[Git][ghc/ghc][master] Refactor the parser a little
Marge Bot
gitlab at gitlab.haskell.org
Mon Jul 27 11:08:13 UTC 2020
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
6ff89c17 by Vladislav Zavialov at 2020-07-27T07:08:07-04:00
Refactor the parser a little
* Create a dedicated production for type operators
* Create a dedicated type for the UNPACK pragma
* Remove an outdated part of Note [Parsing data constructors is hard]
- - - - -
2 changed files:
- compiler/GHC/Parser.y
- compiler/GHC/Parser/PostProcess.hs
Changes:
=====================================
compiler/GHC/Parser.y
=====================================
@@ -1884,9 +1884,9 @@ sigtypes1 :: { (OrdList (LHsSigType GhcPs)) }
-----------------------------------------------------------------------------
-- Types
-unpackedness :: { Located ([AddAnn], SourceText, SrcUnpackedness) }
- : '{-# UNPACK' '#-}' { sLL $1 $> ([mo $1, mc $2], getUNPACK_PRAGs $1, SrcUnpack) }
- | '{-# NOUNPACK' '#-}' { sLL $1 $> ([mo $1, mc $2], getNOUNPACK_PRAGs $1, SrcNoUnpack) }
+unpackedness :: { Located UnpackednessPragma }
+ : '{-# UNPACK' '#-}' { sLL $1 $> (UnpackednessPragma [mo $1, mc $2] (getUNPACK_PRAGs $1) SrcUnpack) }
+ | '{-# NOUNPACK' '#-}' { sLL $1 $> (UnpackednessPragma [mo $1, mc $2] (getNOUNPACK_PRAGs $1) SrcNoUnpack) }
forall_telescope :: { Located ([AddAnn], HsForAllTelescope GhcPs) }
: 'forall' tv_bndrs '.' {% do { hintExplicitForall $1
@@ -1980,13 +1980,16 @@ tyapp :: { Located TyEl }
-- See Note [Whitespace-sensitive operator parsing] in GHC.Parser.Lexer
| PREFIX_AT atype { sLL $1 $> $ (TyElKindApp (comb2 $1 $2) $2) }
- | qtyconop { sL1 $1 $ TyElOpr (unLoc $1) }
- | tyvarop { sL1 $1 $ TyElOpr (unLoc $1) }
- | SIMPLEQUOTE qconop {% ams (sLL $1 $> $ TyElOpr (unLoc $2))
+ | tyop { mapLoc TyElOpr $1 }
+ | unpackedness { sL1 $1 $ TyElUnpackedness (unLoc $1) }
+
+tyop :: { Located RdrName }
+ : qtyconop { $1 }
+ | tyvarop { $1 }
+ | SIMPLEQUOTE qconop {% ams (sLL $1 $> (unLoc $2))
[mj AnnSimpleQuote $1,mj AnnVal $2] }
- | SIMPLEQUOTE varop {% ams (sLL $1 $> $ TyElOpr (unLoc $2))
+ | SIMPLEQUOTE varop {% ams (sLL $1 $> (unLoc $2))
[mj AnnSimpleQuote $1,mj AnnVal $2] }
- | unpackedness { sL1 $1 $ TyElUnpackedness (unLoc $1) }
atype :: { LHsType GhcPs }
: ntgtycon { sL1 $1 (HsTyVar noExtField NotPromoted $1) } -- Not including unit tuples
=====================================
compiler/GHC/Parser/PostProcess.hs
=====================================
@@ -70,6 +70,7 @@ module GHC.Parser.PostProcess (
addFatalError, hintBangPat,
TyEl(..), mergeOps, mergeDataCon,
mkBangTy,
+ UnpackednessPragma(..),
-- Help with processing exports
ImpExpSubSpec(..),
@@ -559,25 +560,6 @@ As the result, in order to determine whether (C t1 t2) declares a data
constructor, a type, or a context, we would need unlimited lookahead which
'happy' is not so happy with.
