invocant
Combined from primary sources listed below. type/X/Method/InvalidQualifier type/Parameter

From type/X/Method/InvalidQualifier§

See primary documentation in context for method invocant

Returns the invocant of the failed, qualified method call

From type/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 $x is rw, Bool :$is-named);
say $sig.params[0].invocant;                       # OUTPUT: «True␤» 
say $sig.params[1].invocant;                       # OUTPUT: «False␤»