Compilation error due to an unallowed placeholder in a signature
class X::Parameter::Placeholder does X::Comp { }
Thrown when a placeholder parameter is used inside a signature where a normal parameter is expected. The reason is often that a named parameter :$param was misspelled as $:param.
For example
sub f($:param) { }
dies with
===SORRY!=== In signature parameter, placeholder variables like $:param are illegal you probably meant a named parameter: ':$param'
The text of the offensive parameter declaration ($:param in the example above).
Suggestion on how to write the parameter declaration instead (:$param in the example above).