Fix: Generate pattern signatures for constructors exported as patterns (#663)

* Fix pretty-printing of pattern signatures

Pattern synonyms can have up to two contexts, both having a
different semantic meaning: The first holds the constraints
required to perform the matching, the second contains the
constraints provided by a successful pattern match. When the
first context is empty but the second is not it is necessary
to render the first, empty context.

* Generate pattern synonym signatures for ctors exported as patterns

This fixes #653.

* Simplify extractPatternSyn

It is not necessary to generate the simplest type signature since
it will be simplified when pretty-printed.

* Add changelog entries for PR #663

* Fix extractPatternSyn error message

1 files changed, 76 insertions, 0 deletions

diff --git a/html-test/ref/PatternSyns.html b/html-test/ref/PatternSyns.html
index 2cf936b3..37596645 100644
--- a/html-test/ref/PatternSyns.html
+++ b/html-test/ref/PatternSyns.html
@@ -101,6 +101,28 @@ window.onload = function () {pageLoad();};
 	  ><li class="src short"
 	  ><span class="keyword"
 	    >data</span
+	    > <a href="#"
+	    >BlubType</a
+	    > = <a href="#"
+	    >Show</a
+	    > x =&gt; <a href="#"
+	    >BlubCtor</a
+	    > x</li
+	  ><li class="src short"
+	  ><span class="keyword"
+	    >pattern</span
+	    > <a href="#"
+	    >Blub</a
+	    > :: () =&gt; <span class="keyword"
+	    >forall</span
+	    > x. <a href="#"
+	    >Show</a
+	    > x =&gt; x -&gt; <a href="#"
+	    >BlubType</a
+	    ></li
+	  ><li class="src short"
+	  ><span class="keyword"
+	    >data</span
 	    > (a :: <a href="#"
 	    >*</a
 	    >) <a href="#"
@@ -237,6 +259,60 @@ window.onload = function () {pageLoad();};
 	><p class="src"
 	  ><span class="keyword"
 	    >data</span
+	    > <a id="t:BlubType" class="def"
+	    >BlubType</a
+	    > <a href="#" class="selflink"
+	    >#</a
+	    ></p
+	  ><div class="doc"
+	  ><p
+	    >BlubType is existentially quantified</p
+	    ></div
+	  ><div class="subs constructors"
+	  ><p class="caption"
+	    >Constructors</p
+	    ><table
+	    ><tr
+	      ><td class="src"
+		><a href="#"
+		  >Show</a
+		  > x =&gt; <a id="v:BlubCtor" class="def"
+		  >BlubCtor</a
+		  > x</td
+		><td class="doc empty"
+		></td
+		></tr
+	      ></table
+	    ></div
+	  ></div
+	><div class="top"
+	><p class="src"
+	  ><span class="keyword"
+	    >pattern</span
+	    > <a id="v:Blub" class="def"
+	    >Blub</a
+	    > :: () =&gt; <span class="keyword"
+	    >forall</span
+	    > x. <a href="#"
+	    >Show</a
+	    > x =&gt; x -&gt; <a href="#"
+	    >BlubType</a
+	    > <a href="#" class="selflink"
+	    >#</a
+	    ></p
+	  ><div class="doc"
+	  ><p
+	    >Pattern synonym for <code
+	      ><a href="#"
+		>Blub</a
+		></code
+	      > x</p
+	    ></div
+	  ></div
+	><div class="top"
+	><p class="src"
+	  ><span class="keyword"
+	    >data</span
 	    > (a :: <a href="#"
 	    >*</a
 	    >) <a id="t:-62--60-" class="def"