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Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC

Commits:

639456a8

by Evgeny Malyshev at 2026-09-04T08:09:25-04:00

HsPat: Add spacing to unary tuple patterns

Use hsep when printing unary boxed TuplePat applications so that the
MkSolo constructor is separated from its argument. The old hcat rendered
wildcard and parenthesized arguments as MkSolo_ and MkSolo().

Add T27034 to exercise the HsPat splice-dump path with wildcard and
variable arguments, and update existing affected golden output.

Fixes #27034

Assisted-By: OpenAI Codex

7 changed files:

compiler/GHC/Hs/Pat.hs
testsuite/tests/th/T17380.stderr
testsuite/tests/th/T18612.stderr
+ testsuite/tests/th/T27034.hs
+ testsuite/tests/th/T27034.stderr
testsuite/tests/th/T8761.stderr
testsuite/tests/th/all.T

Changes:

compiler/GHC/Hs/Pat.hs

@@ -443,7 +443,7 @@ pprPat (TuplePat _ pats bx)
      -- `MkSolo x`, not `(x)`
    | [pat] <- pats
    , Boxed <- bx
 -  = hcat [text (mkTupleStr Boxed dataName 1), pprParendLPat appPrec pat]
 +  = hsep [text (mkTupleStr Boxed dataName 1), pprParendLPat appPrec pat]
    | otherwise
    = tupleParens (boxityTupleSort bx) (pprWithCommas ppr pats)
  pprPat (SumPat _ pat alt arity) = sumParens (pprAlternative ppr pat alt arity)

testsuite/tests/th/T17380.stderr

@@ -19,8 +19,8 @@ T17380.hs:15:6: error: [GHC-83865]
  T17380.hs:18:7: error: [GHC-83865]
      • Couldn't match expected type: Maybe String
                    with actual type: Solo (Maybe String)
 -    • In the pattern: MkSolo(Just "wat")
 -      In an equation for ‘quux’: quux (MkSolo(Just "wat")) = Just "frerf"
 +    • In the pattern: MkSolo (Just "wat")
 +      In an equation for ‘quux’: quux (MkSolo (Just "wat")) = Just "frerf"
  T17380.hs:21:8: error: [GHC-83865]
      • Couldn't match type: Maybe String

testsuite/tests/th/T18612.stderr

@@ -8,6 +8,6 @@ T18612.hs:(10,7)-(11,75): Splicing type
    ======>
      Identity (Solo ()) -> Identity (Solo ())
  T18612.hs:12:4-36: Splicing pattern
 -    conP 'Identity [tupP [tupP []]] ======> Identity (MkSolo())
 +    conP 'Identity [tupP [tupP []]] ======> Identity (MkSolo ())
  T18612.hs:12:41-78: Splicing expression
      conE 'Identity `appE` tupE [tupE []] ======> Identity (MkSolo ())

testsuite/tests/th/T27034.hs

 +{-# LANGUAGE TemplateHaskell #-}
 +module T27034 where
++
 +import Language.Haskell.TH
++
 +f $(tupP [wildP]) = ()
 +g $(tupP [varP (mkName "x")]) = x

testsuite/tests/th/T27034.stderr

 +T27034.hs:6:4-17: Splicing pattern
 +    tupP [wildP] ======> MkSolo _
 +T27034.hs:7:4-29: Splicing pattern
 +    tupP [varP (mkName "x")] ======> MkSolo x

testsuite/tests/th/T8761.stderr

@@ -28,7 +28,7 @@ T8761.hs:(16,1)-(39,13): Splicing declarations
         return pats
    ======>
      pattern Q1 x1 x2 x3 <- ((x1, x2), [x3], _, _)
 -    pattern x1 `Q2` x2 = MkSolo(x1, x2)
 +    pattern x1 `Q2` x2 = MkSolo (x1, x2)
      pattern Q3{qx3, qy3, qz3} <- ((qx3, qy3), [qz3]) where
                                  Q3 qx3 qy3 qz3 = ((qx3, qy3), [qz3])
  T8761.hs:(42,1)-(46,29): Splicing declarations

testsuite/tests/th/all.T

@@ -655,6 +655,7 @@ test('T26099', normal, compile_fail, [''])
  test('T8306_th', only_ways(['ghci']), ghci_script, ['T8306_th.script'])
  test('T26862_th', only_ways(['ghci']), ghci_script, ['T26862_th.script'])
  test('T27022', normal, compile_and_run, [''])
 +test('T27034', normal, compile, ['-v0 -ddump-splices -dsuppress-uniques'])
  test('T20902', normal, compile, [''])
  test('TH_cvt_DefaultDataInstDecl', normal, compile_fail, ['-v0'])
  test('TH_cvt_IllegalDeclaration', normal, compile_fail, ['-v0'])