diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -47,6 +47,7 @@
   bytestring-builder
   cabal-doctest
   case-insensitive
+  cereal
   cheapskate
   clock
   colour
@@ -71,7 +72,6 @@
   dlist
   easy-file
   edit-distance
-  enclosed-exceptions
   entropy
   exceptions
   fast-logger
@@ -83,7 +83,7 @@
   happy
   hashable
   haskeline
-  hinotify
+  hfsevents
   http-date
   http-types
   http2
@@ -129,7 +129,6 @@
   semialign
   semigroupoids
   semigroups
-  shelly
   simple-sendfile
   sourcemap
   split
@@ -138,8 +137,6 @@
   streaming-commons
   stringsearch
   syb
-  system-fileio
-  system-filepath
   tagged
   tagsoup
   template-haskell
@@ -1295,6 +1292,39 @@
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+cereal LICENSE file:
+
+  Copyright (c) Lennart Kolmodin, Galois, Inc.
+
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in the
+     documentation and/or other materials provided with the distribution.
+
+  3. Neither the name of the author nor the names of his contributors
+     may be used to endorse or promote products derived from this software
+     without specific prior written permission.
+
+  THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND ANY EXPRESS
+  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
+  ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+  POSSIBILITY OF SUCH DAMAGE.
+
 cheapskate LICENSE file:
 
   Copyright (c) 2013, John MacFarlane
@@ -2021,29 +2051,6 @@
   IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-enclosed-exceptions LICENSE file:
-
-  Copyright (c) 2012 Michael Snoyman, http://www.yesodweb.com/
-
-  Permission is hereby granted, free of charge, to any person obtaining
-  a copy of this software and associated documentation files (the
-  "Software"), to deal in the Software without restriction, including
-  without limitation the rights to use, copy, modify, merge, publish,
-  distribute, sublicense, and/or sell copies of the Software, and to
-  permit persons to whom the Software is furnished to do so, subject to
-  the following conditions:
-
-  The above copyright notice and this permission notice shall be
-  included in all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
-  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
-  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
 entropy LICENSE file:
 
   Copyright (c) Thomas DuBuisson
@@ -2428,38 +2435,38 @@
   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
   USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-hinotify LICENSE file:
+hfsevents LICENSE file:
 
-  Copyright (c) Lennart Kolmodin
+  Copyright (c) 2012, Luite Stegeman
 
   All rights reserved.
 
   Redistribution and use in source and binary forms, with or without
-  modification, are permitted provided that the following conditions
-  are met:
+  modification, are permitted provided that the following conditions are met:
 
-  1. Redistributions of source code must retain the above copyright
-     notice, this list of conditions and the following disclaimer.
+      * Redistributions of source code must retain the above copyright
+        notice, this list of conditions and the following disclaimer.
 
-  2. Redistributions in binary form must reproduce the above copyright
-     notice, this list of conditions and the following disclaimer in the
-     documentation and/or other materials provided with the distribution.
+      * Redistributions in binary form must reproduce the above
+        copyright notice, this list of conditions and the following
+        disclaimer in the documentation and/or other materials provided
+        with the distribution.
 
-  3. Neither the name of the author nor the names of his contributors
-     may be used to endorse or promote products derived from this software
-     without specific prior written permission.
+      * Neither the name of Luite Stegeman nor the names of other
+        contributors may be used to endorse or promote products derived
+        from this software without specific prior written permission.
 
-  THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND ANY EXPRESS
-  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
-  DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
-  ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
-  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
-  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-  POSSIBILITY OF SUCH DAMAGE.
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 http-date LICENSE file:
 
@@ -3947,39 +3954,6 @@
   ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE.
 
-shelly LICENSE file:
-
-  Copyright (c) 2017, Petr Rockai <me@mornfall.net>
-
-  All rights reserved.
-
-  Redistribution and use in source and binary forms, with or without
-  modification, are permitted provided that the following conditions are met:
-
-      * Redistributions of source code must retain the above copyright
-        notice, this list of conditions and the following disclaimer.
-
-      * Redistributions in binary form must reproduce the above
-        copyright notice, this list of conditions and the following
-        disclaimer in the documentation and/or other materials provided
-        with the distribution.
-
-      * Neither the name of Petr Rockai nor the names of other
-        contributors may be used to endorse or promote products derived
-        from this software without specific prior written permission.
-
-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
 simple-sendfile LICENSE file:
 
   Copyright (c) 2009, IIJ Innovation Institute Inc.
@@ -4289,56 +4263,6 @@
     be a definition of the Haskell 98 Foreign Function Interface.
 
   -----------------------------------------------------------------------------
-
-system-fileio LICENSE file:
-
-  Copyright (c) 2011 John Millikin
-
-  Permission is hereby granted, free of charge, to any person
-  obtaining a copy of this software and associated documentation
-  files (the "Software"), to deal in the Software without
-  restriction, including without limitation the rights to use,
-  copy, modify, merge, publish, distribute, sublicense, and/or sell
-  copies of the Software, and to permit persons to whom the
-  Software is furnished to do so, subject to the following
-  conditions:
-
-  The above copyright notice and this permission notice shall be
-  included in all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
-  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
-  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
-  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-  OTHER DEALINGS IN THE SOFTWARE.
-
-system-filepath LICENSE file:
-
-  Copyright (c) 2010 John Millikin
-
-  Permission is hereby granted, free of charge, to any person
-  obtaining a copy of this software and associated documentation
-  files (the "Software"), to deal in the Software without
-  restriction, including without limitation the rights to use,
-  copy, modify, merge, publish, distribute, sublicense, and/or sell
-  copies of the Software, and to permit persons to whom the
-  Software is furnished to do so, subject to the following
-  conditions:
-
-  The above copyright notice and this permission notice shall be
-  included in all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
-  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
-  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
-  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-  OTHER DEALINGS IN THE SOFTWARE.
 
 tagged LICENSE file:
 
