[perl #130965] [LTA] `but role { ... }` interacts strangely with outer lexicals, and doesn't warn about it

[via RT]

# New Ticket Created by  Sam S. 
# Please include the string:  [perl #130965]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=130965 >


    sub a ($a) {
        return True but role {
            method foo { $a }
        }
    }

    my $x = a 42;
    say $x.foo;         # 42

    my $y = a "Hello";
    say $y.foo;         # Hello
    say $x.foo;         # Hello

I have a suspicion that this is not a bug but rather a consequence of
classes/roles not being proper closures.

But the current behavior is rather LTA in cases like this.
Could this possibly be made to emit a warning?