Thanks, it indeed looks so! I guess better error message would be desirable; reported as #10654. On 07/17/2015 10:53 PM, Jonas Scholl wrote:
I would guess the two arguments are a kind and a type of that kind. The kind is given implicitly, so this corresponds to your one given argument. If we specify a kind, we get the following:
Prelude> :set -XPolyKinds -XDataKinds -XKindSignatures Prelude> type Test a = a Prelude> type Huh a = Test (a :: Bool) Prelude> type Bar = Huh
<interactive>:5:1: Type synonym ‘Huh’ should have 1 argument, but has been given none In the type declaration for ‘Bar’
So it really takes two arguments and we can specify one, leaving one to be specified. Maybe a better error message would be useful, but I would not say this is a bug.
-- Nikolay.