Coercion-type parameters Int()

A parameter that should coerce its argument to a type — parsed, but not yet coercing in Raku++.

A parameter typed Int() (or Str(), Num(), …) is meant to accept an argument of any type that can coerce to Int and convert it as it binds, so the body always sees an Int. Raku++ parses the syntax but does not perform the coercion — the body receives the original type (see the divergence).

The intent #

sub f(Int() $x) { $x.^name }
say f("41");
say f(41.9);

Because the value isn't converted, arithmetic in the body sees the wrong type: sub g(Int() $x) { $x + 1 } gives g(41.9) as 42.9 in Raku++ (Rat kept), but 42 in Rakudo (41.9 coerced to 41 first).

Run the block to see Raku++'s result. Until this is implemented, coerce explicitly in the body — my Int $n = $x.Int; — rather than relying on the Int() parameter.

Notes #

• The syntax is TargetType() on the parameter; it should mean "accept anything, then call .Type on it". Ordinary typed parameters (Int $x) work normally.
• A related form is the coercion return type (--> Str()), subject to the same gap.
• Coercing explicitly with .Int/.Str/.Num inside the body is the reliable approach in Raku++ today.