• Ryan Scott's avatar
    Refactor TcDeriv and TcGenDeriv · 4a03012a
    Ryan Scott authored
    Keeping a promise I made to Simon to clean up these modules.
    This change splits up the massive `TcDeriv` and `TcGenDeriv` modules into
    somewhat more manageable pieces. The new modules are:
    * `TcGenFunctor`: This contains the deriving machinery for `Functor`,
      `Foldable`, and `Traversable` (which all use the same underlying algorithm).
    * `TcDerivInfer`: This is the new home for `inferConstraints`,
      `simplifyInstanceContexts`, and related functions, whose role is to come up
      with the derived instance context and subsequently simplify it.
    * `TcDerivUtils`: This is a grab-bag module that contains several
      error-checking utilities originally in `TcDeriv`, as well as some functions
      that `TcDeriv` and `TcDerivInfer` both need.
    The end result is that `TcDeriv` is now less than 1,600 SLOC (originally 2,686
    SLOC), and `TcGenDeriv` is now about 2,000 SLOC (originally 2,964).
    In addition, this also implements a couple of tiny refactorings:
    * I transformed `type Condition = (DynFlags, TyCon) -> Validity` into
      `type Condition = DynFlags -> TyCon -> Validity`
    * I killed the `DerivSpecGeneric` constructor for `DerivSpecMechanism`, and
      merged its functionality into `DerivSpecStock`. In addition,
      `hasStockDeriving` now contains key-value pairs for `Generic` and `Generic1`,
      so they're no longer treated as an awkward special case in `TcDeriv`.
    Test Plan: ./validate
    Reviewers: simonpj, austin, bgamari
    Reviewed By: simonpj
    Subscribers: thomie, mpickering
    Differential Revision: https://phabricator.haskell.org/D2568
TcDeriv.hs 66.7 KB