| Just before Section D.1 there is the sentence
|
| When inferring the context for the derived instances, type
| synonyms must be expanded out first.
|
| I don't understand it. Which type synonyms need expansion?
Consider
type Foo a = [a]
data T a = MkT (Foo a) deriving( Eq )
> When inferring the context for the derived instances, type synonyms must
> be expanded out first.
>
> I don't understand it. Which type synonyms need expansion? All the u_n
> are type variables.
I worked it out. Given
data cx => T u1 ... uk = K1 t11 ... t1k1 | ...| Kn tn1 ... tnkn deriving
