Documentation for method keyof

Documentation for method keyof, assembled from the following types:

class Hash

From Hash

(Hash) method keyof

Defined as:

method keyof()

Returns the type constraint for the keys of the invocant. For normal hashes the method returns the coercion type (Str(Any)) while for object hashes the type used in the declaration of the Hash is returned.

my %h1 = 'apples' => 3'oranges' => 7;  # (no key type specified) 
say %h1.keyof;                           # OUTPUT: «(Str(Any))␤» 
 
my %h2{Str} = 'oranges' => 7;            # (keys must be of type Str) 
say %h2.keyof;                           # (Str) 
%h2{3} = 'apples';                       # throws exception 
CATCH { default { put .^name''.Str } };
# OUTPUT: «X::TypeCheck::Binding: Type check failed in binding to key; expected Str but got Int (3)␤»