EPA: Remove duplicate AnnOpenP/AnnCloseP in DataDecl

The parens EPAs were added in the tyvars where they belong, but also
at the top level of the declaration.

Closes #20452

5 files changed, 618 insertions, 27 deletions

diff --git a/compiler/GHC/Parser/PostProcess.hs b/compiler/GHC/Parser/PostProcess.hs
index 55b3c0d8a9..198a14ec72 100644
--- a/compiler/GHC/Parser/PostProcess.hs
+++ b/compiler/GHC/Parser/PostProcess.hs
@@ -194,9 +194,9 @@ mkClassDecl loc' (L _ (mcxt, tycl_hdr)) fds where_cls layoutInfo annsIn
   = do { let loc = noAnnSrcSpan loc'
        ; (binds, sigs, ats, at_defs, _, docs) <- cvBindsAndSigs where_cls
        ; (cls, tparams, fixity, ann) <- checkTyClHdr True tycl_hdr
-       ; (tyvars,annst) <- checkTyVars (text "class") whereDots cls tparams
+       ; tyvars <- checkTyVars (text "class") whereDots cls tparams
        ; cs <- getCommentsFor (locA loc) -- Get any remaining comments
-       ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) (ann++annst) cs
+       ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) ann cs
        ; return (L loc (ClassDecl { tcdCExt = (anns', NoAnnSortKey, layoutInfo)
                                   , tcdCtxt = mcxt
                                   , tcdLName = cls, tcdTyVars = tyvars
@@ -220,9 +220,9 @@ mkTyData loc' new_or_data cType (L _ (mcxt, tycl_hdr))
          ksig data_cons (L _ maybe_deriv) annsIn
   = do { let loc = noAnnSrcSpan loc'
        ; (tc, tparams, fixity, ann) <- checkTyClHdr False tycl_hdr
-       ; (tyvars, anns) <- checkTyVars (ppr new_or_data) equalsDots tc tparams
+       ; tyvars <- checkTyVars (ppr new_or_data) equalsDots tc tparams
        ; cs <- getCommentsFor (locA loc) -- Get any remaining comments
-       ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) (ann ++ anns) cs
+       ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) ann cs
        ; defn <- mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv
        ; return (L loc (DataDecl { tcdDExt = anns',
                                    tcdLName = tc, tcdTyVars = tyvars,
@@ -254,9 +254,9 @@ mkTySynonym :: SrcSpan
 mkTySynonym loc lhs rhs annsIn
   = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs
        ; cs1 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp]
-       ; (tyvars, anns) <- checkTyVars (text "type") equalsDots tc tparams
+       ; tyvars <- checkTyVars (text "type") equalsDots tc tparams
        ; cs2 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp]
-       ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) (ann ++ anns) (cs1 Semi.<> cs2)
+       ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) ann (cs1 Semi.<> cs2)
        ; return (L (noAnnSrcSpan loc) (SynDecl
                                 { tcdSExt = anns'
                                 , tcdLName = tc, tcdTyVars = tyvars
@@ -349,9 +349,9 @@ mkFamDecl :: SrcSpan
 mkFamDecl loc info topLevel lhs ksig injAnn annsIn
   = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs
        ; cs1 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp]
-       ; (tyvars, anns) <- checkTyVars (ppr info) equals_or_where tc tparams
+       ; tyvars <- checkTyVars (ppr info) equals_or_where tc tparams
        ; cs2 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp]
-       ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) (ann++anns) (cs1 Semi.<> cs2)
+       ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) ann (cs1 Semi.<> cs2)
        ; return (L (noAnnSrcSpan loc) (FamDecl noExtField
                                          (FamilyDecl
                                            { fdExt       = anns'
@@ -843,13 +843,12 @@ eitherToP (Left err)    = addFatalError err
 eitherToP (Right thing) = return thing
 
 checkTyVars :: SDoc -> SDoc -> LocatedN RdrName -> [LHsTypeArg GhcPs]
-            -> P ( LHsQTyVars GhcPs  -- the synthesized type variables
-                 , [AddEpAnn] )      -- action which adds annotations
+            -> P (LHsQTyVars GhcPs)  -- the synthesized type variables
 -- ^ Check whether the given list of type parameters are all type variables
 -- (possibly with a kind signature).
