I was updating haskell-src-exts for ghc 8.0 recently and found some of
the syntax for injective type families quite confusing.
Is it a problem that the two following snippets have quite different meanings?
1. With the infectivity annotation, this declares an associated type.
class Hcl a b where
type Ht a b = r | r -> b a
2. Without the infectivity annotation, this declares an associate type
synonym default. This isn't valid because Ht is not declared as an
associated type before hand and r is not mentioned on the LHS.
class Hcl a b where
type Ht a b = r
Has this been considered?
Matt
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