Bundle types and constructors with (for future ghc?)

[int-e]

As an experimental feature (enabled by a flag), HSES could use https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms/AssociatingSynonyms to bundle the type aliases with their constructors.

[int-e]

Actually one can only associate patterns with data types, not with type synonyms, so this doesn't help HSE-simple at the moment. I have submitted a feature request for ghc about this.