54 lines
1.9 KiB
Haskell
54 lines
1.9 KiB
Haskell
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module Dhall.LSP.Backend.Parsing (getLetInner, getLetAnnot) where
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import Dhall.Src (Src(..))
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import Dhall.Parser
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import Dhall.Parser.Token
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import Dhall.Parser.Expression
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import Control.Applicative (optional)
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import qualified Text.Megaparsec as Megaparsec
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import Text.Megaparsec (SourcePos(..))
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-- | Parse the outermost binding in a Src descriptor of a let-block and return
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-- the rest. Ex. on input `let a = 0 let b = a in b` parses `let a = 0 ` and
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-- returns the Src descriptor containing `let b = a in b`.
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getLetInner :: Src -> Maybe Src
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getLetInner (Src left _ text) = Megaparsec.parseMaybe (unParser parseLetInnerOffset) text
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where parseLetInnerOffset = do
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setSourcePos left
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_let
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_ <- label
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_ <- optional (do
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_ <- _colon
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expr)
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_equal
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_ <- expr
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_ <- optional _in
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begin <- getSourcePos
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tokens <- Megaparsec.takeRest
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end <- getSourcePos
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return (Src begin end tokens)
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-- | Given an Src of a let expression return the Src containing the type
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-- annotation. If the let expression does not have a type annotation return
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-- a 0-length Src where we can insert one.
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getLetAnnot :: Src -> Maybe Src
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getLetAnnot (Src left _ text) = Megaparsec.parseMaybe (unParser parseLetAnnot) text
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where parseLetAnnot = do
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setSourcePos left
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_let
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_ <- label
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begin <- getSourcePos
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(tokens, _) <- Megaparsec.match $ optional (do
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_ <- _colon
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expr)
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end <- getSourcePos
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_ <- Megaparsec.takeRest
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return (Src begin end tokens)
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setSourcePos :: SourcePos -> Parser ()
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setSourcePos src = Megaparsec.updateParserState
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(\(Megaparsec.State s o (Megaparsec.PosState i o' _ t l)) ->
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Megaparsec.State s o (Megaparsec.PosState i o' src t l))
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