Self quantification in data declarations

[RafaelBocquet]

Currently, this declaration :

data A :: * where B :: forall (x :: A). A

results in a "AThing evaluated unexpectedly" ghc panic.

I think it should be accepted.

[goldfirere]

Yes, it should be accepted. But arranging for it to be accepted is a little challenging (purely from an engineering point of view), and might not make it for 8.0. We'll get there eventually. :)

The panic will go away though.

[RafaelBocquet]

ghc now hangs when compiling this code.