diff --git a/purescript.cabal b/purescript.cabal
--- a/purescript.cabal
+++ b/purescript.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.12
 name: purescript
-version: 0.13.5
+version: 0.13.6
 license: BSD3
 license-file: LICENSE
 copyright: (c) 2013-17 Phil Freeman, (c) 2014-19 Gary Burgess, (c) other contributors (see CONTRIBUTORS.md)
@@ -401,6 +401,7 @@
     tests/purs/passing/3114/VendoredVariant.purs
     tests/purs/passing/3125.purs
     tests/purs/passing/3187-UnusedNameClash.purs
+    tests/purs/passing/3238.purs
     tests/purs/passing/3388.purs
     tests/purs/passing/3410.purs
     tests/purs/passing/3481.purs
diff --git a/src/Language/PureScript/AST/Declarations.hs b/src/Language/PureScript/AST/Declarations.hs
--- a/src/Language/PureScript/AST/Declarations.hs
+++ b/src/Language/PureScript/AST/Declarations.hs
@@ -111,7 +111,7 @@
   | ConstrainedTypeUnified SourceType SourceType
   | OverlappingInstances (Qualified (ProperName 'ClassName)) [SourceType] [Qualified Ident]
   | NoInstanceFound SourceConstraint
-  | AmbiguousTypeVariables SourceType SourceConstraint
+  | AmbiguousTypeVariables SourceType [Int]
   | UnknownClass (Qualified (ProperName 'ClassName))
   | PossiblyInfiniteInstance (Qualified (ProperName 'ClassName)) [SourceType]
   | CannotDerive (Qualified (ProperName 'ClassName)) [SourceType]
diff --git a/src/Language/PureScript/CoreImp/Optimizer/MagicDo.hs b/src/Language/PureScript/CoreImp/Optimizer/MagicDo.hs
--- a/src/Language/PureScript/CoreImp/Optimizer/MagicDo.hs
+++ b/src/Language/PureScript/CoreImp/Optimizer/MagicDo.hs
@@ -48,6 +48,10 @@
   -- Desugar discard
   convert (App _ (App _ bind [m]) [Function s1 Nothing [] (Block s2 js)]) | isDiscard bind =
     Function s1 (Just fnName) [] $ Block s2 (App s2 m [] : map applyReturns js )
+  -- Desugar bind to wildcard
+  convert (App _ (App _ bind [m]) [Function s1 Nothing [] (Block s2 js)])
+    | isBind bind =
+    Function s1 (Just fnName) [] $ Block s2 (App s2 m [] : map applyReturns js )
   -- Desugar bind
   convert (App _ (App _ bind [m]) [Function s1 Nothing [arg] (Block s2 js)]) | isBind bind =
     Function s1 (Just fnName) [] $ Block s2 (VariableIntroduction s2 arg (Just (App s2 m [])) : map applyReturns js)
diff --git a/src/Language/PureScript/Docs/Convert.hs b/src/Language/PureScript/Docs/Convert.hs
--- a/src/Language/PureScript/Docs/Convert.hs
+++ b/src/Language/PureScript/Docs/Convert.hs
@@ -35,11 +35,12 @@
 convertModule ::
   MonadError P.MultipleErrors m =>
   [P.ExternsFile] ->
+  P.Env ->
   P.Environment ->
   P.Module ->
   m Module
-convertModule externs checkEnv m =
-  partiallyDesugar externs [m] >>= \case
+convertModule externs env checkEnv m =
+  partiallyDesugar externs env [m] >>= \case
     [m'] -> pure (insertValueTypes checkEnv (convertSingleModule m'))
     _ -> P.internalError "partiallyDesugar did not return a singleton"
 
@@ -88,9 +89,10 @@
 partiallyDesugar ::
   (MonadError P.MultipleErrors m) =>
   [P.ExternsFile] ->
+  P.Env ->
   [P.Module] ->
   m [P.Module]
-partiallyDesugar externs = evalSupplyT 0 . desugar'
+partiallyDesugar externs env = evalSupplyT 0 . desugar'
   where
   desugar' =
     traverse P.desugarDoModule
@@ -98,10 +100,8 @@
       >=> map P.desugarLetPatternModule
       >>> traverse P.desugarCasesModule
       >=> traverse P.desugarTypeDeclarationsModule
-      >=> ignoreWarnings . P.desugarImports externs
+      >=> fmap fst . runWriterT . P.desugarImports env
       >=> P.rebracketFiltered isInstanceDecl externs
-
-  ignoreWarnings = fmap fst . runWriterT
 
   isInstanceDecl (P.TypeInstanceDeclaration {}) = True
   isInstanceDecl _ = False
diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -286,7 +286,7 @@
   gSimple (ExprDoesNotHaveType e t) = ExprDoesNotHaveType e <$> f t
   gSimple (InvalidInstanceHead t) = InvalidInstanceHead <$> f t
   gSimple (NoInstanceFound con) = NoInstanceFound <$> overConstraintArgs (traverse f) con
-  gSimple (AmbiguousTypeVariables t con) = AmbiguousTypeVariables <$> f t <*> pure con
+  gSimple (AmbiguousTypeVariables t us) = AmbiguousTypeVariables <$> f t <*> pure us
   gSimple (OverlappingInstances cl ts insts) = OverlappingInstances cl <$> traverse f ts <*> pure insts
   gSimple (PossiblyInfiniteInstance cl ts) = PossiblyInfiniteInstance cl <$> traverse f ts
   gSimple (CannotDerive cl ts) = CannotDerive cl <$> traverse f ts
@@ -679,10 +679,16 @@
         where
         go TUnknown{} = True
         go _ = False
-    renderSimpleErrorMessage (AmbiguousTypeVariables t _) =
+    renderSimpleErrorMessage (AmbiguousTypeVariables t us) =
       paras [ line "The inferred type"
             , markCodeBox $ indent $ typeAsBox prettyDepth t
-            , line "has type variables which are not mentioned in the body of the type. Consider adding a type annotation."
+            , line "has type variables which are not determined by those mentioned in the body of the type:"
+            , indent $ Box.hsep 1 Box.left
+              [ Box.vcat Box.left
+                [ line $ markCode ("t" <> T.pack (show u)) <> " could not be determined"
+                | u <- us ]
+              ]
+            , line "Consider adding a type annotation."
             ]
     renderSimpleErrorMessage (PossiblyInfiniteInstance nm ts) =
       paras [ line "Type class instance for"
diff --git a/src/Language/PureScript/Ide.hs b/src/Language/PureScript/Ide.hs
--- a/src/Language/PureScript/Ide.hs
+++ b/src/Language/PureScript/Ide.hs
@@ -51,7 +51,8 @@
   -> m Success
 handleCommand c = case c of
   Load [] ->
-    findAvailableExterns >>= loadModulesAsync
+    -- Clearing the State before populating it to avoid a space leak
+    resetIdeState *> findAvailableExterns >>= loadModulesAsync
   Load modules ->
     loadModulesAsync modules
   LoadSync [] ->
diff --git a/src/Language/PureScript/Ide/Imports.hs b/src/Language/PureScript/Ide/Imports.hs
--- a/src/Language/PureScript/Ide/Imports.hs
+++ b/src/Language/PureScript/Ide/Imports.hs
@@ -303,7 +303,7 @@
     -- This case comes up for newtypes and dataconstructors. Because values and
     -- types don't share a namespace we can get multiple matches from the same
     -- module. This also happens for parameterized types, as these generate both
-    -- a type aswell as a type synonym.
+    -- a type as well as a type synonym.
 
     ms@[Match (m1, d1), Match (m2, d2)] ->
       if m1 /= m2
diff --git a/src/Language/PureScript/Ide/Matcher.hs b/src/Language/PureScript/Ide/Matcher.hs
--- a/src/Language/PureScript/Ide/Matcher.hs
+++ b/src/Language/PureScript/Ide/Matcher.hs
@@ -52,7 +52,7 @@
       Just _ -> mzero
       Nothing -> return mempty
 
--- | Matches any occurence of the search string with intersections
+-- | Matches any occurrence of the search string with intersections
 --
 -- The scoring measures how far the matches span the string where
 -- closer is better.
diff --git a/src/Language/PureScript/Interactive/Directive.hs b/src/Language/PureScript/Interactive/Directive.hs
--- a/src/Language/PureScript/Interactive/Directive.hs
+++ b/src/Language/PureScript/Interactive/Directive.hs
@@ -12,7 +12,7 @@
 import Language.PureScript.Interactive.Types
 
