In Parameter§

See primary documentation in context for method invocant

method invocant(Parameter:D: --> Bool:D)

Returns True if the parameter is the invocant parameter.

my Signature $sig = :($i : Str $x is rwBool :$is-named);
say $sig.params[0].invocant;                       # OUTPUT: «True␤» 
say $sig.params[1].invocant;                       # OUTPUT: «False␤»

In X::Method::InvalidQualifier§

See primary documentation in context for method invocant

Returns the invocant of the failed, qualified method call