[Issue 23416] New: Difference DMD/GDC: Error: non-constant expression `& foo`

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23416

          Issue ID: 23416
           Summary: Difference DMD/GDC: Error: non-constant expression `&
                    foo`
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: kdevel at vogtner.de

```
module dmd_gdc_difference;

template funcptr (alias method) {
   immutable funcptr = &method;
}

struct S {
   void function () fun;
   void foo ()
   {
      fun = funcptr!foo;
   }
}

unittest {
   S m;
}
```

$ dmd -unittest -main dmd-gdc-difference.d
dmd-gdc-difference.d(4): Error: non-constant expression `& foo`

$ gdc -funittest -fmain dmd-gdc-difference.d -o dmd-gdc-difference
$ ./dmd-gdc-difference 
1 modules passed unittests

Versions checked: GDC 12.1, 11.3; DMD v2.100.2, 2.080.0

Found in: https://forum.dlang.org/post/lnjjxiuzuqdjhaeiizhf@forum.dlang.org
(Generate a pointer to a method of a struct)

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