Add a data type we can use to box up equality evidence for -XConstrai…

…ntKind
ghc · Sep 6, 2011 · c7623fc · c7623fc
1 parent 9cd14ba
commit c7623fc
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/GHC/Types.hs b/GHC/Types.hs
@@ -78,6 +78,13 @@ or the '>>' and '>>=' operations from the 'Monad' class.
 newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
 
 
+-- | A data constructor used to box up all unlifted equalities
+--
+-- The type constructor is special in that GHC pretends that it
+-- has kind (? -> ? -> Fact) rather than (* -> * -> *)
+data (~) a b = Eq# ((~#) a b)
+
+
 --------------------------------------------------------------------------------
 -- Generic representations
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