diff --git a/.travis.yml b/.travis.yml
index 5477619dc..803bb1f0c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -36,7 +36,7 @@ install:
 script:
 - cabal new-build
 - cabal new-run semantic:test
-- cabal new-run semantic-core:spec
+- cabal new-run semantic-core:test
 - cabal new-run semantic-core:doctest
 - cabal new-run semantic-python:test
 - cabal new-run semantic-source:test
diff --git a/cabal.project b/cabal.project
index 4dfba75bc..f94f1be91 100644
--- a/cabal.project
+++ b/cabal.project
@@ -33,3 +33,8 @@ source-repository-package
   type: git
   location: https://github.com/tclem/proto-lens-jsonpb
   tag: e4d10b77f57ee25beb759a33e63e2061420d3dc2
+
+source-repository-package
+  type: git
+  location: https://github.com/antitypical/fused-syntax.git
+  tag: 5b7512db962d5b3f973002615b8bc86ab074d5aa
diff --git a/semantic-core/README.md b/semantic-core/README.md
index 6ab2b99d8..b992b12df 100644
--- a/semantic-core/README.md
+++ b/semantic-core/README.md
@@ -7,12 +7,12 @@ Semantic core intermediate language (experimental)
 
 This project consists of a Haskell package named `semantic-core`. The library’s sources are in [`src`][].
 
-Development of `semantic-core` is typically done using `cabal new-build`:
+Development of `semantic-core` is typically done using `cabal v2-build`:
 
 ```shell
-cabal new-build # build the library
-cabal new-repl  # load the package into ghci
-cabal new-test  # build and run the doctests
+cabal v2-build # build the library
+cabal v2-repl  # load the package into ghci
+cabal v2-test  # build and run the doctests
 ```
 
 [`src`]: https://github.com/github/semantic/tree/master/semantic-core/src
diff --git a/semantic-core/semantic-core.cabal b/semantic-core/semantic-core.cabal
index d92b0bed7..7fcd779d2 100644
--- a/semantic-core/semantic-core.cabal
+++ b/semantic-core/semantic-core.cabal
@@ -16,45 +16,11 @@ build-type:          Simple
 stability:           alpha
 extra-source-files:  README.md
 
-tested-with:         GHC == 8.6.4
+tested-with:
+  GHC == 8.6.5
 
-library
-  exposed-modules:     Analysis.Concrete
-                     , Analysis.Eval
-                     , Analysis.FlowInsensitive
-                     , Analysis.ImportGraph
-                     , Analysis.ScopeGraph
-                     , Analysis.Typecheck
-                     , Control.Carrier.Fail.WithLoc
-                     , Control.Effect.Readline
-                     , Control.Monad.Module
-                     , Data.Core
-                     , Data.Core.Parser
-                     , Data.Core.Pretty
-                     , Data.File
-                     , Data.Loc
-                     , Data.Name
-                     , Data.Scope
-                     , Data.Stack
-                     , Data.Term
-  build-depends:       algebraic-graphs            ^>= 0.3
-                     , base                         >= 4.12 && < 5
-                     , containers                  ^>= 0.6
-                     , directory                   ^>= 1.3
-                     , filepath                    ^>= 1.4
-                     , fused-effects               ^>= 0.5
-                     , haskeline                   ^>= 0.7.5
-                     , parsers                     ^>= 0.12.10
-                     , prettyprinter               ^>= 1.2.1
-                     , prettyprinter-ansi-terminal ^>= 1.1.1
-                     , semantic-source             ^>= 0
-                     , semigroupoids               ^>= 5.3
-                     , text                        ^>= 1.2.3.1
-                     , transformers                ^>= 0.5.6
-                     , trifecta                    ^>= 2
-                     , unordered-containers        ^>= 0.2.10
-  hs-source-dirs:      src
-  default-language:    Haskell2010
+common common
+  default-language: Haskell2010
   ghc-options:
     -Weverything
     -Wno-missing-local-signatures
@@ -67,29 +33,74 @@ library
     -Wno-missed-specialisations
     -Wno-all-missed-specialisations
     -Wno-star-is-type
+  if (impl(ghc >= 8.8))
+    ghc-options: -Wno-missing-deriving-strategies
+
+library
+  import: common
+  hs-source-dirs: src
+  exposed-modules:
+    Analysis.Analysis
+    Analysis.Concrete
+    Analysis.Eval
+    Analysis.FlowInsensitive
+    Analysis.ImportGraph
+    Analysis.ScopeGraph
+    Analysis.Typecheck
+    Control.Carrier.Fail.WithLoc
+    Control.Carrier.Readline.Haskeline
+    Control.Effect.Readline
+    Core.Core
+    Core.Core.Parser
+    Core.Core.Pretty
+    Core.File
+    Core.Loc
+    Core.Name
+  build-depends:
+      algebraic-graphs            ^>= 0.3
+    , base                         >= 4.12 && < 5
+    , containers                  ^>= 0.6
+    , directory                   ^>= 1.3
+    , filepath                    ^>= 1.4
+    , fused-effects               ^>= 0.5
+    , fused-syntax
+    , haskeline                   ^>= 0.7.5
+    , parsers                     ^>= 0.12.10
+    , prettyprinter               ^>= 1.2.1
+    , prettyprinter-ansi-terminal ^>= 1.1.1
+    , semantic-source             ^>= 0
+    , semigroupoids               ^>= 5.3
+    , terminal-size               ^>= 0.3
+    , text                        ^>= 1.2.3.1
+    , transformers                ^>= 0.5.6
+    , trifecta                    ^>= 2
+    , unordered-containers        ^>= 0.2.10
 
 test-suite doctest
-  type:                exitcode-stdio-1.0
-  main-is:             Doctest.hs
-  build-depends:       base >=4.9 && <4.13
-                     , doctest >=0.7 && <1.0
-                     , QuickCheck
-                     , semantic-core
-  hs-source-dirs:      test
-  default-language:    Haskell2010
+  import: common
+  type:           exitcode-stdio-1.0
+  hs-source-dirs: test
+  main-is:        Doctest.hs
+  build-depends:
+      base >=4.9 && <4.13
+    , doctest >=0.7 && <1.0
+    , QuickCheck
+    , semantic-core
 
-test-suite spec
-  type:                exitcode-stdio-1.0
-  main-is:             Spec.hs
-  other-modules:       Generators
-  build-depends:       base
-                     , semantic-core
-                     , semantic-source ^>= 0
-                     , fused-effects
-                     , hedgehog ^>= 1
-                     , tasty >= 1.2 && <2
-                     , tasty-hedgehog ^>= 1.0.0.1
-                     , tasty-hunit >= 0.10 && <1
-                     , trifecta
-  hs-source-dirs:      test
-  default-language:    Haskell2010
+test-suite test
+  import: common
+  type:           exitcode-stdio-1.0
+  hs-source-dirs: test
+  main-is:        Test.hs
+  other-modules:  Generators
+  build-depends:
+      base
+    , semantic-core
+    , semantic-source ^>= 0
+    , fused-effects
+    , fused-syntax
+    , hedgehog ^>= 1
+    , tasty >= 1.2 && <2
+    , tasty-hedgehog ^>= 1.0.0.1
+    , tasty-hunit >= 0.10 && <1
+    , trifecta
diff --git a/semantic-core/src/Analysis/Analysis.hs b/semantic-core/src/Analysis/Analysis.hs
new file mode 100644
index 000000000..b14a936a0
--- /dev/null
+++ b/semantic-core/src/Analysis/Analysis.hs
@@ -0,0 +1,27 @@
+{-# LANGUAGE RankNTypes #-}
+module Analysis.Analysis
+( Analysis(..)
+) where
+
+import Core.Name
+import Data.Text (Text)
+
+-- | A record of functions necessary to perform analysis.
+--
+-- This is intended to be replaced with a selection of algebraic effects providing these interfaces and carriers providing reusable implementations.
+data Analysis term address value m = Analysis
+  { alloc     :: Name -> m address
+  , bind      :: forall a . Name -> address -> m a -> m a
+  , lookupEnv :: Name -> m (Maybe address)
+  , deref     :: address -> m (Maybe value)
+  , assign    :: address -> value -> m ()
+  , abstract  :: (term -> m value) -> Name -> term -> m value
+  , apply     :: (term -> m value) -> value -> value -> m value
+  , unit      :: m value
+  , bool      :: Bool -> m value
+  , asBool    :: value -> m Bool
+  , string    :: Text -> m value
+  , asString  :: value -> m Text
+  , record    :: [(Name, value)] -> m value
+  , (...)     :: address -> Name -> m (Maybe address)
+  }
diff --git a/semantic-core/src/Analysis/Concrete.hs b/semantic-core/src/Analysis/Concrete.hs
index 33ddc84ae..24ae13817 100644
--- a/semantic-core/src/Analysis/Concrete.hs
+++ b/semantic-core/src/Analysis/Concrete.hs
@@ -11,7 +11,7 @@ module Analysis.Concrete
 
