compare types of functions.

[vit]

Hello,

Why this doesn't work:
```d
template DestructorType(T){

	alias Get(T) = T;

     alias DestructorType = Get!(typeof((void*){
     	T tmp;
     }));
}

struct Foo{

     ~this()@safe{}
}
```


```d
void main(){
     //Error: static assert:  `is(void function(void*) pure 
nothrow @nogc @safe : void function(void*) @safe)` is false
     static assert(is(void function(void*)pure nothrow @safe @nogc 
: DestructorType!Foo));

}

```

but this work:
```d

void main(){

     alias X = void function(void*)@safe;


     static assert(is(void function(void*)pure nothrow @safe @nogc 
: DestructorType!Foo));

}
```