Further refactoring done. The Parser runs without crashing, however it's output is still to be checked and verified.

lox.c

@@ -1,4 +1,6 @@
 #include "scanner.h"
+#include "parser.h"
+#include "expr.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <sysexits.h>
@@ -37,7 +39,8 @@ void RunFile(const char* path) {
     TokenList* tokens = ScanTokens(contents);
     free(contents);
     Print(tokens);
-
+    Expr* tree = GenerateExpressionTree(tokens);
+    FreeExpressionTree(tree);
     DestroyTokenList(tokens);
 }