Simplification of @trusted

[jfondren]

On Wednesday, 16 June 2021 at 11:38:54 UTC, RazvanN wrote:
> What do you think?

https://github.com/dlang/phobos/blob/master/std/array.d#L283

```d
     auto temp = str.toUTF32;
     /* Unsafe cast. Allowed because toUTF32 makes a new array
        and copies all the elements.
      */
     return () @trusted { return 
cast(CopyTypeQualifiers!(ElementType!String, dchar)[]) temp; } ();
```

https://doc.rust-lang.org/src/core/ptr/non_null.rs.html#81-84

```rust
         // SAFETY: mem::align_of() returns a non-zero usize which 
is then casted
         // to a *mut T. Therefore, `ptr` is not null and the 
conditions for
         // calling new_unchecked() are respected.
         unsafe {
             let ptr = mem::align_of::<T>() as *mut T;
             NonNull::new_unchecked(ptr)
         }
```