Display minimal complete definitions for type classes

This corresponds to the new {-# MINIMAL #-} pragma present in GHC 7.8+.
I also cleaned up some of the places in which ExportDecl is used to make
adding fields easier in the future.

Lots of test cases have been updated since they now render with
minimality information.

2 files changed, 27 insertions, 5 deletions

diff --git a/src/Haddock/Backends/Xhtml/Decl.hs b/src/Haddock/Backends/Xhtml/Decl.hs
index cd504d8e..39276441 100644
--- a/src/Haddock/Backends/Xhtml/Decl.hs
+++ b/src/Haddock/Backends/Xhtml/Decl.hs
@@ -28,7 +28,7 @@ import Haddock.GhcUtils
 import Haddock.Types
 import Haddock.Doc (combineDocumentation)
 
-import           Data.List             ( intersperse )
+import           Data.List             ( intersperse, sort )
 import qualified Data.Map as Map
 import           Data.Maybe
 import           Data.Monoid           ( mempty )
@@ -37,6 +37,7 @@ import           Text.XHtml hiding     ( name, title, p, quote )
 import GHC
 import GHC.Exts
 import Name
+import BooleanFormula
 
 
 ppDecl :: Bool -> LinksInfo -> LHsDecl DocName
@@ -406,7 +407,7 @@ ppShortClassDecl :: Bool -> LinksInfo -> TyClDecl DocName -> SrcSpan
 ppShortClassDecl summary links (ClassDecl { tcdCtxt = lctxt, tcdLName = lname, tcdTyVars = tvs
                                           , tcdFDs = fds, tcdSigs = sigs, tcdATs = ats }) loc
     subdocs splice unicode qual =
-  if null sigs && null ats
+  if not (any isVanillaLSig sigs) && null ats
     then (if summary then id else topDeclElem links loc splice [nm]) hdr
     else (if summary then id else topDeclElem links loc splice [nm]) (hdr <+> keyword "where")
       +++ shortSubDecls
@@ -441,11 +442,11 @@ ppClassDecl summary links instances fixities loc d subdocs
             splice unicode qual
   | summary = ppShortClassDecl summary links decl loc subdocs splice unicode qual
   | otherwise = classheader +++ docSection qual d
-                  +++ atBit +++ methodBit  +++ instancesBit
+                  +++ minimalBit +++ atBit +++ methodBit +++ instancesBit
   where
     classheader
-      | null lsigs = topDeclElem links loc splice [nm] (hdr unicode qual <+> fixs)
-      | otherwise  = topDeclElem links loc splice [nm] (hdr unicode qual <+> keyword "where" <+> fixs)
+      | any isVanillaLSig lsigs = topDeclElem links loc splice [nm] (hdr unicode qual <+> keyword "where" <+> fixs)
+      | otherwise = topDeclElem links loc splice [nm] (hdr unicode qual <+> fixs)
 
     -- Only the fixity relevant to the class header
     fixs = ppFixities [ f | f@(n,_) <- fixities, n == unLoc lname ] qual
@@ -472,6 +473,23 @@ ppClassDecl summary links instances fixities loc d subdocs
                            -- there are different subdocs for different names in a single
                            -- type signature?
 
+    minimalBit = case [ s | L _ (MinimalSig s) <- lsigs ] of
+      -- Miminal complete definition = every method
+      And xs : _ | sort [getName n | Var (L _ n) <- xs] ==
+                   sort [getName n | L _ (TypeSig ns _) <- lsigs, L _ n <- ns]
+        -> noHtml
+
+      -- Minimal complete definition = nothing
+      And [] : _ -> subMinimal $ toHtml "Nothing"
+
+      m : _  -> subMinimal $ ppMinimal False m
+      _ -> noHtml
+
+    ppMinimal _ (Var (L _ n)) = ppDocName qual Prefix True n
+    ppMinimal _ (And fs) = foldr1 (\a b -> a+++", "+++b) $ map (ppMinimal True) fs
+    ppMinimal p (Or fs) = wrap $ foldr1 (\a b -> a+++" | "+++b) $ map (ppMinimal False) fs
+      where wrap | p = parens | otherwise = id
+
     instancesBit = ppInstances instances nm unicode qual
 
 ppClassDecl _ _ _ _ _ _ _ _ _ _ _ = error "declaration type not supported by ppShortClassDecl"
diff --git a/src/Haddock/Backends/Xhtml/Layout.hs b/src/Haddock/Backends/Xhtml/Layout.hs
index 6784fb30..d3d94424 100644
--- a/src/Haddock/Backends/Xhtml/Layout.hs
+++ b/src/Haddock/Backends/Xhtml/Layout.hs
@@ -33,6 +33,7 @@ module Haddock.Backends.Xhtml.Layout (
   subFields,
   subInstances,
   subMethods,
+  subMinimal,
 
   topDeclElem, declElem,
 ) where
@@ -182,6 +183,9 @@ subInstances qual nm = maybe noHtml wrap . instTable
 subMethods :: [Html] -> Html
 subMethods = divSubDecls "methods" "Methods" . subBlock
 
+subMinimal :: Html -> Html
+subMinimal = divSubDecls "minimal" "Minimal complete definition" . Just . declElem
+
 
 -- a box for displaying code
 declElem :: Html -> Html