 -- |
--- List of all avaliable directives.
+-- List of all available directives.
 --
 directives :: [Directive]
 directives = map fst directiveStrings
diff --git a/src/Language/PureScript/Interactive/Types.hs b/src/Language/PureScript/Interactive/Types.hs
--- a/src/Language/PureScript/Interactive/Types.hs
+++ b/src/Language/PureScript/Interactive/Types.hs
@@ -35,6 +35,7 @@
 import qualified Data.Map as M
 import           Data.List (foldl')
 import           Language.PureScript.Sugar.Names.Env (nullImports, primExports)
+import           Control.Monad (foldM)
 import           Control.Monad.Trans.Except (runExceptT)
 import           Control.Monad.Writer.Strict (runWriterT)
 
@@ -118,7 +119,7 @@
 -- ensure that completions remain accurate.
 updateImportExports :: PSCiState -> PSCiState
 updateImportExports st@(PSCiState modules lets externs iprint _ _) =
-  case desugarModule [temporaryModule] of
+  case createEnv (map snd externs) >>= flip desugarModule [temporaryModule] of
     Left _          -> st -- TODO: can this fail and what should we do?
     Right (env, _)  ->
       case M.lookup temporaryName env of
@@ -126,9 +127,11 @@
         _                 -> st -- impossible
   where
 
-  desugarModule :: [P.Module] -> Either P.MultipleErrors (P.Env, [P.Module])
-  desugarModule = runExceptT =<< hushWarnings . P.desugarImportsWithEnv (map snd externs)
-  hushWarnings  = fmap fst . runWriterT
+  desugarModule :: P.Env -> [P.Module] -> Either P.MultipleErrors (P.Env, [P.Module])
+  desugarModule e = runExceptT =<< fmap fst . runWriterT . P.desugarImportsWithEnv e
+
+  createEnv :: [P.ExternsFile] -> Either P.MultipleErrors P.Env
+  createEnv = runExceptT =<< fmap fst . runWriterT . foldM P.externsEnv P.primEnv
 
   temporaryName :: P.ModuleName
   temporaryName = P.ModuleName [P.ProperName "$PSCI"]
diff --git a/src/Language/PureScript/Kinds.hs b/src/Language/PureScript/Kinds.hs
--- a/src/Language/PureScript/Kinds.hs
+++ b/src/Language/PureScript/Kinds.hs
@@ -98,7 +98,7 @@
   go :: Value -> Parser (Kind a)
   go = kindFromJSON defaultAnn annFromJSON
 
--- These overlapping instances exist to preserve compatability for common
+-- These overlapping instances exist to preserve compatibility for common
 -- instances which have a sensible default for missing annotations.
 instance {-# OVERLAPPING #-} A.FromJSON (Kind SourceAnn) where
   parseJSON = kindFromJSON (pure NullSourceAnn) A.parseJSON
diff --git a/src/Language/PureScript/Make.hs b/src/Language/PureScript/Make.hs
--- a/src/Language/PureScript/Make.hs
+++ b/src/Language/PureScript/Make.hs
@@ -17,6 +17,7 @@
 import           Control.Monad.Supply
 import           Control.Monad.Trans.Control (MonadBaseControl(..))
 import           Control.Monad.Writer.Class (MonadWriter(..))
+import           Control.Monad.Writer.Strict (runWriterT)
 import           Data.Function (on)
 import           Data.Foldable (for_)
 import           Data.List (foldl', sortBy)
@@ -57,13 +58,25 @@
   -> [ExternsFile]
   -> Module
   -> m ExternsFile
-rebuildModule MakeActions{..} externs m@(Module _ _ moduleName _ _) = do
+rebuildModule actions externs m = do
+  env <- fmap fst . runWriterT $ foldM externsEnv primEnv externs
+  rebuildModule' actions env externs m
+
+rebuildModule'
+  :: forall m
+   . (Monad m, MonadBaseControl IO m, MonadError MultipleErrors m, MonadWriter MultipleErrors m)
+  => MakeActions m
+  -> Env
+  -> [ExternsFile]
+  -> Module
+  -> m ExternsFile
+rebuildModule' MakeActions{..} exEnv externs m@(Module _ _ moduleName _ _) = do
   progress $ CompilingModule moduleName
   let env = foldl' (flip applyExternsFileToEnvironment) initEnvironment externs
       withPrim = importPrim m
   lint withPrim
   ((Module ss coms _ elaborated exps, env'), nextVar) <- runSupplyT 0 $ do
-    desugar externs [withPrim] >>= \case
+    desugar exEnv externs [withPrim] >>= \case
       [desugared] -> runCheck' (emptyCheckState env) $ typeCheckModule desugared
       _ -> internalError "desugar did not return a singleton"
 
@@ -88,7 +101,7 @@
   -- a bug in the compiler, which should be reported as such.
   -- 2. We do not want to perform any extra work generating docs unless the
   -- user has asked for docs to be generated.
-  let docs = case Docs.convertModule externs env' m of
+  let docs = case Docs.convertModule externs exEnv env' m of
                Left errs -> internalError $
                  "Failed to produce docs for " ++ T.unpack (runModuleName moduleName)
                  ++ "; details:\n" ++ prettyPrintMultipleErrors defaultPPEOptions errs
@@ -138,6 +151,9 @@
   -- Write the updated build cache database to disk
   writeCacheDb $ Cache.removeModules (M.keysSet failures) newCacheDb
 
+  -- If generating docs, also generate them for the Prim modules
+  outputPrimDocs
+
   -- All threads have completed, rethrow any caught errors.
   let errors = M.elems failures
   unless (null errors) $ throwError (mconcat errors)
@@ -192,7 +208,17 @@
 
       case mexterns of
         Just (_, externs) -> do
-          (exts, warnings) <- listen $ rebuildModule ma externs m
+          -- We need to ensure that all dependencies have been included in Env
+          C.modifyMVar_ (bpEnv buildPlan) $ \env -> do
+            let
+              go :: Env -> ModuleName -> m Env
+              go e dep = case lookup dep (zip deps externs) of
+                Just exts
+                  | not (M.member dep e) -> externsEnv e exts
+                _ -> return e
+            foldM go env deps
+          env <- C.readMVar (bpEnv buildPlan)
+          (exts, warnings) <- listen $ rebuildModule' ma env externs m
           return $ BuildJobSucceeded warnings exts
         Nothing -> return BuildJobSkipped
 
diff --git a/src/Language/PureScript/Make/Actions.hs b/src/Language/PureScript/Make/Actions.hs
--- a/src/Language/PureScript/Make/Actions.hs
+++ b/src/Language/PureScript/Make/Actions.hs
@@ -36,6 +36,7 @@
 import qualified Language.PureScript.CoreImp.AST as Imp
 import           Language.PureScript.Crash
 import qualified Language.PureScript.CST as CST
+import qualified Language.PureScript.Docs.Prim as Docs.Prim
 import qualified Language.PureScript.Docs.Types as Docs
 import           Language.PureScript.Errors
 import           Language.PureScript.Externs (ExternsFile)
@@ -100,6 +101,8 @@
   , writeCacheDb :: CacheDb -> m ()
   -- ^ Write the given cache database to some external source (e.g. a file on
   -- disk).
+  , outputPrimDocs :: m ()
+  -- ^ If generating docs, output the documentation for the Prim modules
   }
 
