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/iface/LoadIface.hs b/compiler/iface/LoadIface.hs
index b1a3ef1e6f..01fdaacd9f 100644
--- a/compiler/iface/LoadIface.hs
+++ b/compiler/iface/LoadIface.hs
@@ -144,7 +144,7 @@ importDecl name
         { eps <- getEps
         ; case lookupTypeEnv (eps_PTE eps) name of
             Just thing -> return $ Succeeded thing
-            Nothing    -> let doc = ifPprDebug (found_things_msg eps $$ empty)
+            Nothing    -> let doc = whenPprDebug (found_things_msg eps $$ empty)
                                     $$ not_found_msg
                           in return $ Failed doc
     }}}