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digitalmars.D.bugs - [Issue 22539] New: [dip1000] slicing of returned ref scope static


          Issue ID: 22539
           Summary: [dip1000] slicing of returned ref scope static array
                    should not be allowed
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: dkorpel live.nl

Because there is no transitive scope, taking the address of a scope variable is
not allowed. There are 4 cases:

- ref param &pointer: rejected with `checkAddresVar`
- ref param slice[]: rejected with `checkAddresVar`
- ref return &pointer: too restrictive (issue 22519)
- ref return slice[]: too lenient (this issue)

This allows you to escape scope pointers:
// REQUIRED_ARGS -preview=dip1000
ref int*[1] identity(ref return scope int*[1] x)
        return x;

int* escape()
        int stackVar = 0xFF;
        scope int*[1] x = [&stackVar];
        int*[] y = identity(x)[];
        return y[0];

void main()
        int* dangling = escape();

Nov 23 2021