Should (~) be homogeneous or heterogeneous?

Dan Doel dan.doel at
Mon Nov 23 17:02:32 UTC 2015

I suspect he means that with `t1 :: k1` and `t2 :: k2`, `t1 ~ t2` is
permitted as long as `k1 ~ k2` accompanies it. However, this would
already work with homogeneous ~, wouldn't it (because homogeneity is
up to whatever constraints are in scope)?

On Mon, Nov 23, 2015 at 11:05 AM, Richard Eisenberg <eir at> wrote:
>> Naive question:
>> Would it be "evil" or otherwise complicated to assume that (~) is
>> heterogeneous only in the _presence_ of kind constraint? Or only when
>> the kind can be inferred?
> I'm afraid I don't understand. Do you mean that it's heterogeneous only when -XTypeInType is specified? That just might be possible, but I don't personally like it. Others might, though.
> Richard
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