Return types

Declare what a routine returns with --> in the signature.

A --> in the signature declares the routine's return type. The returned value is type-checked against it, documenting the contract and catching a wrong-typed return.

Declaring a return type #

sub name(--> Type) states the type with no parameters; it can also follow the parameters.

sub answer(--> Int) {
    42;
}
say answer();
say answer().^name;

42
Int

With parameters #

sub double($x --> Int) {
    $x * 2;
}
say double(21);

42

Notes #

• --> is a constraint, not a coercion: returning a value of the wrong type is an error, it isn't silently converted. Use an explicit coercion in the body if needed.
• The return type also documents intent at the call site — tools and readers see the contract in the signature.
• Nil/Failure returns are always allowed regardless of the declared type, so fail still works in a typed routine.