src/Transform/Definition.hs · elk

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elk/src/Transform/Definition.hs

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1{-# OPTIONS_GHC -Wall #-}

2module Transform.Definition where

4import Control.Applicative ((<$>))

5import qualified AST.Pattern as P

6import qualified AST.Expression.Source as Source

7import qualified AST.Expression.Valid as Valid

8import qualified Transform.Expression as Expr

10combineAnnotations :: [Source.Def] -> Either String [Valid.Def]

11combineAnnotations = go

12 where

13 msg x = "Syntax Error: The type annotation for '" ++ x ++

14 "' must be directly above its definition."

16 exprCombineAnnotations = Expr.crawlLet combineAnnotations

18 go defs =

19 case defs of

20 Source.TypeAnnotation name tipe : rest ->

21 case rest of

22 Source.Definition pat@(P.Var name') expr : rest'

23 | name == name' ->

24 do expr' <- exprCombineAnnotations expr

25 let def = Valid.Definition pat expr' (Just tipe)

26 (:) def <$> go rest'

28 _ -> Left (msg name)

30 Source.Definition pat expr : rest ->

31 do expr' <- exprCombineAnnotations expr

32 let def = Valid.Definition pat expr' Nothing

33 (:) def <$> go rest

35 [] -> return []