p, 'tcx>(
let arms = [MatchArm { pat, hir_id: pat_id, has_guard: false }];
let report = compute_match_usefulness(&cx, &arms, pat_id, pat.ty);
- report_arm_reachability(&cx, &report, |arm_span, arm_hir_id, _| {
- unreachable_pattern(cx.tcx, arm_span, arm_hir_id, None)
- });
+ // Report if the pattern is unreachable, which can only occur when the type is uninhabited.
+ // This also reports unreachable sub-patterns though, so we can't just replace it with an
+ // `is_uninhabited` check.
+ report_arm_reachability(&cx, &report);
if report.non_exhaustiveness_witnesses.is_empty() {
// The match is exhaustive, i.e. the `if let` pattern is irrefutable.
@@ -445,18 +442,15 @@ fn check_let_reachability<'p, 'tcx>(
}
/// Report unreachable arms, if any.
-fn report_arm_reachability<'p, 'tcx, F>(
+fn report_arm_reachability<'p, 'tcx>(
cx: &MatchCheckCtxt<'p, 'tcx>,
report: &UsefulnessReport<'p, 'tcx>,
- unreachable: F,
-) where
- F: Fn(Span, HirId, Option<Span>),
-{
+) {
use Reachability::*;
let mut catchall = None;
for (arm, is_useful) in report.arm_usefulness.iter() {
match is_useful {
- Unreachable => unreachable(arm.pat.span, arm.hir_id, catchall),
+ Unreachable => unreachable_pattern(cx.tcx, arm.pat.span, arm.hir_id, catchall),
Reachable(unreachables) if unreachables.is_empty() => {}
// The arm is reachable, but contains unreachable subpatterns (from or-patterns).
Reachable(unreachables) => {