[Issue 21286] New: [DIP1000] Can't return scope reference from a function

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21286

          Issue ID: 21286
           Summary: [DIP1000] Can't return scope reference from a function
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: snarwin+bugzilla at gmail.com

The following program fails to compile with -preview=dip1000:

---
void main() @safe
{
    int[3] a = [1, 2, 3];
    int[] slice;

    // ok
    slice = a[];

    scope ref getSlice() { return slice; }
    // Error: reference to local variable a assigned to non-scope getSlice()
    getSlice() = a[];
}
---

It should be possible for getSlice to return a reference that `a[]` can be
safely assigned to.

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