 checkTyVars pp_what equals_or_where tc tparms
-  = do { (tvs, anns) <- fmap unzip $ mapM check tparms
-       ; return (mkHsQTvs tvs, concat anns) }
+  = do { tvs <- mapM check tparms
+       ; return (mkHsQTvs tvs) }
   where
     check (HsTypeArg _ ki@(L loc _)) = addFatalError $ mkPlainErrorMsgEnvelope (locA loc) $
                                          (PsErrUnexpectedTypeAppInDecl ki pp_what (unLoc tc))
@@ -858,12 +857,10 @@ checkTyVars pp_what equals_or_where tc tparms
                             (PsErrMalformedDecl pp_what (unLoc tc))
         -- Keep around an action for adjusting the annotations of extra parens
     chkParens :: [AddEpAnn] -> EpAnnComments -> LHsType GhcPs
-              -> P (LHsTyVarBndr () GhcPs, [AddEpAnn])
+              -> P (LHsTyVarBndr () GhcPs)
     chkParens acc cs (L l (HsParTy an ty))
       = chkParens (mkParensEpAnn (locA l) ++ acc) (cs Semi.<> epAnnComments an) ty
-    chkParens acc cs ty = do
-      tv <- chk acc cs ty
-      return (tv, reverse acc)
+    chkParens acc cs ty = chk acc cs ty
 
         -- Check that the name space is correct!
     chk :: [AddEpAnn] -> EpAnnComments -> LHsType GhcPs -> P (LHsTyVarBndr () GhcPs)
diff --git a/testsuite/tests/parser/should_compile/DumpParsedAst.stderr b/testsuite/tests/parser/should_compile/DumpParsedAst.stderr
index d68daf6738..d42a808c62 100644
--- a/testsuite/tests/parser/should_compile/DumpParsedAst.stderr
+++ b/testsuite/tests/parser/should_compile/DumpParsedAst.stderr
@@ -189,9 +189,7 @@
         [(AddEpAnn AnnType (EpaSpan { DumpParsedAst.hs:10:1-4 }))
         ,(AddEpAnn AnnFamily (EpaSpan { DumpParsedAst.hs:10:6-11 }))
         ,(AddEpAnn AnnDcolon (EpaSpan { DumpParsedAst.hs:10:32-33 }))
-        ,(AddEpAnn AnnWhere (EpaSpan { DumpParsedAst.hs:10:41-45 }))
-        ,(AddEpAnn AnnCloseP (EpaSpan { DumpParsedAst.hs:10:30 }))
-        ,(AddEpAnn AnnOpenP (EpaSpan { DumpParsedAst.hs:10:20 }))]
+        ,(AddEpAnn AnnWhere (EpaSpan { DumpParsedAst.hs:10:41-45 }))]
         (EpaComments
          []))
        (ClosedTypeFamily
@@ -468,9 +466,7 @@
         { DumpParsedAst.hs:15:1-29 }
         (UnchangedAnchor))
        [(AddEpAnn AnnData (EpaSpan { DumpParsedAst.hs:15:1-4 }))
-       ,(AddEpAnn AnnEqual (EpaSpan { DumpParsedAst.hs:15:19 }))
-       ,(AddEpAnn AnnCloseP (EpaSpan { DumpParsedAst.hs:15:17 }))
-       ,(AddEpAnn AnnOpenP (EpaSpan { DumpParsedAst.hs:15:10 }))]
+       ,(AddEpAnn AnnEqual (EpaSpan { DumpParsedAst.hs:15:19 }))]
        (EpaComments
         []))
       (L
@@ -631,11 +627,7 @@
         [(AddEpAnn AnnType (EpaSpan { DumpParsedAst.hs:17:1-4 }))
         ,(AddEpAnn AnnFamily (EpaSpan { DumpParsedAst.hs:17:6-11 }))
         ,(AddEpAnn AnnDcolon (EpaSpan { DumpParsedAst.hs:17:42-43 }))
-        ,(AddEpAnn AnnWhere (EpaSpan { DumpParsedAst.hs:17:50-54 }))
-        ,(AddEpAnn AnnCloseP (EpaSpan { DumpParsedAst.hs:17:23 }))
-        ,(AddEpAnn AnnOpenP (EpaSpan { DumpParsedAst.hs:17:16 }))
-        ,(AddEpAnn AnnCloseP (EpaSpan { DumpParsedAst.hs:17:40 }))
-        ,(AddEpAnn AnnOpenP (EpaSpan { DumpParsedAst.hs:17:25 }))]
+        ,(AddEpAnn AnnWhere (EpaSpan { DumpParsedAst.hs:17:50-54 }))]
         (EpaComments
          []))
        (ClosedTypeFamily
diff --git a/testsuite/tests/parser/should_compile/T20452.hs b/testsuite/tests/parser/should_compile/T20452.hs
new file mode 100644
index 0000000000..54a7e83908
--- /dev/null
+++ b/testsuite/tests/parser/should_compile/T20452.hs
@@ -0,0 +1,9 @@
+{-# LANGUAGE DataKinds #-}
+{-# OPTIONS -ddump-parsed-ast #-}
+module T20452 where
+
+data Proxy1  (a :: k)  = Proxy1
+data Proxy2 ((a :: k)) = Proxy2
+
+class Prods1  (lhs :: Int)   (name :: String)   (rhs :: [(String, String)])  where {}
+class Prods2 ((lhs :: Int)) ((name :: String)) ((rhs :: [(String, String)])) where {}
diff --git a/testsuite/tests/parser/should_compile/T20452.stderr b/testsuite/tests/parser/should_compile/T20452.stderr
