Only set types of conditional expressions in strong mode.

pkg/front_end/testcases/type_variable_as_super.dart.direct.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 abstract class A<T extends core::Object> extends core::Object {
   constructor •() → void
     : super core::Object::•()
     ;
 }
 abstract class B<T extends core::Object> extends core::Object {
   constructor •() → void
     : super core::Object::•()
     ;
 }
 class C<T extends core::Object> extends core::Object {
   constructor •() → void
     : super core::Object::•()
     ;
 }
-const field dynamic #errors = const <dynamic>["pkg/front_end/testcases/type_variable_as_super.dart: Error: The type variable 'T' can't be used as supertype.", "pkg/front_end/testcases/type_variable_as_super.dart: Error: The type variable 'T' can't be used as supertype.", "pkg/front_end/testcases/type_variable_as_super.dart: Error: The type variable 'T' can't be used as supertype."]/* from null */;
 static method main() → dynamic {
-  throw new core::AbstractClassInstantiationError::•("A");
-  throw new core::AbstractClassInstantiationError::•("B");
+  throw new core::NoSuchMethodError::•(null, #A, <dynamic>[], <dynamic, dynamic>{}, null);
+  throw new core::NoSuchMethodError::•(null, #B, <dynamic>[], <dynamic, dynamic>{}, null);
   new self::C::•<dynamic>();
 }