The pattern _ has been extended to accept any number of arguments. If you think of it

type foo = Foo of int * bool

let f (Foo _) = ()

is already quite strange (replacing _ by a variable here doesn't work), but extremely convenient (you don't want to have to remember the constructor's arity just to ignore it). It was extended to 0-ary constructors for consistency, but you can disable this allowance by marking warning 28 (ocamlc -warn-help) as an error.

On Thu, Oct 24, 2013 at 3:47 PM, Matej Kosik <5764c029b688c1c0d24a2e97cd764f@gmail.com> wrote:

Hi,

Today I noticed a strange compiler's tolerance.
The compiler will not protest here:

type foo = Bar | Baz

;;

match Bar with
| Bar _ -> ()
| Baz -> ()

Why doesn't the compiler protest that I used wildcard after "Bar" constructor?
(It does protest if I put any other pattern except for the wildcard).

This slightly breaks the logic. Doesn't it?

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