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

5 files changed, 27 insertions, 87 deletions

diff --git a/html-test/ref/Bug548.html b/html-test/ref/Bug548.html
index cff64ca2..e040e603 100644
--- a/html-test/ref/Bug548.html
+++ b/html-test/ref/Bug548.html
@@ -148,7 +148,9 @@
 			><p class="src"
 			><a href="#"
 			  >from1</a
-			  > :: <a href="#" title="Bug548"
+			  > :: <span class="keyword"
+			  >forall</span
+			  > (a0 :: k). <a href="#" title="Bug548"
 			  >WrappedArrow</a
 			  > a b a0 -&gt; <a href="#" title="GHC.Generics"
 			  >Rep1</a
@@ -160,7 +162,9 @@
 			><p class="src"
 			><a href="#"
 			  >to1</a
-			  > :: <a href="#" title="GHC.Generics"
+			  > :: <span class="keyword"
+			  >forall</span
+			  > (a0 :: k). <a href="#" title="GHC.Generics"
 			  >Rep1</a
 			  > (<a href="#" title="Bug548"
 			  >WrappedArrow</a
diff --git a/html-test/ref/Instances.html b/html-test/ref/Instances.html
index 4f51f049..0cf0fc92 100644
--- a/html-test/ref/Instances.html
+++ b/html-test/ref/Instances.html
@@ -2038,8 +2038,6 @@
 			  >Int</a
 			  > c <a href="#" title="Data.Bool"
 			  >Bool</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -2050,9 +2048,7 @@
 			  >Thud</a
 			  > <a href="#" title="Data.Int"
 			  >Int</a
-			  > c :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > c <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -2112,9 +2108,7 @@
 			  >type</span
 			  > <a href="#" title="Instances"
 			  >Plugh</a
-			  > [a] c [b] :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > [a] c [b] <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -2122,9 +2116,7 @@
 			  >data</span
 			  > <a href="#" title="Instances"
 			  >Thud</a
-			  > [a] c :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > [a] c <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
diff --git a/html-test/ref/Operators.html b/html-test/ref/Operators.html
index 8c7746af..d0c42a08 100644
--- a/html-test/ref/Operators.html
+++ b/html-test/ref/Operators.html
@@ -96,9 +96,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >(:+)</a
-	      > :: <span class="keyword"
-	      >forall</span
-	      > a. a -&gt; a -&gt; [a]</li
+	      > :: a -&gt; a -&gt; [a]</li
 	    ><li class="src short"
 	    ><span class="keyword"
 	      >data</span
@@ -285,9 +283,7 @@
 	    >pattern</span
 	    > <a id="v::-43-" class="def"
 	    >(:+)</a
-	    > :: <span class="keyword"
-	    >forall</span
-	    > a. a -&gt; a -&gt; [a] <span class="fixity"
+	    > :: a -&gt; a -&gt; [a] <span class="fixity"
 	    >infixr 3</span
 	    ><span class="rightedge"
 	    ></span
@@ -529,4 +525,4 @@
     ></div
     ></body
   ></html
->
+>
\ No newline at end of file
diff --git a/html-test/ref/PatternSyns.html b/html-test/ref/PatternSyns.html
index af6d0210..6b4f8fda 100644
--- a/html-test/ref/PatternSyns.html
+++ b/html-test/ref/PatternSyns.html
@@ -68,9 +68,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >Foo</a
-	      > :: <span class="keyword"
-	      >forall</span
-	      > x. x -&gt; <a href="#" title="PatternSyns"
+	      > :: x -&gt; <a href="#" title="PatternSyns"
 	      >FooType</a
 	      > x</li
 	    ><li class="src short"
@@ -78,9 +76,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >Bar</a
-	      > :: <span class="keyword"
-	      >forall</span
-	      > x. x -&gt; <a href="#" title="PatternSyns"
+	      > :: x -&gt; <a href="#" title="PatternSyns"
 	      >FooType</a
 	      > (<a href="#" title="PatternSyns"
 	      >FooType</a
@@ -90,9 +86,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >(:&lt;-&gt;)</a
-	      > :: <span class="keyword"
-	      >forall</span
-	      > x x1. x -&gt; x1 -&gt; (<a href="#" title="PatternSyns"
+	      > :: x -&gt; x1 -&gt; (<a href="#" title="PatternSyns"
 	      >FooType</a
 	      > x, <a href="#" title="PatternSyns"
 	      >FooType</a
@@ -114,9 +108,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >Blub</a
-	      > :: () =&gt; <span class="keyword"
-	      >forall</span
-	      > x. <a href="#" title="Text.Show"
+	      > :: () =&gt; <a href="#" title="Text.Show"
 	      >Show</a
 	      > x =&gt; x -&gt; <a href="#" title="PatternSyns"
 	      >BlubType</a
@@ -134,9 +126,7 @@
 	      >pattern</span
 	      > <a href="#"
 	      >E</a
-	      > :: <span class="keyword"
-	      >forall</span
-	      > k a (b :: k). a <a href="#" title="PatternSyns"
+	      > :: a <a href="#" title="PatternSyns"
 	      >&gt;&lt;</a
 	      > b</li
 	    ><li class="src short"
@@ -189,9 +179,7 @@
 	    >pattern</span
 	    > <a id="v:Foo" class="def"
