Rename Statement::successors to cleanup_target

src/librustc/mir/cache.rs

@@ -81,8 +81,8 @@ fn calculate_successors(mir: &Mir) -> IndexVec<Block, Vec<Block>> {
     let mut result = IndexVec::from_elem(vec![], mir.basic_blocks());
     for (bb, data) in mir.basic_blocks().iter_enumerated() {
         for stmt in &data.statements {
-            for &tgt in stmt.successors().iter() {
-                result[bb].push(tgt);
+            if let Some(cleanup) = stmt.cleanup_target() {
+                result[bb].push(cleanup);
             }
         }
 

src/librustc/mir/mod.rs

@@ -735,21 +735,21 @@ impl<'tcx> Statement<'tcx> {
         self.kind = StatementKind::Nop
     }
 
-    pub fn successors(&self) -> Cow<[Block]> {
+    pub fn cleanup_target(&self) -> Option<Block> {
         match self.kind {
             StatementKind::Assert { cleanup: Some(unwind), .. } => {
-                vec![unwind].into_cow()
+                Some(unwind)
             }
-            _ => (&[]).into_cow(),
+            _ => None
         }
     }
 
-    pub fn successors_mut(&mut self) -> Vec<&mut Block> {
+    pub fn cleanup_target_mut(&mut self) -> Option<&mut Block> {
         match self.kind {
             StatementKind::Assert { cleanup: Some(ref mut unwind), .. } => {
-                vec![unwind]
+                Some(unwind)
             }
-            _ => Vec::new(),
+            _ => None
         }
     }
 }

src/librustc_mir/transform/simplify.rs

@@ -273,8 +273,8 @@ pub fn remove_dead_blocks(mir: &mut Mir) {
 
     for block in basic_blocks {
         for stmt in &mut block.statements {
-            for tgt in stmt.successors_mut() {
-                *tgt = replacements[tgt.index()];
+            if let Some(cleanup) = stmt.cleanup_target_mut() {
+                *cleanup = replacements[cleanup.index()];
             }
         }