[perl #126951] [BUG] Interpolating a typed hash into an argument list produces wrong keys

[Sam S. via RT]

Shorter test-case:

    ➜  say :{ a => 1, b => 2 }.FLATTENABLE_HASH;
    {Str|a => a => 1, Str|b => b => 2}

Compare to a normal Hash which works fine:

    ➜  say { a => 1, b => 2 }.FLATTENABLE_HASH;
    {a => 1, b => 2}