 import qualified Algebra.Graph as G
 import qualified Algebra.Graph.Export.Dot as G
-import           Analysis.Eval
+import           Analysis.Analysis
 import           Control.Applicative (Alternative (..))
 import           Control.Carrier.Fail.WithLoc
 import           Control.Effect
@@ -20,13 +20,13 @@ import           Control.Effect.NonDet
 import           Control.Effect.Reader hiding (Local)
 import           Control.Effect.State
 import           Control.Monad ((<=<), guard)
-import           Data.File
+import           Core.File
+import           Core.Loc
+import           Core.Name
 import           Data.Function (fix)
 import qualified Data.IntMap as IntMap
 import qualified Data.IntSet as IntSet
-import           Data.Loc
 import qualified Data.Map as Map
-import           Data.Name
 import           Data.Semigroup (Last (..))
 import qualified Data.Set as Set
 import           Data.Text (Text, pack)
@@ -221,5 +221,7 @@ data EdgeType term
 
 
 -- $setup
+-- >>> :seti -XFlexibleContexts
 -- >>> :seti -XOverloadedStrings
--- >>> import qualified Data.Core as Core
+-- >>> import Analysis.Eval (eval)
+-- >>> import qualified Core.Core as Core
diff --git a/semantic-core/src/Analysis/Eval.hs b/semantic-core/src/Analysis/Eval.hs
index 21064d82a..ae95cf281 100644
--- a/semantic-core/src/Analysis/Eval.hs
+++ b/semantic-core/src/Analysis/Eval.hs
@@ -8,26 +8,25 @@ module Analysis.Eval
 , prog5
 , prog6
 , ruby
-, Analysis(..)
 ) where
 
+import Analysis.Analysis
 import Control.Applicative (Alternative (..))
 import Control.Effect.Carrier
 import Control.Effect.Fail
 import Control.Effect.Reader
 import Control.Monad ((>=>))
-import Data.Core as Core
-import Data.File
+import Core.Core as Core
+import Core.File
+import Core.Loc
+import Core.Name
 import Data.Functor
-import Data.Loc
 import Data.Maybe (fromJust, fromMaybe)
-import Data.Name
-import Data.Scope
-import Data.Term
-import Data.Text (Text)
 import GHC.Stack
 import Prelude hiding (fail)
 import Source.Span
+import Syntax.Scope
+import Syntax.Term
 
 eval :: ( Carrier sig m
         , Member (Reader Span) sig
@@ -39,7 +38,7 @@ eval :: ( Carrier sig m
      -> (Term (Ann Span :+: Core) Name -> m value)
 eval Analysis{..} eval = \case
   Var n -> lookupEnv' n >>= deref' n
-  Term (R c) -> case c of
+  Alg (R c) -> case c of
     Rec (Named (Ignored n) b) -> do
       addr <- alloc n
       v <- bind n addr (eval (instantiate1 (pure n) b))
@@ -73,7 +72,7 @@ eval Analysis{..} eval = \case
       b' <- eval b
       addr <- ref a
       b' <$ assign addr b'
-  Term (L (Ann span c)) -> local (const span) (eval c)
+  Alg (L (Ann span c)) -> local (const span) (eval c)
   where freeVariable s = fail ("free variable: " <> s)
         uninitialized s = fail ("uninitialized variable: " <> s)
         invalidRef s = fail ("invalid ref: " <> s)
@@ -83,7 +82,7 @@ eval Analysis{..} eval = \case
 
         ref = \case
           Var n -> lookupEnv' n
-          Term (R c) -> case c of
+          Alg (R c) -> case c of
             If c t e -> do
               c' <- eval c >>= asBool
               if c' then ref t else ref e
@@ -91,7 +90,7 @@ eval Analysis{..} eval = \case
               a' <- ref a
               a' ... b >>= maybe (freeVariable (show b)) pure
             c -> invalidRef (show c)
-          Term (L (Ann span c)) -> local (const span) (ref c)
+          Alg (L (Ann span c)) -> local (const span) (ref c)
 
 
 prog1 :: (Carrier sig t, Member Core sig) => File (t Name)
@@ -213,21 +212,3 @@ ruby = fromBody $ annWith callStack (rec (named' __semantic_global) (do' stateme
         __semantic_global = "__semantic_global"
         __semantic_super  = "__semantic_super"
         __semantic_truthy = "__semantic_truthy"
-
-
-data Analysis term address value m = Analysis
-  { alloc     :: Name -> m address
-  , bind      :: forall a . Name -> address -> m a -> m a
-  , lookupEnv :: Name -> m (Maybe address)
-  , deref     :: address -> m (Maybe value)
-  , assign    :: address -> value -> m ()
-  , abstract  :: (term -> m value) -> Name -> term -> m value
-  , apply     :: (term -> m value) -> value -> value -> m value
-  , unit      :: m value
-  , bool      :: Bool -> m value
-  , asBool    :: value -> m Bool
-  , string    :: Text -> m value
-  , asString  :: value -> m Text
-  , record    :: [(Name, value)] -> m value
-  , (...)     :: address -> Name -> m (Maybe address)
-  }
diff --git a/semantic-core/src/Analysis/ImportGraph.hs b/semantic-core/src/Analysis/ImportGraph.hs
index acf2f49aa..a1a436593 100644
--- a/semantic-core/src/Analysis/ImportGraph.hs
+++ b/semantic-core/src/Analysis/ImportGraph.hs
@@ -5,7 +5,7 @@ module Analysis.ImportGraph
 , importGraphAnalysis
 ) where
 
-import           Analysis.Eval
+import           Analysis.Analysis
 import           Analysis.FlowInsensitive
 import           Control.Applicative (Alternative(..))
 import           Control.Carrier.Fail.WithLoc
@@ -14,13 +14,13 @@ import           Control.Effect.Fresh
 import           Control.Effect.Reader
 import           Control.Effect.State
 import           Control.Monad ((>=>))
-import           Data.File
+import           Core.File
+import           Core.Loc
+import           Core.Name
 import           Data.Foldable (fold, for_)
 import           Data.Function (fix)
 import           Data.List.NonEmpty (nonEmpty)
-import           Data.Loc
 import qualified Data.Map as Map
-import           Data.Name
 import           Data.Proxy
 import qualified Data.Set as Set
 import           Data.Text (Text)
diff --git a/semantic-core/src/Analysis/ScopeGraph.hs b/semantic-core/src/Analysis/ScopeGraph.hs
index fafe49f3d..79547ebb0 100644
--- a/semantic-core/src/Analysis/ScopeGraph.hs
+++ b/semantic-core/src/Analysis/ScopeGraph.hs
@@ -7,7 +7,7 @@ module Analysis.ScopeGraph
 , scopeGraphAnalysis
 ) where
 
