anchor.diff:  
   definition
   	: callbackOrInterfaceOrMixin
  -	| namespace
  +	| namespace_
   	| partial
   	| dictionary
   	| enum_
  
positive.code: 	: 'setlike' '<' typeWithExtendedAttributes '>' ';'
  ;
  
  namespace
      : 'namespace' IDENTIFIER_WEBIDL '{' namespaceMembers '}' ';'
  ;
  
  
negative.code:  */
  grammar WebIDL;
  
  /* Note: appended underscore to keywords for CPP compat:
      const, default, enum, namespace, null
      see github.com/antlr/grammars-v4/issues/2099 for more info
  */
  // Note: Added "wrapper" rule webIDL with EOF token.
  
  webIDL
  