Only set types of conditional expressions in strong mode.

pkg/front_end/testcases/void-methods.dart.direct.expect

Index: pkg/front_end/testcases/void-methods.dart.direct.expect
diff --git a/pkg/front_end/testcases/void-methods.dart.direct.expect b/pkg/front_end/testcases/void-methods.dart.direct.expect
index 96c850f6690f3879d0e453e2cadc70ea6d1c22e8..e0dc634666252499a95fbdf2f07949aae8e01fd7 100644
--- a/pkg/front_end/testcases/void-methods.dart.direct.expect
+++ b/pkg/front_end/testcases/void-methods.dart.direct.expect
@@ -8,9 +8,9 @@ class Foo extends core::Object {
     : super core::Object::•()
     ;
   set first(dynamic x) → dynamic
-    return let final dynamic #t1 = this.list in let final dynamic #t2 = 0 in let final dynamic #t3 = x in let final dynamic #t4 = #t1.[]=(#t2, #t3) in #t3;
+    this.list.[]=(0, x);
   operator []=(dynamic x, dynamic y) → dynamic
-    return let final dynamic #t5 = this.list in let final dynamic #t6 = x in let final dynamic #t7 = y in let final dynamic #t8 = #t5.[]=(#t6, #t7) in #t7;
+    this.list.[]=(x, y);
   method clear() → void
     return this.list.clear();
 }