FUCK YEAH, it works, it was the is_valid thing fo slices that was inverted, did the test by brute force and damn, is the expected AST

src/main.c

@@ -9,7 +9,6 @@ int main(void) {
     tokenize("3 + 4 * 5", &context);
 
     AST tree = parse(&context);
-    print_AST(tree);
 
     printf("Hola\n");