[Issue 24253] New: fn "is not accessible from module" with overload reflection regressed in v2.105

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24253

          Issue ID: 24253
           Summary: fn "is not accessible from module" with overload
                    reflection regressed in v2.105
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P5
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: destructionator at gmail.com

Must have two modules so `private` applies:

---
// bug.d
import bug2;

private void fooImpl() { }

void main() {
    mvd!fooImpl();
}
---

And:

---
// bug2.d
void mvd(alias fn)() {
        auto this_ = null;
        // we could call `fn` directly here since we got an alias
        ov: foreach(overload; __traits(getOverloads, __traits(parent, fn),
__traits(identifier, fn))) {
                __traits(child, this_, overload)(); // but cannot use through
traits
        }
}
---

You actually don't need the overload loop here, you could remove that to
minimize further

```
void mvd(alias fn)() {
        auto this_ = null;
        fn(); // this allowed
        //__traits(child, this_, fn)(); // this is not
}
```

But I wanted to show the loop to give you an idea of the real world use case
this is affecting; it is a multiple virtual dispatch implementation.


Interestingly, in dmd 2.098:

```
fn; // bug2.d(3): Deprecation: Function `bug.fooImpl` of type `void()` is not
accessible from module `bug2`

fn(); // perfectly OK; it let me call it through the alias, but not reference
it
```

Which is a bit bizarre. I suspect the fix was intended to treat these two cases
the same, but it awkward in any case.


Anyway, the error when calling the function was introduced by this commit:

https://github.com/dlang/dmd/commit/421ebfe8b5777707c7a415f64523bedf6ff2dd66


Before that, it worked without issue, after that, it deprecated, then a future
commit (36043ded818506936790be55f9353d6132527541) turned the deprecation into
an error.

The first release to fail with this was
https://dlang.org/changelog/2.105.0.html

--