EPA: Capture '+' location for NPlusKPatwip/az/T20243-n-plus-k-patterns

The location of the plus symbol was being discarded, we now capture
it.

Closes #20243

5 files changed, 15 insertions, 6 deletions

diff --git a/compiler/GHC/Hs/Dump.hs b/compiler/GHC/Hs/Dump.hs
index 9be0f96640..247e8099da 100644
--- a/compiler/GHC/Hs/Dump.hs
+++ b/compiler/GHC/Hs/Dump.hs
@@ -62,6 +62,7 @@ showAstData bs ba a0 = blankLine $$ showAstData' a0
               `extQ` annotationEpAnnImportDecl
               `extQ` annotationAnnParen
               `extQ` annotationTrailingAnn
+              `extQ` annotationEpaLocation
               `extQ` addEpAnn
               `extQ` lit `extQ` litr `extQ` litt
               `extQ` sourceText
@@ -254,6 +255,9 @@ showAstData bs ba a0 = blankLine $$ showAstData' a0
             annotationTrailingAnn :: EpAnn TrailingAnn -> SDoc
             annotationTrailingAnn = annotation' (text "EpAnn TrailingAnn")
 
+            annotationEpaLocation :: EpAnn EpaLocation -> SDoc
+            annotationEpaLocation = annotation' (text "EpAnn EpaLocation")
+
             annotation' :: forall a .(Data a, Typeable a)
                        => SDoc -> EpAnn a -> SDoc
             annotation' tag anns = case ba of
diff --git a/compiler/GHC/Hs/Pat.hs b/compiler/GHC/Hs/Pat.hs
index f300c4a2ca..a4b3bed851 100644
--- a/compiler/GHC/Hs/Pat.hs
+++ b/compiler/GHC/Hs/Pat.hs
@@ -147,7 +147,7 @@ type instance XNPat GhcPs = EpAnn [AddEpAnn]
 type instance XNPat GhcRn = EpAnn [AddEpAnn]
 type instance XNPat GhcTc = Type
 
-type instance XNPlusKPat GhcPs = EpAnn [AddEpAnn]
+type instance XNPlusKPat GhcPs = EpAnn EpaLocation -- Of the "+"
 type instance XNPlusKPat GhcRn = NoExtField
 type instance XNPlusKPat GhcTc = Type
 
diff --git a/compiler/GHC/Hs/Utils.hs b/compiler/GHC/Hs/Utils.hs
index 87fc46ff12..ac73720456 100644
--- a/compiler/GHC/Hs/Utils.hs
+++ b/compiler/GHC/Hs/Utils.hs
@@ -309,7 +309,7 @@ mkHsCompAnns   :: HsDoFlavour -> [ExprLStmt GhcPs] -> LHsExpr GhcPs
 
 mkNPat      :: Located (HsOverLit GhcPs) -> Maybe (SyntaxExpr GhcPs) -> EpAnn [AddEpAnn]
             -> Pat GhcPs
-mkNPlusKPat :: LocatedN RdrName -> Located (HsOverLit GhcPs) -> EpAnn [AddEpAnn]
+mkNPlusKPat :: LocatedN RdrName -> Located (HsOverLit GhcPs) -> EpAnn EpaLocation
             -> Pat GhcPs
 
 -- NB: The following functions all use noSyntaxExpr: the generated expressions
diff --git a/compiler/GHC/Parser/Annotation.hs b/compiler/GHC/Parser/Annotation.hs
index 19925b0678..a914a14b71 100644
--- a/compiler/GHC/Parser/Annotation.hs
+++ b/compiler/GHC/Parser/Annotation.hs
@@ -13,7 +13,7 @@ module GHC.Parser.Annotation (
 
   -- * In-tree Exact Print Annotations
   AddEpAnn(..),
-  EpaLocation(..), epaLocationRealSrcSpan,
+  EpaLocation(..), epaLocationRealSrcSpan, epaLocationFromSrcAnn,
   DeltaPos(..), deltaPos, getDeltaLine,
 
   EpAnn(..), Anchor(..), AnchorOperation(..),
@@ -440,6 +440,10 @@ epaLocationRealSrcSpan :: EpaLocation -> RealSrcSpan
 epaLocationRealSrcSpan (EpaSpan r) = r
 epaLocationRealSrcSpan (EpaDelta _) = panic "epaLocationRealSrcSpan"
 
+epaLocationFromSrcAnn :: SrcAnn ann -> EpaLocation
+epaLocationFromSrcAnn (SrcSpanAnn EpAnnNotUsed l) = EpaSpan (realSrcSpan l)
+epaLocationFromSrcAnn (SrcSpanAnn (EpAnn anc _ _) _) = EpaSpan (anchor anc)
+
 instance Outputable EpaLocation where
   ppr (EpaSpan r) = text "EpaSpan" <+> ppr r
   ppr (EpaDelta d) = text "EpaDelta" <+> ppr d
diff --git a/compiler/GHC/Parser/PostProcess.hs b/compiler/GHC/Parser/PostProcess.hs
index 4eab0c1486..d1ec88f7fa 100644
--- a/compiler/GHC/Parser/PostProcess.hs
+++ b/compiler/GHC/Parser/PostProcess.hs
@@ -1146,11 +1146,12 @@ checkAPat loc e0 = do
    -- n+k patterns
    PatBuilderOpApp
            (L _ (PatBuilderVar (L nloc n)))
-           (L _ plus)
+           (L l plus)
            (L lloc (PatBuilderOverLit lit@(OverLit {ol_val = HsIntegral {}})))
-           anns
+           (EpAnn anc _ cs)
                      | nPlusKPatterns && (plus == plus_RDR)
-                     -> return (mkNPlusKPat (L nloc n) (L (locA lloc) lit) anns)
+                     -> return (mkNPlusKPat (L nloc n) (L (locA lloc) lit)
+                                (EpAnn anc (epaLocationFromSrcAnn l) cs))
 
    -- Improve error messages for the @-operator when the user meant an @-pattern
    PatBuilderOpApp _ op _ _ | opIsAt (unLoc op) -> do