-- |

module Language.PureScript.Linter (lint, module L) where

import Prelude.Compat

import Control.Monad.Writer.Class

import Data.List (nub, (\\))

import Data.Maybe (mapMaybe)

import Data.Monoid

import qualified Data.Set as S

import Data.Text (Text)

import Language.PureScript.AST

import Language.PureScript.Crash

import Language.PureScript.Errors

import Language.PureScript.Linter.Exhaustive as L

import Language.PureScript.Linter.Imports as L

import Language.PureScript.Names

import Language.PureScript.Types

-- | Lint the PureScript AST.

lint :: forall m. (MonadWriter MultipleErrors m) => Module -> m ()

lint (Module _ _ mn ds _) = censor (addHint (ErrorInModule mn)) $ mapM_ lintDeclaration ds

where

moduleNames :: S.Set Ident

moduleNames = S.fromList (nub (mapMaybe getDeclIdent ds))

getDeclIdent :: Declaration -> Maybe Ident

getDeclIdent (PositionedDeclaration _ _ d) = getDeclIdent d

getDeclIdent (ValueDeclaration ident _ _ _) = Just ident

getDeclIdent (ExternDeclaration ident _) = Just ident

getDeclIdent (TypeInstanceDeclaration ident _ _ _ _) = Just ident

getDeclIdent (BindingGroupDeclaration _) = internalError "lint: binding groups should not be desugared yet."

getDeclIdent _ = Nothing

lintDeclaration :: Declaration -> m ()

lintDeclaration = tell . f

where

(warningsInDecl, _, _, _, _) = everythingWithScope (\_ _ -> mempty) stepE stepB (\_ _ -> mempty) stepDo

f :: Declaration -> MultipleErrors

f (PositionedDeclaration pos _ dec) = addHint (PositionedError pos) (f dec)

f (TypeClassDeclaration name args _ _ decs) = addHint (ErrorInTypeClassDeclaration name) (foldMap (f' (S.fromList $ fst <$> args)) decs)

f dec = f' S.empty dec

f' :: S.Set Text -> Declaration -> MultipleErrors

f' s (PositionedDeclaration pos _ dec) = addHint (PositionedError pos) (f' s dec)

f' s dec@(ValueDeclaration name _ _ _) = addHint (ErrorInValueDeclaration name) (warningsInDecl moduleNames dec <> checkTypeVarsInDecl s dec)

f' s (TypeDeclaration name ty) = addHint (ErrorInTypeDeclaration name) (checkTypeVars s ty)

f' s dec = warningsInDecl moduleNames dec <> checkTypeVarsInDecl s dec

stepE :: S.Set Ident -> Expr -> MultipleErrors

stepE s (Abs (Left name) _) | name `S.member` s = errorMessage (ShadowedName name)

stepE s (Let ds' _) = foldMap go ds'

where

go d | Just i <- getDeclIdent d

, i `S.member` s = errorMessage (ShadowedName i)

| otherwise = mempty

stepE _ _ = mempty

stepB :: S.Set Ident -> Binder -> MultipleErrors

stepB s (VarBinder name) | name `S.member` s = errorMessage (ShadowedName name)

stepB s (NamedBinder name _) | name `S.member` s = errorMessage (ShadowedName name)

stepB _ _ = mempty

stepDo :: S.Set Ident -> DoNotationElement -> MultipleErrors

stepDo s (DoNotationLet ds') = foldMap go ds'

where

go d | Just i <- getDeclIdent d

, i `S.member` s = errorMessage (ShadowedName i)

| otherwise = mempty

stepDo _ _ = mempty

checkTypeVarsInDecl :: S.Set Text -> Declaration -> MultipleErrors

checkTypeVarsInDecl s d = let (f, _, _, _, _) = accumTypes (checkTypeVars s) in f d

checkTypeVars :: S.Set Text -> Type -> MultipleErrors

checkTypeVars set ty = everythingWithContextOnTypes set mempty mappend step ty <> findUnused ty

where

step :: S.Set Text -> Type -> (S.Set Text, MultipleErrors)

step s (ForAll tv _ _) = bindVar s tv

step s _ = (s, mempty)

bindVar :: S.Set Text -> Text -> (S.Set Text, MultipleErrors)

bindVar = bind ShadowedTypeVar

findUnused :: Type -> MultipleErrors

findUnused ty' =

let used = usedTypeVariables ty'

declared = everythingOnTypes (++) go ty'

unused = nub declared \\ nub used

in foldl (<>) mempty $ map (errorMessage . UnusedTypeVar) unused

where

go :: Type -> [Text]

go (ForAll tv _ _) = [tv]

go _ = []

bind :: (Ord a) => (a -> SimpleErrorMessage) -> S.Set a -> a -> (S.Set a, MultipleErrors)

bind mkError s name | name `S.member` s = (s, errorMessage (mkError name))

| otherwise = (S.insert name s, mempty)