anchor.diff:      |    symbolLiteral
       |    setOrMapLiteral
       |    listLiteral
  +    |    recordLiteral
       ;
   
   nullLiteral
  
positive.code: 
  typeList
      :    type (',' type)*
      ;
  
  typeNotVoidNotFunctionList
  
negative.code: // NB: It is an anomaly that VAR can be a return type (`var this.x()`).
  fieldFormalParameter
      :    finalConstVarOrType? THIS '.' identifier (formalParameterPart '?'?)?
      ;
  
  superFormalParameter
      :    type? SUPER '.' identifier (formalParameterPart '?'?)?
      ;
  
  defaultFormalParameter
  