Miscellaneous improvements to `Convert` (#1020)

Now that Haddock is moving towards working entirely over `.hi` and `.hie` files,
all declarations and types are going to be synthesized via the `Convert` module.
In preparation for this change, here are a bunch of fixes to this module:

  * Add kind annotations to type variables in `forall`'s whose kind is not `Type`,
    unless the kind can be inferred from some later use of the variable. See
    `implicitForAll` and `noKindTyVars` in particular if you wish to dive into this.

  * Properly detect `HsQualTy` in `synifyType`. This is done by following suit with
    what GHC's `toIfaceTypeX` does and checking the first argument of
    `FunTy{} :: Type` to see if it classified as a given/wanted in the typechecker
    (see `isPredTy`). 

  * Beef up the logic around figuring out when an explicit `forall` is needed. This
    includes: observing if any of the type variables will need kind signatures, if the
    inferred type variable order _without_ a forall will still match the one GHC
    claims, and some other small things.

  * Add some (not yet used) functionality for default levity polymorphic type
    signatures. This functionality similar to `fprint-explicit-runtime-reps`.

Couple other smaller fixes only worth mentioning:

  * Show the family result signature only when it isn't `Type`
  * Fix rendering of implicit parameters in the LaTeX and Hoogle backends
  * Better handling of the return kind of polykinded H98 data declarations
  * Class decls produced by `tyThingToLHsDecl` now contain associated type
    defaults and default method signatures when appropriate
  * Filter out more `forall`'s in pattern synonyms

1 files changed, 7 insertions, 2 deletions

diff --git a/haddock-api/src/Haddock/Backends/Hoogle.hs b/haddock-api/src/Haddock/Backends/Hoogle.hs
index 16ec582e..9e3186e5 100644
--- a/haddock-api/src/Haddock/Backends/Hoogle.hs
+++ b/haddock-api/src/Haddock/Backends/Hoogle.hs
@@ -263,8 +263,13 @@ ppCtor dflags dat subdocs con@ConDeclH98 {}
         -- docs for con_names on why it is a list to begin with.
         name = commaSeparate dflags . map unL $ getConNames con
 
-        resType = apps $ map (reL . HsTyVar NoExt NotPromoted . reL) $
-                        (tcdName dat) : [hsTyVarName v | L _ v@(UserTyVar _ _) <- hsQTvExplicit $ tyClDeclTyVars dat]
+        tyVarArg (UserTyVar _ n) = HsTyVar NoExt NotPromoted n
+        tyVarArg (KindedTyVar _ n lty) = HsKindSig NoExt (reL (HsTyVar NoExt NotPromoted n)) lty
+        tyVarArg _ = panic "ppCtor"
+
+        resType = apps $ map reL $
+                        (HsTyVar NoExt NotPromoted (reL (tcdName dat))) :
+                        map (tyVarArg . unLoc) (hsQTvExplicit $ tyClDeclTyVars dat)
 
 ppCtor dflags _dat subdocs con@(ConDeclGADT { })
    = concatMap (lookupCon dflags subdocs) (getConNames con) ++ f