// <TokenDef> ::= "STRING" "=" "STRING" .
private void ParseTokenDef()
{
_astBuilder.AddTokenName(_scanner.CurrentToken);
Match(TokenKind.String);
_scanner.Advance();
Match(TokenKind.Equal);
_scanner.Advance();
_astBuilder.SetTokenDef(_scanner.CurrentToken);
Match(TokenKind.String);
_scanner.Advance();
}