More explicit foralls (GHC Proposal 0007)

Allow the user to explicitly bind type/kind variables in type and data
family instances (including associated instances), closed type family
equations, and RULES pragmas. Follows the specification of GHC
Proposal 0007, also fixes #2600. Advised by Richard Eisenberg.

This modifies the Template Haskell AST -- old code may break!

Other Changes:
- convert HsRule to a record
- make rnHsSigWcType more general
- add repMaybe to DsMeta

Includes submodule update for Haddock.

Test Plan: validate

Reviewers: goldfire, bgamari, alanz

Subscribers: simonpj, RyanGlScott, goldfire, rwbarton,
             thomie, mpickering, carter

GHC Trac Issues: #2600, #14268

Differential Revision: https://phabricator.haskell.org/D4894

1 files changed, 4 insertions, 1 deletions

diff --git a/compiler/rename/RnUtils.hs b/compiler/rename/RnUtils.hs
index 0451e288be..2f27720ee5 100644
--- a/compiler/rename/RnUtils.hs
+++ b/compiler/rename/RnUtils.hs
@@ -244,11 +244,14 @@ warnUnused1 flag fld_env name
   = when (reportable name occ) $
     addUnusedWarning flag
                      occ (nameSrcSpan name)
-                     (text "Defined but not used")
+                     (text $ "Defined but not used" ++ opt_str)
   where
     occ = case lookupNameEnv fld_env name of
               Just (fl, _) -> mkVarOccFS fl
               Nothing      -> nameOccName name
+    opt_str = case flag of
+                Opt_WarnUnusedTypePatterns -> " on the right hand side"
+                _ -> ""
 
 warnUnusedGRE :: GlobalRdrElt -> RnM ()
 warnUnusedGRE gre@(GRE { gre_name = name, gre_lcl = lcl, gre_imp = is })