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, 6 insertions, 2 deletions

diff --git a/compiler/deSugar/Desugar.hs b/compiler/deSugar/Desugar.hs
index c1e728b734..c7973ca4f3 100644
--- a/compiler/deSugar/Desugar.hs
+++ b/compiler/deSugar/Desugar.hs
@@ -379,7 +379,11 @@ Reason
 -}
 
 dsRule :: LRuleDecl GhcTc -> DsM (Maybe CoreRule)
-dsRule (L loc (HsRule _ name rule_act vars lhs rhs))
+dsRule (L loc (HsRule { rd_name = name
+                      , rd_act  = rule_act
+                      , rd_tmvs = vars
+                      , rd_lhs  = lhs
+                      , rd_rhs  = rhs }))
   = putSrcSpanDs loc $
     do  { let bndrs' = [var | L _ (RuleBndr _ (L _ var)) <- vars]
 
@@ -497,7 +501,7 @@ switching off EnableRewriteRules.  See DsExpr.dsExplicitList.
 That keeps the desugaring of list comprehensions simple too.
 
 Nor do we want to warn of conversion identities on the LHS;
-the rule is precisly to optimise them:
+the rule is precisely to optimise them:
   {-# RULES "fromRational/id" fromRational = id :: Rational -> Rational #-}
 
 Note [Desugaring coerce as cast]