infer letrec expressions

small

.ghci

@@ -0,0 +1,18 @@
+:set -XOverloadedStrings
+
+:set -package process
+
+:{
+import System.Exit qualified
+import System.Process qualified
+
+_reload_and_make _ = do
+    p <- System.Process.spawnCommand "make -f Makefile_happysrcs"
+    r <- System.Process.waitForProcess p
+    case r of
+        System.Exit.ExitSuccess -> pure ":reload"
+        _                       -> pure ""
+:}
+
+:def! r _reload_and_make
+

Makefile_happysrcs

@@ -0,0 +1,25 @@
+HAPPY = happy
+HAPPY_OPTS = -a -g -c
+ALEX = alex
+ALEX_OPTS = -g
+
+SRC = src
+CABAL_BUILD = dist-newstyle/build/x86_64-osx/ghc-9.6.2/rlp-0.1.0.0/build
+
+all: parsers lexers
+
+parsers: $(CABAL_BUILD)/Rlp/Parse.hs $(CABAL_BUILD)/Core/Parse.hs
+lexers: $(CABAL_BUILD)/Rlp/Lex.hs $(CABAL_BUILD)/Core/Lex.hs
+
+$(CABAL_BUILD)/Rlp/Parse.hs: $(SRC)/Rlp/Parse.y
+	$(HAPPY) $(HAPPY_OPTS) $< -o $@
+
+$(CABAL_BUILD)/Rlp/Lex.hs: $(SRC)/Rlp/Lex.x
+	$(ALEX) $(ALEX_OPTS) $< -o $@
+
+$(CABAL_BUILD)/Core/Parse.hs: $(SRC)/Core/Parse.y
+	$(HAPPY) $(HAPPY_OPTS) $< -o $@
+
+$(CABAL_BUILD)/Core/Lex.hs: $(SRC)/Core/Lex.x
+	$(ALEX) $(ALEX_OPTS) $< -o $@
+

doc/src/conf.py

@@ -32,6 +32,7 @@ html_theme = 'alabaster'
 imgmath_latex_preamble = r'''
 \usepackage{amsmath}
 \usepackage{tabularray}
+\usepackage{syntax}
 
 \newcommand{\transrule}[2]
     {\begin{tblr}{|rrrlc|}

doc/src/references/rlp-grammar.rst

@@ -0,0 +1,67 @@
+The Complete Syntax of rl'
+==========================
+
+WIP.
+
+Provided is the complete syntax of rl' in (pseudo) EBNF. {A} represents zero or
+more A's, [A] means optional A, and terminals are wrapped in 'single-quotes'.
+
+.. math
+   :nowrap:
+
+   \setlength{\grammarparsep}{20pt plus 1pt minus 1pt}
+   \setlength{\grammarindent}{12em}
+   \begin{grammar}
+       <Decl> ::= <InfixDecl>
+       \alt <DataDecl>
+       \alt <TypeSig>
+       \alt <FunDef>
+
+       <InfixDecl> ::= <InfixWord> `litint' <Name>
+       <InfixWord> ::= `infix'
+       \alt `infixl'
+       \alt `infixr'
+
+       <DataDecl> ::= `data' `conname' {}
+
+   \end{grammar}
+
+.. code-block:: bnf
+
+   Decl      ::= InfixDecl
+               | DataDecl
+               | TypeSig
+               | FunDef
+
+   InfixDecl ::= InfixWord 'litint' Operator
+   InfixWord ::= 'infix'
+               | 'infixl'
+               | 'infixr'
+
+   DataDecl  ::= 'data' 'conname' {'name'} '=' Data
+   DataCons  ::= 'conname' {Type1} ['|' DataCons]
+
+   TypeSig   ::= Var '::' Type
+   FunDef    ::= Var {Pat1} '=' Expr
+
+   Type      ::= Type1 {Type1}
+               -- note that (->) is right-associative,
+               -- and extends as far as possible
+               | Type '->' Type
+   Type1     ::= '(' Type ')'
+               | 'conname'
+
+   Pat       ::= 'conname' Pat1 {Pat1}
+               | Pat 'consym' Pat
+
+   Pat1      ::= Literal
+               | 'conname'
+               | '(' Pat ')'
+
+   Literal   ::= 'litint'
+
+   Var ::= 'varname'
+         | '(' 'varsym' ')'
+   Con ::= 'conname'
+         | '(' 'consym' ')'
+

rlp.cabal

@@ -12,6 +12,7 @@ category:           Language
 build-type:         Simple
 extra-doc-files:    README.md
 -- extra-source-files:
+tested-with:        GHC==9.6.2
 
 common warnings
 --    ghc-options: -Wall -Wno-incomplete-uni-patterns -Wno-unused-top-binds
@@ -30,6 +31,12 @@ library
                     , Core.TH
                     , Core.HindleyMilner
                     , Control.Monad.Errorful
+                    , Rlp.Syntax
+                    -- , Rlp.Parse.Decls
+                    , Rlp.Parse
+                    , Rlp.Parse.Associate
+                    , Rlp.Lex
+                    , Rlp.Parse.Types
 
     other-modules:    Data.Heap
                     , Data.Pretty
@@ -37,34 +44,38 @@ library
                     , Core.Lex
                     , Core2Core
                     , Control.Monad.Utils
-                    , RLP.Syntax
 
     build-tool-depends: happy:happy, alex:alex
 
     -- other-extensions:
     build-depends:    base ^>=4.18.0.0
-                    , containers
-                    , microlens
-                    , microlens-mtl
-                    , microlens-th
-                    , microlens-platform
-                    , mtl
-                    , template-haskell
                     -- required for happy
-                    , array
-                    , data-default-class
-                    , unordered-containers
-                    , hashable
-                    , pretty
-                    -- TODO: either learn recursion-schemes, or stop depending
-                    -- on it.
-                    , recursion-schemes
-                    , megaparsec
-                    , text
+                    , array >= 0.5.5 && < 0.6
+                    , containers >= 0.6.7 && < 0.7
+                    , template-haskell >= 2.20.0 && < 2.21
+                    , pretty >= 1.1.3 && < 1.2
+                    , data-default >= 0.7.1 && < 0.8
+                    , data-default-class >= 0.1.2 && < 0.2
+                    , hashable >= 1.4.3 && < 1.5
+                    , mtl >= 2.3.1 && < 2.4
+                    , text >= 2.0.2 && < 2.1
+                    , megaparsec >= 9.6.1 && < 9.7
+                    , microlens >= 0.4.13 && < 0.5
+                    , microlens-mtl >= 0.2.0 && < 0.3
+                    , microlens-platform >= 0.4.3 && < 0.5
+                    , microlens-th >= 0.4.3 && < 0.5
+                    , unordered-containers >= 0.2.20 && < 0.3
+                    , recursion-schemes >= 5.2.2 && < 5.3
+                    , data-fix >= 0.3.2 && < 0.4
+                    , utf8-string >= 1.0.2 && < 1.1
+                    , extra >= 1.7.0 && < 2
 
     hs-source-dirs:   src
     default-language: GHC2021
 
+    default-extensions:
+        OverloadedStrings
+
 executable rlpc
     import:           warnings
     main-is:          Main.hs
@@ -72,12 +83,12 @@ executable rlpc
     -- other-extensions:
     build-depends: base ^>=4.18.0.0
                  , rlp
-                 , optparse-applicative
-                 , microlens
-                 , microlens-mtl
-                 , mtl
-                 , unordered-containers
-                 , text
+                 , optparse-applicative >= 0.18.1 && < 0.19
+                 , microlens >= 0.4.13 && < 0.5
+                 , microlens-mtl >= 0.2.0 && < 0.3
+                 , mtl >= 2.3.1 && < 2.4
+                 , unordered-containers >= 0.2.20 && < 0.3
+                 , text >= 2.0.2 && < 2.1
 
     hs-source-dirs:   app
     default-language: GHC2021

src/Compiler/JustRun.hs

@@ -26,21 +26,23 @@ import Data.Function                    ((&))
 import GM
 ----------------------------------------------------------------------------------
 
-justLexSrc :: String -> Either RlpcError [CoreToken]
+justLexSrc :: String -> Either [MsgEnvelope RlpcError] [CoreToken]
 justLexSrc s = lexCoreR (T.pack s)
              & fmap (map $ \ (Located _ _ _ t) -> t)
              & rlpcToEither
 
-justParseSrc :: String -> Either RlpcError Program'
+justParseSrc :: String -> Either [MsgEnvelope RlpcError] Program'
 justParseSrc s = parse (T.pack s)
                & rlpcToEither
     where parse = lexCoreR >=> parseCoreProgR
 
-justTypeCheckSrc :: String -> Either RlpcError Program'
+justTypeCheckSrc :: String -> Either [MsgEnvelope RlpcError] Program'
 justTypeCheckSrc s = typechk (T.pack s)
                    & rlpcToEither
     where typechk = lexCoreR >=> parseCoreProgR >=> checkCoreProgR
 
