Language.Haskell.TH.ExpandSyns

Calls expandSynsWith with the default settings.

Expands all type synonyms in the given type. Type families currently won't be expanded (but will be passed through).

Suppresses the warning that type families are unsupported.

Capture-free substitution

Capture-free substitution

Make a list of names (based on the first arg) such that every name in the result is distinct from every name in the second arg, and from the other results

Make a name (based on the first arg) that's distinct from every name in the second arg

Example why this is necessary:

type E x = forall y. Either x y

... expandSyns [t| forall y. y -> E y |]

The example as given may actually work correctly without any special capture-avoidance depending on how GHC handles the ys, but in any case, the input type to expandSyns may be an explicit AST using mkName to ensure a collision.