-import           Analysis.Eval
+import           Analysis.Analysis
 import           Analysis.FlowInsensitive
 import           Control.Applicative (Alternative (..))
 import           Control.Carrier.Fail.WithLoc
@@ -16,13 +16,13 @@ import           Control.Effect.Fresh
 import           Control.Effect.Reader
 import           Control.Effect.State
 import           Control.Monad ((>=>))
-import           Data.File
+import           Core.File
+import           Core.Loc
+import           Core.Name
 import           Data.Foldable (fold)
 import           Data.Function (fix)
 import           Data.List.NonEmpty
-import           Data.Loc
 import qualified Data.Map as Map
-import           Data.Name
 import           Data.Proxy
 import qualified Data.Set as Set
 import           Data.Traversable (for)
diff --git a/semantic-core/src/Analysis/Typecheck.hs b/semantic-core/src/Analysis/Typecheck.hs
index 3188c65fd..f4c2c0603 100644
--- a/semantic-core/src/Analysis/Typecheck.hs
+++ b/semantic-core/src/Analysis/Typecheck.hs
@@ -7,7 +7,7 @@ module Analysis.Typecheck
 , typecheckingAnalysis
 ) where
 
-import           Analysis.Eval
+import           Analysis.Analysis
 import           Analysis.FlowInsensitive
 import           Control.Applicative (Alternative (..))
 import           Control.Carrier.Fail.WithLoc
@@ -16,28 +16,29 @@ import           Control.Effect.Fresh as Fresh
 import           Control.Effect.Reader hiding (Local)
 import           Control.Effect.State
 import           Control.Monad ((>=>), unless)
-import           Control.Monad.Module
-import           Data.File
+import           Core.File
+import           Core.Loc
+import           Core.Name as Name
 import           Data.Foldable (for_)
 import           Data.Function (fix)
 import           Data.Functor (($>))
 import qualified Data.IntMap as IntMap
 import qualified Data.IntSet as IntSet
 import           Data.List.NonEmpty (nonEmpty)
-import           Data.Loc
 import qualified Data.Map as Map
 import           Data.Maybe (fromJust, fromMaybe)
-import           Data.Name as Name
 import           Data.Proxy
-import           Data.Scope
 import           Data.Semigroup (Last (..))
 import qualified Data.Set as Set
-import           Data.Term
 import           Data.Traversable (for)
 import           Data.Void
 import           GHC.Generics (Generic1)
 import           Prelude hiding (fail)
 import           Source.Span
+import           Syntax.Module
+import           Syntax.Scope
+import           Syntax.Term
+import           Syntax.Var (closed)
 
 data Monotype f a
   = Bool
@@ -166,24 +167,24 @@ typecheckingAnalysis = Analysis{..}
           arg <- meta
           assign addr arg
           ty <- eval body
-          pure (Term (Arr arg ty))
+          pure (Alg (Arr arg ty))
         apply _ f a = do
           _A <- meta
           _B <- meta
-          unify (Term (Arr _A _B)) f
+          unify (Alg (Arr _A _B)) f
           unify _A a
           pure _B
-        unit = pure (Term Unit)
-        bool _ = pure (Term Bool)
-        asBool b = unify (Term Bool) b >> pure True <|> pure False
-        string _ = pure (Term String)
-        asString s = unify (Term String) s $> mempty
+        unit = pure (Alg Unit)
+        bool _ = pure (Alg Bool)
+        asBool b = unify (Alg Bool) b >> pure True <|> pure False
+        string _ = pure (Alg String)
+        asString s = unify (Alg String) s $> mempty
         record fields = do
           fields' <- for fields $ \ (k, v) -> do
             addr <- alloc k
             (k, v) <$ assign addr v
           -- FIXME: should records reference types by address instead?
-          pure (Term (Record (Map.fromList fields')))
+          pure (Alg (Record (Map.fromList fields')))
         _ ... m = pure (Just m)
 
 
@@ -212,8 +213,8 @@ solve :: (Carrier sig m, Member (State Substitution) sig, MonadFail m) => Set.Se
 solve cs = for_ cs solve
   where solve = \case
           -- FIXME: how do we enforce proper subtyping? row polymorphism or something?
-          Term (Record f1) :===: Term (Record f2) -> traverse solve (Map.intersectionWith (:===:) f1 f2) $> ()
-          Term (Arr a1 b1) :===: Term (Arr a2 b2) -> solve (a1 :===: a2) *> solve (b1 :===: b2)
+          Alg (Record f1) :===: Alg (Record f2) -> traverse solve (Map.intersectionWith (:===:) f1 f2) $> ()
+          Alg (Arr a1 b1) :===: Alg (Arr a2 b2) -> solve (a1 :===: a2) *> solve (b1 :===: b2)
           Var m1   :===: Var m2   | m1 == m2 -> pure ()
           Var m1   :===: t2         -> do
             sol <- solution m1
diff --git a/semantic-core/src/Control/Carrier/Fail/WithLoc.hs b/semantic-core/src/Control/Carrier/Fail/WithLoc.hs
index 33790a5c3..f2e8b62ea 100644
--- a/semantic-core/src/Control/Carrier/Fail/WithLoc.hs
+++ b/semantic-core/src/Control/Carrier/Fail/WithLoc.hs
@@ -12,7 +12,7 @@ import Control.Effect.Carrier
 import Control.Effect.Error
 import Control.Effect.Fail (Fail(..), MonadFail(..))
 import Control.Effect.Reader
-import Data.Loc
+import Core.Loc
 import Prelude hiding (fail)
 import Source.Span
 
diff --git a/semantic-core/src/Control/Carrier/Readline/Haskeline.hs b/semantic-core/src/Control/Carrier/Readline/Haskeline.hs
new file mode 100644
index 000000000..3849a3a73
--- /dev/null
+++ b/semantic-core/src/Control/Carrier/Readline/Haskeline.hs
@@ -0,0 +1,66 @@
+{-# LANGUAGE FlexibleInstances, GeneralizedNewtypeDeriving, MultiParamTypeClasses, ScopedTypeVariables, TypeApplications, TypeOperators, UndecidableInstances #-}
+module Control.Carrier.Readline.Haskeline
+( -- * Readline effect
+  module Control.Effect.Readline
+  -- * Readline carrier
+, runReadline
+, runReadlineWithHistory
+, ReadlineC (..)
+  -- * Re-exports
+, Carrier
+, run
+, runM
+) where
+
+import Control.Effect.Carrier
+import Control.Effect.Lift
+import Control.Effect.Reader
+import Control.Effect.Readline hiding (Carrier)
+import Control.Monad.Fix
+import Control.Monad.IO.Class
+import Data.Coerce
+import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Render.Terminal (renderIO)
+import System.Console.Haskeline hiding (Handler, handle)
+import System.Console.Terminal.Size as Size
+import System.Directory
+import System.FilePath
+import System.IO (stdout)
+
+runReadline :: MonadException m => Prefs -> Settings m -> ReadlineC m a -> m a
+runReadline prefs settings = runInputTWithPrefs prefs (coerce settings) . runM . runReader (Line 0) . runReadlineC
+
+runReadlineWithHistory :: MonadException m => ReadlineC m a -> m a
+runReadlineWithHistory block = do
+  homeDir <- liftIO getHomeDirectory
+  prefs <- liftIO $ readPrefs (homeDir </> ".haskeline")
+  let settingsDir = homeDir </> ".local/semantic-core"
+      settings = Settings
+        { complete = noCompletion
+        , historyFile = Just (settingsDir <> "/repl_history")
+        , autoAddHistory = True
+        }
+  liftIO $ createDirectoryIfMissing True settingsDir
+
+  runReadline prefs settings block
+
+newtype ReadlineC m a = ReadlineC { runReadlineC :: ReaderC Line (LiftC (InputT m)) a }
+  deriving (Applicative, Functor, Monad, MonadFix, MonadIO)
+
+instance MonadException m => Carrier Readline (ReadlineC m) where
+  eff (Prompt prompt k) = ReadlineC $ do
+    str <- sendM (getInputLine @m (cyan <> prompt <> plain))
+    Line line <- ask
+    local increment (runReadlineC (k line str))
+    where cyan = "\ESC[1;36m\STX"
+          plain = "\ESC[0m\STX"
+  eff (Print doc k) = do
+    s <- maybe 80 Size.width <$> liftIO size
+    liftIO (renderIO stdout (layoutSmart defaultLayoutOptions { layoutPageWidth = AvailablePerLine s 0.8 } (doc <> line)))
+    k
+
+
+newtype Line = Line Int
+
+increment :: Line -> Line
+increment (Line n) = Line (n + 1)
diff --git a/semantic-core/src/Control/Effect/Readline.hs b/semantic-core/src/Control/Effect/Readline.hs
index 5f862c7ce..1a4b31639 100644
--- a/semantic-core/src/Control/Effect/Readline.hs
+++ b/semantic-core/src/Control/Effect/Readline.hs
@@ -1,108 +1,30 @@
-{-# LANGUAGE DeriveAnyClass, DeriveFunctor, DeriveGeneric, DerivingStrategies, FlexibleContexts, FlexibleInstances, GeneralizedNewtypeDeriving, KindSignatures, MultiParamTypeClasses, OverloadedStrings, RankNTypes, StandaloneDeriving, TypeApplications, TypeOperators, UndecidableInstances #-}
-
+{-# LANGUAGE DeriveFunctor, DeriveGeneric, FlexibleContexts, OverloadedStrings #-}
 module Control.Effect.Readline
-( Readline (..)
+( -- * Readline effect
+  Readline (..)
 , prompt
 , print
-, println
-, askLine
-, Line (..)
-, increment
-, ReadlineC (..)
-, runReadline
-, runReadlineWithHistory
-, ControlIOC (..)
-, runControlIO
+  -- * Re-exports
+, Carrier
 ) where
 