-rlpcToEither :: RLPC e a -> Either e a
-rlpcToEither = evalRLPC def >>> fmap fst
+rlpcToEither :: RLPC a -> Either [MsgEnvelope RlpcError] a
+rlpcToEither r = case evalRLPC def r of
+    (Just a,   _) -> Right a
+    (Nothing, es) -> Left es
 

src/Compiler/RLPC.hs

@@ -16,9 +16,9 @@ module Compiler.RLPC
     , RLPCT(..)
     , RLPCIO
     , RLPCOptions(RLPCOptions)
-    , RlpcError(..)
     , IsRlpcError(..)
-    , rlpc
+    , RlpcError(..)
+    , MsgEnvelope(..)
     , addFatal
     , addWound
     , MonadErrorful
@@ -27,9 +27,6 @@ module Compiler.RLPC
     , evalRLPCT
     , evalRLPCIO
     , evalRLPC
-    , addRlpcWound
-    , addRlpcFatal
-    , liftRlpcErrs
     , rlpcLogFile
     , rlpcDebugOpts
     , rlpcEvaluator
@@ -40,6 +37,7 @@ module Compiler.RLPC
     , flagDDumpOpts
     , flagDDumpAST
     , def
+    , liftErrorful
     )
     where
 ----------------------------------------------------------------------------------
@@ -51,6 +49,7 @@ import Control.Monad.Errorful
 import Compiler.RlpcError
 import Data.Functor.Identity
 import Data.Default.Class
+import Data.Foldable
 import GHC.Generics             (Generic)
 import Data.Hashable            (Hashable)
 import Data.HashSet             (HashSet)
@@ -58,48 +57,44 @@ import Data.HashSet             qualified as S
 import Data.Coerce
 import Lens.Micro
 import Lens.Micro.TH
+import System.Exit
 ----------------------------------------------------------------------------------
 
--- TODO: fancy errors
-newtype RLPCT e m a = RLPCT {
-        runRLPCT :: ReaderT RLPCOptions (ErrorfulT e m) a
+newtype RLPCT m a = RLPCT {
+        runRLPCT :: ReaderT RLPCOptions (ErrorfulT (MsgEnvelope RlpcError) m) a
     }
-    -- TODO: incorrect ussage of MonadReader. RLPC should have its own
-    -- environment access functions
-    deriving (Functor, Applicative, Monad, MonadReader RLPCOptions)
+    deriving (Functor, Applicative, Monad)
 
-deriving instance (MonadIO m) => MonadIO (RLPCT e m)
+type RLPC = RLPCT Identity
 
-instance MonadTrans (RLPCT e) where
-    lift = RLPCT . lift . lift
-
-instance (MonadState s m) => MonadState s (RLPCT e m) where
-    state = lift . state
-
-type RLPC e = RLPCT e Identity
-
-type RLPCIO e = RLPCT e IO
-
-evalRLPCT :: RLPCOptions
-          -> RLPCT e m a
-          -> m (Either e (a, [e]))
-evalRLPCT o = runRLPCT >>> flip runReaderT o >>> runErrorfulT
+type RLPCIO = RLPCT IO
 
 evalRLPC :: RLPCOptions
-         -> RLPC e a
-         -> Either e (a, [e])
-evalRLPC o m = coerce $ evalRLPCT o m
+         -> RLPC a
+         -> (Maybe a, [MsgEnvelope RlpcError])
+evalRLPC opt r = runRLPCT r
+               & flip runReaderT opt
+               & runErrorful
 
-evalRLPCIO :: (Exception e)
+evalRLPCT :: (Monad m)
           => RLPCOptions
-           -> RLPCIO e a
-           -> IO (a, [e])
-evalRLPCIO o m = do
-    m' <- evalRLPCT o m
-    case m' of
-        -- TODO: errors
-        Left e -> throwIO e
-        Right a -> pure a
+          -> RLPCT m a
+          -> m (Maybe a, [MsgEnvelope RlpcError])
+evalRLPCT = undefined
+
+evalRLPCIO :: RLPCOptions -> RLPCIO a -> IO a
+evalRLPCIO opt r = do
+    (ma,es) <- evalRLPCT opt r
+    putRlpcErrs es
+    case ma of
+        Just x  -> pure x
+        Nothing -> die "Failed, no code compiled."
+
+putRlpcErrs :: [MsgEnvelope RlpcError] -> IO ()
+putRlpcErrs = traverse_ print
+
+liftErrorful :: (Monad m, IsRlpcError e) => ErrorfulT (MsgEnvelope e) m a -> RLPCT m a
+liftErrorful e = RLPCT $ lift (fmap liftRlpcError `mapErrorful` e)
 
 data RLPCOptions = RLPCOptions
     { _rlpcLogFile     :: Maybe FilePath
@@ -113,32 +108,6 @@ data RLPCOptions = RLPCOptions
 data Evaluator = EvaluatorGM | EvaluatorTI
     deriving Show
 
-data Severity = Error
-              | Warning
-              | Debug
-              deriving Show
-
--- temporary until we have a new doc building system
-type ErrorDoc = String
-
-instance (Monad m) => MonadErrorful e (RLPCT e m) where
-    addWound = RLPCT . lift . addWound
-    addFatal = RLPCT . lift . addFatal
-
-liftRlpcErrs :: (IsRlpcError e, Monad m)
-             => RLPCT e m a -> RLPCT RlpcError m a
-liftRlpcErrs m = RLPCT . ReaderT $ \r ->
-    mapErrors liftRlpcErr $ runRLPCT >>> (`runReaderT` r) $ m
-
-addRlpcWound :: (IsRlpcError e, Monad m) => e -> RLPCT RlpcError m ()
-addRlpcWound = addWound . liftRlpcErr
-
-addRlpcFatal :: (IsRlpcError e, Monad m) => e -> RLPCT RlpcError m ()
-addRlpcFatal = addWound . liftRlpcErr
-
-rlpc :: (Monad m) => ErrorfulT e m a -> RLPCT e m a
-rlpc = RLPCT . ReaderT . const
-
 ----------------------------------------------------------------------------------
 
 instance Default RLPCOptions where

src/Compiler/RlpcError.hs

@@ -1,15 +1,70 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE PatternSynonyms, ViewPatterns #-}
 module Compiler.RlpcError
-    ( RlpcError(..)
-    , IsRlpcError(..)
+    ( IsRlpcError(..)
+    , MsgEnvelope(..)
+    , Severity(..)
+    , RlpcError(..)
+    , SrcSpan(..)
+    , msgSpan
+    , msgDiagnostic
+    , msgSeverity
+    , liftRlpcErrors
+    , errorMsg
     )
     where
 ----------------------------------------------------------------------------------
 import Control.Monad.Errorful
+import Data.Text                (Text)
+import Data.Text                qualified as T
+import GHC.Exts                 (IsString(..))
+import Lens.Micro.Platform
+import Lens.Micro.Platform.Internal
 ----------------------------------------------------------------------------------
 
-data RlpcError = RlpcErr String -- temp
+data MsgEnvelope e = MsgEnvelope
+   { _msgSpan        :: SrcSpan
+   , _msgDiagnostic  :: e
+   , _msgSeverity    :: Severity
+   }
+   deriving (Functor, Show)
+
+newtype RlpcError = Text [Text]
     deriving Show
 
-class IsRlpcError a where
-    liftRlpcErr :: a -> RlpcError
+instance IsString RlpcError where
+    fromString = Text . pure . T.pack
+
+class IsRlpcError e where
+    liftRlpcError :: e -> RlpcError
+
+instance IsRlpcError RlpcError where
+    liftRlpcError = id
+
+data Severity = SevWarning
+              | SevError
+              deriving Show
+
+data SrcSpan = SrcSpan
+    !Int -- ^ Line
+    !Int -- ^ Column
+    !Int -- ^ Length
+    deriving Show
+
+makeLenses ''MsgEnvelope
+
+liftRlpcErrors :: (Functor m, IsRlpcError e)
+               => ErrorfulT e m a
+               -> ErrorfulT RlpcError m a
+liftRlpcErrors = mapErrorful liftRlpcError
+
+instance (IsRlpcError e) => IsRlpcError (MsgEnvelope e) where
+    liftRlpcError msg = msg ^. msgDiagnostic & liftRlpcError
+
+errorMsg :: SrcSpan -> e -> MsgEnvelope e
+errorMsg s e = MsgEnvelope
+    { _msgSpan = s
+    , _msgDiagnostic = e
+    , _msgSeverity = SevError
+    }
 

src/Control/Monad/Errorful.hs

@@ -1,73 +1,79 @@
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE TupleSections, PatternSynonyms #-}
+{-# LANGUAGE UndecidableInstances #-}
 module Control.Monad.Errorful
     ( ErrorfulT
     , runErrorfulT
     , Errorful
     , runErrorful
-    , mapErrors
+    , mapErrorful
     , MonadErrorful(..)
     )
     where
 ----------------------------------------------------------------------------------
+import Control.Monad.State.Strict
 import Control.Monad.Trans
 import Data.Functor.Identity
 import Data.Coerce
+import Data.HashSet                 (HashSet)
+import Data.HashSet                 qualified as H
 import Lens.Micro
 ----------------------------------------------------------------------------------
 
-newtype ErrorfulT e m a = ErrorfulT { runErrorfulT :: m (Either e (a, [e])) }
+newtype ErrorfulT e m a = ErrorfulT { runErrorfulT :: m (Maybe a, [e]) }
 
 type Errorful e = ErrorfulT e Identity
 
-pattern Errorful :: (Either e (a, [e])) -> Errorful e a
+pattern Errorful :: (Maybe a, [e]) -> Errorful e a
 pattern Errorful a = ErrorfulT (Identity a)
 
-runErrorful :: Errorful e a -> Either e (a, [e])
+runErrorful :: Errorful e a -> (Maybe a, [e])
 runErrorful m = coerce (runErrorfulT m)
 
 class (Applicative m) => MonadErrorful e m | m -> e where
     addWound :: e -> m ()
     addFatal :: e -> m a
 