new file mode 100644
index 0000000000..47a05d5770
--- /dev/null
+++ b/testsuite/tests/parser/should_compile/T20452.stderr
@@ -0,0 +1,592 @@
+
+==================== Parser AST ====================
+
+(L
+ { T20452.hs:1:1 }
+ (HsModule
+  (EpAnn
+   (Anchor
+    { T20452.hs:1:1 }
+    (UnchangedAnchor))
+   (AnnsModule
+    [(AddEpAnn AnnModule (EpaSpan { T20452.hs:3:1-6 }))
+    ,(AddEpAnn AnnWhere (EpaSpan { T20452.hs:3:15-19 }))]
+    (AnnList
+     (Nothing)
+     (Nothing)
+     (Nothing)
+     []
+     []))
+   (EpaCommentsBalanced
+    []
+    [(L
+      (Anchor
+       { T20452.hs:10:1 }
+       (UnchangedAnchor))
+      (EpaComment
+       (EpaEofComment)
+       { T20452.hs:10:1 }))]))
+  (VirtualBraces
+   (1))
+  (Just
+   (L
+    { T20452.hs:3:8-13 }
+    {ModuleName: T20452}))
+  (Nothing)
+  []
+  [(L
+    (SrcSpanAnn (EpAnn
+                 (Anchor
+                  { T20452.hs:5:1-31 }
+                  (UnchangedAnchor))
+                 (AnnListItem
+                  [])
+                 (EpaComments
+                  [])) { T20452.hs:5:1-31 })
+    (TyClD
+     (NoExtField)
+     (DataDecl
+      (EpAnn
+       (Anchor
+        { T20452.hs:5:1-31 }
+        (UnchangedAnchor))
+       [(AddEpAnn AnnData (EpaSpan { T20452.hs:5:1-4 }))
+       ,(AddEpAnn AnnEqual (EpaSpan { T20452.hs:5:24 }))]
+       (EpaComments
+        []))
+      (L
+       (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:6-11 })
+       (Unqual
+        {OccName: Proxy1}))
+      (HsQTvs
+       (NoExtField)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:14-21 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:5:14-21 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:5:17-18 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:5:14 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:5:21 }))]
+           (EpaComments
+            []))
+          (())
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:15 })
+           (Unqual
+            {OccName: a}))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:20 })
+           (HsTyVar
+            (EpAnn
+             (Anchor
+              { T20452.hs:5:20 }
+              (UnchangedAnchor))
+             []
+             (EpaComments
+              []))
+            (NotPromoted)
+            (L
+             (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:20 })
+             (Unqual
+              {OccName: k}))))))])
+      (Prefix)
+      (HsDataDefn
+       (NoExtField)
+       (DataType)
+       (Nothing)
+       (Nothing)
+       (Nothing)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:26-31 })
+         (ConDeclH98
+          (EpAnn
+           (Anchor
+            { T20452.hs:5:26-31 }
+            (UnchangedAnchor))
+           []
+           (EpaComments
+            []))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:5:26-31 })
+           (Unqual
+            {OccName: Proxy1}))
+          (False)
+          []
+          (Nothing)
+          (PrefixCon
+           []
+           [])
+          (Nothing)))]
+       []))))
+  ,(L
+    (SrcSpanAnn (EpAnn
+                 (Anchor
+                  { T20452.hs:6:1-31 }
+                  (UnchangedAnchor))
+                 (AnnListItem
+                  [])
+                 (EpaComments
+                  [])) { T20452.hs:6:1-31 })
+    (TyClD
+     (NoExtField)
+     (DataDecl
+      (EpAnn
+       (Anchor
+        { T20452.hs:6:1-31 }
+        (UnchangedAnchor))
+       [(AddEpAnn AnnData (EpaSpan { T20452.hs:6:1-4 }))
+       ,(AddEpAnn AnnEqual (EpaSpan { T20452.hs:6:24 }))]
+       (EpaComments
+        []))
+      (L
+       (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:6-11 })
+       (Unqual
+        {OccName: Proxy2}))
+      (HsQTvs
