Apply x clippy --fix and x fmt

compiler/rustc_data_structures/src/graph/dominators/mod.rs

@@ -93,7 +93,7 @@ fn dominators_impl<G: ControlFlowGraph>(graph: &G) -> Inner<G::Node> {
     // These are all done here rather than through one of the 'standard'
     // graph traversals to help make this fast.
     'recurse: while let Some(frame) = stack.last_mut() {
-        while let Some(successor) = frame.iter.next() {
+        for successor in frame.iter.by_ref() {
             if real_to_pre_order[successor].is_none() {
                 let pre_order_idx = pre_order_to_real.push(successor);
                 real_to_pre_order[successor] = Some(pre_order_idx);

compiler/rustc_data_structures/src/graph/iterate/mod.rs

@@ -48,7 +48,7 @@ fn post_order_walk<G: DirectedGraph + Successors>(
         let node = frame.node;
         visited[node] = true;
 
-        while let Some(successor) = frame.iter.next() {
+        for successor in frame.iter.by_ref() {
             if !visited[successor] {
                 stack.push(PostOrderFrame { node: successor, iter: graph.successors(successor) });
                 continue 'recurse;
@@ -112,7 +112,7 @@ where
     /// This is equivalent to just invoke `next` repeatedly until
     /// you get a `None` result.
     pub fn complete_search(&mut self) {
-        while let Some(_) = self.next() {}
+        for _ in self.by_ref() {}
     }
 
     /// Returns true if node has been visited thus far.

compiler/rustc_data_structures/src/graph/scc/mod.rs

@@ -40,7 +40,7 @@ pub struct SccData<S: Idx> {
 }
 
 impl<N: Idx, S: Idx + Ord> Sccs<N, S> {
-    pub fn new(graph: &(impl DirectedGraph<Node = N> + Successors)) -> Self {
+    pub fn new(graph: &impl Successors<Node = N>) -> Self {
         SccsConstruction::construct(graph)
     }