Make local param shadowing detection print a warning instead of throwing a SyntaxError. This way it's easier to test that particular scenario, since this is actually a bug in the Preprocessor.

Objective-J/Preprocessor.js

@@ -670,7 +670,7 @@ Preprocessor.prototype.method = function(/*Lexer*/ tokens, ivar_names)
             parameters[parameters.length] = token;
 
             if (token in ivar_names)
-                throw new SyntaxError(this.error_message("*** Method ( "+selector+" ) uses a parameter name that is already in use ( "+token+" )"));
+                CPLog.warn(this.error_message("*** Warning: Method ( "+selector+" ) uses a parameter name that is already in use ( "+token+" )"));
         }
         else if (token == TOKEN_OPEN_PARENTHESIS)
         {