Tweak block management

Author: Nadrieril

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

@@ -1421,7 +1421,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         span: Span,
         scrutinee_span: Span,
         candidates: &mut [&mut Candidate<'_, 'tcx>],
-        block: BasicBlock,
+        start_block: BasicBlock,
         otherwise_block: BasicBlock,
         fake_borrows: &mut Option<FxIndexSet<Place<'tcx>>>,
     ) {
@@ -1431,7 +1431,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 span,
                 scrutinee_span,
                 candidates,
-                block,
+                start_block,
                 otherwise_block,
                 fake_borrows,
             );
@@ -1442,12 +1442,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let (first_match_pair, remaining_match_pairs) = match_pairs.split_first().unwrap();
         let PatKind::Or { ref pats } = &first_match_pair.pattern.kind else { unreachable!() };
 
-        first_candidate.pre_binding_block = Some(block);
         let remainder_start = self.cfg.start_new_block();
         let or_span = first_match_pair.pattern.span;
         // Test the alternatives of this or-pattern.
         self.test_or_pattern(
             first_candidate,
+            start_block,
             remainder_start,
             pats,
             or_span,
@@ -1493,6 +1493,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn test_or_pattern<'pat>(
         &mut self,
         candidate: &mut Candidate<'pat, 'tcx>,
+        start_block: BasicBlock,
         otherwise: BasicBlock,
         pats: &'pat [Box<Pat<'tcx>>],
         or_span: Span,
@@ -1513,11 +1514,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         self.match_candidates(
             or_span,
             or_span,
-            candidate.pre_binding_block.unwrap(),
+            start_block,
             otherwise,
             &mut or_candidate_refs,
             fake_borrows,
         );
+        candidate.pre_binding_block = Some(start_block);
         candidate.subcandidates = or_candidates;
         self.merge_trivial_subcandidates(candidate, self.source_info(or_span));
     }