[perl #127841] :U smiley shows weird error when .WHAT is called

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# New Ticket Created by  Zoffix Znet 
# Please include the string:  [perl #127841]
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# <URL: https://rt.perl.org/Ticket/Display.html?id=127841 >


As seen from the code evals below, applying a :U smiley on a variable and then 
trying to see .WHAT it is shows an error:

<ZoffixW> m: my Int:U $x; say $x.WHAT
<camelia> rakudo-moar 600eb5: OUTPUT«Method 'shortname' not found for invocant 
of class 'Perl6::Metamodel::DefiniteHOW'␤  in block <unit> at /tmp/f25jG54p5v 
line 1␤␤»
<ZoffixW> m: my Any:U $x; say $x
<camelia> rakudo-moar 600eb5: OUTPUT«Method 'shortname' not found for invocant 
of class 'Perl6::Metamodel::DefiniteHOW'␤  in block <unit> at /tmp/93HKLtR89U 
line 1␤␤»