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Add : to isOpSymbol (#326) #430

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Add : to isOpSymbol (#326) #430

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3 changes: 2 additions & 1 deletion src/Language/Haskell/Exts/InternalLexer.hs
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Expand Up @@ -368,8 +368,9 @@ isPragmaChar c = isAlphaNum c || c == '_'
-- Used in the lexing of type applications
-- Why is it like this? I don't know exactly but this is how it is in
-- GHC's parser.
-- Symbol `:` is added so that `@:` is lexed as `VarSym "@:"`. See Issue #326
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@autotaker autotaker Mar 12, 2019 •
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GHC's counterpart notFollowedBySymbol does not contain :.

notFollowedBySymbol :: AlexAccPred ExtsBitmap
notFollowedBySymbol _ _ _ (AI _ buf)
  = nextCharIsNot buf (`elem` "!#$%&*+./<=>?@\\^|-~")

There are two rules that matches for @: in Lexer.x.

  -- See Note [Lexing type applications]
<0> {
    [^ $idchar \) ] ^
  "@"
    / { ifExtension TypeApplicationsBit `alexAndPred` notFollowedBySymbol }
    { token ITtypeApp }
}

and

<0> {
  @varsym                                          { varsym }
  ...
}

Then, alex chooses the rule that consumes the longest prefix. Thus it is recognized as an operator "@:".

When the input stream matches more than one rule, the rule which matches the longest prefix of the input stream wins. If there are still several rules which match an equal number of characters, then the rule which appears earliest in the file wins.

(Cited from 3.2. Syntax of Alex files)

This patch may be ad-hoc. Nonetheless it is correct because isOpSymbol is only used for TypeApplications.

isOpSymbol :: Char -> Bool
isOpSymbol c = c `elem` "!#$%&*+./<=>?@\\^|-~"
isOpSymbol c = c `elem` ":!#$%&*+./<=>?@\\^|-~"

-- | Checks whether the character would be legal in some position of a qvar.
-- Means that '..' and "AAA" will pass the test.
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4 changes: 4 additions & 0 deletions tests/examples/T326.hs
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@@ -0,0 +1,4 @@
{-# LANGUAGE TypeApplications #-}
module T326 where

(@:) a b = a
1 change: 1 addition & 0 deletions tests/examples/T326.hs.exactprinter.golden
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@@ -0,0 +1 @@
Match
116 changes: 116 additions & 0 deletions tests/examples/T326.hs.parser.golden
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@@ -0,0 +1,116 @@
ParseOk
( Module
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 1 1 5 1
, srcInfoPoints =
[ SrcSpan "tests/examples/T326.hs" 1 1 1 1
, SrcSpan "tests/examples/T326.hs" 2 1 2 1
, SrcSpan "tests/examples/T326.hs" 2 1 2 1
, SrcSpan "tests/examples/T326.hs" 4 1 4 1
, SrcSpan "tests/examples/T326.hs" 5 1 5 1
, SrcSpan "tests/examples/T326.hs" 5 1 5 1
]
}
(Just
(ModuleHead
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 2 1 2 18
, srcInfoPoints =
[ SrcSpan "tests/examples/T326.hs" 2 1 2 7
, SrcSpan "tests/examples/T326.hs" 2 13 2 18
]
}
(ModuleName
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 2 8 2 12
, srcInfoPoints = []
}
"T326")
Nothing
Nothing))
[ LanguagePragma
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 1 1 1 34
, srcInfoPoints =
[ SrcSpan "tests/examples/T326.hs" 1 1 1 13
, SrcSpan "tests/examples/T326.hs" 1 31 1 34
]
}
[ Ident
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 1 14 1 30
, srcInfoPoints = []
}
"TypeApplications"
]
]
[]
[ FunBind
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 1 4 13
, srcInfoPoints = []
}
[ Match
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 1 4 13
, srcInfoPoints =
[ SrcSpan "tests/examples/T326.hs" 4 1 4 2
, SrcSpan "tests/examples/T326.hs" 4 2 4 4
, SrcSpan "tests/examples/T326.hs" 4 4 4 5
]
}
(Symbol
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 2 4 4
, srcInfoPoints = []
}
"@:")
[ PVar
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 6 4 7
, srcInfoPoints = []
}
(Ident
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 6 4 7
, srcInfoPoints = []
}
"a")
, PVar
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 8 4 9
, srcInfoPoints = []
}
(Ident
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 8 4 9
, srcInfoPoints = []
}
"b")
]
(UnGuardedRhs
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 10 4 13
, srcInfoPoints = [ SrcSpan "tests/examples/T326.hs" 4 10 4 11 ]
}
(Var
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 12 4 13
, srcInfoPoints = []
}
(UnQual
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 12 4 13
, srcInfoPoints = []
}
(Ident
SrcSpanInfo
{ srcInfoSpan = SrcSpan "tests/examples/T326.hs" 4 12 4 13
, srcInfoPoints = []
}
"a"))))
Nothing
]
]
, []
)
1 change: 1 addition & 0 deletions tests/examples/T326.hs.prettyparser.golden
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@@ -0,0 +1 @@
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3 changes: 3 additions & 0 deletions tests/examples/T326.hs.prettyprinter.golden
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@@ -0,0 +1,3 @@
{-# LANGUAGE TypeApplications #-}
module T326 where
(@:) a b = a