-    -- not sure if i want to add this yet...
-    -- catchWound :: m a -> (e -> m a) -> m a
-
 instance (Applicative m) => MonadErrorful e (ErrorfulT e m) where
-    addWound e = ErrorfulT $ pure . Right $ ((), [e])
-    addFatal e = ErrorfulT $ pure . Left  $ e
+    addWound e = ErrorfulT $ pure (Just (), [e])
+    addFatal e = ErrorfulT $ pure (Nothing, [e])
 
 instance MonadTrans (ErrorfulT e) where
-    lift m = ErrorfulT (Right . (,[]) <$> m)
+    lift m = ErrorfulT ((\x -> (Just x,[])) <$> m)
 
 instance (MonadIO m) => MonadIO (ErrorfulT e m) where
     liftIO = lift . liftIO
 
 instance (Functor m) => Functor (ErrorfulT e m) where
-    fmap f (ErrorfulT m) = ErrorfulT $ fmap (_1 %~ f) <$> m
+    fmap f (ErrorfulT m) = ErrorfulT (m & mapped . _1 . _Just %~ f)
 
 instance (Applicative m) => Applicative (ErrorfulT e m) where
-    pure a = ErrorfulT (pure . Right $ (a, []))
+    pure a = ErrorfulT . pure $ (Just a, [])
 
-    m <*> a = ErrorfulT (m' `apply` a')
-        where
-            m' = runErrorfulT m
-            a' = runErrorfulT a
-            -- TODO: strict concatenation
-            apply = liftA2 $ liftA2 (\ (f,e1) (x,e2) -> (f x, e1 ++ e2)) 
+    ErrorfulT m <*> ErrorfulT n = ErrorfulT $ m `apply` n where
+        apply :: m (Maybe (a -> b), [e]) -> m (Maybe a, [e]) -> m (Maybe b, [e])
+        apply = liftA2 $ \ (mf,e1) (ma,e2) -> (mf <*> ma, e1 <> e2)
 
 instance (Monad m) => Monad (ErrorfulT e m) where
     ErrorfulT m >>= k = ErrorfulT $ do
-        m' <- m
-        case m' of
-            Right (a,es) -> runErrorfulT (k a)
-            Left e       -> pure (Left e)
+        (a,es) <- m
+        case a of
+            Just x      -> runErrorfulT (k x)
+            Nothing     -> pure (Nothing, es)
 
-mapErrors :: (Monad m) => (e -> e') -> ErrorfulT e m a -> ErrorfulT e' m a
-mapErrors f m = ErrorfulT $ do
-    x <- runErrorfulT m
-    case x of
-        Left  e      -> pure . Left  $ f e
-        Right (a,es) -> pure . Right $ (a, f <$> es)
+mapErrorful :: (Functor m) => (e -> e') -> ErrorfulT e m a -> ErrorfulT e' m a
+mapErrorful f (ErrorfulT m) = ErrorfulT $
+    m & mapped . _2 . mapped %~ f
+
+-- when microlens-pro drops we can write this as
+--    mapErrorful f = coerced . mapped . _2 . mappd %~ f
+-- lol
+
+--------------------------------------------------------------------------------
+-- daily dose of n^2 instances
+
+instance (Monad m, MonadErrorful e m) => MonadErrorful e (StateT s m) where
+    addWound = undefined
+    addFatal = undefined
 

src/Core/Examples.hs

@@ -15,6 +15,13 @@ import Core.Syntax
 import Core.TH
 ----------------------------------------------------------------------------------
 
+-- fac3 = undefined
+-- sumList = undefined
+-- constDivZero = undefined
+-- idCase = undefined
+
+---
+
 letrecExample :: Program'
 letrecExample = [coreProg|
     pair x y f = f x y;
@@ -216,3 +223,4 @@ idCase = [coreProg|
 --         , ScDef "Cons" [] $ Con 2 2
 --         ]
 
+--}

src/Core/HindleyMilner.hs

@@ -3,6 +3,7 @@ Module      : Core.HindleyMilner
 Description : Hindley-Milner type system
 -}
 {-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
 module Core.HindleyMilner
     ( Context'
     , infer
@@ -16,15 +17,17 @@ module Core.HindleyMilner
 ----------------------------------------------------------------------------------
 import Lens.Micro
 import Lens.Micro.Mtl
+import Lens.Micro.Platform
 import Data.Maybe               (fromMaybe)
 import Data.Text                qualified as T
 import Data.HashMap.Strict      qualified as H
 import Data.Foldable            (traverse_)
 import Compiler.RLPC
-import Control.Monad            (foldM, void)
+import Control.Monad            (foldM, void, forM)
 import Control.Monad.Errorful   (Errorful, addFatal)
 import Control.Monad.State
 import Control.Monad.Utils      (mapAccumLM)
+import Text.Printf
 import Core.Syntax
 ----------------------------------------------------------------------------------
 
@@ -48,9 +51,20 @@ data TypeError
     | TyErrMissingTypeSig Name
     deriving (Show, Eq)
 
--- TODO:
 instance IsRlpcError TypeError where
-    liftRlpcErr = RlpcErr . show
+    liftRlpcError = \case
+        -- todo: use anti-parser instead of show
+        TyErrCouldNotUnify t u -> Text
+            [ T.pack $ printf "Could not match type `%s' with `%s'."
+                              (show t) (show u)
+            , "Expected: " <> tshow t
+            , "Got: " <> tshow u
+            ]
+        TyErrRecursiveType t x -> Text
+            [ T.pack $ printf "recursive type error lol"
+            ]
+
+        where tshow = T.pack . show
 
 -- | Synonym for @Errorful [TypeError]@. This means an @HMError@ action may
 -- throw any number of fatal or nonfatal errors. Run with @runErrorful@.
@@ -88,10 +102,10 @@ checkCoreProg p = scDefs
              where scname = sc ^. _lhs._1
 
 -- | @checkCoreProgR p@ returns @p@ if @p@ successfully typechecks.
-checkCoreProgR :: Program' -> RLPC RlpcError Program'
-checkCoreProgR p = do
-    liftRlpcErrs . rlpc . checkCoreProg $ p
-    pure p
+checkCoreProgR :: Program' -> RLPC Program'
+checkCoreProgR p = undefined
+
+{-# WARNING checkCoreProgR "unimpl" #-}
 
 -- | Infer the type of an expression under some context.
 --
@@ -140,7 +154,27 @@ gather = \g e -> runStateT (go g e) ([],0) <&> \ (t,(cs,_)) -> (t,cs) where
         Let NonRec bs e -> do
             g' <- buildLetContext g bs
             go g' e
-        -- TODO letrec, lambda, case
+        Let Rec bs e -> do
+            g' <- buildLetrecContext g bs
+            go g' e
+
+        -- TODO lambda, case
+
+    buildLetrecContext :: Context' -> [Binding']
+                       -> StateT ([Constraint], Int) HMError Context'
+    buildLetrecContext g bs = do
+        let f ag (k := _) = do
+                n <- uniqueVar
+                pure ((k,n) : ag)
+        rg <- foldM f g bs
+        let k ag (k := v) = do
+                t <- go rg v
+                pure ((k,t) : ag)
+        foldM k g bs
+
+    -- | augment a context with the inferred types of each binder. the returned
+    -- context is linearly accumulated, meaning that the context used to infer each binder
+    -- will include the inferred types of all previous binder
 
     buildLetContext :: Context' -> [Binding']
                     -> StateT ([Constraint], Int) HMError Context'
@@ -218,3 +252,20 @@ subst x t (TyVar y) | x == y  = t
 subst x t (a :-> b)           = subst x t a :-> subst x t b
 subst _ _ e                   = e
 
+--------------------------------------------------------------------------------
+
+demoContext :: Context'
+demoContext =
+    [ ("fix", (TyVar "a" :-> TyVar "a") :-> TyVar "a")
+    , ("add", TyInt :-> TyInt :-> TyInt)
+    , ("==", TyInt :-> TyInt :-> TyCon "Bool")
+    , ("True", TyCon "Bool")
+    , ("False", TyCon "Bool")
+    ]
+
+pprintType :: Type -> String
+pprintType (s :-> t) = "(" <> pprintType s <> " -> " <> pprintType t <> ")"
+pprintType TyFun = "(->)"
+pprintType (TyVar x) = x ^. unpacked
+pprintType (TyCon t) = t ^. unpacked
+

src/Core/Lex.x

@@ -167,24 +167,19 @@ lexWith :: (Text -> CoreToken) -> Lexer
 lexWith f (AlexPn _ y x,_,_,s) l = pure $ Located y x l (f $ T.take l s)
 
 -- | The main lexer driver.
-lexCore :: Text -> RLPC SrcError [Located CoreToken]
+lexCore :: Text -> RLPC [Located CoreToken]
 lexCore s = case m of
-    Left e   -> addFatal err
-        where err = SrcError
-                { _errSpan       = (0,0,0) -- TODO: location
-                , _errSeverity   = Error
-                , _errDiagnostic = SrcErrLexical e
-                }
+    Left e   -> error "core lex error"
     Right ts -> pure ts
     where
         m = runAlex s lexStream
 
-lexCoreR :: Text -> RLPC RlpcError [Located CoreToken]
-lexCoreR = liftRlpcErrs . lexCore
+lexCoreR :: Text -> RLPC [Located CoreToken]
+lexCoreR = lexCore
 