+import Control.Effect.Carrier
+import Data.Text.Prettyprint.Doc
+import Data.Text.Prettyprint.Doc.Render.Terminal
+import GHC.Generics (Generic1)
 import Prelude hiding (print)
 
-import Control.Effect.Carrier
-import Control.Effect.Lift
-import Control.Effect.Reader
-import Control.Monad.IO.Class
-import Control.Monad.Trans.Class
-import Data.Int
-import Data.String
-import Data.Text.Prettyprint.Doc
-import Data.Text.Prettyprint.Doc.Render.Text
-import GHC.Generics (Generic1)
-import System.Console.Haskeline hiding (Handler, handle)
-import System.Directory
-import System.FilePath
-
 data Readline m k
-  = Prompt String (Maybe String -> m k)
-  | Print AnyDoc (m k)
-  | AskLine (Line -> m k)
-  deriving stock (Functor, Generic1)
-  deriving anyclass (Effect, HFunctor)
+  = Prompt String (Int -> Maybe String -> m k)
+  | Print (Doc AnsiStyle) (m k)
+  deriving (Functor, Generic1)
 
-newtype AnyDoc = AnyDoc { unAnyDoc :: forall a . Doc a }
+instance HFunctor Readline
+instance Effect   Readline
 
-prompt :: (IsString str, Member Readline sig, Carrier sig m) => String -> m (Maybe str)
-prompt p = fmap fromString <$> send (Prompt p pure)
 
-print :: (Pretty a, Carrier sig m, Member Readline sig) => a -> m ()
-print s = send (Print (AnyDoc (pretty s)) (pure ()))
+prompt :: (Member Readline sig, Carrier sig m) => String -> m (Int, Maybe String)
+prompt p = send (Prompt p (curry pure))
 
-println :: (Pretty a, Carrier sig m, Member Readline sig) => a -> m ()
-println s = print s >> print @String "\n"
-
-askLine :: (Carrier sig m, Member Readline sig) => m Line
-askLine = send (AskLine pure)
-
-newtype Line = Line Int64
-
-increment :: Line -> Line
-increment (Line n) = Line (n + 1)
-
-newtype ReadlineC m a = ReadlineC { runReadlineC :: ReaderC Line (LiftC (InputT m)) a }
-  deriving newtype (Applicative, Functor, Monad, MonadIO)
-
-runReadline :: MonadException m => Prefs -> Settings m -> ReadlineC m a -> m a
-runReadline prefs settings = runInputTWithPrefs prefs settings . runM . runReader (Line 0) . runReadlineC
-
-instance (MonadException m, MonadIO m) => Carrier (Readline :+: Lift (InputT m)) (ReadlineC m) where
-  eff (L (Prompt prompt k)) = ReadlineC $ do
-    str <- lift (lift (getInputLine (cyan <> prompt <> plain)))
-    local increment (runReadlineC (k str))
-    where cyan = "\ESC[1;36m\STX"
-          plain = "\ESC[0m\STX"
-  eff (L (Print text k)) = liftIO (putDoc (unAnyDoc text)) *> k
-  eff (L (AskLine k)) = ReadlineC ask >>= k
-  eff (R other) = ReadlineC (eff (R (handleCoercible other)))
-
-runReadlineWithHistory :: MonadException m => ReadlineC m a -> m a
-runReadlineWithHistory block = do
-  homeDir <- liftIO getHomeDirectory
-  prefs <- liftIO $ readPrefs (homeDir </> ".haskeline")
-  let settingsDir = homeDir </> ".local/semantic-core"
-      settings = Settings
-        { complete = noCompletion
-        , historyFile = Just (settingsDir <> "/repl_history")
-        , autoAddHistory = True
-        }
-  liftIO $ createDirectoryIfMissing True settingsDir
-
-  runReadline prefs settings block
-
-runControlIO :: (forall x . m x -> IO x) -> ControlIOC m a -> m a
-runControlIO handler = runReader (Handler handler) . runControlIOC
-
--- | This exists to work around the 'MonadException' constraint that haskeline entails.
-newtype ControlIOC m a = ControlIOC { runControlIOC :: ReaderC (Handler m) m a }
-  deriving newtype (Applicative, Functor, Monad, MonadIO)
-
-newtype Handler m = Handler (forall x . m x -> IO x)
-
-runHandler :: Handler m -> ControlIOC m a -> IO a
-runHandler h@(Handler handler) = handler . runReader h . runControlIOC
-
-instance Carrier sig m => Carrier sig (ControlIOC m) where
-  eff op = ControlIOC (eff (R (handleCoercible op)))
-
-instance (Carrier sig m, MonadIO m) => MonadException (ControlIOC m) where
-  controlIO f = ControlIOC $ do
-    handler <- ask
-    liftIO (f (RunIO (fmap pure . runHandler handler)) >>= runHandler handler)
+print :: (Carrier sig m, Member Readline sig) => Doc AnsiStyle -> m ()
+print s = send (Print s (pure ()))
diff --git a/semantic-core/src/Control/Monad/Module.hs b/semantic-core/src/Control/Monad/Module.hs
deleted file mode 100644
index 84087d45d..000000000
--- a/semantic-core/src/Control/Monad/Module.hs
+++ /dev/null
@@ -1,50 +0,0 @@
-{-# LANGUAGE FlexibleInstances, QuantifiedConstraints, MultiParamTypeClasses, TypeOperators #-}
-module Control.Monad.Module
-( RightModule(..)
-, (>=>*)
-, (<=<*)
-, joinr
-) where
-
-import Control.Effect.Carrier
-
--- | Modules over monads allow lifting of a monad’s product (i.e. 'Control.Monad.join') into another structure composed with the monad. A right-module @f m@ over a monad @m@ therefore allows one to extend @m@’s '>>=' operation to values of @f m@ using the '>>=*' operator.
---
---   In practical terms, this means that we can describe syntax which cannot itself bind or be substituted for variables, but which can be substituted inside when containing a substitutable expression monad. For example, we might not want to allow variables in a declaration context, but might still want to be able to substitute for e.g. globally-bound variables inside declarations; a 'RightModule' instance expresses this relationship nicely.
---
---   Note that we are calling this a right-module following Maciej Piróg, Nicolas Wu, & Jeremy Gibbons in _Modules Over Monads and their Algebras_; confusingly, other sources refer to this as a left-module.
---
---   Laws:
---
---   Right-identity:
---
--- @
--- m >>=* return = m
--- @
---
---   Associativity:
---
--- @
--- m >>=* (k >=> h) = (m >>=* k) >>=* h
--- @
-class (forall g . Functor g => Functor (f g), HFunctor f) => RightModule f where
-  (>>=*) :: Monad m => f m a -> (a -> m b) -> f m b
-  infixl 1 >>=*
-
-instance (RightModule f, RightModule g) => RightModule (f :+: g) where
-  L l >>=* f = L (l >>=* f)
-  R r >>=* f = R (r >>=* f)
-
-
-(>=>*) :: (RightModule f, Monad m) => (a -> f m b) -> (b -> m c) -> (a -> f m c)
-f >=>* g = \x -> f x >>=* g
-
-infixl 1 >=>*
-
-(<=<*) :: (RightModule f, Monad m) => (b -> m c) -> (a -> f m b) -> (a -> f m c)
-g <=<* f = \x -> f x >>=* g
-
-infixl 1 <=<*
-
-joinr :: (RightModule f, Monad m) => f m (m a) -> f m a
-joinr = (>>=* id)
diff --git a/semantic-core/src/Data/Core.hs b/semantic-core/src/Core/Core.hs
similarity index 89%
rename from semantic-core/src/Data/Core.hs
rename to semantic-core/src/Core/Core.hs
index bb7e46b56..1647c6c6b 100644
--- a/semantic-core/src/Data/Core.hs
+++ b/semantic-core/src/Core/Core.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE DeriveGeneric, DeriveTraversable, FlexibleContexts, LambdaCase, MultiParamTypeClasses, OverloadedStrings, QuantifiedConstraints, RankNTypes,
              ScopedTypeVariables, StandaloneDeriving, TypeFamilies, TypeOperators, UndecidableInstances #-}
-module Data.Core
+module Core.Core
 ( Core(..)
 , rec
 , (>>>)
@@ -37,20 +37,20 @@ module Data.Core
 
