[Issue 23952] New: Cannot declare pointer to function with linkage

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23952

          Issue ID: 23952
           Summary: Cannot declare pointer to function with linkage
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: qs.il.paperinik at gmail.com

Similar to issue 2753 (Cannot declare pointer to function returning ref), the
type syntax cannot express explicit linkage of a function pointer:

```d
alias CFunc = extern(C) int function(int);
void f(CFunc fp) { } // okay
pragma(msg, CFunc);

void g(extern(C) int function(int) fp) { } // does not parse
```

The same is true for delegates:
```d
struct S
{
    int x;
    extern(C) int f() => x;
}
pragma(msg, typeof(&S().f)); // extern (C) int delegate()

//void h(extern (C) int delegate() dg) { } // does not parse
```

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