 -- | @lexCore@, but the tokens are stripped of location info. Useful for
 -- debugging
-lexCore' :: Text -> RLPC SrcError [CoreToken]
+lexCore' :: Text -> RLPC [CoreToken]
 lexCore' s = fmap f <$> lexCore s
     where f (Located _ _ _ t) = t
 
@@ -201,11 +196,11 @@ data ParseError = ParErrLexical String
 
 -- TODO:
 instance IsRlpcError SrcError where
-    liftRlpcErr = RlpcErr . show
+    liftRlpcError = Text . pure . T.pack . show
 
 -- TODO:
 instance IsRlpcError ParseError where
-    liftRlpcErr = RlpcErr . show
+    liftRlpcError = Text . pure . T.pack . show
 
 alexEOF :: Alex (Located CoreToken)
 alexEOF = Alex $ \ st@(AlexState { alex_pos = AlexPn _ y x }) ->

src/Core/Parse.y

@@ -10,7 +10,6 @@ module Core.Parse
     , parseCoreProg
     , parseCoreProgR
     , module Core.Lex -- temp convenience
-    , parseTmp
     , SrcError
     , Module
     )
@@ -34,7 +33,7 @@ import Data.HashMap.Strict  qualified as H
 %name parseCoreProg StandaloneProgram
 %tokentype { Located CoreToken }
 %error { parseError }
-%monad { RLPC SrcError }
+%monad { RLPC } { happyBind } { happyPure }
 
 %token
       let             { Located _ _ _ TokenLet }
@@ -99,6 +98,8 @@ ScDefs          : ScDef ';' ScDefs              { $1 : $3 }
 
 ScDef           :: { ScDef Name }
 ScDef           : Var ParList '=' Expr          { ScDef $1 $2 $4 }
+                -- hack to allow constructors to be compiled into scs
+                | Con ParList '=' Expr          { ScDef $1 $2 $4 }
 
 Type            :: { Type }
 Type            : Type1                         { $1 }
@@ -189,34 +190,23 @@ Con             : '(' consym ')'                    { $2 }
 
 {
 
-parseError :: [Located CoreToken] -> RLPC SrcError a
-parseError (Located y x l _ : _) = addFatal err
-    where err = SrcError
-            { _errSpan       = (y,x,l)
-            , _errSeverity   = Error
-            , _errDiagnostic = SrcErrParse
-            }
+parseError :: [Located CoreToken] -> RLPC a
+parseError (Located y x l t : _) =
+    error $ show y <> ":" <> show x
+         <> ": parse error at token `" <> show t <> "'"
 
-parseTmp :: IO (Module Name)
-parseTmp = do
-    s <- TIO.readFile "/tmp/t.hs"
-    case parse s of
-        Left e -> error (show e)
-        Right (ts,_) -> pure ts
-    where
-        parse = evalRLPC def . (lexCore >=> parseCore)
+{-# WARNING parseError "unimpl" #-}
 
-exprPragma :: [String] -> RLPC SrcError (Expr Name)
-exprPragma ("AST" : e) = astPragma e
-exprPragma _           = addFatal err
-    where err = SrcError
-            { _errSpan       = (0,0,0) -- TODO: span
-            , _errSeverity   = Warning
-            , _errDiagnostic = SrcErrUnknownPragma "" -- TODO: missing pragma
-            }
+exprPragma :: [String] -> RLPC (Expr Name)
+exprPragma ("AST" : e) = undefined
+exprPragma _           = undefined
 
-astPragma :: [String] -> RLPC SrcError (Expr Name)
-astPragma = pure . read . unwords
+{-# WARNING exprPragma "unimpl" #-}
+
+astPragma :: [String] -> RLPC (Expr Name)
+astPragma _ = undefined
+
+{-# WARNING astPragma "unimpl" #-}
 
 insTypeSig :: (Hashable b) => (b, Type) -> Program b -> Program b
 insTypeSig ts = programTypeSigs %~ uncurry H.insert ts
@@ -230,8 +220,14 @@ insScDef sc = programScDefs %~ (sc:)
 singletonScDef :: (Hashable b) => ScDef b -> Program b
 singletonScDef sc = insScDef sc mempty
 
-parseCoreProgR :: [Located CoreToken] -> RLPC RlpcError Program'
-parseCoreProgR = liftRlpcErrs . parseCoreProg
+parseCoreProgR :: [Located CoreToken] -> RLPC Program'
+parseCoreProgR = parseCoreProg
+
+happyBind :: RLPC a -> (a -> RLPC b) -> RLPC b
+happyBind m k = m >>= k
+
+happyPure :: a -> RLPC a
+happyPure a = pure a
 
 }
 

src/Core/TH.hs

@@ -6,7 +6,6 @@ module Core.TH
     ( coreExpr
     , coreProg
     , coreProgT
-    , core
     )
     where
 ----------------------------------------------------------------------------------
@@ -14,74 +13,38 @@ import Language.Haskell.TH
 import Language.Haskell.TH.Syntax   hiding (Module)
 import Language.Haskell.TH.Quote
 import Control.Monad                ((>=>))
+import Control.Monad.IO.Class
+import Control.Arrow                ((>>>))
 import Compiler.RLPC
 import Data.Default.Class           (def)
+import Data.Text                    (Text)
 import Data.Text                    qualified as T
 import Core.Parse
 import Core.Lex
+import Core.Syntax
 import Core.HindleyMilner           (checkCoreProgR)
 ----------------------------------------------------------------------------------
 
--- TODO: write in terms of a String -> QuasiQuoter
-
-core :: QuasiQuoter
-core = QuasiQuoter
-    { quoteExp = qCore
-    , quotePat = error "core quasiquotes may only be used in expressions"
-    , quoteType = error "core quasiquotes may only be used in expressions"
-    , quoteDec = error "core quasiquotes may only be used in expressions"
-    }
-
 coreProg :: QuasiQuoter
-coreProg = QuasiQuoter
-    { quoteExp = qCoreProg
-    , quotePat = error "core quasiquotes may only be used in expressions"
-    , quoteType = error "core quasiquotes may only be used in expressions"
-    , quoteDec = error "core quasiquotes may only be used in expressions"
-    }
+coreProg = mkqq $ lexCoreR >=> parseCoreProgR
 
 coreExpr :: QuasiQuoter
-coreExpr = QuasiQuoter
-    { quoteExp = qCoreExpr
-    , quotePat = error "core quasiquotes may only be used in expressions"
-    , quoteType = error "core quasiquotes may only be used in expressions"
-    , quoteDec = error "core quasiquotes may only be used in expressions"
-    }
+coreExpr = mkqq $ lexCoreR >=> parseCoreExpr
 
 -- | Type-checked @coreProg@
 coreProgT :: QuasiQuoter
-coreProgT = QuasiQuoter
-    { quoteExp = qCoreProgT
+coreProgT = mkqq $ lexCoreR >=> parseCoreProgR >=> checkCoreProgR
+
+mkqq :: (Lift a) => (Text -> RLPC a) -> QuasiQuoter
+mkqq p = QuasiQuoter
+    { quoteExp = mkq p
     , quotePat = error "core quasiquotes may only be used in expressions"
     , quoteType = error "core quasiquotes may only be used in expressions"
     , quoteDec = error "core quasiquotes may only be used in expressions"
     }
 
-qCore :: String -> Q Exp
-qCore s = case parse (T.pack s) of
-    Left e       -> error (show e)
-    Right (m,ts) -> lift m
-    where
-        parse = evalRLPC def . (lexCore >=> parseCore)
-
-qCoreExpr :: String -> Q Exp
-qCoreExpr s = case parseExpr (T.pack s) of
-    Left e       -> error (show e)
-    Right (m,ts) -> lift m
-    where
-        parseExpr = evalRLPC def . (lexCore >=> parseCoreExpr)
-
-qCoreProg :: String -> Q Exp
-qCoreProg s = case parse (T.pack s) of
-    Left e       -> error (show e)
-    Right (m,ts) -> lift m
-    where
-        parse = evalRLPC def . (lexCoreR >=> parseCoreProgR)
-
-qCoreProgT :: String -> Q Exp
-qCoreProgT s = case parse (T.pack s) of
-    Left e      -> error (show e)
-    Right (m,_) -> lift m
-    where
-        parse = evalRLPC def . (lexCoreR >=> parseCoreProgR >=> checkCoreProgR)
+mkq :: (Lift a) => (Text -> RLPC a) -> String -> Q Exp
+mkq parse s = case evalRLPC def (parse $ T.pack s) of
+    (Just a,  _) -> lift a
+    (Nothing, _) -> error "todo: aaahhbbhjhbdjhabsjh"
 