 	    >Foo</a
-	    > :: <span class="keyword"
-	    >forall</span
-	    > x. x -&gt; <a href="#" title="PatternSyns"
+	    > :: x -&gt; <a href="#" title="PatternSyns"
 	    >FooType</a
 	    > x <a href="#" class="selflink"
 	    >#</a
@@ -211,9 +199,7 @@
 	    >pattern</span
 	    > <a id="v:Bar" class="def"
 	    >Bar</a
-	    > :: <span class="keyword"
-	    >forall</span
-	    > x. x -&gt; <a href="#" title="PatternSyns"
+	    > :: x -&gt; <a href="#" title="PatternSyns"
 	    >FooType</a
 	    > (<a href="#" title="PatternSyns"
 	    >FooType</a
@@ -235,9 +221,7 @@
 	    >pattern</span
 	    > <a id="v::-60--45--62-" class="def"
 	    >(:&lt;-&gt;)</a
-	    > :: <span class="keyword"
-	    >forall</span
-	    > x x1. x -&gt; x1 -&gt; (<a href="#" title="PatternSyns"
+	    > :: x -&gt; x1 -&gt; (<a href="#" title="PatternSyns"
 	    >FooType</a
 	    > x, <a href="#" title="PatternSyns"
 	    >FooType</a
@@ -291,9 +275,7 @@
 	    >pattern</span
 	    > <a id="v:Blub" class="def"
 	    >Blub</a
-	    > :: () =&gt; <span class="keyword"
-	    >forall</span
-	    > x. <a href="#" title="Text.Show"
+	    > :: () =&gt; <a href="#" title="Text.Show"
 	    >Show</a
 	    > x =&gt; x -&gt; <a href="#" title="PatternSyns"
 	    >BlubType</a
@@ -347,9 +329,7 @@
 	    >pattern</span
 	    > <a id="v:E" class="def"
 	    >E</a
-	    > :: <span class="keyword"
-	    >forall</span
-	    > k a (b :: k). a <a href="#" title="PatternSyns"
+	    > :: a <a href="#" title="PatternSyns"
 	    >&gt;&lt;</a
 	    > b <a href="#" class="selflink"
 	    >#</a
@@ -388,4 +368,4 @@
     ></div
     ></body
   ></html
->
+>
\ No newline at end of file
diff --git a/html-test/ref/TypeFamilies.html b/html-test/ref/TypeFamilies.html
index 492b7ec1..8e1e7364 100644
--- a/html-test/ref/TypeFamilies.html
+++ b/html-test/ref/TypeFamilies.html
@@ -286,8 +286,6 @@
 			  >AssocD</a
 			  > <a href="#" title="TypeFamilies"
 			  >X</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -298,8 +296,6 @@
 			  >AssocT</a
 			  > <a href="#" title="TypeFamilies"
 			  >X</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -720,8 +716,6 @@
 			  >AssocD</a
 			  > <a href="#" title="TypeFamilies"
 			  >Y</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -732,8 +726,6 @@
 			  >AssocT</a
 			  > <a href="#" title="TypeFamilies"
 			  >Y</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -1107,11 +1099,7 @@
 			><li class="inst"
 			  ><a id="v:BatZ1" class="def"
 			    >BatZ1</a
-			    > :: <span class="keyword"
-			    >forall</span
-			    > (z :: <a href="#" title="TypeFamilies"
-			    >Z</a
-			    >). <a href="#" title="TypeFamilies"
+			    > :: <a href="#" title="TypeFamilies"
 			    >Z</a
 			    > -&gt; <a href="#" title="TypeFamilies"
 			    >Bat</a
@@ -1121,11 +1109,7 @@
 			  ><li class="inst"
 			  ><a id="v:BatZ2" class="def"
 			    >BatZ2</a
-			    > :: <span class="keyword"
-			    >forall</span
-			    > (z :: <a href="#" title="TypeFamilies"
-			    >Z</a
-			    >). {..} -&gt; <a href="#" title="TypeFamilies"
+			    > :: {..} -&gt; <a href="#" title="TypeFamilies"
 			    >Bat</a
 			    > '<a href="#" title="TypeFamilies"
 			    >ZB</a
@@ -1393,11 +1377,7 @@
 			><li class="inst"
 			  ><a id="v:BatZ1" class="def"
 			    >BatZ1</a
-			    > :: <span class="keyword"
-			    >forall</span
-			    > (z :: <a href="#" title="TypeFamilies"
-			    >Z</a
-			    >). <a href="#" title="TypeFamilies"
+			    > :: <a href="#" title="TypeFamilies"
 			    >Z</a
 			    > -&gt; <a href="#" title="TypeFamilies"
 			    >Bat</a
@@ -1407,11 +1387,7 @@
 			  ><li class="inst"
 			  ><a id="v:BatZ2" class="def"
 			    >BatZ2</a
-			    > :: <span class="keyword"
-			    >forall</span
-			    > (z :: <a href="#" title="TypeFamilies"
-			    >Z</a
-			    >). {..} -&gt; <a href="#" title="TypeFamilies"
+			    > :: {..} -&gt; <a href="#" title="TypeFamilies"
 			    >Bat</a
 			    > '<a href="#" title="TypeFamilies"
 			    >ZB</a
@@ -1620,8 +1596,6 @@
 			  >AssocD</a
 			  > <a href="#" title="TypeFamilies"
 			  >Y</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -1632,8 +1606,6 @@
 			  >AssocT</a
 			  > <a href="#" title="TypeFamilies"
 			  >Y</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -1678,8 +1650,6 @@
 			  >AssocD</a
 			  > <a href="#" title="TypeFamilies"
 			  >X</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -1690,8 +1660,6 @@
 			  >AssocT</a
 			  > <a href="#" title="TypeFamilies"
 			  >X</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p