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, 1 insertions, 1 deletions

diff --git a/hoogle-test/ref/Bug873/test.txt b/hoogle-test/ref/Bug873/test.txt
index 3c0e1870..68873317 100644
--- a/hoogle-test/ref/Bug873/test.txt
+++ b/hoogle-test/ref/Bug873/test.txt
@@ -21,7 +21,7 @@ module Bug873
 --   Note that <tt>(<a>$</a>)</tt> is levity-polymorphic in its result
 --   type, so that <tt>foo <a>$</a> True</tt> where <tt>foo :: Bool -&gt;
 --   Int#</tt> is well-typed.
-($) :: () => (a -> b) -> a -> b
+($) :: forall (r :: RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b
 infixr 0 $
 ($$) :: (a -> b) -> a -> b
 infixr 0 $$