Add debugPprType

We pretty-print a type by converting it to an IfaceType and
pretty-printing that.  But
 (a) that's a bit indirect, and
 (b) delibrately loses information about (e.g.) the kind
      on the /occurrences/ of a type variable

So this patch implements debugPprType, which pretty prints
the type directly, with no fancy formatting.  It's just used
for debugging.

I took the opportunity to refactor the debug-pretty-printing
machinery a little.  In particular, define these functions
and use them:

  ifPprDeubug :: SDoc -> SDOc -> SDoc
    -- Says what to do with and without -dppr-debug
  whenPprDebug :: SDoc -> SDoc
    -- Says what to do with  -dppr-debug; without is empty
  getPprDebug :: (Bool -> SDoc) -> SDoc

getPprDebug used to be called sdocPprDebugWith
whenPprDebug used to be called ifPprDebug

So a lot of files get touched in a very mechanical way

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/hsSyn/HsPat.hs b/compiler/hsSyn/HsPat.hs
index 5caf1a0f6c..bcdcca2677 100644
--- a/compiler/hsSyn/HsPat.hs
+++ b/compiler/hsSyn/HsPat.hs
@@ -495,7 +495,7 @@ instance (Outputable arg)
   ppr (HsRecFields { rec_flds = flds, rec_dotdot = Just n })
         = braces (fsep (punctuate comma (map ppr (take n flds) ++ [dotdot])))
         where
-          dotdot = text ".." <+> ifPprDebug (ppr (drop n flds))
+          dotdot = text ".." <+> whenPprDebug (ppr (drop n flds))
 
 instance (Outputable p, Outputable arg)
       => Outputable (HsRecField' p arg) where