[Haskell-cafe] Why this doesn't type checked
Martijn van Steenbergen
martijn at van.steenbergen.nl
Mon Jun 28 06:05:49 EDT 2010
On 6/27/10 21:52, Victor Nazarov wrote:
>> class Sizeable sizeable
>> where type Sizeof sizeable
>> sizeof :: Sizeof sizeable
This is where the type checker should complain. There is no valid way to
call sizeof, regardless of what instances are available.
The situation is similar to this:
> class C a where x :: Int
In which case the compiler says:
> The class method `x'
> mentions none of the type variables of the class C a
> When checking the class method: x :: Int
> In the class declaration for `C'
I thought there was already a trac ticket for this, but I can't find it
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