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Author: nnethercote

compiler/rustc_middle/src/mir/basic_blocks.rs

@@ -20,6 +20,10 @@ pub struct BasicBlocks<'tcx> {
 // Typically 95%+ of basic blocks have 4 or fewer predecessors.
 type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>;
 
+// Note: this type is currently never instantiated, because it's only used for
+// `BasicBlocks::switch_sources`, which is only called by backwards analyses
+// that do `SwitchInt` handling, and we don't have any of those, not even in
+// tests. See #95120 and #94576.
 type SwitchSources = FxHashMap<(BasicBlock, BasicBlock), SmallVec<[u128; 1]>>;
 
 #[derive(Clone, Default, Debug)]