Consistently merge simplifiable or-patterns

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -1293,8 +1293,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  // At least one of the candidates has been split into subcandidates.
  // We need to change the candidate list to include those.
  let mut new_candidates = Vec::new();
-
- for candidate in candidates {
+ for candidate in candidates.iter_mut() {
  candidate.visit_leaves(|leaf_candidate| new_candidates.push(leaf_candidate));
  }
  self.match_simplified_candidates(
@@ -1304,6 +1303,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
  otherwise_block,
  &mut *new_candidates,
  );
+
+ for candidate in candidates {
+ self.merge_trivial_subcandidates(candidate);
+ }
  } else {
  self.match_simplified_candidates(
  span,

tests/mir-opt/issues/issue_75439.foo.MatchBranchSimplification.diff

@@ -26,18 +26,20 @@
  _3 = _1;
  _2 = move _3 as [u32; 4] (Transmute);
  StorageDead(_3);
- switchInt(_2[0 of 4]) -> [0: bb1, otherwise: bb6];
+ switchInt(_2[0 of 4]) -> [0: bb1, otherwise: bb4];
  }
 
  bb1: {
- switchInt(_2[1 of 4]) -> [0: bb2, otherwise: bb6];
+ switchInt(_2[1 of 4]) -> [0: bb2, otherwise: bb4];
  }
 
  bb2: {
- switchInt(_2[2 of 4]) -> [0: bb4, 4294901760: bb5, otherwise: bb6];
+ switchInt(_2[2 of 4]) -> [0: bb3, 4294901760: bb3, otherwise: bb4];
  }
 
  bb3: {
+ StorageLive(_4);
+ _4 = _2[3 of 4];
  StorageLive(_5);
  StorageLive(_6);
  _6 = _4;
@@ -46,27 +48,15 @@
  _0 = Option::<[u8; 4]>::Some(move _5);
  StorageDead(_5);
  StorageDead(_4);
- goto -> bb7;
+ goto -> bb5;
  }
 
  bb4: {
- StorageLive(_4);
- _4 = _2[3 of 4];
- goto -> bb3;
- }
-
- bb5: {
- StorageLive(_4);
- _4 = _2[3 of 4];
- goto -> bb3;
- }
-
- bb6: {
  _0 = Option::<[u8; 4]>::None;
- goto -> bb7;
+ goto -> bb5;
  }
 
- bb7: {
+ bb5: {
  StorageDead(_2);
  return;
  }