src/RLP/Syntax.hs

@@ -1,59 +0,0 @@
-{-# LANGUAGE OverloadedStrings #-}
-module RLP.Syntax
-    ( RlpExpr
-    )
-    where
-----------------------------------------------------------------------------------
-import Data.Text                    (Text)
-import Lens.Micro
-import Core                         (HasRHS(..), HasLHS(..))
-----------------------------------------------------------------------------------
-
-newtype RlpProgram b = RlpProgram [Decl b]
-
-data Decl b = InfixD  InfixAssoc Int VarId
-            | FunD    VarId [Pat b] (RlpExpr b)
-            | DataD   ConId [ConId] [ConAlt]
-
-data ConAlt = ConAlt ConId [ConId]
-
-data InfixAssoc = Assoc | AssocL | AssocR
-
-data RlpExpr b = LetE  [Bind b] (RlpExpr b)
-               | VarE  VarId
-               | ConE  ConId
-               | LamE  [Pat b] (RlpExpr b)
-               | CaseE (RlpExpr b) [Alt b]
-               | IfE   (RlpExpr b) (RlpExpr b) (RlpExpr b)
-               | AppE  (RlpExpr b) (RlpExpr b)
-               | LitE  (Lit b)
-
--- do we want guards?
-data Alt b = AltA (Pat b) (RlpExpr b)
-
-data Bind b = PatB (Pat b) (RlpExpr b)
-            | FunB VarId [Pat b] (RlpExpr b)
-
-data VarId = NameVar Text
-           | SymVar Text
-
-data ConId = NameCon Text
-           | SymCon Text
-
-data Pat b = VarP VarId
-           | LitP (Lit b)
-           | ConP ConId [Pat b]
-
-data Lit b = IntL Int
-           | CharL Char
-           | ListL [RlpExpr b]
-
--- instance HasLHS Alt Alt Pat Pat where
---     _lhs = lens
---         (\ (AltA p _) -> p)
---         (\ (AltA _ e) p' -> AltA p' e)
-
--- instance HasRHS Alt Alt RlpExpr RlpExpr where
---     _rhs = lens
---         (\ (AltA _ e) -> e)
---         (\ (AltA p _) e' -> AltA p e')

src/Rlp/Lex.x

@@ -0,0 +1,349 @@
+{
+{-# LANGUAGE ViewPatterns, LambdaCase #-}
+{-# LANGUAGE GeneralisedNewtypeDeriving #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Rlp.Lex
+    ( P(..)
+    , RlpToken(..)
+    , Located(..)
+    , lexToken
+    , lexStream
+    , lexDebug
+    , lexCont
+    )
+    where
+import Codec.Binary.UTF8.String (encodeChar)
+import Control.Monad
+import Control.Monad.Errorful
+import Core.Syntax              (Name)
+import Data.Functor.Identity
+import Data.Char                (digitToInt)
+import Data.Monoid              (First)
+import Data.Maybe
+import Data.Text                (Text)
+import Data.Text                qualified as T
+import Data.Word
+import Data.Default
+import Lens.Micro.Mtl
+import Lens.Micro
+
+import Debug.Trace
+import Rlp.Parse.Types
+}
+
+$whitechar      = [ \t\n\r\f\v]
+
+$nl             = [\n\r]
+$white_no_nl    = $white # $nl
+
+$lower          = [a-z \_]
+$upper          = [A-Z]
+$alpha          = [$lower $upper]
+$digit          = 0-9
+
+$special        = [\(\)\,\;\[\]\{\}]
+$namechar       = [$alpha $digit \' \#]
+$asciisym       = [\!\#\$\%\&\*\+\.\/\<\=\>\?\@\\\^\|\-\~\:]
+
+@decimal        = $digit+
+
+@varname        = $lower $namechar*
+@conname        = $upper $namechar*
+@consym         = \: $asciisym*
+@varsym         = $asciisym+
+
+@reservedname = 
+    case|data|do|import|in|let|letrec|module|of|where
+    |infixr|infixl|infix
+
+@reservedop =
+    "=" | \\ | "->" | "|"
+
+rlp :-
+    
+-- everywhere: skip whitespace
+$white_no_nl+       ;
+
+-- everywhere: skip comments
+-- TODO: don't treat operators like (-->) as comments
+"--".*              ;
+
+-- we are indentation-sensitive! do not skip NLs!. upon encountering a newline,
+-- we check indentation and potentially insert extra tokens. search this file
+-- for the definition of `doBol`
+<0> \n                  { beginPush bol }
+
+-- scan various identifiers and reserved words. order is important here!
+<0>
+{
+    @reservedname       { tokenWith lexReservedName }
+    @conname            { tokenWith TokenConName }
+    @varname            { tokenWith TokenVarName }
+    @reservedop         { tokenWith lexReservedOp }
+    @consym             { tokenWith TokenConSym }
+    @varsym             { tokenWith TokenVarSym }
+}
+
+-- literals -- currently this is just unsigned integer literals
+<0>
+{
+    @decimal            { tokenWith (TokenLitInt . readInt) }
+}
+
+-- control characters
+<0>
+{
+    "("                 { constToken TokenLParen }
+    ")"                 { constToken TokenRParen }
+    "{"                 { explicitLBrace }
+    "}"                 { explicitRBrace }
+    ";"                 { constToken TokenSemicolon }
+}
+
+-- consume all whitespace leaving us at the beginning of the next non-empty
+-- line. we then compare the indentation of that line to the enclosing layout
+-- context and proceed accordingly
+<bol>
+{
+    $whitechar          ;
+    \n                  ;
+    ()                  { doBol }
+}
+
+<layout_top>
+{
+    \n                  ;
+    "{"                 { explicitLBrace `thenDo` popLexState }
+    ()                  { doLayout }
+}
+
+{
+
+lexReservedName :: Text -> RlpToken
+lexReservedName = \case
+    "data"      -> TokenData
+    "case"      -> TokenCase
+    "of"        -> TokenOf
+    "let"       -> TokenLet
+    "in"        -> TokenIn
+    "infix"     -> TokenInfix
+    "infixl"    -> TokenInfixL
+    "infixr"    -> TokenInfixR
+
+lexReservedOp :: Text -> RlpToken
+lexReservedOp = \case
+    "="     -> TokenEquals
+    "::"    -> TokenHasType
+    "|"     -> TokenPipe
+
+-- | @andBegin@, with the subtle difference that the start code is set
+--   /after/ the action
+thenBegin :: LexerAction a -> Int -> LexerAction a
+thenBegin act c inp l = do
+    a <- act inp l
+    psLexState . _head .= c
+    pure a
+
+andBegin :: LexerAction a -> Int -> LexerAction a
+andBegin act c inp l = do
+    psLexState . _head .= c
+    act inp l
+
+beginPush :: Int -> LexerAction (Located RlpToken)
+beginPush n _ _ = pushLexState n >> lexToken
+
+alexGetByte :: AlexInput -> Maybe (Word8, AlexInput)
+alexGetByte inp = case inp ^. aiBytes of
+    [] -> do
+        (c,t) <- T.uncons (inp ^. aiSource)
+        let (b:bs) = encodeChar c
+                       -- tail the source
+            inp' = inp & aiSource .~ t
+                       -- record the excess bytes for successive calls
+                       & aiBytes .~ bs
+                       -- report the previous char
+                       & aiPrevChar .~ c
+                       -- update the position
+                       & aiPos %~ \ (ln,col) ->
+                                   if c == '\n'
+                                   then (ln+1,1)
+                                   else (ln,col+1)
+        pure (b, inp')
+    
+    _ -> Just (head bs, inp')
+        where
+            (bs, inp') = inp & aiBytes <<%~ drop 1
+
+getInput :: P AlexInput
+getInput = use psInput
+
+getLexState :: P Int
+getLexState = use (psLexState . singular _head)
+
+alexInputPrevChar :: AlexInput -> Char
+alexInputPrevChar = view aiPrevChar
+
+pushLexState :: Int -> P ()
+pushLexState n = psLexState %= (n:)
+
+readInt :: Text -> Int
+readInt = T.foldr f 0 where
+    f c n = digitToInt c + 10*n
+
+constToken :: RlpToken -> LexerAction (Located RlpToken)
+constToken t inp l = do
+    pos <- use (psInput . aiPos)
+    pure (Located (pos,l) t)
+
+tokenWith :: (Text -> RlpToken) -> LexerAction (Located RlpToken)
+tokenWith tf inp l = do
+    pos <- getPos
+    let t = tf (T.take l $ inp ^. aiSource)
+    pure (Located (pos,l) t)
+
+getPos :: P Position
+getPos = use (psInput . aiPos)
+
+alexEOF :: P (Located RlpToken)
+alexEOF = do
+    inp <- getInput
+    pure (Located undefined TokenEOF)
+
+initParseState :: Text -> ParseState
+initParseState s = ParseState
+    { _psLayoutStack = []
+    -- IMPORTANT: the initial state is `bol` to begin the top-level layout,
+    -- which then returns to state 0 which continues the normal lexing process.
+    , _psLexState = [layout_top,0]
+    , _psInput = initAlexInput s
+    , _psOpTable = mempty
+    }
+
+initAlexInput :: Text -> AlexInput
+initAlexInput s = AlexInput
+    { _aiPrevChar   = '\0'
+    , _aiSource     = s
+    , _aiBytes      = []
+    , _aiPos        = (1,1)
+    }
+
+runP' :: P a -> Text -> (ParseState, [MsgEnvelope RlpParseError], Maybe a)
+runP' p s = runP p st where
+    st = initParseState s
+
+lexToken :: P (Located RlpToken)
+lexToken = do
+    inp <- getInput
+    c <- getLexState
+    st <- use id
+    -- traceM $ "st: " <> show st
+    case alexScan inp c of
+        AlexEOF -> pure $ Located (inp ^. aiPos, 0) TokenEOF
+        AlexSkip inp' l -> do
+            psInput .= inp'
+            lexToken
+        AlexToken inp' l act -> do
+            psInput .= inp'
+            act inp l
+        AlexError inp' -> addFatalHere 1 RlpParErrLexical
+
+lexCont :: (Located RlpToken -> P a) -> P a
+lexCont = (lexToken >>=)
+
+lexStream :: P [RlpToken]
+lexStream = do
+    t <- lexToken
+    case t of
+        Located _ TokenEOF -> pure [TokenEOF]
+        Located _ t        -> (t:) <$> lexStream
+
+lexDebug :: (Located RlpToken -> P a) -> P a
+lexDebug k = do
+    t <- lexToken
+    traceM $ "token: " <> show t
+    k t
+
+lexTest :: Text -> Maybe [RlpToken]
+lexTest s = runP' lexStream s ^. _3
+
+indentLevel :: P Int
+indentLevel = do
+    pos <- use (psInput . aiPos)
+    pure (pos ^. _2)
+
+insertToken :: RlpToken -> P (Located RlpToken)
+insertToken t = do
+    pos <- use (psInput . aiPos)
+    pure (Located (pos, 0) t)
+
+popLayout :: P Layout
+popLayout = do
+    -- traceM "pop layout"
+    ctx <- preuse (psLayoutStack . _head)
+    psLayoutStack %= (drop 1)
+    case ctx of
+        Just l      -> pure l
+        Nothing     -> error "uhh"
+
+pushLayout :: Layout -> P ()
+pushLayout l = do
+    -- traceM "push layout"
+    psLayoutStack %= (l:)
+
+popLexState :: P ()
+popLexState = do
+    psLexState %= tail
+
+insertSemicolon, insertLBrace, insertRBrace :: P (Located RlpToken)
+insertSemicolon = {- traceM "inserting semi"   >> -} insertToken TokenSemicolonV
+insertLBrace    = {- traceM "inserting lbrace" >> -} insertToken TokenLBraceV
+insertRBrace    = {- traceM "inserting rbrace" >> -} insertToken TokenRBraceV
+
+cmpLayout :: P Ordering
+cmpLayout = do
+    i <- indentLevel
+    ctx <- preuse (psLayoutStack . _head)
+    case ctx of
+        Just (Implicit n) -> pure (i `compare` n)
+        _                 -> pure GT
+
+doBol :: LexerAction (Located RlpToken)
+doBol inp l = do
+    off <- cmpLayout
+    i <- indentLevel
+    traceM $ "i: " <> show i
+    -- important that we pop the lex state lest we find our lexer diverging
+    popLexState
+    case off of
+        -- the line is aligned with the previous. it therefore belongs to the
+        -- same list
+        EQ -> insertSemicolon
+        -- the line is indented further than the previous, so we assume it is a
+        -- line continuation. ignore it and move on!
+        GT -> lexToken
+        -- the line is indented less than the previous, pop the layout stack and
+        -- insert a closing brace.
+        LT -> popLayout >> insertRBrace
+
+thenDo :: LexerAction a -> P b -> LexerAction a
+thenDo act p inp l = act inp l <* p
+
+explicitLBrace :: LexerAction (Located RlpToken)
+explicitLBrace inp l = do
+    pushLayout Explicit
+    constToken TokenLBrace inp l
+
+explicitRBrace :: LexerAction (Located RlpToken)
+explicitRBrace inp l = do
+    popLayout
+    constToken TokenRBrace inp l
+
+doLayout :: LexerAction (Located RlpToken)
+doLayout _ _ = do
+    i <- indentLevel
+    pushLayout (Implicit i)
+    popLexState
+    insertLBrace
+
+}
+

