Clean up handling of known-key Names in interface files

Previously BinIface had some dedicated logic for handling tuple names in
the symbol table. As it turns out, this logic was essentially dead code
as it was superceded by the special handling of known-key things. Here
we cull the tuple code-path and use the known-key codepath for all
tuple-ish things.

This had a surprising number of knock-on effects,

 * constraint tuple datacons had to be made known-key (previously they
   were not)

 * IfaceTopBndr was changed from being a synonym of OccName to a
   synonym of Name (since we now need to be able to deserialize Names
   directly from interface files)

 * the change to IfaceTopBndr complicated fingerprinting, since we need
   to ensure that we don't go looking for the fingerprint of the thing
   we are currently fingerprinting in the fingerprint environment (see
   notes in MkIface). Handling this required distinguishing between
   binding and non-binding Name occurrences in the Binary serializers.

 * the original name cache logic which previously lived in IfaceEnv has
   been moved to a new NameCache module

 * I ripped tuples and sums out of knownKeyNames since they introduce a
   very large number of entries. During interface file deserialization
   we use static functions (defined in the new KnownUniques module) to
   map from a Unique to a known-key Name (the Unique better correspond
   to a known-key name!) When we need to do an original name cache
   lookup we rely on the parser implemented in isBuiltInOcc_maybe.

 * HscMain.allKnownKeyNames was folded into PrelInfo.knownKeyNames.

 * Lots of comments were sprinkled about describing the new scheme.

Updates haddock submodule.

Test Plan: Validate

Reviewers: niteria, simonpj, austin, hvr

Reviewed By: simonpj

Subscribers: simonmar, niteria, thomie

Differential Revision: https://phabricator.haskell.org/D2467

GHC Trac Issues: #12532, #12415

1 files changed, 5 insertions, 3 deletions

diff --git a/compiler/iface/LoadIface.hs b/compiler/iface/LoadIface.hs
index 97f288f7ba..48bc316d0a 100644
--- a/compiler/iface/LoadIface.hs
+++ b/compiler/iface/LoadIface.hs
@@ -141,8 +141,10 @@ importDecl name
         -- Now look it up again; this time we should find it
         { eps <- getEps
         ; case lookupTypeEnv (eps_PTE eps) name of
-            Just thing -> return (Succeeded thing)
-            Nothing    -> return $ Failed (ifPprDebug (found_things_msg eps) $$ not_found_msg)
+            Just thing -> return $ Succeeded thing
+            Nothing    -> let doc = ifPprDebug (found_things_msg eps $$ empty)
+                                    $$ not_found_msg
+                          in return $ Failed doc
     }}}
   where
     nd_doc = text "Need decl for" <+> ppr name
@@ -653,7 +655,7 @@ loadDecl :: Bool                    -- Don't load pragmas into the decl pool
 loadDecl ignore_prags (_version, decl)
   = do  {       -- Populate the name cache with final versions of all
                 -- the names associated with the decl
-          main_name      <- lookupIfaceTop (ifName decl)
+          let main_name = ifName decl
 
         -- Typecheck the thing, lazily
         -- NB. Firstly, the laziness is there in case we never need the