• d-bugmail puremagic.com (36/36) Jun 14 2019 https://issues.dlang.org/show_bug.cgi?id=19966

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=19966

          Issue ID: 19966
           Summary: [DIP1000] DIP1000 with a template behaves differently
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: safe
          Severity: critical
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: doob me.com

The following code compile successfully with DIP1000 enabled:

struct Foo()
{
    int* bar;

    int* foo()  safe return
    {
        return bar;
    }
}

int* a;

void main()  safe
{
    Foo!() f;
    a = f.foo;
}

But if `Foo` is not a template it fails to compile, complaining that the return
value of `foo` outlives `f`.

I think there are two errors here:

1. `Foo` as a template and as a non-template struct behaves differently
2. I think the above code is actually valid because it's not provable that
`foo` escapes a pointer to the internal state of `Foo`

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