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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2015-02-06 14:48:33 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2015-02-06 14:48:33 +0000 |
| commit | 111e5870803bcccd1c0736fdba432f8f9410454f (patch) | |
| tree | 583acc8e1cab7b76eef6f4fe8ac7a14e18e4cd71 /libraries/template-haskell/Language/Haskell/TH | |
| parent | da78af367dfa5050c2c19b758ab046218ee4dd91 (diff) | |
| download | haskell-111e5870803bcccd1c0736fdba432f8f9410454f.tar.gz | |
Put parens around (ty :: kind) when pretty-printing TH syntax
See Note [Pretty-printing kind signatures] in Language.Haskell.TH.Ppr.hs,
and Trac #10050.
Diffstat (limited to 'libraries/template-haskell/Language/Haskell/TH')
| -rw-r--r-- | libraries/template-haskell/Language/Haskell/TH/Ppr.hs | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/libraries/template-haskell/Language/Haskell/TH/Ppr.hs b/libraries/template-haskell/Language/Haskell/TH/Ppr.hs index 4ba43f3973..e5cab65185 100644 --- a/libraries/template-haskell/Language/Haskell/TH/Ppr.hs +++ b/libraries/template-haskell/Language/Haskell/TH/Ppr.hs @@ -498,14 +498,25 @@ pprParendType PromotedNilT = text "'[]" pprParendType PromotedConsT = text "(':)" pprParendType StarT = char '*' pprParendType ConstraintT = text "Constraint" +pprParendType (SigT ty k) = parens (ppr ty <+> text "::" <+> ppr k) pprParendType other = parens (ppr other) instance Ppr Type where ppr (ForallT tvars ctxt ty) = text "forall" <+> hsep (map ppr tvars) <+> text "." <+> sep [pprCxt ctxt, ppr ty] - ppr (SigT ty k) = ppr ty <+> text "::" <+> ppr k - ppr ty = pprTyApp (split ty) + ppr ty = pprTyApp (split ty) + -- Works, in a degnerate way, for SigT, and puts parens round (ty :: kind) + -- See Note [Pretty-printing kind signatures] + +{- Note [Pretty-printing kind signatures] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +GHC's parser only recognises a kind signature in a type when there are +parens around it. E.g. the parens are required here: + f :: (Int :: *) + type instance F Int = (Bool :: *) +So we always print a SigT with parens (see Trac #10050). -} + pprTyApp :: (Type, [Type]) -> Doc pprTyApp (ArrowT, [arg1,arg2]) = sep [pprFunArgType arg1 <+> text "->", ppr arg2] |