[Issue 22990] New: [dip1000] extended return semantics doesn't work on auto return

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22990

          Issue ID: 22990
           Summary: [dip1000] extended return semantics doesn't work on
                    auto return
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: dkorpel at live.nl

```
auto assign(ref scope int* x, return ref int y) @safe
{
    x = &y;
}

auto assign(ref scope int* x, return scope int* y) @safe
{
    x = y;
}
```

Error: address of variable `y` assigned to `x` with longer lifetime
Error: scope variable `y` assigned to `x` with longer lifetime

Change the return type to `void` and it passes. The function `isFirstRef()`
returns false when the return type is not determined yet.

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