[Issue 22989] New: Missing error wrt. assigning cast function pointer to incompatible funcptr

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22989

          Issue ID: 22989
           Summary: Missing error wrt. assigning cast function pointer to
                    incompatible funcptr
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: kinke at gmx.net

With DMD v2.099.0:

```
extern(C) bool foo1(int i) { return i != 0; }
extern(C) char foo2(int i) { return i != 0; }

alias F1 = extern(C) bool function(int);
alias F2 = extern(C) char function(int);

void main() {
    { // normal
        F1 f1 = &foo1;
        F2 f2 = &foo2;
    }

    { // explicit cast
        F2 f1 = cast(F2) &foo1;
        F1 f2 = cast(F1) &foo2;
    }

    { // cast, but mismatch
        F1 f1 = cast(F2) &foo1; // bug: no error - cast seems omitted
        F2 f2 = cast(F1) &foo2; // ditto
    }
}
```

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