 -- | A set of make actions that read and write modules from the given directory.
@@ -114,7 +117,7 @@
   -- ^ Generate a prefix comment?
   -> MakeActions Make
 buildMakeActions outputDir filePathMap foreigns usePrefix =
-    MakeActions getInputTimestampsAndHashes getOutputTimestamp readExterns codegen ffiCodegen progress readCacheDb writeCacheDb
+    MakeActions getInputTimestampsAndHashes getOutputTimestamp readExterns codegen ffiCodegen progress readCacheDb writeCacheDb outputPrimDocs
   where
 
   getInputTimestampsAndHashes
@@ -156,6 +159,12 @@
   readExterns mn = do
     let path = outputDir </> T.unpack (runModuleName mn) </> "externs.json"
     (path, ) <$> readExternsFile path
+
+  outputPrimDocs :: Make ()
+  outputPrimDocs = do
+    codegenTargets <- asks optionsCodegenTargets
+    when (S.member Docs codegenTargets) $ for_ Docs.Prim.primModules $ \docsMod@Docs.Module{..} ->
+      writeJSONFile (outputFilename modName "docs.json") docsMod
 
   codegen :: CF.Module CF.Ann -> Docs.Module -> ExternsFile -> SupplyT Make ()
   codegen m docs exts = do
diff --git a/src/Language/PureScript/Make/BuildPlan.hs b/src/Language/PureScript/Make/BuildPlan.hs
--- a/src/Language/PureScript/Make/BuildPlan.hs
+++ b/src/Language/PureScript/Make/BuildPlan.hs
@@ -1,5 +1,5 @@
 module Language.PureScript.Make.BuildPlan
-  ( BuildPlan()
+  ( BuildPlan(bpEnv)
   , BuildJobResult(..)
   , buildJobSuccess
   , buildJobFailure
@@ -29,12 +29,14 @@
 import           Language.PureScript.Make.Actions as Actions
 import           Language.PureScript.Make.Cache
 import           Language.PureScript.Names (ModuleName)
+import           Language.PureScript.Sugar.Names.Env
 
 -- | The BuildPlan tracks information about our build progress, and holds all
 -- prebuilt modules for incremental builds.
 data BuildPlan = BuildPlan
   { bpPrebuilt :: M.Map ModuleName Prebuilt
   , bpBuildJobs :: M.Map ModuleName BuildJob
+  , bpEnv :: C.MVar Env
   }
 
 data Prebuilt = Prebuilt
@@ -140,8 +142,9 @@
           mapMaybe (\s -> (statusModuleName s, statusRebuildNever s,) <$> statusPrebuilt s) rebuildStatuses
   let toBeRebuilt = filter (not . flip M.member prebuilt) sortedModuleNames
   buildJobs <- foldM makeBuildJob M.empty toBeRebuilt
+  env <- C.newMVar primEnv
   pure
-    ( BuildPlan prebuilt buildJobs
+    ( BuildPlan prebuilt buildJobs env
     , let
         update = flip $ \s ->
           M.alter (const (statusNewCacheInfo s)) (statusModuleName s)
diff --git a/src/Language/PureScript/PSString.hs b/src/Language/PureScript/PSString.hs
--- a/src/Language/PureScript/PSString.hs
+++ b/src/Language/PureScript/PSString.hs
@@ -18,7 +18,7 @@
 import Control.DeepSeq (NFData)
 import Control.Exception (try, evaluate)
 import Control.Applicative ((<|>))
-import Data.Char (chr)
+import qualified Data.Char as Char
 import Data.Bits (shiftR)
 import Data.List (unfoldr)
 import Data.Scientific (toBoundedInteger)
@@ -67,7 +67,7 @@
 -- we do not export it.
 --
 codePoints :: PSString -> String
-codePoints = map (either (chr . fromIntegral) id) . decodeStringEither
+codePoints = map (either (Char.chr . fromIntegral) id) . decodeStringEither
 
 -- |
 -- Decode a PSString as UTF-16 text. Lone surrogates will be replaced with
@@ -94,14 +94,6 @@
   unsurrogate h l = toEnum ((toInt h - 0xD800) * 0x400 + (toInt l - 0xDC00) + 0x10000)
 
 -- |
--- Pretty print a PSString, using Haskell/PureScript escape sequences.
--- This is identical to the Show instance except that we get a Text out instead
--- of a String.
---
-prettyPrintString :: PSString -> Text
-prettyPrintString = T.pack . show
-
--- |
 -- Attempt to decode a PSString as UTF-16 text. This will fail (returning
 -- Nothing) if the argument contains lone surrogates.
 --
@@ -156,6 +148,52 @@
     parseCodeUnit b = A.withScientific "two-byte non-negative integer" (maybe (A.typeMismatch "" b) return . toBoundedInteger) b
 
 -- |
+-- Pretty print a PSString, using PureScript escape sequences.
+--
+prettyPrintString :: PSString -> Text
+prettyPrintString s = "\"" <> foldMap encodeChar (decodeStringEither s) <> "\""
+  where
+  encodeChar :: Either Word16 Char -> Text
+  encodeChar (Left c) = "\\x" <> showHex' 6 c
+  encodeChar (Right c)
+    | c == '\t' = "\\t"
+    | c == '\r' = "\\r"
+    | c == '\n' = "\\n"
+    | c == '"'  = "\\\""
+    | c == '\''  = "\\\'"
+    | c == '\\' = "\\\\"
+    | shouldPrint c = T.singleton c
+    | otherwise = "\\x" <> showHex' 6 (Char.ord c)
+
+  -- Note we do not use Data.Char.isPrint here because that includes things
+  -- like zero-width spaces and combining punctuation marks, which could be
+  -- confusing to print unescaped.
+  shouldPrint :: Char -> Bool
+  -- The standard space character, U+20 SPACE, is the only space char we should
+  -- print without escaping
+  shouldPrint ' ' = True
+  shouldPrint c =
+    Char.generalCategory c `elem`
+      [ Char.UppercaseLetter
+      , Char.LowercaseLetter
+      , Char.TitlecaseLetter
+      , Char.OtherLetter
+      , Char.DecimalNumber
+      , Char.LetterNumber
+      , Char.OtherNumber
+      , Char.ConnectorPunctuation
+      , Char.DashPunctuation
+      , Char.OpenPunctuation
+      , Char.InitialQuote
+      , Char.FinalQuote
+      , Char.OtherPunctuation
+      , Char.MathSymbol
+      , Char.CurrencySymbol
+      , Char.ModifierSymbol
+      , Char.OtherSymbol
+      ]
+
+-- |
 -- Pretty print a PSString, using JavaScript escape sequences. Intended for
 -- use in compiled JS output.
 --
@@ -163,8 +201,8 @@
 prettyPrintStringJS s = "\"" <> foldMap encodeChar (toUTF16CodeUnits s) <> "\""
   where
   encodeChar :: Word16 -> Text
-  encodeChar c | c > 0xFF = "\\u" <> hex 4 c
-  encodeChar c | c > 0x7E || c < 0x20 = "\\x" <> hex 2 c
+  encodeChar c | c > 0xFF = "\\u" <> showHex' 4 c
+  encodeChar c | c > 0x7E || c < 0x20 = "\\x" <> showHex' 2 c
   encodeChar c | toChar c == '\b' = "\\b"
   encodeChar c | toChar c == '\t' = "\\t"
   encodeChar c | toChar c == '\n' = "\\n"
@@ -175,10 +213,10 @@
   encodeChar c | toChar c == '\\' = "\\\\"
   encodeChar c = T.singleton $ toChar c
 