 import Control.Applicative (Alternative (..))
 import Control.Effect.Carrier
-import Control.Monad.Module
+import Core.Loc
+import Core.Name
 import Data.Bifunctor (Bifunctor (..))
 import Data.Foldable (foldl')
 import Data.List.NonEmpty (NonEmpty (..))
-import Data.Loc
 import Data.Maybe (fromMaybe)
-import Data.Name
-import Data.Scope
-import Data.Stack
-import Data.Term
 import Data.Text (Text)
 import GHC.Generics (Generic1)
 import GHC.Stack
 import Source.Span
+import Syntax.Scope
+import Syntax.Stack
+import Syntax.Module
+import Syntax.Term
 
 data Core f a
   -- | Recursive local binding of a name in a scope; strict evaluation of the name in the body will diverge.
@@ -118,8 +118,8 @@ a >>> b = send (a :>> b)
 infixr 1 >>>
 
 unseq :: (Alternative m, Member Core sig) => Term sig a -> m (Term sig a, Term sig a)
-unseq (Term sig) | Just (a :>> b) <- prj sig = pure (a, b)
-unseq _                                      = empty
+unseq (Alg sig) | Just (a :>> b) <- prj sig = pure (a, b)
+unseq _                                     = empty
 
 unseqs :: Member Core sig => Term sig a -> NonEmpty (Term sig a)
 unseqs = go
@@ -135,8 +135,8 @@ Named u n :<- a >>>= b = send (Named u a :>>= abstract1 n b)
 infixr 1 >>>=
 
 unbind :: (Alternative m, Member Core sig, RightModule sig) => a -> Term sig a -> m (Named a :<- Term sig a, Term sig a)
-unbind n (Term sig) | Just (Named u a :>>= b) <- prj sig = pure (Named u n :<- a, instantiate1 (pure n) b)
-unbind _ _                                               = empty
+unbind n (Alg sig) | Just (Named u a :>>= b) <- prj sig = pure (Named u n :<- a, instantiate1 (pure n) b)
+unbind _ _                                              = empty
 
 unstatement :: (Alternative m, Member Core sig, RightModule sig) => a -> Term sig a -> m (Maybe (Named a) :<- Term sig a, Term sig a)
 unstatement n t = first (first Just) <$> unbind n t <|> first (Nothing :<-) <$> unseq t
@@ -164,8 +164,8 @@ lams :: (Eq a, Foldable t, Carrier sig m, Member Core sig) => t (Named a) -> m a
 lams names body = foldr lam body names
 
 unlam :: (Alternative m, Member Core sig, RightModule sig) => a -> Term sig a -> m (Named a, Term sig a)
-unlam n (Term sig) | Just (Lam b) <- prj sig = pure (n <$ b, instantiate1 (pure n) (namedValue b))
-unlam _ _                                    = empty
+unlam n (Alg sig) | Just (Lam b) <- prj sig = pure (n <$ b, instantiate1 (pure n) (namedValue b))
+unlam _ _                                   = empty
 
 ($$) :: (Carrier sig m, Member Core sig) => m a -> m a -> m a
 f $$ a = send (f :$ a)
@@ -179,8 +179,8 @@ infixl 8 $$
 infixl 8 $$*
 
 unapply :: (Alternative m, Member Core sig) => Term sig a -> m (Term sig a, Term sig a)
-unapply (Term sig) | Just (f :$ a) <- prj sig = pure (f, a)
-unapply _                                     = empty
+unapply (Alg sig) | Just (f :$ a) <- prj sig = pure (f, a)
+unapply _                                    = empty
 
 unapplies :: Member Core sig => Term sig a -> (Term sig a, Stack (Term sig a))
 unapplies core = case unapply core of
@@ -237,6 +237,6 @@ annWith callStack = maybe id (annAt . snd) (stackLoc callStack)
 
 
 stripAnnotations :: forall ann a sig . (HFunctor sig, forall g . Functor g => Functor (sig g)) => Term (Ann ann :+: sig) a -> Term sig a
-stripAnnotations (Var v)              = Var v
-stripAnnotations (Term (L (Ann _ b))) = stripAnnotations b
-stripAnnotations (Term (R        b))  = Term (hmap stripAnnotations b)
+stripAnnotations (Var v)             = Var v
+stripAnnotations (Alg (L (Ann _ b))) = stripAnnotations b
+stripAnnotations (Alg (R        b))  = Alg (hmap stripAnnotations b)
diff --git a/semantic-core/src/Data/Core/Parser.hs b/semantic-core/src/Core/Core/Parser.hs
similarity index 97%
rename from semantic-core/src/Data/Core/Parser.hs
rename to semantic-core/src/Core/Core/Parser.hs
index c62ffc75d..563089ad0 100644
--- a/semantic-core/src/Data/Core/Parser.hs
+++ b/semantic-core/src/Core/Core/Parser.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE FlexibleContexts, TypeOperators #-}
-module Data.Core.Parser
+module Core.Core.Parser
   ( core
   , lit
   , expr
@@ -12,11 +12,11 @@ module Data.Core.Parser
 
 import           Control.Applicative
 import           Control.Effect.Carrier
+import           Core.Core ((:<-) (..), Core)
+import qualified Core.Core as Core
+import           Core.Name
 import qualified Data.Char as Char
-import           Data.Core ((:<-) (..), Core)
-import qualified Data.Core as Core
 import           Data.Foldable (foldl')
-import           Data.Name
 import           Data.String
 import qualified Text.Parser.Token as Token
 import qualified Text.Parser.Token.Highlight as Highlight
diff --git a/semantic-core/src/Data/Core/Pretty.hs b/semantic-core/src/Core/Core/Pretty.hs
similarity index 76%
rename from semantic-core/src/Data/Core/Pretty.hs
rename to semantic-core/src/Core/Core/Pretty.hs
index dd095ccb7..0e955d3dc 100644
--- a/semantic-core/src/Data/Core/Pretty.hs
+++ b/semantic-core/src/Core/Core/Pretty.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE FlexibleContexts, LambdaCase, OverloadedStrings, TypeApplications #-}
 
