3 files changed, 18 insertions, 4 deletions
diff --git a/compiler/Language/Haskell/Syntax/Expr.hs b/compiler/Language/Haskell/Syntax/Expr.hs
index 326c9903dc..5f774de2e4 100644
--- a/compiler/Language/Haskell/Syntax/Expr.hs
+++ b/compiler/Language/Haskell/Syntax/Expr.hs
@@ -976,8 +976,8 @@ data Match p body
   = Match {
         m_ext :: XCMatch p body,
         m_ctxt :: HsMatchContext p,
-          -- See Note [m_ctxt in Match]
-        m_pats :: [LPat p], -- The patterns
+          -- See note [m_ctxt in Match]
+        m_pats :: [LMatchPat p], -- The patterns
         m_grhss :: (GRHSs p body)
   }
   | XMatch !(XXMatch p body)
diff --git a/compiler/Language/Haskell/Syntax/Extension.hs b/compiler/Language/Haskell/Syntax/Extension.hs
index 4bdb3ce3cb..bea00f86f8 100644
--- a/compiler/Language/Haskell/Syntax/Extension.hs
+++ b/compiler/Language/Haskell/Syntax/Extension.hs
@@ -604,6 +604,10 @@ type family XSigPat      x
 type family XCoPat       x
 type family XXPat        x
 type family XHsFieldBind x
+type family XVisPat      x
+type family XInvisTyVarPat  x
+type family XInvisWildTyPat x
+type family XXMatchPat   x
 
 -- =====================================================================
 -- Type families for the HsTypes type families
diff --git a/compiler/Language/Haskell/Syntax/Pat.hs b/compiler/Language/Haskell/Syntax/Pat.hs
index 95abde9ce0..5f5f73362c 100644
--- a/compiler/Language/Haskell/Syntax/Pat.hs
+++ b/compiler/Language/Haskell/Syntax/Pat.hs
@@ -19,8 +19,7 @@
 
 -- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.*
 module Language.Haskell.Syntax.Pat (
-        Pat(..), LPat,
-        ConLikeP,
+        Pat(..), LPat, MatchPat(..), LMatchPat, ConLikeP,
 
         HsConPatDetails, hsConPatArgs,
         HsConPatTyArg(..),
@@ -224,6 +223,17 @@ data Pat p
 
 type family ConLikeP x
 
+-- | A pattern to be used in a sequence of patterns, like what appears
+-- to the right of @f@ in @f a b True = ...@. A 'MatchPat' allows for the
+-- possibility of binding a /type variable/ with \@.
+data MatchPat pass
+  = VisPat (XVisPat pass) (LPat pass)
+  -- () means that we don't accept f @{x} syntax
+  | InvisTyVarPat (XInvisTyVarPat pass) (LHsTyVarBndr () pass)
+  | InvisWildTyPat (XInvisWildTyPat pass)
+  | XMatchPat !(XXMatchPat pass)
+
+type LMatchPat pass = XRec pass (MatchPat pass)
 
 -- ---------------------------------------------------------------------