anchor.diff:      );
     }
   
  -  /**
  -   * Return the non-nullable variant of the [type] if NNBD is enabled, otherwise
  -   * return the type itself.
  -   *
  -   * TODO(scheglov) Use [_noneOrStarSuffix] instead
  -   */
  -  DartType _nonNullable(DartType type) {
  -    if (_isNonNullableByDefault) {
  -      return _typeSystem.promoteToNonNull(type);
  -    }
  -    return type;
  -  }
  -
     void _pushCollectionTypesDown(CollectionElement element,
         {DartType elementType,
         @required DartType iterableType,
  
positive.code: 
      // If we have explicit arguments, use them.
      if (typeArguments != null) {
        DartType staticType = _dynamicType;
        NodeList<TypeAnnotation> arguments = typeArguments.arguments;
        if (arguments != null && arguments.length == 1) {
          DartType argumentType = _getType(arguments[0]);
          if (argumentType != null) {
            staticType = argumentType;
          }
        }
        _recordStaticType(
            node, _nonNullable(_typeProvider.listType2(staticType)));
        return;
      }
  
  
negative.code:         (node as SetOrMapLiteralImpl).becomeSet();
          var elementType = _getType(typeArguments[0]) ?? _dynamicType;
          _recordStaticType(
            node,
            _typeProvider.setElement.instantiate(
              typeArguments: [elementType],
              nullabilitySuffix: _noneOrStarSuffix,
            ),
          );
          return;
        } else if (typeArguments.length == 2) {
          (node as SetOrMapLiteralImpl).becomeMap();
          var keyType = _getType(typeArguments[0]) ?? _dynamicType;
          var valueType = _getType(typeArguments[1]) ?? _dynamicType;
          _recordStaticType(
            node,
            _typeProvider.mapElement.instantiate(
              typeArguments: [keyType, valueType],
              nullabilitySuffix: _noneOrStarSuffix,
            ),
          );
          return;
        }
        // If we get here, then a nonsense number of type arguments were provided,
  