Cap the number of patterns pointed to by the lint

2 files changed, 18 insertions, 3 deletions

diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index a45a0311e32..76b765ad4cd 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -596,6 +596,7 @@ pub(crate) struct UnreachablePattern<'tcx> {
     pub(crate) covered_by_one: Option<Span>,
     #[note(mir_build_unreachable_covered_by_many)]
     pub(crate) covered_by_many: Option<MultiSpan>,
+    pub(crate) covered_by_many_n_more_count: usize,
 }
 
 #[derive(Subdiagnostic)]
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 a948e5d0c21..ca563e01569 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -917,6 +917,7 @@ fn report_unreachable_pattern<'p, 'tcx>(
     pat: &DeconstructedPat<'p, 'tcx>,
     explanation: &RedundancyExplanation<'p, 'tcx>,
 ) {
+    static CAP_COVERED_BY_MANY: usize = 4;
     let pat_span = pat.data().span;
     let mut lint = UnreachablePattern {
         span: Some(pat_span),
@@ -925,6 +926,7 @@ fn report_unreachable_pattern<'p, 'tcx>(
         covered_by_catchall: None,
         covered_by_one: None,
         covered_by_many: None,
+        covered_by_many_n_more_count: 0,
     };
     match explanation.covered_by.as_slice() {
         [] => {
@@ -950,15 +952,27 @@ fn report_unreachable_pattern<'p, 'tcx>(
             lint.covered_by_one = Some(covering_pat.data().span);
         }
         covering_pats => {
+            let mut iter = covering_pats.iter();
             let mut multispan = MultiSpan::from_span(pat_span);
-            for p in covering_pats {
+            for p in iter.by_ref().take(CAP_COVERED_BY_MANY) {
                 multispan.push_span_label(
                     p.data().span,
                     fluent::mir_build_unreachable_matches_same_values,
                 );
             }
-            multispan
-                .push_span_label(pat_span, fluent::mir_build_unreachable_making_this_unreachable);
+            let remain = iter.count();
+            if remain == 0 {
+                multispan.push_span_label(
+                    pat_span,
+                    fluent::mir_build_unreachable_making_this_unreachable,
+                );
+            } else {
+                lint.covered_by_many_n_more_count = remain;
+                multispan.push_span_label(
+                    pat_span,
+                    fluent::mir_build_unreachable_making_this_unreachable_n_more,
+                );
+            }
             lint.covered_by_many = Some(multispan);
         }
     }