+       (NoExtField)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:13-22 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:6:13-22 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:6:17-18 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:6:14 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:6:21 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:6:13 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:6:22 }))]
+           (EpaComments
+            []))
+          (())
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:15 })
+           (Unqual
+            {OccName: a}))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:20 })
+           (HsTyVar
+            (EpAnn
+             (Anchor
+              { T20452.hs:6:20 }
+              (UnchangedAnchor))
+             []
+             (EpaComments
+              []))
+            (NotPromoted)
+            (L
+             (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:20 })
+             (Unqual
+              {OccName: k}))))))])
+      (Prefix)
+      (HsDataDefn
+       (NoExtField)
+       (DataType)
+       (Nothing)
+       (Nothing)
+       (Nothing)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:26-31 })
+         (ConDeclH98
+          (EpAnn
+           (Anchor
+            { T20452.hs:6:26-31 }
+            (UnchangedAnchor))
+           []
+           (EpaComments
+            []))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:6:26-31 })
+           (Unqual
+            {OccName: Proxy2}))
+          (False)
+          []
+          (Nothing)
+          (PrefixCon
+           []
+           [])
+          (Nothing)))]
+       []))))
+  ,(L
+    (SrcSpanAnn (EpAnn
+                 (Anchor
+                  { T20452.hs:8:1-85 }
+                  (UnchangedAnchor))
+                 (AnnListItem
+                  [])
+                 (EpaComments
+                  [])) { T20452.hs:8:1-85 })
+    (TyClD
+     (NoExtField)
+     (ClassDecl
+      ((,,)
+       (EpAnn
+        (Anchor
+         { T20452.hs:8:1-85 }
+         (UnchangedAnchor))
+        [(AddEpAnn AnnClass (EpaSpan { T20452.hs:8:1-5 }))
+        ,(AddEpAnn AnnWhere (EpaSpan { T20452.hs:8:78-82 }))
+        ,(AddEpAnn AnnOpenC (EpaSpan { T20452.hs:8:84 }))
+        ,(AddEpAnn AnnCloseC (EpaSpan { T20452.hs:8:85 }))]
+        (EpaComments
+         []))
+       (NoAnnSortKey)
+       (ExplicitBraces))
+      (Nothing)
+      (L
+       (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:7-12 })
+       (Unqual
+        {OccName: Prods1}))
+      (HsQTvs
+       (NoExtField)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:15-26 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:8:15-26 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:8:20-21 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:8:15 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:8:26 }))]
+           (EpaComments
+            []))
+          (())
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:16-18 })
+           (Unqual
+            {OccName: lhs}))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:23-25 })
+           (HsTyVar
+            (EpAnn
+             (Anchor
+              { T20452.hs:8:23-25 }
+              (UnchangedAnchor))
+             []
+             (EpaComments
+              []))
+            (NotPromoted)
+            (L
+             (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:23-25 })
+             (Unqual
+              {OccName: Int}))))))
+       ,(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:30-45 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:8:30-45 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:8:36-37 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:8:30 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:8:45 }))]
+           (EpaComments
+            []))
+          (())
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:31-34 })
+           (Unqual
+            {OccName: name}))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:39-44 })
