[Issue 17977] [DIP1000] destructor allows escaping reference to a temporary struct instance

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17977

Dennis <dkorpel at live.nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |Vision
                 CC|                            |dkorpel at live.nl
            Summary|[scope] escaping reference  |[DIP1000] destructor allows
                   |to a temporary struct       |escaping reference to a
                   |instance                    |temporary struct instance

--- Comment #1 from Dennis <dkorpel at live.nl> ---
The issue description looks incomplete, but I gather this is an accepts-invalid
bug in DIP1000 and the comment shows the expected error? Currently I see
nothing wrong: `List()` is not scope, and `front()` does not return by ref, so
there's no references escaping here. I tried fixing and reducing the code, and
I think this is the actual issue:

```
// compile with -preview=dip1000
@safe:
struct List {
    int* data;
    ~this();
    int* front() return;
}

void test() {
    auto elem = List().front;
}
```

Without the destructor, there's an error:

> onlineapp.d(11): Error: address of struct literal `List(null)` assigned 
> to longer lived variable `elem`

Commenting it out makes it go away, which is wrong.

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