src/Rlp/Parse.y

@@ -0,0 +1,181 @@
+{
+{-# LANGUAGE LambdaCase #-}
+module Rlp.Parse
+    ( parseRlpProg
+    )
+    where
+import Compiler.RlpcError
+import Rlp.Lex
+import Rlp.Syntax
+import Rlp.Parse.Types
+import Rlp.Parse.Associate
+import Lens.Micro
+import Lens.Micro.Mtl
+import Lens.Micro.Platform          ()
+import Data.List.Extra
+import Data.Fix
+import Data.Functor.Const
+import Data.Text                    qualified as T
+}
+
+%name parseRlpProg StandaloneProgram
+
+%monad { P }
+%lexer { lexCont } { Located _ TokenEOF }
+%error { parseError }
+%tokentype { Located RlpToken }
+
+%token
+    varname         { Located _ (TokenVarName $$) }
+    conname         { Located _ (TokenConName $$) }
+    consym          { Located _ (TokenConSym $$) }
+    varsym          { Located _ (TokenVarSym $$) }
+    data            { Located _ TokenData }
+    litint          { Located _ (TokenLitInt $$) }
+    '='             { Located _ TokenEquals }
+    '|'             { Located _ TokenPipe }
+    ';'             { Located _ TokenSemicolon }
+    '('             { Located _ TokenLParen }
+    ')'             { Located _ TokenRParen }
+    '->'            { Located _ TokenArrow }
+    vsemi           { Located _ TokenSemicolonV }
+    '{'             { Located _ TokenLBrace }
+    '}'             { Located _ TokenRBrace }
+    vlbrace         { Located _ TokenLBraceV }
+    vrbrace         { Located _ TokenRBraceV }
+    infixl          { Located _ TokenInfixL }
+    infixr          { Located _ TokenInfixR }
+    infix           { Located _ TokenInfix }
+
+%right '->'
+
+%%
+
+StandaloneProgram   :: { RlpProgram' }
+StandaloneProgram   : '{' Decls  '}'        {% mkProgram $2 }
+                    | VL  DeclsV VR         {% mkProgram $2 }
+
+VL  :: { () }
+VL  : vlbrace       { () }
+
+VR  :: { () }
+VR  : vrbrace       { () }
+    | error         { () }
+
+Decls               :: { [PartialDecl'] }
+Decls               : Decl ';' Decls        { $1 : $3 }
+                    | Decl ';'              { [$1] }
+                    | Decl                  { [$1] }
+
+DeclsV              :: { [PartialDecl'] }
+DeclsV              : Decl VS Decls         { $1 : $3 }
+                    | Decl VS               { [$1] }
+                    | Decl                  { [$1] }
+
+VS                  :: { Located RlpToken }
+VS                  : ';'                   { $1 }
+                    | vsemi                 { $1 }
+
+Decl        :: { PartialDecl' }
+            : FunDecl                   { $1 }
+            | DataDecl                  { $1 }
+            | InfixDecl                 { $1 }
+
+InfixDecl   :: { PartialDecl' }
+            : InfixWord litint InfixOp  {% mkInfixD $1 $2 $3 }
+
+InfixWord   :: { Assoc }
+            : infixl                    { InfixL }
+            | infixr                    { InfixR }
+            | infix                     { Infix  }
+
+DataDecl    :: { PartialDecl' }
+            : data Con TyParams '=' DataCons    { DataD $2 $3 $5 }
+
+TyParams    :: { [Name] }
+            : {- epsilon -}             { [] }
+            | TyParams varname          { $1 `snoc` $2 }
+
+DataCons    :: { [ConAlt] }
+            : DataCons '|' DataCon      { $1 `snoc` $3 }
+            | DataCon                   { [$1] }
+
+DataCon     :: { ConAlt }
+            : Con Type1s                { ConAlt $1 $2 }
+
+Type1s      :: { [Type] }
+            : {- epsilon -}             { [] }
+            | Type1s Type1              { $1 `snoc` $2 }
+
+Type1       :: { Type }
+            : '(' Type ')'              { $2 }
+            | conname                   { TyCon $1 }
+            | varname                   { TyVar $1 }
+
+Type        :: { Type }
+            : Type '->' Type            { $1 :-> $3 }
+            | Type1                     { $1 }
+
+FunDecl     :: { PartialDecl' }
+FunDecl     : Var Params '=' Expr       { FunD $1 $2 (Const $4) Nothing }
+
+Params      :: { [Pat'] }
+Params      : {- epsilon -}             { [] }
+            | Params Pat1               { $1 `snoc` $2 }
+
+Pat1        :: { Pat' }
+            : Var                       { VarP $1 }
+            | Lit                       { LitP $1 }
+
+Expr        :: { PartialExpr' }
+            : Expr1 varsym Expr         { Fix $ B $2 (unFix $1) (unFix $3) }
+            | Expr1                     { $1 }
+
+Expr1       :: { PartialExpr' }
+            : '(' Expr ')'              { wrapFix . Par . unwrapFix $ $2 }
+            | Lit                       { Fix . E $ LitEF $1 }
+            | Var                       { Fix . E $ VarEF $1 }
+
+-- TODO: happy prefers left-associativity. doing such would require adjusting
+-- the code in Rlp.Parse.Associate to expect left-associative input rather than
+-- right.
+InfixExpr   :: { PartialExpr' }
+            : Expr1 varsym Expr         { Fix $ B $2 (unFix $1) (unFix $3) }
+
+InfixOp     :: { Name }
+            : consym                    { $1 }
+            | varsym                    { $1 }
+
+Lit         :: { Lit' }
+Lit         : litint                    { IntL $1 }
+
+Var         :: { VarId }
+Var         : varname                   { NameVar $1 }
+
+Con         :: { ConId }
+            : conname                   { NameCon $1 }
+
+{
+
+mkProgram :: [PartialDecl'] -> P RlpProgram'
+mkProgram ds = do
+    pt <- use psOpTable
+    pure $ RlpProgram (associate pt <$> ds)
+
+parseError :: Located RlpToken -> P a
+parseError (Located ((l,c),s) t) = addFatal $
+    errorMsg (SrcSpan l c s) RlpParErrUnexpectedToken
+
+mkInfixD :: Assoc -> Int -> Name -> P PartialDecl'
+mkInfixD a p n = do
+    let opl :: Lens' ParseState (Maybe OpInfo)
+        opl = psOpTable . at n
+    opl <~ (use opl >>= \case
+        Just o  -> addWoundHere l e >> pure (Just o) where
+            e = RlpParErrDuplicateInfixD n
+            l = T.length n
+        Nothing -> pure (Just (a,p))
+        )
+    pure $ InfixD a p n
+
+}

