[Issue 24208] [DIP1000] Nested function can pass scope pointer to non-scope parameter

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24208

--- Comment #1 from Paul Backus <snarwin+bugzilla at gmail.com> ---
Actually, it turns out the second function is not necessary:

---
void main() @safe
{
    int* escaped;

    void escape(int* p) @safe
    {
        escaped = p;
    }

    int n;
    escape(&n);
    assert(escaped == &n);
}
---

So, I guess the problem is either that the compiler is incorrectly inferring
`p` as `return scope`, or it's *correctly* inferring `p` as `return scope` but
failing to notice at the calls site that the "return value" has a longer
lifetime than `n`.

If it's the second case, the error should be the same one produced by this
program:

---
void main() @safe
{
    int* escaped;

    static void escape(ref int* ret, return scope int* p) @safe
    {
        ret = p;
    }

    int n;
    escape(escaped, &n);
    // Error: address of variable `n` assigned to `escaped` 
    // with longer lifetime
    assert(escaped == &n);
}
---

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