Add HsSyn prettyprinter tests

Summary:
Add prettyprinter tests, which take a file, parse it, pretty print it,
re-parse the pretty printed version and then compare the original and
new ASTs (ignoring locations)

Updates haddock submodule to match the AST changes.

There are three issues outstanding

1. Extra parens around a context are not reproduced. This will require an
   AST change and will be done in a separate patch.

2. Currently if an `HsTickPragma` is found, this is not pretty-printed,
   to prevent noise in the output.

   I am not sure what the desired behaviour in this case is, so have left
   it as before. Test Ppr047 is marked as expected fail for this.

3. Apart from in a context, the ParsedSource AST keeps all the parens from
   the original source.  Something is happening in the renamer to remove the
   parens around visible type application, causing T12530 to fail, as the
   dumped splice decl is after the renamer.

   This needs to be fixed by keeping the parens, but I do not know where they
   are being removed.  I have amended the test to pass, by removing the parens
   in the expected output.

Test Plan: ./validate

Reviewers: goldfire, mpickering, simonpj, bgamari, austin

Reviewed By: simonpj, bgamari

Subscribers: simonpj, goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D2752

GHC Trac Issues: #3384

3 files changed, 4 insertions, 3 deletions

diff --git a/compiler/iface/BuildTyCl.hs b/compiler/iface/BuildTyCl.hs
index 0337abcefc..b291bc53fd 100644
--- a/compiler/iface/BuildTyCl.hs
+++ b/compiler/iface/BuildTyCl.hs
@@ -390,7 +390,7 @@ buildClass tycon_name binders roles sc_theta
         ; traceIf (text "buildClass" <+> ppr tycon)
         ; return result }
   where
-    no_bang = HsSrcBang Nothing NoSrcUnpack NoSrcStrict
+    no_bang = HsSrcBang NoSourceText NoSrcUnpack NoSrcStrict
 
     mk_op_item :: Class -> TcMethInfo -> TcRnIf n m ClassOpItem
     mk_op_item rec_clas (op_name, _, dm_spec)
diff --git a/compiler/iface/LoadIface.hs b/compiler/iface/LoadIface.hs
index 48bc316d0a..921943afb9 100644
--- a/compiler/iface/LoadIface.hs
+++ b/compiler/iface/LoadIface.hs
@@ -923,7 +923,8 @@ ghcPrimIface
         mi_fix_fn  = mkIfaceFixCache fixities
     }
   where
-    fixities = (getOccName seqId, Fixity "0" 0 InfixR)  -- seq is infixr 0
+    fixities = (getOccName seqId, Fixity NoSourceText 0 InfixR)
+                                      -- seq is infixr 0
              : (occName funTyConName, funTyFixity)  -- trac #10145
              : mapMaybe mkFixity allThePrimOps
     mkFixity op = (,) (primOpOcc op) <$> primOpFixity op
diff --git a/compiler/iface/TcIface.hs b/compiler/iface/TcIface.hs
index 6baffedc67..123b02fc81 100644
--- a/compiler/iface/TcIface.hs
+++ b/compiler/iface/TcIface.hs
@@ -803,7 +803,7 @@ tcIfaceDataCons tycon_name tycon tc_tybinders if_cons
                                       ; return (HsUnpack (Just co)) }
 
     src_strict :: IfaceSrcBang -> HsSrcBang
-    src_strict (IfSrcBang unpk bang) = HsSrcBang Nothing unpk bang
+    src_strict (IfSrcBang unpk bang) = HsSrcBang NoSourceText unpk bang
 
 tcIfaceEqSpec :: IfaceEqSpec -> IfL [EqSpec]
 tcIfaceEqSpec spec