Add core printer file

core_polymorph.cpp

@@ -204,6 +204,8 @@ void next(Ast_Iter *iter) {
             For(node->ret) iter->stack.add(it);
             For(node->args) iter->stack.add(it);
         } break;
+
+        default: assert(!"Invalid default case");
     }
 end_of_switch:
 
@@ -479,6 +481,8 @@ Ast *ast_copy(Ast *ast, Ast_Scope *parent_scope) {
             dst->scope = (Ast_Scope *)ast_copy(src->scope, parent_scope);
             return dst;
         } break;
+
+        default: assert(!"Invalid default case");
     }
     invalid_return;
 }