fix Issue 22541 - DIP1000: Resolve ambiguity of ref-return-scope para…

[WalterBright]

…meters

Actually, fixes https://issues.dlang.org/show_bug.cgi?id=22541#c7

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22541	enhancement	DIP1000: Resolve ambiguity of ref-return-scope parameters

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#13677"

[thewilsonator]

Should this target stable?

[WalterBright]

I'd rather not. It could be a disruptive change.

[dkorpel]

This should be marked @safe

[maxhaton]

@dkorpel @WalterBright Should this have a changelog

[dkorpel]

It already has a changelog: https://dlang.org/changelog/2.099.0.html#22541
It just needs a correct implementation still 🙂

This patch makes the compiler accept the function definition, but on a function call it still thinks it's return scope allowing you to escape the data. The problem also still persists with actual ref parameters, here's a bigger test case:

struct S
{
    int i;
    int* ptr;

    int* wannabeReturnRef() scope return @safe
    {
        return &i;
    }
}

int* wannabeReturnRefFree(scope return ref S s) @safe
{
	return &s.i; // should be accepted
}

int* gPtr;
void main() @safe 
{
	S s;
	gPtr = s.wannabeReturnRef(); // should be rejected
	gPtr = s.wannabeReturnRefFree(); // should be rejected
}

[maxhaton]

@dkorpel I think that changelog is very poor.

[dkorpel]

@dkorpel I think that changelog is very poor.

It is, should we remove it until it's actually implemented correctly, or expand it but also add a footnote that the implementation isn't ready?