[perl #130906] [REGRESSION] Reducing a Seq with `=>` fails with "P6opaque: no such attribute '$!reified' in type List"

[via RT]

# New Ticket Created by  Sam S. 
# Please include the string:  [perl #130906]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=130906 >


    ➜  say [=>] (1, 2).Seq;
    P6opaque: no such attribute '$!reified' in type List when trying
to get a value

Expected output:

    1 => 2

This used to work correctly until a recent commit:

    https://gist.github.com/Whateverable/4e4a3cfd591978358e188efda98113fa
    
https://github.com/rakudo/rakudo/commit/60a8f9e7151825bcd1d4ab829ef78bebc359cbdb