+           (HsTyVar
+            (EpAnn
+             (Anchor
+              { T20452.hs:8:39-44 }
+              (UnchangedAnchor))
+             []
+             (EpaComments
+              []))
+            (NotPromoted)
+            (L
+             (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:39-44 })
+             (Unqual
+              {OccName: String}))))))
+       ,(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:49-75 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:8:49-75 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:8:54-55 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:8:49 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:8:75 }))]
+           (EpaComments
+            []))
+          (())
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:50-52 })
+           (Unqual
+            {OccName: rhs}))
+          (L
+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:57-74 })
+           (HsListTy
+            (EpAnn
+             (Anchor
+              { T20452.hs:8:57 }
+              (UnchangedAnchor))
+             (AnnParen
+              (AnnParensSquare)
+              (EpaSpan { T20452.hs:8:57 })
+              (EpaSpan { T20452.hs:8:74 }))
+             (EpaComments
+              []))
+            (L
+             (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:58-73 })
+             (HsTupleTy
+              (EpAnn
+               (Anchor
+                { T20452.hs:8:58 }
+                (UnchangedAnchor))
+               (AnnParen
+                (AnnParens)
+                (EpaSpan { T20452.hs:8:58 })
+                (EpaSpan { T20452.hs:8:73 }))
+               (EpaComments
+                []))
+              (HsBoxedOrConstraintTuple)
+              [(L
+                (SrcSpanAnn (EpAnn
+                             (Anchor
+                              { T20452.hs:8:59-64 }
+                              (UnchangedAnchor))
+                             (AnnListItem
+                              [(AddCommaAnn
+                                (EpaSpan { T20452.hs:8:65 }))])
+                             (EpaComments
+                              [])) { T20452.hs:8:59-64 })
+                (HsTyVar
+                 (EpAnn
+                  (Anchor
+                   { T20452.hs:8:59-64 }
+                   (UnchangedAnchor))
+                  []
+                  (EpaComments
+                   []))
+                 (NotPromoted)
+                 (L
+                  (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:59-64 })
+                  (Unqual
+                   {OccName: String}))))
+              ,(L
+                (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:67-72 })
+                (HsTyVar
+                 (EpAnn
+                  (Anchor
+                   { T20452.hs:8:67-72 }
+                   (UnchangedAnchor))
+                  []
+                  (EpaComments
+                   []))
+                 (NotPromoted)
+                 (L
+                  (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:8:67-72 })
+                  (Unqual
+                   {OccName: String}))))]))))))])
+      (Prefix)
+      []
+      []
+      {Bag(LocatedA (HsBind GhcPs)):
+       []}
+      []
+      []
+      [])))
+  ,(L
+    (SrcSpanAnn (EpAnn
+                 (Anchor
+                  { T20452.hs:9:1-85 }
+                  (UnchangedAnchor))
+                 (AnnListItem
+                  [])
+                 (EpaComments
+                  [])) { T20452.hs:9:1-85 })
+    (TyClD
+     (NoExtField)
+     (ClassDecl
+      ((,,)
+       (EpAnn
+        (Anchor
+         { T20452.hs:9:1-85 }
+         (UnchangedAnchor))
+        [(AddEpAnn AnnClass (EpaSpan { T20452.hs:9:1-5 }))
+        ,(AddEpAnn AnnWhere (EpaSpan { T20452.hs:9:78-82 }))
+        ,(AddEpAnn AnnOpenC (EpaSpan { T20452.hs:9:84 }))
