[perl #115358] [BUG] LTA error message when doing a role that's declared the same way twice in Rakudo

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
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<diakopter> r: role F { }; role F { }; class G does F { };
<p6eval> rakudo d171b9: OUTPUT«===SORRY!===␤None of the parametric
role variants for 'F' matched the arguments supplied.␤Ambiguous call
to ''; these signatures all match:␤:(Mu )␤:(Mu )␤␤»
<diakopter> masak: masakbot ^^
* masak submits rakudobug

What's LTA about this error message is mainly that it first says that
none of the role variants matched, because both of the signatures
matched. While technically correct, it's unnecessarily confusing. Also
"Ambiguous call to ''" looks wrong.