class X::Attribute::NoPackage does X::MOP { }

Compile time error thrown when a required attribute is not assigned when creating an object.

For example

my class Uses-required {
    has $.req is required
my $object =

Dies with

OUTPUT: «(exit code 1) The attribute '$!req' is required, but you did not provide a value for it.␤»


method name§

method name(--> Str:D)

Returns the name of the attribute.

method why§

method why(--> Str:D)

Returns the reason why that attribute is required, and it will be included in the message if provided. That reason is taken directly from the is required trait.

my class Uses-required {
    has $.req is required("because yes")
my $object =;                                  │
# «(exit code 1) The attribute '$!req' is required because because yes,␤ 
# but you did not provide a value for it.␤»