Confusing casting error

```c3
typedef Foo = char[<4>];

fn void main(String[] args) {
  int[<4>] a;
  Foo f = (Foo)a;
}
```
```
 5: fn void main(String[] args) {
 6:   int[<4>] a;
 7:   Foo f = (Foo)a;
              ^^^^^^
(/tmp/test/src/main.c3:7:11) Error: Implicitly casting 'char[<4>]' to 'Foo' is not permitted, but you may do an explicit cast by placing '(Foo)' before the expression.
```