diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index a268e32f8..0e7d26535 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -41,9 +41,9 @@ jobs:
             unison-core/.stack-work
             yaks/easytest/.stack-work
             # Main cache key: commit hash. This should always result in a cache miss...
-          key: stack-work-0_${{matrix.os}}-${{github.sha}}
+          key: stack-work-1_${{matrix.os}}-${{github.sha}}
           # ...but then fall back on the latest cache stored (on this branch)
-          restore-keys: stack-work-0_${{matrix.os}}-
+          restore-keys: stack-work-1_${{matrix.os}}-
 
       # Install stack by downloading the binary from GitHub. The installation process is different for Linux and macOS,
       # so this is split into two steps, only one of which will run on any particular build.
diff --git a/parser-typechecker/src/Unison/Codebase/Conversion/Sync12.hs b/parser-typechecker/src/Unison/Codebase/Conversion/Sync12.hs
index 1de51313a..8ef7a60c8 100644
--- a/parser-typechecker/src/Unison/Codebase/Conversion/Sync12.hs
+++ b/parser-typechecker/src/Unison/Codebase/Conversion/Sync12.hs
@@ -295,7 +295,7 @@ checkTermComponent t h n = do
             typeDeps = Type.dependencies typ
         let checkDecl = \case
               Reference.Builtin {} -> pure ()
-              Reference.DerivedId (Reference.Id h' _ n') ->
+              Reference.Derived h' _ n' ->
                 getDeclStatus h' >>= \case
                   Just DeclOk -> pure ()
                   Just _ -> Except.throwError TermMissingDependencies
@@ -303,10 +303,10 @@ checkTermComponent t h n = do
             checkTerm = \case
               Reference.Builtin {} ->
                 pure ()
-              Reference.DerivedId (Reference.Id h' _ _)
+              Reference.Derived h' _ _
                 | h == h' ->
                   pure () -- ignore self-references
-              Reference.DerivedId (Reference.Id h' _ n') ->
+              Reference.Derived h' _ n' ->
                 getTermStatus h' >>= \case
                   Just TermOk -> pure ()
                   Just _ -> Except.throwError TermMissingDependencies
@@ -330,7 +330,7 @@ checkWatchComponent t k r@(Reference.Id h _ _) = do
       let deps = Term.labeledDependencies watchResult
       let checkDecl = \case
             Reference.Builtin {} -> pure ()
-            Reference.DerivedId (Reference.Id h' _ n') ->
+            Reference.Derived h' _ n' ->
               getDeclStatus h' >>= \case
                 Just DeclOk -> pure ()
                 Just _ -> Except.throwError WatchMissingDependencies
@@ -338,10 +338,10 @@ checkWatchComponent t k r@(Reference.Id h _ _) = do
           checkTerm = \case
             Reference.Builtin {} ->
               pure ()
-            Reference.DerivedId (Reference.Id h' _ _)
+            Reference.Derived h' _ _
               | h == h' ->
                 pure () -- ignore self-references
-            Reference.DerivedId (Reference.Id h' _ n') ->
+            Reference.Derived h' _ n' ->
               getTermStatus h' >>= \case
                 Just TermOk -> pure ()
                 Just _ -> Except.throwError WatchMissingDependencies
@@ -366,8 +366,8 @@ checkDeclComponent t h n = do
         let deps = DD.declDependencies decl
             checkDecl = \case
               Reference.Builtin {} -> pure ()
-              Reference.DerivedId (Reference.Id h' _ _) | h == h' -> pure ()
-              Reference.DerivedId (Reference.Id h' _ n') ->
+              Reference.Derived h' _ _ | h == h' -> pure ()
+              Reference.Derived h' _ n' ->
                 getDeclStatus h' >>= \case
                   Just DeclOk -> pure ()
                   Just _ -> Except.throwError DeclMissingDependencies
@@ -450,14 +450,14 @@ repairPatch (Patch termEdits typeEdits) = do
     -- reference to it.  See Sync22.syncPatchLocalIds
     helpTermEdit = \case
       Reference.Builtin _ -> pure True
-      Reference.DerivedId (Reference.Id h _ n) ->
+      Reference.Derived h _ n ->
         getTermStatus h >>= \case
           Nothing -> Validate.refute . Set.singleton $ T h n
           Just TermOk -> pure True
           Just _ -> pure False
     helpTypeEdit = \case
       Reference.Builtin _ -> pure True
-      Reference.DerivedId (Reference.Id h _ n) ->
+      Reference.Derived h _ n ->
         getDeclStatus h >>= \case
           Nothing -> Validate.refute . Set.singleton $ D h n
           Just DeclOk -> pure True
@@ -506,7 +506,7 @@ validateTermReferent = \case
 validateTermReference :: (S m n, V m n) => Reference.Reference -> n Bool
 validateTermReference = \case
   Reference.Builtin {} -> pure True
-  Reference.DerivedId (Reference.Id h _i n) ->
+  Reference.Derived h _i n ->
     getTermStatus h >>= \case
       Nothing -> Validate.refute . Set.singleton $ T h n
       Just TermOk -> pure True
@@ -515,7 +515,7 @@ validateTermReference = \case
 validateTypeReference :: (S m n, V m n) => Reference.Reference -> n Bool
 validateTypeReference = \case
   Reference.Builtin {} -> pure True
-  Reference.DerivedId (Reference.Id h _i n) ->
+  Reference.Derived h _i n ->
     getDeclStatus h >>= \case
       Nothing -> Validate.refute . Set.singleton $ D h n
       Just DeclOk -> pure True
diff --git a/parser-typechecker/src/Unison/Codebase/Serialization/V1.hs b/parser-typechecker/src/Unison/Codebase/Serialization/V1.hs
index ecb7b0754..7793eff07 100644
--- a/parser-typechecker/src/Unison/Codebase/Serialization/V1.hs
+++ b/parser-typechecker/src/Unison/Codebase/Serialization/V1.hs
@@ -239,7 +239,6 @@ putReference r = case r of
     putHash hash
     putLength i
     putLength n
-  _ -> error "unpossible"
 