src/Rlp/Parse/Associate.hs

@@ -0,0 +1,100 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms, ViewPatterns, ImplicitParams #-}
+module Rlp.Parse.Associate
+    ( associate
+    )
+    where
+--------------------------------------------------------------------------------
+import Data.HashMap.Strict              qualified as H
+import Data.Functor.Foldable
+import Data.Functor.Const
+import Lens.Micro
+import Rlp.Parse.Types
+import Rlp.Syntax
+--------------------------------------------------------------------------------
+
+associate :: OpTable -> PartialDecl' -> Decl' RlpExpr
+associate pt (FunD n as b w)    = FunD n as b' w
+    where b' = let ?pt = pt in completeExpr (getConst b)
+associate pt (TySigD ns t)      = TySigD ns t
+associate pt (DataD n as cs)    = DataD n as cs
+associate pt (InfixD a p n)     = InfixD a p n
+
+completeExpr :: (?pt :: OpTable) => PartialExpr' -> RlpExpr'
+completeExpr = cata completePartial
+
+completePartial :: (?pt :: OpTable) => PartialE -> RlpExpr'
+completePartial (E e)        = completeRlpExpr e
+completePartial p@(B o l r)  = completeB (build p)
+completePartial (Par e)      = completePartial e
+
+completeRlpExpr :: (?pt :: OpTable) => RlpExprF' RlpExpr' -> RlpExpr'
+completeRlpExpr = embed
+
+completeB :: (?pt :: OpTable) => PartialE -> RlpExpr'
+completeB p = case build p of
+    B o l r     -> (o' `AppE` l') `AppE` r'
+        where
+            -- TODO: how do we know it's symbolic?
+            o' = VarE (SymVar o)
+            l' = completeB l
+            r' = completeB r
+    Par e       -> completeB e
+    E e         -> completeRlpExpr e
+
+build :: (?pt :: OpTable) => PartialE -> PartialE
+build e = go id e (rightmost e) where
+    rightmost :: PartialE -> PartialE
+    rightmost (B _ _ r) = rightmost r
+    rightmost p@(E _)   = p
+    rightmost p@(Par _) = p
+
+    go :: (?pt :: OpTable)
+       => (PartialE -> PartialE)
+       -> PartialE -> PartialE -> PartialE
+    go f p@(WithInfo o _ r) = case r of
+            E _     -> mkHole o (f . f')
+            Par _   -> mkHole o (f . f')
+            B _ _ _ -> go (mkHole o (f . f')) r
+        where f' r' = p & pR .~ r'
+    go f _ = id
+
+mkHole :: (?pt :: OpTable)
+       => OpInfo
+       -> (PartialE -> PartialE)
+       -> PartialE
+       -> PartialE
+mkHole _     hole p@(Par _)                 = hole p
+mkHole _     hole p@(E _)                   = hole p
+mkHole (a,d) hole p@(WithInfo (a',d') _ _)
+    | d' < d  = above
+    | d' > d  = below
+    | d == d' = case (a,a') of
+                  -- left-associative operators of equal precedence are
+                  -- associated left
+                  (InfixL,InfixL) -> above
+                  -- right-associative operators are handled similarly
+                  (InfixR,InfixR) -> below
+                  -- non-associative operators of equal precedence, or equal
+                  -- precedence operators of different associativities are
+                  -- invalid
+                  (_,     _)      -> error "invalid expression"
+    where
+        above = p & pL %~ hole
+        below = hole p
+
+examplePrecTable :: OpTable
+examplePrecTable = H.fromList
+    [ ("+",    (InfixL,6))
+    , ("*",    (InfixL,7))
+    , ("^",    (InfixR,8))
+    , (".",    (InfixR,7))
+    , ("~",    (Infix, 9))
+    , ("=",    (Infix, 4))
+    , ("&&",   (Infix, 3))
+    , ("||",   (Infix, 2))
+    , ("$",    (InfixR,0))
+    , ("&",    (InfixL,0))
+    ]
+
+

src/Rlp/Parse/Types.hs

@@ -0,0 +1,242 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE ImplicitParams, ViewPatterns, PatternSynonyms #-}
+{-# LANGUAGE LambdaCase #-}
+module Rlp.Parse.Types
+    ( LexerAction
+    , MsgEnvelope(..)
+    , RlpcError(..)
+    , AlexInput(..)
+    , Position(..)
+    , RlpToken(..)
+    , P(..)
+    , ParseState(..)
+    , psLayoutStack
+    , psLexState
+    , psInput
+    , psOpTable
+    , Layout(..)
+    , Located(..)
+    , OpTable
+    , OpInfo
+    , RlpParseError(..)
+    , PartialDecl'
+    , Partial(..)
+    , pL, pR
+    , PartialE
+    , pattern WithInfo
+    , opInfoOrDef
+    , PartialExpr'
+    , aiPrevChar
+    , aiSource
+    , aiBytes
+    , aiPos
+    , addFatal
+    , addWound
+    , addFatalHere
+    , addWoundHere
+    )
+    where
+--------------------------------------------------------------------------------
+import Core.Syntax                  (Name)
+import Control.Monad
+import Control.Monad.State.Strict
+import Control.Monad.Errorful
+import Compiler.RlpcError
+import Data.Text                    (Text)
+import Data.Maybe
+import Data.Fix
+import Data.Functor.Foldable
+import Data.Functor.Const
+import Data.Functor.Classes
+import Data.HashMap.Strict          qualified as H
+import Data.Word                    (Word8)
+import Lens.Micro.TH
+import Lens.Micro
+import Rlp.Syntax
+--------------------------------------------------------------------------------
+
+type LexerAction a = AlexInput -> Int -> P a
+
+data AlexInput = AlexInput
+    { _aiPrevChar   :: Char
+    , _aiSource     :: Text
+    , _aiBytes      :: [Word8]
+    , _aiPos        :: Position
+    }
+    deriving Show
+
+type Position =
+    ( Int -- line
+    , Int -- column
+    )
+
+posLine :: Lens' Position Int
+posLine = _1
+
+posColumn :: Lens' Position Int
+posColumn = _2
+
+data RlpToken
+    -- literals
+    = TokenLitInt Int
+    -- identifiers
+    | TokenVarName Name
+    | TokenConName Name
+    | TokenVarSym Name
+    | TokenConSym Name
+    -- reserved words
+    | TokenData
+    | TokenCase
+    | TokenOf
+    | TokenLet
+    | TokenIn
+    | TokenInfixL
+    | TokenInfixR
+    | TokenInfix
+    -- reserved ops
+    | TokenArrow
+    | TokenPipe
+    | TokenHasType
+    | TokenLambda
+    | TokenEquals
+    -- control symbols
+    | TokenSemicolon
+    | TokenLBrace
+    | TokenRBrace
+    | TokenLParen
+    | TokenRParen
+    -- 'virtual' control symbols, inserted by the lexer without any correlation
+    -- to a specific symbol
+    | TokenSemicolonV
+    | TokenLBraceV
+    | TokenRBraceV
+    | TokenEOF
+    deriving (Show)
+
+newtype P a = P {
+        runP :: ParseState
+             -> (ParseState, [MsgEnvelope RlpParseError], Maybe a)
+    }
+    deriving (Functor)
+
+instance Applicative P where
+    pure a = P $ \st -> (st, [], pure a)
+    liftA2 = liftM2
+
+instance Monad P where
+    p >>= k = P $ \st ->
+        let (st',es,ma) = runP p st
+        in case ma of
+            Just a  -> runP (k a) st'
+                     & _2 %~ (es<>)
+            Nothing -> (st',es,Nothing)
+
+    {-# INLINE (>>=) #-}
+
+instance MonadState ParseState P where
+    state f = P $ \st ->
+        let (a,st') = f st
+        in (st', [], Just a)
+
+instance MonadErrorful (MsgEnvelope RlpParseError) P where
+    addWound e = P $ \st -> (st, [e], Just ())
+    addFatal e = P $ \st -> (st, [e], Nothing)
+
+data ParseState = ParseState
+    { _psLayoutStack        :: [Layout]
+    , _psLexState           :: [Int]
+    , _psInput              :: AlexInput
+    , _psOpTable            :: OpTable
+    }
+    deriving Show
+
+data Layout = Explicit
+            | Implicit Int
+            deriving (Show, Eq)
+
+data Located a = Located (Position, Int) a
+    deriving (Show)
+
+type OpTable = H.HashMap Name OpInfo
+type OpInfo = (Assoc, Int)
+
+-- data WithLocation a = WithLocation [String] a
+
+data RlpParseError = RlpParErrOutOfBoundsPrecedence Int
+                   | RlpParErrDuplicateInfixD Name
+                   | RlpParErrLexical
+                   | RlpParErrUnexpectedToken
+                   deriving (Eq, Ord, Show)
+
+instance IsRlpcError RlpParseError where
+
+----------------------------------------------------------------------------------
+-- absolute psycho shit (partial ASTs)
+
+type PartialDecl' = Decl (Const PartialExpr') Name
+
+data Partial a = E (RlpExprF Name a)
+               | B Name (Partial a) (Partial a)
+               | Par (Partial a)
+               deriving (Show, Functor)
+
+pL :: Traversal' (Partial a) (Partial a)
+pL k (B o l r) = (\l' -> B o l' r) <$> k l
+pL _ x         = pure x
+
+pR :: Traversal' (Partial a) (Partial a)
+pR k (B o l r) = (\r' -> B o l r') <$> k r
+pR _ x         = pure x
+
+type PartialE = Partial RlpExpr'
+
+-- i love you haskell
+pattern WithInfo :: (?pt :: OpTable) => OpInfo -> PartialE -> PartialE -> PartialE
+pattern WithInfo p l r <- B (opInfoOrDef -> p) l r
+
+opInfoOrDef :: (?pt :: OpTable) => Name -> OpInfo
+opInfoOrDef c = fromMaybe (InfixL,9) $ H.lookup c ?pt
+
+-- required to satisfy constraint on Fix's show instance
+instance Show1 Partial where
+    liftShowsPrec :: forall a. (Int -> a -> ShowS)
+                  -> ([a] -> ShowS)
+                  -> Int -> Partial a -> ShowS
+
+    liftShowsPrec sp sl p m = case m of
+        (E e)       -> showsUnaryWith lshow "E" p e
+        (B f a b)   -> showsTernaryWith showsPrec lshow lshow "B" p f a b
+        (Par e)     -> showsUnaryWith lshow "Par" p e
+        where
+            lshow :: forall f. (Show1 f) => Int -> f a -> ShowS
+            lshow = liftShowsPrec sp sl
+
+type PartialExpr' = Fix Partial
+
+makeLenses ''AlexInput
+makeLenses ''ParseState
+
+addWoundHere :: Int -> RlpParseError -> P ()
+addWoundHere l e = P $ \st ->
+    let e' = MsgEnvelope
+            { _msgSpan = let pos = psInput . aiPos
+                         in SrcSpan (st ^. pos . posLine)
+                                   (st ^. pos . posColumn)
+                                   l
+            , _msgDiagnostic = e
+            , _msgSeverity = SevError
+            }
+    in (st, [e'], Just ())
+
+addFatalHere :: Int -> RlpParseError -> P a
+addFatalHere l e = P $ \st ->
+    let e' = MsgEnvelope
+            { _msgSpan = let pos = psInput . aiPos
+                         in SrcSpan (st ^. pos . posLine)
+                                    (st ^. pos . posColumn)
+                                    l
+            , _msgDiagnostic = e
+            , _msgSeverity = SevError
+            }
+    in (st, [e'], Nothing)
+

