Documentation for method keyof, assembled from the following types:
Returns the type constraint for the keys of the invocant. For normal hashes the method returns the coercion type
(Str(Any)) while for non-string keys hashes the type used in the declaration of the
Hash is returned.
my = 'apples' => 3, 'oranges' => 7; # (no key type specified)say .keyof; # OUTPUT: «(Str(Any))␤»my = 'oranges' => 7; # (keys must be of type Str)say .keyof; # (Str)= 'apples'; # throws exceptionCATCH ;# OUTPUT: «X::TypeCheck::Binding: Type check failed in binding to key; expected Str but got Int (3)␤»my ; # (this time, keys must be of type Int)= 4096;say .keyof; # (Int)