type synonyms about co4 HOT 2 CLOSED

Yes. that would be convenient for writing (documenting) constraint programs.

Implementation should be easy (and needs no expansion)?

• ignore type synonyms when generating code (you do type inference anyway)
• copy the type synonym declarations verbatim (for the "original" code that is used for testing at the end)

from co4.

you do type inference anyway

But type inference fails with type synonyms.

data Bool = False | True
type Foo   = Bool
data Maybe = Just Foo | Nothing
main x = case x of
  Just b     -> b
  Nothing -> False

gives

No unifier found for 'Foo' and 'Bool'

Anyway, I implemented synonym expansion in TH frontend (cf. 60c8dba). It's supposed to work with both non-parametrized synonyms

type Foo = ....

and parametrized synonyms

type Foo x = ... x ....

from co4.