From @hoelzro

For example, if you use Bool with a native sub, you don't get an error until you actually try to run that function. It would be Awesome if NativeCall could tell you about invalid signatures at compile time.

From @FROGGS

Aye, we only check the arity until now​: https://github.com/rakudo/rakudo/blob/nom/lib/NativeCall.pm#L240

And even that is not compile time...
I have no idea though how to implement compile time checking for signatures there. Mind that rakudo's optimizer does that for non-NativeCall subs.

The RT System itself - Status changed from 'new' to 'open'

From @timo

Skarsnik implemented a sanity checking routine as well as tests in rakudo commit 532c11abbcc8409a03d4a585296149f94c219e08

@timo - Status changed from 'open' to 'resolved'