Cleanup + little polymorph + ast_copy

base_arena.cpp

@@ -76,6 +76,15 @@ arena_push_size(Arena *a, size_t size) {
     return result;
 }
 
+#define push_struct_copy(a, T, p) (T *)push_copy(a, p, sizeof(T))
+CORE_Static void *
+push_copy(Arena *a, void *p, size_t size) {
+    if (p == 0) return 0;
+    void *result = arena_push_size(a, size);
+    memory_copy(result, p, size);
+    return result;
+}
+
 CORE_Static Arena
 push_arena(Allocator *allocator, size_t size, String debug_name) {
     Arena result = {};