Fix Issue 22228 - [CTFE] taking address of immutable in frame function causes ICE on Unix platform

[RazvanN7]

auto f()
{   immutable int i;
    auto p = (() => &i)();

    return 0;
}

enum ctfeInvocation = f;

&i is viewed as a SymOffExp before being rewritten to an AddrExp. If the delegate is not present, this code never calls visit(AddrExp) and therefore the bug does not manifest. In the delegate scenario, the FuncExp is interpreted and it peels of the delegate, returning &i, but then, a subsequent call to interpret is made which rewrites the expression to &0 that in turn fails the assert.

I don't really understand the subtleties of why certain calls to interpret are made, so this fix might not be the best. But to me it seems that it is wrong that visit(VarExp) with goal = LValue is allowed to return an rvalue. Fixing this, seems to pass the testsuite.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22228	regression	[CTFE] taking address of immutable in frame function causes ICE on Unix platforms

⚠️⚠️⚠️ Warnings ⚠️⚠️⚠️

• Regression or critical bug fixes should always target the stable branch. Learn more about rebasing to stable or the D release process.

To target stable perform these two steps:

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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#13005"

[UplinkCoder]

@RazvanN7 if you could add a comment in the code why the change works.
unfortunately It's not oblivious.

[RazvanN7]

@UplinkCoder Yes, I had one comment but somehow screwed up the commits. Should be fine now.

[UplinkCoder]

it still doesn't explain why just assigning the VarExp to result works.

[BorisCarvajal]

This regression was caused by #11545, you are applying a workaround over another one.
The solution is first to revert #11545, and then use a proper fix for it.

I've tested these two working:

1. to cache (push it on CTFE stack) the pointed variable of ref arguments in interpretFunction().
   or easier:
2. add an special case for non-CTFE variables that are const/immutable inside the if (goal == CTFEGoal.LValue).

[BorisCarvajal]

Alternative solution #13007 (Sorry for somewhat hijacking this, but I was working on it too)