 getReference :: MonadGet m => m Reference
 getReference = do
diff --git a/parser-typechecker/src/Unison/Codecs.hs b/parser-typechecker/src/Unison/Codecs.hs
index f1dceddc1..85c85ed88 100644
--- a/parser-typechecker/src/Unison/Codecs.hs
+++ b/parser-typechecker/src/Unison/Codecs.hs
@@ -315,7 +315,6 @@ serializeReference ref = case ref of
     putByteString bs
     putLength i
     putLength n
-  _ -> error "impossible"
 
 serializeConstructorArities :: MonadPut m => Reference -> [Int] -> m ()
 serializeConstructorArities r constructorArities = do
diff --git a/unison-core/src/Unison/Reference.hs b/unison-core/src/Unison/Reference.hs
index 8bf809b5a..fb07f91ee 100644
--- a/unison-core/src/Unison/Reference.hs
+++ b/unison-core/src/Unison/Reference.hs
@@ -57,8 +57,7 @@ data Reference
 pattern Derived :: H.Hash -> Pos -> Size -> Reference
 pattern Derived h i n = DerivedId (Id h i n)
 
--- A good idea, but causes a weird problem with view patterns in PatternP.hs in ghc 8.4.3
---{-# COMPLETE Builtin, Derived #-}
+{-# COMPLETE Builtin, Derived #-}
 
 -- | @Pos@ is a position into a cycle of size @Size@, as cycles are hashed together.
 data Id = Id H.Hash Pos Size deriving (Generic)
@@ -80,7 +79,6 @@ toShortHash (Derived h i n) = SH.ShortHash (H.base32Hex h) index Nothing
   where
     -- todo: remove `n` parameter; must also update readSuffix
     index = Just $ showSuffix i n
-toShortHash (DerivedId _) = error "this should be covered above"
 
 -- toShortHash . fromJust . fromShortHash == id and
 -- fromJust . fromShortHash . toShortHash == id
@@ -127,11 +125,9 @@ newtype Component = Component { members :: Set Reference }
 
 -- Gives the component (dependency cycle) that the reference is a part of
 componentFor :: Reference -> Component
-componentFor b@(Builtin        _         ) = Component (Set.singleton b)
-componentFor (  DerivedId (Id h _ n)) = Component
-  (Set.fromList
-    [ DerivedId (Id h i n) | i <- take (fromIntegral n) [0 ..] ]
-  )
+componentFor b@Builtin {} = Component (Set.singleton b)
+componentFor (Derived h _ n) =
+  Component $ Set.fromList [Derived h i n | i <- take (fromIntegral n) [0 ..]]
 
 derivedBase32Hex :: Text -> Pos -> Size -> Reference
 derivedBase32Hex b32Hex i n = DerivedId (Id (fromMaybe msg h) i n)
diff --git a/unison-core/src/Unison/Term.hs b/unison-core/src/Unison/Term.hs
index 71526acc5..0e0df4dfe 100644
--- a/unison-core/src/Unison/Term.hs
+++ b/unison-core/src/Unison/Term.hs
@@ -1093,8 +1093,6 @@ instance Var v => Hashable1 (F v a p) where
                   Or     x y -> [tag 17, hashed $ hash x, hashed $ hash y]
                   TermLink r -> [tag 18, accumulateToken r]
                   TypeLink r -> [tag 19, accumulateToken r]
-                  _ ->
-                    error $ "unhandled case in hash: " <> show (void e)
 
 -- mostly boring serialization code below ...