[perl #129278] [BUG] Can't assign to `int` private attribute using signature

[jn...@jnthn.net via RT]

On Thu Sep 15 11:49:35 2016, c...@zoffix.com wrote:
> #Doesn't work:
> <TestNinja> m: class { has int $!n = 0; method x ($!n) {} }.new.x: 42
> <camelia> rakudo-moar 2c95f7: OUTPUT«Cannot modify an immutable int␤
> in method x at <tmp> line 1␤  in block <unit> at <tmp> line 1␤␤»
> 
I've fixed this and added tests to S12-methods/attribute-params.t. It works for 
named parameters too. So in terms of the originally reported issue this ticket 
could be considered done.

But.

Unfortunately, the moment you have a role instead of a class, or a a more 
complex signature (for example, involving an unpack), it fails. So, some more 
work and tests needed.