-module Data.Core.Pretty
+module Core.Core.Pretty
   ( showCore
   , printCore
   , showFile
@@ -8,16 +8,17 @@ module Data.Core.Pretty
   , prettyCore
   ) where
 
-import           Data.Core
-import           Data.File
+import           Core.Core
+import           Core.File
+import           Core.Name
 import           Data.Foldable (toList)
-import           Data.Name
-import           Data.Scope
-import           Data.Stack
-import           Data.Term
 import           Data.Text.Prettyprint.Doc
 import qualified Data.Text.Prettyprint.Doc.Render.String as Pretty
 import qualified Data.Text.Prettyprint.Doc.Render.Terminal as Pretty
+import           Syntax.Pretty
+import           Syntax.Scope
+import           Syntax.Stack
+import           Syntax.Term
 
 showCore :: Term Core Name -> String
 showCore = Pretty.renderString . layoutSmart defaultLayoutOptions . unAnnotate . prettyCore Ascii
@@ -45,10 +46,10 @@ name :: Name -> AnsiDoc
 name n = if needsQuotation n then enclose (symbol "#{") (symbol "}") (pretty n) else pretty n
 
 prettyCore :: Style -> Term Core Name -> AnsiDoc
-prettyCore style = precBody . go . fmap name
+prettyCore style = unPrec . go . fmap name
   where go = \case
           Var v -> atom v
-          Term t -> case t of
+          Alg t -> case t of
             Rec (Named (Ignored x) b) -> prec 3 . group . nest 2 $ vsep
               [ keyword "rec" <+> name x
               , symbol "=" <+> align (withPrec 0 (go (instantiate1 (pure (name x)) b)))
@@ -66,9 +67,9 @@ prettyCore style = precBody . go . fmap name
             f :$ x -> prec 8 (withPrec 8 (go f) <+> withPrec 9 (go x))
 
             If con tru fal -> prec 3 . group $ vsep
-              [ keyword "if"   <+> precBody (go con)
-              , keyword "then" <+> precBody (go tru)
-              , keyword "else" <+> precBody (go fal)
+              [ keyword "if"   <+> unPrec (go con)
+              , keyword "then" <+> unPrec (go tru)
+              , keyword "else" <+> unPrec (go fal)
               ]
 
             Load p -> prec 3 (keyword "load" <+> withPrec 9 (go p))
@@ -80,16 +81,16 @@ prettyCore style = precBody . go . fmap name
               ]
 
             statement ->
-              let (bindings, return) = unstatements (Term statement)
+              let (bindings, return) = unstatements (Alg statement)
                   statements = toList (bindings :> (Nothing :<- return))
                   names = zipWith (\ i (n :<- _) -> maybe (pretty @Int i) (name . namedName) n) [0..] statements
                   statements' = map (prettyStatement names) statements
               in atom (block "; " statements')
         block _ [] = braces mempty
         block s ss = encloseSep "{ " " }" s ss
-        keyValue x v = name x <+> symbol ":" <+> precBody (go v)
-        prettyStatement names (Just (Named (Ignored u) _) :<- t) = name u <+> arrowL <+> precBody (go (either (names !!) id <$> t))
-        prettyStatement names (Nothing                    :<- t) = precBody (go (either (names !!) id <$> t))
+        keyValue x v = name x <+> symbol ":" <+> unPrec (go v)
+        prettyStatement names (Just (Named (Ignored u) _) :<- t) = name u <+> arrowL <+> unPrec (go (either (names !!) id <$> t))
+        prettyStatement names (Nothing                    :<- t) = unPrec (go (either (names !!) id <$> t))
         lambda = case style of
           Unicode -> symbol "λ"
           Ascii   -> symbol "\\"
@@ -99,21 +100,3 @@ prettyCore style = precBody . go . fmap name
         arrowL = case style of
           Unicode -> symbol "←"
           Ascii   -> symbol "<-"
-
-
-data Prec a = Prec
-  { precLevel :: Maybe Int
-  , precBody  :: a
-  }
-  deriving (Eq, Ord, Show)
-
-prec :: Int -> a -> Prec a
-prec = Prec . Just
-
-atom :: a -> Prec a
-atom = Prec Nothing
-
-withPrec :: Int -> Prec AnsiDoc -> AnsiDoc
-withPrec d (Prec d' a)
-  | maybe False (d >) d' = parens a
-  | otherwise            = a
diff --git a/semantic-core/src/Data/File.hs b/semantic-core/src/Core/File.hs
similarity index 92%
rename from semantic-core/src/Data/File.hs
rename to semantic-core/src/Core/File.hs
index 65b2623a1..69f765162 100644
--- a/semantic-core/src/Data/File.hs
+++ b/semantic-core/src/Core/File.hs
@@ -1,10 +1,10 @@
 {-# LANGUAGE DeriveTraversable #-}
-module Data.File
+module Core.File
 ( File(..)
 , fromBody
 ) where
 
