TypeVisitor: use ControlFlow in rustc_{mir,privacy,traits,typeck}

compiler/rustc_mir/src/util/pretty.rs

@@ -19,6 +19,7 @@ use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, TyCtxt, TypeFoldable, TypeVisitor};
 use rustc_target::abi::Size;
+use std::ops::ControlFlow;
 
 const INDENT: &str = "    ";
 /// Alignment for lining up comments following MIR statements
@@ -639,7 +640,7 @@ pub fn write_allocations<'tcx>(
     }
     struct CollectAllocIds(BTreeSet<AllocId>);
     impl<'tcx> TypeVisitor<'tcx> for CollectAllocIds {
-        fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool {
+        fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<(), ()> {
             if let ty::ConstKind::Value(val) = c.val {
                 self.0.extend(alloc_ids_from_const(val));
             }