-  hex :: (Enum a) => Int -> a -> Text
-  hex width c =
-    let hs = showHex (fromEnum c) "" in
-    T.pack (replicate (width - length hs) '0' <> hs)
+showHex' :: Enum a => Int -> a -> Text
+showHex' width c =
+  let hs = showHex (fromEnum c) "" in
+  T.pack (replicate (width - length hs) '0' <> hs)
 
 isLead :: Word16 -> Bool
 isLead h = h >= 0xD800 && h <= 0xDBFF
diff --git a/src/Language/PureScript/Sugar.hs b/src/Language/PureScript/Sugar.hs
--- a/src/Language/PureScript/Sugar.hs
+++ b/src/Language/PureScript/Sugar.hs
@@ -54,10 +54,11 @@
 --
 desugar
   :: (MonadSupply m, MonadError MultipleErrors m, MonadWriter MultipleErrors m)
-  => [ExternsFile]
+  => Env
+  -> [ExternsFile]
   -> [Module]
   -> m [Module]
-desugar externs =
+desugar env externs =
   map desugarSignedLiterals
     >>> traverse desugarObjectConstructors
     >=> traverse desugarDoModule
@@ -65,7 +66,7 @@
     >=> map desugarLetPatternModule
     >>> traverse desugarCasesModule
     >=> traverse desugarTypeDeclarationsModule
-    >=> desugarImports externs
+    >=> desugarImports env
     >=> rebracket externs
     >=> traverse checkFixityExports
     >=> traverse (deriveInstances externs)
diff --git a/src/Language/PureScript/Sugar/AdoNotation.hs b/src/Language/PureScript/Sugar/AdoNotation.hs
--- a/src/Language/PureScript/Sugar/AdoNotation.hs
+++ b/src/Language/PureScript/Sugar/AdoNotation.hs
@@ -25,43 +25,44 @@
 -- | Desugar a single ado statement
 desugarAdo :: forall m. (MonadSupply m, MonadError MultipleErrors m) => Declaration -> m Declaration
 desugarAdo d =
-  let (f, _, _) = everywhereOnValuesM return replace return
-  in f d
+  let ss = declSourceSpan d
+      (f, _, _) = everywhereOnValuesM return (replace ss) return
+  in rethrowWithPosition ss $ f d
   where
-  pure' :: Maybe ModuleName -> Expr
-  pure' m = Var nullSourceSpan (Qualified m (Ident C.pure'))
+  pure' :: SourceSpan -> Maybe ModuleName -> Expr
+  pure' ss m = Var ss (Qualified m (Ident C.pure'))
 
-  map' :: Maybe ModuleName -> Expr
-  map' m = Var nullSourceSpan (Qualified m (Ident C.map))
+  map' :: SourceSpan -> Maybe ModuleName -> Expr
+  map' ss m = Var ss (Qualified m (Ident C.map))
 
-  apply :: Maybe ModuleName -> Expr
-  apply m = Var nullSourceSpan (Qualified m (Ident C.apply))
+  apply :: SourceSpan -> Maybe ModuleName -> Expr
+  apply ss m = Var ss (Qualified m (Ident C.apply))
 
-  replace :: Expr -> m Expr
-  replace (Ado m els yield) = do
-    (func, args) <- foldM go (yield, []) (reverse els)
+  replace :: SourceSpan -> Expr -> m Expr
+  replace pos (Ado m els yield) = do
+    (func, args) <- foldM (go pos) (yield, []) (reverse els)
     return $ case args of
-      [] -> App (pure' m) func
-      hd : tl -> foldl' (\a b -> App (App (apply m) a) b) (App (App (map' m) func) hd) tl
-  replace (PositionedValue pos com v) = PositionedValue pos com <$> rethrowWithPosition pos (replace v)
-  replace other = return other
+      [] -> App (pure' pos m) func
+      hd : tl -> foldl' (\a b -> App (App (apply pos m) a) b) (App (App (map' pos m) func) hd) tl
+  replace _ (PositionedValue pos com v) = PositionedValue pos com <$> rethrowWithPosition pos (replace pos v)
+  replace _ other = return other
 
-  go :: (Expr, [Expr]) -> DoNotationElement -> m (Expr, [Expr])
-  go (yield, args) (DoNotationValue val) =
+  go :: SourceSpan -> (Expr, [Expr]) -> DoNotationElement -> m (Expr, [Expr])
+  go _ (yield, args) (DoNotationValue val) =
     return (Abs NullBinder yield, val : args)
-  go (yield, args) (DoNotationBind (VarBinder ss ident) val) =
+  go _ (yield, args) (DoNotationBind (VarBinder ss ident) val) =
     return (Abs (VarBinder ss ident) yield, val : args)
-  go (yield, args) (DoNotationBind binder val) = do
+  go ss (yield, args) (DoNotationBind binder val) = do
     ident <- freshIdent'
-    let abs = Abs (VarBinder nullSourceSpan ident)
-                  (Case [Var nullSourceSpan (Qualified Nothing ident)]
+    let abs = Abs (VarBinder ss ident)
+                  (Case [Var ss (Qualified Nothing ident)]
                         [CaseAlternative [binder] [MkUnguarded yield]])
     return (abs, val : args)
-  go (yield, args) (DoNotationLet ds) = do
+  go _ (yield, args) (DoNotationLet ds) = do
     return (Let FromLet ds yield, args)
-  go acc (PositionedDoNotationElement pos com el) =
+  go _ acc (PositionedDoNotationElement pos com el) =
     rethrowWithPosition pos $ do
-      (yield, args) <- go acc el
+      (yield, args) <- go pos acc el
       return $ case args of
         [] -> (PositionedValue pos com yield, args)
         (a : as) -> (yield, PositionedValue pos com a : as)
diff --git a/src/Language/PureScript/Sugar/CaseDeclarations.hs b/src/Language/PureScript/Sugar/CaseDeclarations.hs
--- a/src/Language/PureScript/Sugar/CaseDeclarations.hs
+++ b/src/Language/PureScript/Sugar/CaseDeclarations.hs
@@ -171,8 +171,8 @@
           -- if the binder is a var binder we must not add
           -- the fail case as it results in unreachable
           -- alternative
-          alt_fail' | all isIrrefutable vb = []
-                    | otherwise = alt_fail
+          alt_fail' n | all isIrrefutable vb = []
+                      | otherwise = alt_fail n
 
