ah, yes, that is hardcoded

src/Database/Esqueleto/Internal/Sql.hs

@@ -970,18 +970,24 @@ deleteCount = rawEsqueleto DELETE
 -- 'set' p [ PersonAge '=.' 'just' ('val' thisYear) -. p '^.' PersonBorn ]
 -- 'where_' $ isNothing (p '^.' PersonAge)
 -- @
-update :: ( MonadIO m
-          , SqlEntity val
-          , BackendCompatible SqlBackend backend
-          , PersistQueryWrite backend
-          , PersistUniqueWrite backend)
-       => (SqlExpr (Entity val) -> SqlQuery ())
-       -> R.ReaderT backend m ()
+update
+  ::
+  ( PersistEntityBackend val ~ backend
+  , PersistEntity val
+  , PersistUniqueWrite backend
+  , PersistQueryWrite backend
+  , BackendCompatible SqlBackend backend
+  , PersistEntity val
+  , MonadIO m
+  )
+  => (SqlExpr (Entity val) -> SqlQuery ())
+  -> R.ReaderT backend m ()
 update = void . updateCount
 
 -- | Same as 'update', but returns the number of rows affected.
 updateCount :: ( MonadIO m
-               , SqlEntity val
+               , PersistEntity val
+               , PersistEntityBackend val ~ backend
                , BackendCompatible SqlBackend backend
                , PersistQueryWrite backend
                , PersistUniqueWrite backend)

stack-8.2.yaml

@@ -25,6 +25,8 @@ extra-deps:
 - quickcheck-properties-0.1
 - monad-logger-0.3.28
 - mono-traversable-1.0.8.1
+- typed-process-0.2.1.0
+- persistent-2.8.0
   # - persistent-2.7.1
 # - http-client-0.5.0
 # - fail-4.9.0.0