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 =

12 go

13 where

14 errorMessage x =

15 "Syntax Error: The type annotation for '" ++ x ++

16 "' must be directly above its definition."

18 exprCombineAnnotations =

19 Expr.crawlLet combineAnnotations

21 go defs =

22 case defs of

23 Source.TypeAnnotation name tipe : rest ->

24 case rest of

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

26 | name == name' ->

27 do expr' <- exprCombineAnnotations expr

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

29 (:) def <$> go rest'

31 _ ->

32 Left (errorMessage name)

34 Source.Definition pat expr : rest ->

35 do expr' <- exprCombineAnnotations expr

36 let def = Valid.Definition pat expr' Nothing

37 (:) def <$> go rest

39 [] ->

40 return []