[eqvinox]

The fact that the loop case is rare does not mean it isn't still problematic. It's creating a new opportunity to shoot yourself in the foot while trying to solve another one. (This is with the separate guard{} block.)

I would strongly agree that the dedicated guard{} block is a bad idea and this should just tie into the innermost scope. I see what this is trying to do ("if (...) { foo.x = malloc(); defer free(foo.x); }") but you don't solve a UI problem (as in, user interface for the programmer to their code) by adding more weird UI.

("Worst" example for shooting yourself in the foot: defer inside macros. Programmer then forgets that the macro contains a defer, and the defer defaults to the function-implicit outer guard block. But it's really in a nested loop. That's gonna be a fun week of debugging... much less of a risk when you have the guarantee in terms of innermost scope.)

[gpderetta]

Closures capturing iteration variables by reference is a common footgun in many languages unfortunately.