[perl #115916] "my (Str $a) = 3" should die but doesn't.

[Christian Bartolomaeus via RT]

This dies no with a typed exception X::TypeCheck

$ perl6-m -e 'my (Str $a) = 3'
Type check failed in assignment to '$a'; expected 'Str' but got 'Int'
  in method STORE at src/gen/m-CORE.setting:9265
  in block <unit> at -e:1

I added a test to S04-declarations/my.t with commit 
https://github.com/perl6/roast/commit/d561d4977c. Actually there was already a 
very similiar test 'my (Int $a); $a = "str"', but since I didn't want to merge 
both tickets (which was primarily about native types) I added this extra test 
which refers to this ticket.

I'm closing this ticket as 'resolved'.