[perl #39249] Can't use literal unicode string as a hash key.

[Will Coleda]

# New Ticket Created by Will Coleda
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The following code:

.sub test
$P1 = new .Hash
$P1[unicode:"\u7777"] = 'ok'
$S1 = $P1[unicode:"\u7777"]
say $S1
.end

fails to compile. (should print "ok")

$ ./parrot foo.pir
build_key: unknown type 0x10001 on unicode:"\u7777"

Note that the same code works fine if the unicode string is put into
a string register instead of used as a literal.