-import Data.Loc
+import Core.Loc
 import Data.Maybe (fromJust)
 import GHC.Stack
 import Source.Span
diff --git a/semantic-core/src/Data/Loc.hs b/semantic-core/src/Core/Loc.hs
similarity index 97%
rename from semantic-core/src/Data/Loc.hs
rename to semantic-core/src/Core/Loc.hs
index 0d5f2193e..b6c2016f7 100644
--- a/semantic-core/src/Data/Loc.hs
+++ b/semantic-core/src/Core/Loc.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE RecordWildCards #-}
-module Data.Loc
+module Core.Loc
 ( Path(..)
 , here
 , stackLoc
diff --git a/semantic-core/src/Data/Name.hs b/semantic-core/src/Core/Name.hs
similarity index 99%
rename from semantic-core/src/Data/Name.hs
rename to semantic-core/src/Core/Name.hs
index e70816e08..01efa8b65 100644
--- a/semantic-core/src/Data/Name.hs
+++ b/semantic-core/src/Core/Name.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE DeriveGeneric, DeriveTraversable, GeneralizedNewtypeDeriving, LambdaCase, OverloadedLists #-}
-module Data.Name
+module Core.Name
 ( Name (..)
 , Named(..)
 , named
diff --git a/semantic-core/src/Data/Scope.hs b/semantic-core/src/Data/Scope.hs
deleted file mode 100644
index 63fa2ced1..000000000
--- a/semantic-core/src/Data/Scope.hs
+++ /dev/null
@@ -1,132 +0,0 @@
-{-# LANGUAGE DeriveTraversable, LambdaCase, RankNTypes, QuantifiedConstraints, StandaloneDeriving #-}
-module Data.Scope
-( Incr(..)
-, incr
-, closed
-, Scope(..)
-, fromScope
-, toScope
-, abstract1
-, abstract
-, abstractEither
-, instantiate1
-, instantiate
-, instantiateEither
-, unprefix
-, unprefixEither
-) where
-
-import Control.Applicative (liftA2)
-import Control.Effect.Carrier
-import Control.Monad ((>=>), guard)
-import Control.Monad.Module
-import Control.Monad.Trans.Class
-import Data.Function (on)
-import Data.Stack
-
-data Incr a b
-  = Z a
-  | S b
-  deriving (Eq, Foldable, Functor, Ord, Show, Traversable)
-
-instance Applicative (Incr a) where
-  pure = S
-  Z a <*> _ = Z a
-  S f <*> a = f <$> a
-
-instance Monad (Incr a) where
-  Z a >>= _ = Z a
-  S a >>= f = f a
-
-match :: Applicative f => (b -> Either a c) -> b -> Incr a (f c)
-match f x = either Z (S . pure) (f x)
-
-matchMaybe :: (b -> Maybe a) -> (b -> Either a b)
-matchMaybe f a = maybe (Right a) Left (f a)
-
-incr :: (a -> c) -> (b -> c) -> Incr a b -> c
-incr z s = \case { Z a -> z a ; S b -> s b }
-
-
-closed :: Traversable f => f a -> Maybe (f b)
-closed = traverse (const Nothing)
-
-
-newtype Scope a f b = Scope { unScope :: f (Incr a (f b)) }
-  deriving (Foldable, Functor, Traversable)
-
-instance HFunctor (Scope a) where
-  hmap f = Scope . f . fmap (fmap f) . unScope
-
-instance (Eq   a, Eq   b, forall a . Eq   a => Eq   (f a), Monad f) => Eq   (Scope a f b) where
-  (==) = (==) `on` fromScope
-
-instance (Ord  a, Ord  b, forall a . Eq   a => Eq   (f a)
-                        , forall a . Ord  a => Ord  (f a), Monad f) => Ord  (Scope a f b) where
-  compare = compare `on` fromScope
-
-deriving instance (Show a, Show b, forall a . Show a => Show (f a)) => Show (Scope a f b)
-
-instance Applicative f => Applicative (Scope a f) where
-  pure = Scope . pure . S . pure
-  Scope f <*> Scope a = Scope (liftA2 (liftA2 (<*>)) f a)
-
-instance Monad f => Monad (Scope a f) where
-  Scope e >>= f = Scope (e >>= incr (pure . Z) (>>= unScope . f))
-
-instance MonadTrans (Scope a) where
-  lift = Scope . pure . S
-
-instance RightModule (Scope a) where
-  Scope m >>=* f = Scope (fmap (>>= f) <$> m)
-
-
-fromScope :: Monad f => Scope a f b -> f (Incr a b)
-fromScope = unScope >=> sequenceA
-
-toScope :: Applicative f => f (Incr a b) -> Scope a f b
-toScope = Scope . fmap (fmap pure)
-
-
--- | Bind occurrences of a variable in a term, producing a term in which the variable is bound.
-abstract1 :: (Applicative f, Eq a) => a -> f a -> Scope () f a
-abstract1 n = abstract (guard . (== n))
-
-abstract :: Applicative f => (b -> Maybe a) -> f b -> Scope a f b
-abstract f = abstractEither (matchMaybe f)
-
-abstractEither :: Applicative f => (b -> Either a c) -> f b -> Scope a f c
-abstractEither f = Scope . fmap (match f) -- FIXME: succ as little of the expression as possible, cf https://twitter.com/ollfredo/status/1145776391826358273
-
-
--- | Substitute a term for the free variable in a given term, producing a closed term.
-instantiate1 :: Monad f => f b -> Scope a f b -> f b
-instantiate1 t = instantiate (const t)
-
-instantiate :: Monad f => (a -> f b) -> Scope a f b -> f b
-instantiate f = instantiateEither (either f pure)
-
-instantiateEither :: Monad f => (Either a b -> f c) -> Scope a f b -> f c
-instantiateEither f = unScope >=> incr (f . Left) (>>= f . Right)
-
-
--- | Unwrap a (possibly-empty) prefix of @a@s wrapping a @t@ using a helper function.
---
---   This allows us to peel a prefix of syntax, typically binders, off of a term, returning a stack of prefixing values (e.g. variables) and the outermost subterm rejected by the function.
-unprefix
-  :: (Int -> t -> Maybe (a, t)) -- ^ A function taking the 0-based index into the prefix & the current term, and optionally returning a pair of the prefixing value and the inner subterm.
-  -> t                          -- ^ The initial term.
-  -> (Stack a, t)               -- ^ A stack of prefixing values & the final subterm.
-unprefix from = unprefixEither (matchMaybe . from)
-
--- | Unwrap a (possibly-empty) prefix of @a@s wrapping a @b@ within a @t@ using a helper function.
---
---   Compared to 'unprefix', this allows the helper function to extract inner terms of a different type, for example when @t@ is a right @b@-module.
-unprefixEither
-  :: (Int -> t -> Either (a, t) b) -- ^ A function taking the 0-based index into the prefix & the current term, and returning either a pair of the prefixing value and the next inner subterm of type @t@, or the final inner subterm of type @b@.
-  -> t                             -- ^ The initial term.
-  -> (Stack a, b)                  -- ^ A stack of prefixing values & the final subterm.
-unprefixEither from = go (0 :: Int) Nil
-  where go i bs t = case from i t of
-          Left (b, t) -> go (succ i) (bs :> b) t
-          Right b     -> (bs, b)
diff --git a/semantic-core/src/Data/Stack.hs b/semantic-core/src/Data/Stack.hs
deleted file mode 100644
index 71fec9dc2..000000000
--- a/semantic-core/src/Data/Stack.hs
+++ /dev/null
@@ -1,18 +0,0 @@
-{-# LANGUAGE DeriveTraversable #-}
-module Data.Stack
-( Stack(..)
-) where
-
-data Stack a
-  = Nil
-  | Stack a :> a
-  deriving (Eq, Foldable, Functor, Ord, Show, Traversable)
-
-infixl 4 :>
-
-instance Semigroup (Stack a) where
-  xs <> Nil       = xs
-  xs <> (ys :> y) = (xs <> ys) :> y
-
-instance Monoid (Stack a) where
-  mempty = Nil
diff --git a/semantic-core/src/Data/Term.hs b/semantic-core/src/Data/Term.hs
deleted file mode 100644
index 54bc6bf70..000000000
--- a/semantic-core/src/Data/Term.hs
+++ /dev/null
@@ -1,50 +0,0 @@
-{-# LANGUAGE DeriveTraversable, FlexibleInstances, MultiParamTypeClasses, QuantifiedConstraints, RankNTypes, StandaloneDeriving, UndecidableInstances #-}
-module Data.Term
-( Term(..)
-, hoistTerm
-) where
-
-import Control.Effect.Carrier
-import Control.Monad (ap)
-import Control.Monad.Module
-
-data Term sig a
-  = Var a
-  | Term (sig (Term sig) a)
-
-deriving instance ( Eq a
-                  , RightModule sig
-                  , forall g x . (Eq  x, Monad g, forall y . Eq  y => Eq  (g y)) => Eq  (sig g x)
-                  )
-               => Eq  (Term sig a)
-deriving instance ( Ord a
-                  , RightModule sig
-                  , forall g x . (Eq  x, Monad g, forall y . Eq  y => Eq  (g y)) => Eq  (sig g x)
-                  , forall g x . (Ord x, Monad g, forall y . Eq  y => Eq  (g y)
-                                                , forall y . Ord y => Ord (g y)) => Ord (sig g x)
-                  )
-               => Ord (Term sig a)
-deriving instance (Show a, forall g x . (Show x, forall y . Show y => Show (g y)) => Show (sig g x)) => Show (Term sig a)
-
-deriving instance ( forall g . Foldable    g => Foldable    (sig g)) => Foldable    (Term sig)
-deriving instance ( forall g . Functor     g => Functor     (sig g)) => Functor     (Term sig)
-deriving instance ( forall g . Foldable    g => Foldable    (sig g)
-                  , forall g . Functor     g => Functor     (sig g)
-                  , forall g . Traversable g => Traversable (sig g)) => Traversable (Term sig)
-
-instance RightModule sig => Applicative (Term sig) where
-  pure = Var
-  (<*>) = ap
-
-instance RightModule sig => Monad (Term sig) where
-  Var  a >>= f = f a
-  Term t >>= f = Term (t >>=* f)
-
-instance RightModule sig => Carrier sig (Term sig) where
-  eff = Term
-
-
-hoistTerm :: (HFunctor sig, forall g . Functor g => Functor (sig g)) => (forall m x . sig m x -> sig' m x) -> Term sig a -> Term sig' a
-hoistTerm f = go
-  where go (Var v)  = Var v
-        go (Term t) = Term (f (hmap (hoistTerm f) t))
diff --git a/semantic-core/test/Generators.hs b/semantic-core/test/Generators.hs
index c14701344..01cfd6feb 100644
--- a/semantic-core/test/Generators.hs
+++ b/semantic-core/test/Generators.hs
@@ -17,9 +17,8 @@ import qualified Hedgehog.Gen as Gen
 import qualified Hedgehog.Range as Range
 
 import Control.Effect.Carrier
-import qualified Data.Core as Core
-import Data.Name
-import Data.Term
+import qualified Core.Core as Core
+import Core.Name
 
