(no-nullable-dict-arg) Validation error at line 13 in argument-dict-nullable.webidl, inside `interface X -> operation x1 -> argument dict`:
 x1(optional Dict? dict);
                   ^ Dictionary arguments cannot be nullable.
(no-nullable-dict-arg) Validation error at line 14 in argument-dict-nullable.webidl, inside `interface X -> operation x2 -> argument dict`:
 x2(optional Dict? dict = {})
                   ^ Dictionary arguments cannot be nullable.
(no-nullable-union-dict) Validation error at line 15 in argument-dict-nullable.webidl:
(optional (boolean or Dict)? union =
                      ^ Nullable union cannot include a dictionary type.
(no-nullable-dict-arg) Validation error at line 15 in argument-dict-nullable.webidl, inside `interface X -> operation y2 -> argument union`:
boolean or Dict)? union = {})
                  ^ Dictionary arguments cannot be nullable.
(no-nullable-union-dict) Validation error at line 16 in argument-dict-nullable.webidl:
  undefined z2(optional Union? union = {
                        ^ Nullable union cannot include a dictionary type.
(no-nullable-dict-arg) Validation error at line 16 in argument-dict-nullable.webidl, inside `interface X -> operation z2 -> argument union`:
 z2(optional Union? union = {})
                    ^ Dictionary arguments cannot be nullable.
(no-nullable-dict-arg) Validation error at line 17 in argument-dict-nullable.webidl, inside `interface X -> operation r -> argument req`:
  undefined r(Required? req);
                        ^ Dictionary arguments cannot be nullable.
(no-nullable-dict-arg) Validation error at line 19 in argument-dict-nullable.webidl, inside `interface X -> iterable -> argument dict`:
>(optional Dict? dict);
                 ^ Dictionary arguments cannot be nullable.