C# grammar using ANTLR 3

Question

I'm now writing C# grammar using Antlr 3 based on this grammar file.

But, I found some definitions I can't understand.

NUMBER:
    Decimal_digits INTEGER_TYPE_SUFFIX? ;
// For the rare case where 0.ToString() etc is used.
GooBall
@after        
{
    CommonToken int_literal = new CommonToken(NUMBER, $dil.text);
    CommonToken dot = new CommonToken(DOT, ".");
    CommonToken iden = new CommonToken(IDENTIFIER, $s.text);

    Emit(int_literal); 
    Emit(dot); 
    Emit(iden); 
    Console.Error.WriteLine("\tFound GooBall {0}", $text); 
}
    :
    dil = Decimal_integer_literal d = '.' s=GooBallIdentifier
    ;

fragment GooBallIdentifier
    : IdentifierStart IdentifierPart* ;

The above fragments contain the definition of 'GooBall'. I have some questions about this definition.

Why is GooBall needed? Why does this grammar define lexer rules to parse '0.ToString()' instead of parser rules?

antiduh antiduh · Accepted Answer · 2013-12-30T07:10:21

It's because that's a valid expression that's not handled by any of the other rules - I guess you'd call it something like an anonymous object, for lack of a better term. Similar to "hello world".ToUpper(). Normally method calls are only valid on variable identifiers or return values ala GetThing().Method(), or otherwise bare.

C# grammar using ANTLR 3

2 Answers