 -- The 'prune' call here ensures that we don't spend all our time just generating
 -- fresh names for variables, since the length of variable names is not an
@@ -31,7 +30,7 @@ name = Gen.prune (named' <$> names) where
 boolean :: (Carrier sig t, Member Core.Core sig, MonadGen m) => m (t Name)
 boolean = Core.bool <$> Gen.bool
 
-variable :: (Carrier sig t, Member Core.Core sig, MonadGen m) => m (t Name)
+variable :: (Applicative t, MonadGen m) => m (t Name)
 variable = pure . namedValue <$> name
 
 ifthenelse :: (Carrier sig t, Member Core.Core sig, MonadGen m) => m (t Name) -> m (t Name)
diff --git a/semantic-core/test/Spec.hs b/semantic-core/test/Test.hs
similarity index 93%
rename from semantic-core/test/Spec.hs
rename to semantic-core/test/Test.hs
index 4001a4f51..84ca8304a 100644
--- a/semantic-core/test/Spec.hs
+++ b/semantic-core/test/Test.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE OverloadedStrings, TypeApplications, TypeOperators #-}
 module Main (main) where
 
-import           Data.String
 import qualified Text.Trifecta as Trifecta
 
 import           Hedgehog hiding (Var)
@@ -9,17 +8,15 @@ import           Test.Tasty
 import           Test.Tasty.Hedgehog
 import           Test.Tasty.HUnit
 
-import           Control.Effect.Sum
-import           Data.File
-import           Data.Loc (Path)
-import qualified Generators as Gen
 import qualified Analysis.Eval as Eval
-import           Data.Core
-import           Data.Core.Pretty
-import           Data.Core.Parser as Parse
-import           Data.Name
-import           Data.Term
+import           Core.Core
+import           Core.Core.Pretty
+import           Core.Core.Parser as Parse
+import           Core.File
+import           Core.Name
+import qualified Generators as Gen
 import           Source.Span
+import           Syntax.Term
 
 -- * Helpers
 
diff --git a/semantic-python/semantic-python.cabal b/semantic-python/semantic-python.cabal
index e7847e591..4732ec4e5 100644
--- a/semantic-python/semantic-python.cabal
+++ b/semantic-python/semantic-python.cabal
@@ -22,6 +22,7 @@ common haskell
   default-language:    Haskell2010
   build-depends:       base ^>=4.12
                      , fused-effects ^>= 0.5
+                     , fused-syntax
                      , semantic-core ^>= 0.0
                      , semantic-source ^>= 0.0
                      , semantic-tags ^>= 0.0
diff --git a/semantic-python/src/Language/Python/Core.hs b/semantic-python/src/Language/Python/Core.hs
index fe437dd47..b74b38f20 100644
--- a/semantic-python/src/Language/Python/Core.hs
+++ b/semantic-python/src/Language/Python/Core.hs
@@ -13,14 +13,14 @@ import           AST.Element
 import           Control.Effect hiding ((:+:))
 import           Control.Effect.Reader
 import           Control.Monad.Fail
+import           Core.Core as Core
+import           Core.Name as Name
 import           Data.Coerce
-import           Data.Core as Core
 import           Data.Foldable
-import           Data.Name as Name
-import           Data.Stack (Stack)
-import qualified Data.Stack as Stack
 import           GHC.Records
 import           Source.Span (Span)
+import           Syntax.Stack (Stack)
+import qualified Syntax.Stack as Stack
 import qualified TreeSitter.Python.AST as Py
 
 -- | Keeps track of the current scope's bindings (so that we can, when
diff --git a/semantic-python/test/Directive.hs b/semantic-python/test/Directive.hs
index c3a0cfcdc..3c4bc20a0 100644
--- a/semantic-python/test/Directive.hs
+++ b/semantic-python/test/Directive.hs
@@ -6,13 +6,13 @@ module Directive ( Directive (..)
 
 import           Control.Applicative
 import           Control.Monad
-import           Data.Name (Name)
-import           Data.Term (Term)
-import           Data.Core (Core)
-import qualified Data.Core.Parser as Core.Parser
-import qualified Data.Core.Pretty as Core.Pretty
+import           Core.Core (Core)
+import qualified Core.Core.Parser as Core.Parser
+import qualified Core.Core.Pretty as Core.Pretty
+import           Core.Name (Name)
 import           Data.ByteString.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as ByteString
+import           Syntax.Term (Term)
 import           System.Process
 import qualified Text.Trifecta as Trifecta
 
diff --git a/semantic-python/test/Instances.hs b/semantic-python/test/Instances.hs
index 1f52ab4f9..3db17c44a 100644
--- a/semantic-python/test/Instances.hs
+++ b/semantic-python/test/Instances.hs
@@ -8,11 +8,11 @@ module Instances () where
 -- we should keep track of them in a dedicated file.
 
 import           Analysis.ScopeGraph
+import           Core.File
+import           Core.Loc
+import           Core.Name (Name (..))
 import           Data.Aeson
-import           Data.File
-import           Data.Loc
 import qualified Data.Map as Map
-import           Data.Name (Name (..))
 import           Data.Text (Text)
 
 deriving newtype instance ToJSON Name
diff --git a/semantic-python/test/Test.hs b/semantic-python/test/Test.hs
index 8a230ca19..739174b9d 100644
--- a/semantic-python/test/Test.hs
+++ b/semantic-python/test/Test.hs
@@ -3,6 +3,7 @@
 module Main (main) where
 
 import qualified Analysis.Eval as Eval
+import           Analysis.ScopeGraph
 import           Control.Effect
 import           Control.Effect.Fail
 import           Control.Effect.Reader
@@ -10,21 +11,20 @@ import           Control.Monad hiding (fail)
 import           Control.Monad.Catch
 import           Control.Monad.IO.Class
 import           Control.Monad.Trans.Resource (ResourceT, runResourceT)
+import           Core.Core
+import           Core.Core.Pretty
+import           Core.File
+import           Core.Loc
+import           Core.Name
 import qualified Data.Aeson as Aeson
 import qualified Data.Aeson.Encode.Pretty as Aeson
 import qualified Data.ByteString.Char8 as ByteString
 import qualified Data.ByteString.Lazy.Char8 as ByteString.Lazy
 import qualified Data.ByteString.Streaming.Char8 as ByteStream
-import           Data.Core
-import           Data.Core.Pretty
-import           Data.File
 import           Data.Foldable
 import           Data.Function
 import           Data.List (sort)
-import           Data.Loc
 import           Data.Maybe
-import           Data.Name
-import           Data.Term
 import           GHC.Stack
 import qualified Language.Python.Core as Py
 import           Prelude hiding (fail)
@@ -32,19 +32,19 @@ import           Source.Span
 import           Streaming
 import qualified Streaming.Prelude as Stream
 import qualified Streaming.Process
+import           Syntax.Term
 import           System.Directory
 import           System.Exit
-import qualified TreeSitter.Python as TSP
-import qualified TreeSitter.Unmarshal as TS
-import           Text.Show.Pretty (ppShow)
 import qualified System.Path as Path
 import qualified System.Path.Directory as Path
 import           System.Path ((</>))
+import           Text.Show.Pretty (ppShow)
+import qualified TreeSitter.Python as TSP
+import qualified TreeSitter.Unmarshal as TS
 
 import qualified Test.Tasty as Tasty
 import qualified Test.Tasty.HUnit as HUnit
 
-import           Analysis.ScopeGraph
 import qualified Directive
 import           Instances ()