 
           -- we are here:
@@ -186,18 +186,18 @@
           --
         in Case scrut
             (CaseAlternative vb [MkUnguarded (desugarGuard gs e alt_fail)]
-              : alt_fail')
+              : (alt_fail' (length scrut)))
 
       return [ CaseAlternative scrut_nullbinder [MkUnguarded rhs]]
 
-    desugarGuard :: [Guard] -> Expr -> [CaseAlternative] -> Expr
+    desugarGuard :: [Guard] -> Expr -> (Int ->[CaseAlternative]) -> Expr
     desugarGuard [] e _ = e
     desugarGuard (ConditionGuard c : gs) e match_failed
       | isTrueExpr c = desugarGuard gs e match_failed
       | otherwise =
         Case [c]
           (CaseAlternative [LiteralBinder ss (BooleanLiteral True)]
-            [MkUnguarded (desugarGuard gs e match_failed)] : match_failed)
+            [MkUnguarded (desugarGuard gs e match_failed)] : match_failed 1)
 
     desugarGuard (PatternGuard vb g : gs) e match_failed =
       Case [g]
@@ -206,7 +206,7 @@
       where
         -- don't consider match_failed case if the binder is irrefutable
         match_failed' | isIrrefutable vb = []
-                      | otherwise        = match_failed
+                      | otherwise        = match_failed 1
 
     -- we generate a let-binding for the remaining guards
     -- and alternatives. A CaseAlternative is passed (or in
@@ -215,7 +215,7 @@
     desugarAltOutOfLine :: [Binder]
                         -> [GuardedExpr]
                         -> [CaseAlternative]
-                        -> ([CaseAlternative] -> Expr)
+                        -> ((Int -> [CaseAlternative]) -> Expr)
                         -> m Expr
     desugarAltOutOfLine alt_binder rem_guarded rem_alts mk_body
       | Just rem_case <- mkCaseOfRemainingGuardsAndAlts = do
@@ -228,7 +228,8 @@
           goto_rem_case :: Expr
           goto_rem_case = Var ss (Qualified Nothing rem_case_id)
             `App` Literal ss (BooleanLiteral True)
-          alt_fail = [CaseAlternative [NullBinder] [MkUnguarded goto_rem_case]]
+          alt_fail :: Int -> [CaseAlternative]
+          alt_fail n = [CaseAlternative (replicate n NullBinder) [MkUnguarded goto_rem_case]]
 
         pure $ Let FromLet [
           ValueDecl (ss, []) rem_case_id Private []
@@ -236,7 +237,7 @@
           ] (mk_body alt_fail)
 
       | otherwise
-      = pure $ mk_body []
+      = pure $ mk_body (const [])
       where
         mkCaseOfRemainingGuardsAndAlts
           | not (null rem_guarded)
diff --git a/src/Language/PureScript/Sugar/DoNotation.hs b/src/Language/PureScript/Sugar/DoNotation.hs
--- a/src/Language/PureScript/Sugar/DoNotation.hs
+++ b/src/Language/PureScript/Sugar/DoNotation.hs
@@ -7,8 +7,10 @@
 
 import           Prelude.Compat
 
+import           Control.Applicative ((<|>))
 import           Control.Monad.Error.Class (MonadError(..))
 import           Control.Monad.Supply.Class
+import           Data.Maybe (fromMaybe)
 import           Data.Monoid (First(..))
 import           Language.PureScript.AST
 import           Language.PureScript.Crash
@@ -40,6 +42,13 @@
   replace _ (PositionedValue pos com v) = PositionedValue pos com <$> rethrowWithPosition pos (replace pos v)
   replace _ other = return other
 
+  stripPositionedBinder :: Binder -> (Maybe SourceSpan, Binder)
+  stripPositionedBinder (PositionedBinder ss _ b) =
+    let (ss', b') = stripPositionedBinder b
+     in (ss' <|> Just ss, b')
+  stripPositionedBinder b =
+    (Nothing, b)
+
   go :: SourceSpan -> Maybe ModuleName -> [DoNotationElement] -> m Expr
   go _ _ [] = internalError "The impossible happened in desugarDo"
   go _ _ [DoNotationValue val] = return val
@@ -52,13 +61,18 @@
     where
       fromIdent (Ident i) | i `elem` [ C.bind, C.discard ] = First (Just i)
       fromIdent _ = mempty
-  go pos m (DoNotationBind (VarBinder ss ident) val : rest) = do
-    rest' <- go pos m rest
-    return $ App (App (bind pos m) val) (Abs (VarBinder ss ident) rest')
   go pos m (DoNotationBind binder val : rest) = do
     rest' <- go pos m rest
-    ident <- freshIdent'
-    return $ App (App (bind pos m) val) (Abs (VarBinder pos ident) (Case [Var pos (Qualified Nothing ident)] [CaseAlternative [binder] [MkUnguarded rest']]))
+    let (mss, binder') = stripPositionedBinder binder
+    let ss = fromMaybe pos mss
+    case binder' of
+      NullBinder ->
+        return $ App (App (bind pos m) val) (Abs (VarBinder ss UnusedIdent) rest')
+      VarBinder _ ident ->
+        return $ App (App (bind pos m) val) (Abs (VarBinder ss ident) rest')
+      _ -> do
+        ident <- freshIdent'
+        return $ App (App (bind pos m) val) (Abs (VarBinder pos ident) (Case [Var pos (Qualified Nothing ident)] [CaseAlternative [binder] [MkUnguarded rest']]))
   go _ _ [DoNotationLet _] = throwError . errorMessage $ InvalidDoLet
   go pos m (DoNotationLet ds : rest) = do
     let checkBind :: Declaration -> m ()
diff --git a/src/Language/PureScript/Sugar/Names.hs b/src/Language/PureScript/Sugar/Names.hs
--- a/src/Language/PureScript/Sugar/Names.hs
+++ b/src/Language/PureScript/Sugar/Names.hs
@@ -2,6 +2,7 @@
   ( desugarImports
   , desugarImportsWithEnv
   , Env
+  , externsEnv
   , primEnv
   , ImportRecord(..)
   , ImportProvenance(..)
@@ -16,7 +17,7 @@
 import Control.Monad
 import Control.Monad.Error.Class (MonadError(..))
 import Control.Monad.State.Lazy
-import Control.Monad.Writer (MonadWriter(..), censor)
+import Control.Monad.Writer (MonadWriter(..))
 