src/Rlp/Syntax.hs

@@ -0,0 +1,177 @@
+-- recursion-schemes
+{-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable #-}
+-- recursion-schemes
+{-# LANGUAGE TemplateHaskell, TypeFamilies #-}
+{-# LANGUAGE OverloadedStrings, PatternSynonyms #-}
+module Rlp.Syntax
+    ( RlpModule(..)
+    , RlpProgram(..)
+    , RlpProgram'
+    , rlpmodName
+    , rlpmodProgram
+    , RlpExpr(..)
+    , RlpExpr'
+    , RlpExprF(..)
+    , RlpExprF'
+    , Decl(..)
+    , Decl'
+    , Bind(..)
+    , Where
+    , Where'
+    , ConAlt(..)
+    , Type(..)
+    , pattern (:->)
+    , Assoc(..)
+    , VarId(..)
+    , ConId(..)
+    , Pat(..)
+    , Pat'
+    , Lit(..)
+    , Lit'
+    , Name
+
+    -- TODO: ugh move this somewhere else later
+    , showsTernaryWith
+
+    -- * Convenience re-exports
+    , Text
+    )
+    where
+----------------------------------------------------------------------------------
+import Data.Text                    (Text)
+import Data.Text                    qualified as T
+import Data.String                  (IsString(..))
+import Data.Functor.Foldable.TH     (makeBaseFunctor)
+import Data.Functor.Classes
+import Lens.Micro
+import Lens.Micro.TH
+import Core.Syntax                  hiding (Lit)
+import Core                         (HasRHS(..), HasLHS(..))
+----------------------------------------------------------------------------------
+
+data RlpModule b = RlpModule
+    { _rlpmodName       :: Text
+    , _rlpmodProgram    :: RlpProgram b
+    }
+
+newtype RlpProgram b = RlpProgram [Decl RlpExpr b]
+    deriving Show
+
+type RlpProgram' = RlpProgram Name
+
+-- | The @e@ parameter is used for partial results. When parsing an input, we
+-- first parse all top-level declarations in order to extract infix[lr]
+-- declarations. This process yields a @[Decl (Const Text) Name]@, where @Const
+-- Text@ stores the remaining unparsed function bodies. Once infixities are
+-- accounted for, we may complete the parsing task and get a proper @[Decl
+-- RlpExpr Name]@.
+
+data Decl e b = FunD    VarId [Pat b] (e b) (Maybe (Where b))
+              | TySigD  [VarId] Type
+              | DataD   ConId [Name] [ConAlt]
+              | InfixD  Assoc Int Name
+              deriving Show
+
+type Decl' e = Decl e Name
+
+data Assoc = InfixL
+           | InfixR
+           | Infix
+           deriving Show
+
+data ConAlt = ConAlt ConId [Type]
+            deriving Show
+
+data RlpExpr b = LetE  [Bind b] (RlpExpr b)
+               | VarE  VarId
+               | ConE  ConId
+               | LamE  [Pat b] (RlpExpr b)
+               | CaseE (RlpExpr b) [(Alt b, Where b)]
+               | IfE   (RlpExpr b) (RlpExpr b) (RlpExpr b)
+               | AppE  (RlpExpr b) (RlpExpr b)
+               | LitE  (Lit b)
+               deriving Show
+
+type RlpExpr' = RlpExpr Name
+
+type Where b = [Bind b]
+type Where' = [Bind Name]
+
+-- do we want guards?
+data Alt b = AltA (Pat b) (RlpExpr b)
+           deriving Show
+
+data Bind b = PatB (Pat b) (RlpExpr b)
+            | FunB VarId [Pat b] (RlpExpr b)
+            deriving Show
+
+data VarId = NameVar Text
+           | SymVar Text
+           deriving Show
+
+instance IsString VarId where
+    -- TODO: use symvar if it's an operator
+    fromString = NameVar . T.pack
+
+data ConId = NameCon Text
+           | SymCon Text
+           deriving Show
+
+data Pat b = VarP VarId
+           | LitP (Lit b)
+           | ConP ConId [Pat b]
+           deriving Show
+
+type Pat' = Pat Name
+
+data Lit b = IntL Int
+           | CharL Char
+           | ListL [RlpExpr b]
+           deriving Show
+
+type Lit' = Lit Name
+
+-- instance HasLHS Alt Alt Pat Pat where
+--     _lhs = lens
+--         (\ (AltA p _) -> p)
+--         (\ (AltA _ e) p' -> AltA p' e)
+
+-- instance HasRHS Alt Alt RlpExpr RlpExpr where
+--     _rhs = lens
+--         (\ (AltA _ e) -> e)
+--         (\ (AltA p _) e' -> AltA p e')
+
+makeBaseFunctor ''RlpExpr
+
+deriving instance (Show b, Show a) => Show (RlpExprF b a)
+
+type RlpExprF' = RlpExprF Name
+
+-- society if derivable Show1
+instance (Show b) => Show1 (RlpExprF b) where
+    liftShowsPrec sp _ p m = case m of
+        (LetEF bs e)            -> showsBinaryWith showsPrec sp "LetEF" p bs e
+        (VarEF n)               -> showsUnaryWith showsPrec "VarEF" p n
+        (ConEF n)               -> showsUnaryWith showsPrec "ConEF" p n
+        (LamEF bs e)            -> showsBinaryWith showsPrec sp "LamEF" p bs e
+        (CaseEF e as)           -> showsBinaryWith sp showsPrec "CaseEF" p e as
+        (IfEF a b c)            -> showsTernaryWith sp sp sp "IfEF" p a b c
+        (AppEF f x)             -> showsBinaryWith sp sp "AppEF" p f x
+        (LitEF l)               -> showsUnaryWith showsPrec "LitEF" p l
+
+showsTernaryWith :: (Int -> x -> ShowS)
+                 -> (Int -> y -> ShowS)
+                 -> (Int -> z -> ShowS)
+                 -> String -> Int
+                 -> x -> y -> z
+                 -> ShowS
+showsTernaryWith sa sb sc name p a b c = showParen (p > 10)
+    $ showString name
+    . showChar ' ' . sa 11 a 
+    . showChar ' ' . sb 11 b
+    . showChar ' ' . sc 11 c
+
+--------------------------------------------------------------------------------
+
+makeLenses ''RlpModule
+

tst/Core/HindleyMilnerSpec.hs

@@ -38,9 +38,13 @@ spec = do
         let e = [coreExpr|3|]
         in check' [] (TyCon "Bool") e `shouldSatisfy` isLeft
 
-infer' :: Context' -> Expr' -> Either TypeError Type
-infer' g e = fmap fst . runErrorful $ infer g e
+infer' :: Context' -> Expr' -> Either [TypeError] Type
+infer' g e = case runErrorful $ infer g e of
+    (Just t,   _) -> Right t
+    (Nothing, es) -> Left es
 
-check' :: Context' -> Type -> Expr' -> Either TypeError ()
-check' g t e = fmap fst . runErrorful $ check g t e
+check' :: Context' -> Type -> Expr' -> Either [TypeError] ()
+check' g t e = case runErrorful $ check g t e of
+    (Just t,   _) -> Right ()
+    (Nothing, es) -> Left es