anchor.diff:    DartType visitTypeParameterType(ir.TypeParameterType node) {
       DartType typeParameter = currentFunctionTypeParameters[node.parameter];
       if (typeParameter != null) {
  -      return _convertNullability(typeParameter, node.nullability);
  +      return _convertNullability(typeParameter, node);
       }
       if (node.parameter.parent is ir.Typedef) {
         // Typedefs are only used in type literals so we never need their type
  
positive.code: 
    @override
    DartType visitNeverType(ir.NeverType node) {
      return _convertNullability(_dartTypes.neverType(), node.nullability);
    }
  
    @override
  
negative.code:     }
      return _convertNullability(
          _dartTypes.typeVariableType(elementMap.getTypeVariable(node.parameter)),
          node);
    }
  
    @override
  