 import Data.Maybe (fromMaybe, mapMaybe)
 import qualified Data.Map as M
@@ -42,73 +43,22 @@
 desugarImports
   :: forall m
    . (MonadError MultipleErrors m, MonadWriter MultipleErrors m)
-  => [ExternsFile]
+  => Env
   -> [Module]
   -> m [Module]
-desugarImports externs modules =
-  fmap snd (desugarImportsWithEnv externs modules)
+desugarImports env modules =
+  fmap snd (desugarImportsWithEnv env modules)
 
 desugarImportsWithEnv
   :: forall m
   . (MonadError MultipleErrors m, MonadWriter MultipleErrors m)
-  => [ExternsFile]
+  => Env
   -> [Module]
   -> m (Env, [Module])
-desugarImportsWithEnv externs modules = do
-  env <- silence $ foldM externsEnv primEnv externs
-  (modules', env') <- first reverse <$> foldM updateEnv ([], env) modules
+desugarImportsWithEnv e modules = do
+  (modules', env') <- first reverse <$> foldM updateEnv ([], e) modules
   (env',) <$> traverse (renameInModule' env') modules'
   where
-  silence :: m a -> m a
-  silence = censor (const mempty)
-
-  -- | Create an environment from a collection of externs files
-  externsEnv :: Env -> ExternsFile -> m Env
-  externsEnv env ExternsFile{..} = do
-    let members = Exports{..}
-        env' = M.insert efModuleName (efSourceSpan, nullImports, members) env
-        fromEFImport (ExternsImport mn mt qmn) = (mn, [(efSourceSpan, Just mt, qmn)])
-    imps <- foldM (resolveModuleImport env') nullImports (map fromEFImport efImports)
-    exps <- resolveExports env' efSourceSpan efModuleName imps members efExports
-    return $ M.insert efModuleName (efSourceSpan, imps, exps) env
-    where
-
-    -- An ExportSource for declarations local to the module which the given
-    -- ExternsFile corresponds to.
-    localExportSource =
-      ExportSource { exportSourceDefinedIn = efModuleName
-                   , exportSourceImportedFrom = Nothing
-                   }
-
-    exportedTypes :: M.Map (ProperName 'TypeName) ([ProperName 'ConstructorName], ExportSource)
-    exportedTypes = M.fromList $ mapMaybe toExportedType efExports
-      where
-      toExportedType (TypeRef _ tyCon dctors) = Just (tyCon, (fromMaybe (mapMaybe forTyCon efDeclarations) dctors, localExportSource))
-        where
-        forTyCon :: ExternsDeclaration -> Maybe (ProperName 'ConstructorName)
-        forTyCon (EDDataConstructor pn _ tNm _ _) | tNm == tyCon = Just pn
-        forTyCon _ = Nothing
-      toExportedType _ = Nothing
-
-    exportedTypeOps :: M.Map (OpName 'TypeOpName) ExportSource
-    exportedTypeOps = exportedRefs getTypeOpRef
-
-    exportedTypeClasses :: M.Map (ProperName 'ClassName) ExportSource
-    exportedTypeClasses = exportedRefs getTypeClassRef
-
-    exportedValues :: M.Map Ident ExportSource
-    exportedValues = exportedRefs getValueRef
-
-    exportedValueOps :: M.Map (OpName 'ValueOpName) ExportSource
-    exportedValueOps = exportedRefs getValueOpRef
-
-    exportedKinds :: M.Map (ProperName 'KindName) ExportSource
-    exportedKinds = exportedRefs getKindRef
-
-    exportedRefs :: Ord a => (DeclarationRef -> Maybe a) -> M.Map a ExportSource
-    exportedRefs f =
-      M.fromList $ (, localExportSource) <$> mapMaybe f efExports
-
   updateEnv :: ([Module], Env) -> Module -> m ([Module], Env)
   updateEnv (ms, env) m@(Module ss _ mn _ refs) = do
     members <- findExportable m
@@ -125,6 +75,58 @@
       let m'' = elaborateExports exps m'
       lintImports m'' env used
       return m''
+
+-- | Create an environment from a collection of externs files
+externsEnv
+  :: forall m
+   . (MonadError MultipleErrors m, MonadWriter MultipleErrors m)
+  => Env
+  -> ExternsFile
+  -> m Env
+externsEnv env ExternsFile{..} = do
+  let members = Exports{..}
+      env' = M.insert efModuleName (efSourceSpan, nullImports, members) env
+      fromEFImport (ExternsImport mn mt qmn) = (mn, [(efSourceSpan, Just mt, qmn)])
+  imps <- foldM (resolveModuleImport env') nullImports (map fromEFImport efImports)
+  exps <- resolveExports env' efSourceSpan efModuleName imps members efExports
+  return $ M.insert efModuleName (efSourceSpan, imps, exps) env
+  where
+
+  -- An ExportSource for declarations local to the module which the given
+  -- ExternsFile corresponds to.
+  localExportSource =
+    ExportSource { exportSourceDefinedIn = efModuleName
+                  , exportSourceImportedFrom = Nothing
+                  }
+
+  exportedTypes :: M.Map (ProperName 'TypeName) ([ProperName 'ConstructorName], ExportSource)
+  exportedTypes = M.fromList $ mapMaybe toExportedType efExports
+    where
+    toExportedType (TypeRef _ tyCon dctors) = Just (tyCon, (fromMaybe (mapMaybe forTyCon efDeclarations) dctors, localExportSource))
+      where
+      forTyCon :: ExternsDeclaration -> Maybe (ProperName 'ConstructorName)
+      forTyCon (EDDataConstructor pn _ tNm _ _) | tNm == tyCon = Just pn
+      forTyCon _ = Nothing
+    toExportedType _ = Nothing
+
+  exportedTypeOps :: M.Map (OpName 'TypeOpName) ExportSource
+  exportedTypeOps = exportedRefs getTypeOpRef
+
+  exportedTypeClasses :: M.Map (ProperName 'ClassName) ExportSource
+  exportedTypeClasses = exportedRefs getTypeClassRef
+
+  exportedValues :: M.Map Ident ExportSource
+  exportedValues = exportedRefs getValueRef
+
+  exportedValueOps :: M.Map (OpName 'ValueOpName) ExportSource
+  exportedValueOps = exportedRefs getValueOpRef
+
+  exportedKinds :: M.Map (ProperName 'KindName) ExportSource
+  exportedKinds = exportedRefs getKindRef
+
+  exportedRefs :: Ord a => (DeclarationRef -> Maybe a) -> M.Map a ExportSource
+  exportedRefs f =
+    M.fromList $ (, localExportSource) <$> mapMaybe f efExports
 
 -- |
 -- Make all exports for a module explicit. This may still affect modules that
diff --git a/src/Language/PureScript/Sugar/Operators/Common.hs b/src/Language/PureScript/Sugar/Operators/Common.hs
--- a/src/Language/PureScript/Sugar/Operators/Common.hs
+++ b/src/Language/PureScript/Sugar/Operators/Common.hs
@@ -96,7 +96,7 @@
   -- grouping them by shared precedence, then if any of the following conditions
   -- are met, we have something to report:
   --   1. any of the groups have mixed associativity
-  --   2. there is more than one occurance of a non-associative operator in a
+  --   2. there is more than one occurrence of a non-associative operator in a
   --      precedence group
   mkErrors :: Chain a -> [ErrorMessage]
   mkErrors chain =
diff --git a/src/Language/PureScript/TypeChecker/Skolems.hs b/src/Language/PureScript/TypeChecker/Skolems.hs
--- a/src/Language/PureScript/TypeChecker/Skolems.hs
+++ b/src/Language/PureScript/TypeChecker/Skolems.hs
@@ -30,7 +30,7 @@
   modify $ \st -> st { checkNextSkolem = s + 1 }
   return s
 
