Trace the source code position in the lexer

source/Parser.def

@@ -4,6 +4,11 @@ FROM Common IMPORT Identifier, PIdentifier, ShortString;
 FROM Lexer IMPORT PLexer;
 
 TYPE
+  Parser = RECORD
+    lexer: PLexer
+  END;
+  PParser = POINTER TO Parser;
+
   AstLiteralKind = (
     astLiteralKindInteger,
     astLiteralKindString,