anchor.diff:  }
   ''');
   
  -    var nullable_i = decoratedTypeAnnotation('int i').node.nullable;
  -    var nullable_return = decoratedTypeAnnotation('int f').node.nullable;
  -    assertConstraint([nullable_i],
  -        _either(nullable_return, checkExpression('i/*check*/').nullCheck));
  +    var nullable_i = decoratedTypeAnnotation('int i').node;
  +    var nullable_return = decoratedTypeAnnotation('int f').node;
  +    assertNullCheck(checkExpression('i/*check*/'), nullable_i,
  +        contextNode: nullable_return);
     }
   
     test_intLiteral() async {
  
positive.code: int f(int i, int j) => i + j;
  ''');
  
      assertConstraint([decoratedTypeAnnotation('int j').node.nullable],
          checkExpression('j;').nullCheck);
    }
  
    test_binaryExpression_add_right_check_custom() async {
  
negative.code: }
  ''');
  
      assertNullCheck(
          checkExpression('b) {}'), decoratedTypeAnnotation('bool b').node);
    }
  
    test_if_conditional_control_flow_after() async {
  