--- | Introduce skolem scope at every occurence of a ForAll
+-- | Introduce skolem scope at every occurrence of a ForAll
 introduceSkolemScope :: MonadState CheckState m => Type a -> m (Type a)
 introduceSkolemScope = everywhereOnTypesM go
   where
diff --git a/src/Language/PureScript/TypeChecker/Types.hs b/src/Language/PureScript/TypeChecker/Types.hs
--- a/src/Language/PureScript/TypeChecker/Types.hs
+++ b/src/Language/PureScript/TypeChecker/Types.hs
@@ -25,7 +25,7 @@
 -}
 
 import Prelude.Compat
-import Protolude (ordNub)
+import Protolude (ordNub, fold, atMay)
 
 import Control.Arrow (first, second, (***))
 import Control.Monad
@@ -110,21 +110,56 @@
           . throwError
           . errorMessage' ss
           $ CannotGeneralizeRecursiveFunction ident generalized
-        -- Make sure any unsolved type constraints only use type variables which appear
-        -- unknown in the inferred type.
-        forM_ unsolved $ \(_, _, con) -> do
-          -- We need information about functional dependencies, since we allow
-          -- ambiguous types to be inferred if they can be solved by some functional
-          -- dependency.
+        -- We need information about functional dependencies, since we allow
+        -- ambiguous types to be inferred if they can be solved by some functional
+        -- dependency.
+        conData <- forM unsolved $ \(_, _, con) -> do
           let findClass = fromMaybe (internalError "entails: type class not found in environment") . M.lookup (constraintClass con)
           TypeClassData{ typeClassDependencies } <- gets (findClass . typeClasses . checkEnv)
-          let solved = foldMap (S.fromList . fdDetermined) typeClassDependencies
-          let constraintTypeVars = ordNub . foldMap (unknownsInType . fst) . filter ((`notElem` solved) . snd) $ zip (constraintArgs con) [0..]
-          when (any (`notElem` unsolvedTypeVars) constraintTypeVars) .
-            throwError
-              . onErrorMessages (replaceTypes currentSubst)
-              . errorMessage' ss
-              $ AmbiguousTypeVariables generalized con
+          let
+            -- The set of unknowns mentioned in each argument.
+            unknownsForArg :: [S.Set Int]
+            unknownsForArg =
+              map (S.fromList . map snd . unknownsInType) (constraintArgs con)
+          pure (typeClassDependencies, unknownsForArg)
+        -- Make sure any unsolved type constraints are determined by the
+        -- type variables which appear unknown in the inferred type.
+        let
+          -- Take the closure of fundeps across constraints, to get more
+          -- and more solved variables until reaching a fixpoint.
+          solveFrom :: S.Set Int -> S.Set Int
+          solveFrom determined = do
+            let solved = solve1 determined
+            if solved `S.isSubsetOf` determined
+              then determined
+              else solveFrom (determined <> solved)
+          solve1 :: S.Set Int -> S.Set Int
+          solve1 determined = fold $ do
+            (tcDeps, conArgUnknowns) <- conData
+            let
+              lookupUnknowns :: Int -> Maybe (S.Set Int)
+              lookupUnknowns = atMay conArgUnknowns
+              unknownsDetermined :: Maybe (S.Set Int) -> Bool
+              unknownsDetermined Nothing = False
+              unknownsDetermined (Just unknowns) =
+                unknowns `S.isSubsetOf` determined
+            -- If all of the determining arguments of a particular fundep are
+            -- already determined, add the determined arguments from the fundep
+            tcDep <- tcDeps
+            guard $ all (unknownsDetermined . lookupUnknowns) (fdDeterminers tcDep)
+            map (fromMaybe S.empty . lookupUnknowns) (fdDetermined tcDep)
+        -- These unknowns can be determined from the body of the inferred
+        -- type (i.e. excluding the unknowns mentioned in the constraints)
+        let determinedFromType = S.fromList . map snd $ unsolvedTypeVars
+        -- These are all the unknowns mentioned in the constraints
+        let constraintTypeVars = fold (conData >>= snd)
+        let solved = solveFrom determinedFromType
+        let unsolvedVars = S.difference constraintTypeVars solved
+        when (not (S.null unsolvedVars)) .
+          throwError
+            . onErrorMessages (replaceTypes currentSubst)
+            . errorMessage' ss
+            $ AmbiguousTypeVariables generalized (S.toList unsolvedVars)
 
       -- Check skolem variables did not escape their scope
       skolemEscapeCheck val'
diff --git a/src/Language/PureScript/Types.hs b/src/Language/PureScript/Types.hs
--- a/src/Language/PureScript/Types.hs
+++ b/src/Language/PureScript/Types.hs
@@ -321,7 +321,7 @@
   go :: A.Value -> A.Parser (Type a)
   go = typeFromJSON defaultAnn annFromJSON
 
--- These overlapping instances exist to preserve compatability for common
+-- These overlapping instances exist to preserve compatibility for common
 -- instances which have a sensible default for missing annotations.
 instance {-# OVERLAPPING #-} A.FromJSON (Type SourceAnn) where
   parseJSON = typeFromJSON (pure NullSourceAnn) A.parseJSON
diff --git a/tests/purs/passing/3238.purs b/tests/purs/passing/3238.purs
new file mode 100644
--- /dev/null
+++ b/tests/purs/passing/3238.purs
@@ -0,0 +1,14 @@
+module Main where
+
+import Effect.Console (log)
+
+class C a
+
+class FD a b | a -> b
+
+fn1 :: forall a b. FD a b => C b => a -> String
+fn1 _ = ""
+
+fn2 x = fn1 x
+
+main = log "Done"
diff --git a/tests/purs/passing/Guards.purs b/tests/purs/passing/Guards.purs
--- a/tests/purs/passing/Guards.purs
+++ b/tests/purs/passing/Guards.purs
@@ -34,6 +34,12 @@
             = x
 clunky1 a _ = a
 
+clunky1_refutable :: Int -> Int -> Int
+clunky1_refutable 0 a | x <- max a a
+                      , x > 5
+                      = x
+clunky1_refutable a _ = a
+
 clunky2 :: Int -> Int -> Int
 clunky2 a b | x <- max a b
             , x > 5
diff --git a/tests/purs/warning/ScopeShadowing.purs b/tests/purs/warning/ScopeShadowing.purs
--- a/tests/purs/warning/ScopeShadowing.purs
+++ b/tests/purs/warning/ScopeShadowing.purs
@@ -7,7 +7,7 @@
 data Unit = Unit
 
 -- This is only a warning as the `Prelude` import is implicit. If `Unit` was
--- named explicitly in an import list, then this refernce to `Unit`
+-- named explicitly in an import list, then this reference to `Unit`
 -- would be a `ScopeConflict` error instead.
 test :: Unit
 test = const Unit unit