RFC: Make role parameters reusable in does clauses

[taboege]

The Problem

A parameterized role can't refer to its arguments in roles it does itself:

role B[$n] { method n { $n } }
role C[$n] does B[$n] { }
C[5].n.say # OUTPUT: (Mu)

Expected Behavior

The n method from B is there but the value is lost. I would have expected it to print "5". The syntax role C[$n] does B[$n] is legal and it seems natural that the latter $n is in the same scope as the role parameter.