four more CoreSyn questions

[Adam Megacz]

Simon Peyton-Jones <simonpj at microsoft.com> writes:
> |     I assume this is only the
> |     value variables, and that the type/coercion variables come from
> |     DataCon.{dataConExTyVars,dcEqSpec}, right?
>
> Not so at all.  Why did you assume that?

You're right, that was a silly assumption.  However, without it, I have
another question:

> The variables bound in a case alternative are the [b] in CoreSyn.Alt.
> These binders include all the type variables, coercion variables, and
> value variables bound in the alternative.

Are there any rules about the order in which the different types of
variables appear (e.g., extyvars first, then covars, then valvars)?
There is a natural order within each of the three sorts dictated by the
DataCon, but I see ambiguity in how those three lists get merged.

> The variables in Datacon.dataConExTyVars are irrelevant.

Hrm, can't they occur in the types of dataConEqTheta like this?

  tycon T a
  datacon FooT :: forall b. forall c. (EqPred b (list c)) -> T b

I suppose in this example (dataConExTyVars FooT) would be [c], right?

> They are the same in number and kind but not necessarily identity.

Ah, that helps!

> 		tycon  T a b
> 		datacon MkT :: forall p q. T p q
> the p,q in the MkT might not be identical to the a,b stored in the
> TyCon.  Why should they be -- the result is alpha-equivalent

Ah, I see: getTyConTyVars gives you a list of variables bound by the
tycon declaration, whereas dcUnivTyVars tells you how they are
instantiated in the type of a particular datacon.

  - a