+        ,(AddEpAnn AnnCloseC (EpaSpan { T20452.hs:9:85 }))]
+        (EpaComments
+         []))
+       (NoAnnSortKey)
+       (ExplicitBraces))
+      (Nothing)
+      (L
+       (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:7-12 })
+       (Unqual
+        {OccName: Prods2}))
+      (HsQTvs
+       (NoExtField)
+       [(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:14-27 })
+         (KindedTyVar
+          (EpAnn
+           (Anchor
+            { T20452.hs:9:14-27 }
+            (UnchangedAnchor))
+           [(AddEpAnn AnnDcolon (EpaSpan { T20452.hs:9:20-21 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:9:15 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:9:26 }))
+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:9:14 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:9:27 }))]
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+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:16-18 })
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+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:23-25 })
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+            (EpAnn
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+              (UnchangedAnchor))
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+              []))
+            (NotPromoted)
+            (L
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+              {OccName: Int}))))))
+       ,(L
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+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:9:29 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:9:46 }))]
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+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:31-34 })
+           (Unqual
+            {OccName: name}))
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+           (HsTyVar
+            (EpAnn
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+              (UnchangedAnchor))
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+             (EpaComments
+              []))
+            (NotPromoted)
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+             (Unqual
+              {OccName: String}))))))
+       ,(L
+         (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:48-76 })
+         (KindedTyVar
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+           ,(AddEpAnn AnnOpenP (EpaSpan { T20452.hs:9:48 }))
+           ,(AddEpAnn AnnCloseP (EpaSpan { T20452.hs:9:76 }))]
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+           (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:50-52 })
+           (Unqual
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+             (HsTupleTy
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+                (EpaSpan { T20452.hs:9:58 })
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+                  (Unqual
+                   {OccName: String}))))
+              ,(L
+                (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:67-72 })
+                (HsTyVar
+                 (EpAnn
+                  (Anchor
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+                 (L
+                  (SrcSpanAnn (EpAnnNotUsed) { T20452.hs:9:67-72 })
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+      (Prefix)
+      []
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+      {Bag(LocatedA (HsBind GhcPs)):
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+  (Nothing)
+  (Nothing)))
diff --git a/testsuite/tests/parser/should_compile/all.T b/testsuite/tests/parser/should_compile/all.T
index e2d4303b7e..d24321a103 100644
--- a/testsuite/tests/parser/should_compile/all.T
+++ b/testsuite/tests/parser/should_compile/all.T
@@ -178,3 +178,4 @@ test('T19082', normal, compile, [''])
 test('T19521', normal, compile, [''])
 
 test('T20186', normal, compile, [''])
+test('T20452', normal, compile, [''])