Make coercion more specific about the source type
Make coercion more specific about the source type

The purpose of the test is to have same exception in different cases of
attribute initialization. Because coercion as such is now closer to
implement DWIM semantics, `Int()` is now handling `"42"` as expected and
exception is not thrown. To get it failing more specific `Int(Rat)` is
used.

dogbert17/roast,dogbert17/roast,perl6/roast