-To further complicate matters, the interpretation of (!) and (~) is different
-in constructors and types:
-
- (b1) type T = C ! D
- (b2) data T = C ! D
- (b3) data T = C ! D => E
-
-In (b1) and (b3), (!) is a type operator with two arguments: 'C' and 'D'. At
-the same time, in (b2) it is a strictness annotation: 'C' is a data constructor
-with a single strict argument 'D'. For the programmer, these cases are usually
-easy to tell apart due to whitespace conventions:
-
- (b2) data T = C !D -- no space after the bang hints that
- -- it is a strictness annotation
-
-For the parser, on the other hand, this whitespace does not matter. We cannot
-tell apart (b2) from (b3) until we encounter (=>), so it requires unlimited
-lookahead.
-
The solution that accounts for all of these issues is to initially parse data
declarations and types as a reversed list of TyEl:
@@ -1324,7 +1306,7 @@ isFunLhs e = go e [] []
data TyEl = TyElOpr RdrName | TyElOpd (HsType GhcPs)
| TyElKindApp SrcSpan (LHsType GhcPs)
-- See Note [TyElKindApp SrcSpan interpretation]
- | TyElUnpackedness ([AddAnn], SourceText, SrcUnpackedness)
+ | TyElUnpackedness UnpackednessPragma
{- Note [TyElKindApp SrcSpan interpretation]
@@ -1345,20 +1327,15 @@ instance Outputable TyEl where
ppr (TyElOpr name) = ppr name
ppr (TyElOpd ty) = ppr ty
ppr (TyElKindApp _ ki) = text "@" <> ppr ki
- ppr (TyElUnpackedness (_, _, unpk)) = ppr unpk
+ ppr (TyElUnpackedness (UnpackednessPragma _ _ unpk)) = ppr unpk
-- | Extract a strictness/unpackedness annotation from the front of a reversed
-- 'TyEl' list.
pUnpackedness
:: [Located TyEl] -- reversed TyEl
- -> Maybe ( SrcSpan
- , [AddAnn]
- , SourceText
- , SrcUnpackedness
- , [Located TyEl] {- remaining TyEl -})
-pUnpackedness (L l x1 : xs)
- | TyElUnpackedness (anns, prag, unpk) <- x1
- = Just (l, anns, prag, unpk, xs)
+ -> Maybe (SrcSpan, UnpackednessPragma,
+ [Located TyEl] {- remaining TyEl -})
+pUnpackedness (L l x1 : xs) | TyElUnpackedness up <- x1 = Just (l, up, xs)
pUnpackedness _ = Nothing
pBangTy
@@ -1371,7 +1348,7 @@ pBangTy
pBangTy lt@(L l1 _) xs =
case pUnpackedness xs of
Nothing -> (False, lt, pure (), xs)
- Just (l2, anns, prag, unpk, xs') ->
+ Just (l2, UnpackednessPragma anns prag unpk, xs') ->
let bl = combineSrcSpans l1 l2
bt = addUnpackedness (prag, unpk) lt
in (True, L bl bt, addAnnsAt bl anns, xs')
@@ -1380,6 +1357,10 @@ mkBangTy :: SrcStrictness -> LHsType GhcPs -> HsType GhcPs
mkBangTy strictness =
HsBangTy noExtField (HsSrcBang NoSourceText NoSrcUnpack strictness)
+-- Result of parsing {-# UNPACK #-} or {-# NOUNPACK #-}
+data UnpackednessPragma =
+ UnpackednessPragma [AddAnn] SourceText SrcUnpackedness
+
addUnpackedness :: (SourceText, SrcUnpackedness) -> LHsType GhcPs -> HsType GhcPs
addUnpackedness (prag, unpk) (L _ (HsBangTy x bang t))
| HsSrcBang NoSourceText NoSrcUnpack strictness <- bang
@@ -1411,7 +1392,7 @@ mergeOps all_xs = go (0 :: Int) [] id all_xs
-- clause [unpk]:
-- handle (NO)UNPACK pragmas
- go k acc ops_acc ((L l (TyElUnpackedness (anns, unpkSrc, unpk))):xs) =
+ go k acc ops_acc ((L l (TyElUnpackedness (UnpackednessPragma anns unpkSrc unpk))):xs) =
if not (null acc) && null xs
then do { acc' <- eitherToP $ mergeOpsAcc acc
; let a = ops_acc acc'
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6ff89c173f39813f74d7bbf95770c5e40039f155
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6ff89c173f39813f74d7bbf95770c5e40039f155
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