diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,14 @@
 # Revision history for reflex
 
+## 0.9.4.0
+
+* Add note about `requesting` semantics by @LightAndLight in https://github.com/reflex-frp/reflex/pull/508
+* Dropped lens by @ilyakooo0 in https://github.com/reflex-frp/reflex/pull/463
+* Build with ghc(js) 9.8.2 + 9.10.1 + 9.12.2 by @ymeister in https://github.com/reflex-frp/reflex/pull/502
+* headless: Add MonadThrow (Performable m) by @ali-abrar in https://github.com/reflex-frp/reflex/pull/523
+* Don't check in newSubscriberCoincidenceInner whether occRef is already set by @parenthetical in https://github.com/reflex-frp/reflex/pull/496
+* Always enable Template Haskell by @Ericson2314 in https://github.com/reflex-frp/reflex/pull/484
+
 ## 0.9.3.4
 
 * Support random 1.3
diff --git a/reflex.cabal b/reflex.cabal
--- a/reflex.cabal
+++ b/reflex.cabal
@@ -1,503 +1,510 @@
-Name: reflex
-Version: 0.9.3.4
-Synopsis: Higher-order Functional Reactive Programming
-Description:
-  Interactive programs without callbacks or side-effects.
-  Functional Reactive Programming (FRP) uses composable events and time-varying
-  values to describe interactive systems as pure functions.
-  Just like other pure functional code, functional reactive code is easier
-  to get right on the first try, maintain, and reuse.
-  .
-  Reflex is a fully-deterministic, higher-order Functional Reactive Programming
-  interface and an engine that efficiently implements that interface.
-  .
-  <https://reflex-frp.org>
-License: BSD3
-License-file: LICENSE
-Author: Ryan Trinkle
-Maintainer: ryan.trinkle@gmail.com
-Stability: Experimental
-Category: FRP
-Build-type: Simple
-Cabal-version: 1.22
-homepage: https://reflex-frp.org
-bug-reports: https://github.com/reflex-frp/reflex/issues
-extra-source-files:
-  README.md
-  Quickref.md
-  ChangeLog.md
-
+cabal-version:      1.22
+name:               reflex
+version:            0.9.4.0
+license:            BSD3
+license-file:       LICENSE
+maintainer:         ryan.trinkle@gmail.com
+author:             Ryan Trinkle
+stability:          Experimental
 tested-with:
-  GHC  ==8.4.4 || ==8.6.5 || ==8.8.1 || ==8.10.7 || ==9.0.1 || ==9.2.5 || ==9.4.5 || ==9.6.1 || ==9.8.2 || ==9.10.1 || ==9.12.1,
-  GHCJS ==8.6 || ==8.10
+    ghc ==8.4.4 || ==8.6.5 || ==8.8.1 || ==8.10.7 || ==9.0.1 || ==9.2.5 || ==9.4.5 || ==9.6.1 || ==9.8.2 || ==9.10.1 || ==9.12.2
 
-flag use-reflex-optimizer
-  description: Use the GHC plugin Reflex.Optimizer on some of the modules in the package.  This is still experimental.
-  default: False
-  manual: True
+homepage:           https://reflex-frp.org
+bug-reports:        https://github.com/reflex-frp/reflex/issues
+synopsis:           Higher-order Functional Reactive Programming
+description:
+    Interactive programs without callbacks or side-effects.
+    Functional Reactive Programming (FRP) uses composable events and time-varying
+    values to describe interactive systems as pure functions.
+    Just like other pure functional code, functional reactive code is easier
+    to get right on the first try, maintain, and reuse.
+    .
+    Reflex is a fully-deterministic, higher-order Functional Reactive Programming
+    interface and an engine that efficiently implements that interface.
+    .
+    <https://reflex-frp.org>
 
-flag use-template-haskell
-  description: Use template haskell to generate lenses
-  default: True
-  manual: True
+category:           FRP
+build-type:         Simple
+extra-source-files:
+    README.md
+    Quickref.md
+    ChangeLog.md
 
+source-repository head
+    type:     git
+    location: https://github.com/reflex-frp/reflex
+
 flag debug-trace-events
-  description: Add instrumentation that outputs the stack trace of the definition of an event whenever it is subscribed to. Warning: It is very slow!
-  default: False
-  manual: True
+    description:
+        Add instrumentation that outputs the stack trace of the definition of an event whenever it is subscribed to. Warning: It is very slow!
 
+    default:     False
+    manual:      True
+
 flag fast-weak
-  description: Use the primitive implementation of FastWeak in GHCJS; note that this requires GHCJS to be built with FastWeak and FastWeakBag present in the RTS, which is not the default
-  default: False
-  manual: True
+    description:
+        Use the primitive implementation of FastWeak in GHCJS; note that this requires GHCJS to be built with FastWeak and FastWeakBag present in the RTS, which is not the default
 
+    default:     False
+    manual:      True
+
 flag debug-propagation
-  description: Enable debugging of spider internals
-  default: False
-  manual: True
+    description: Enable debugging of spider internals
+    default:     False
+    manual:      True
 
 flag debug-cycles
-  description: Enable debugging of event cycles
-  default: False
-  manual: True
+    description: Enable debugging of event cycles
+    default:     False
+    manual:      True
 
 flag split-these
-  description: Use split these/semialign packages
-  manual:      False
-  default:     True
+    description: Use split these/semialign packages
+    manual:      False
+    default:     True
 
 library
-  default-language: Haskell2010
-  hs-source-dirs: src
-  build-depends:
-    MemoTrie == 0.6.*,
-    base >= 4.11 && < 4.22,
-    bifunctors >= 5.2 && < 5.7,
-    comonad >= 5.0.4 && < 5.1,
-    commutative-semigroups >= 0.1 && <0.3,
-    constraints >= 0.10 && <0.15,
-    constraints-extras >= 0.3 && < 0.5,
-    containers >= 0.6 && < 0.8,
-    data-default >= 0.5 && < 0.9,
-    dependent-map >= 0.3 && < 0.5,
-    dependent-sum >= 0.6 && < 0.8,
-    exceptions >= 0.10 && < 0.11,
-    exception-transformers >= 0.4 && < 0.5,
-    lens >= 4.7 && < 5.4,
-    mmorph >= 1.0 && < 1.3,
-    monad-control >= 1.0.1 && < 1.1,
-    mtl >= 2.1 && < 2.4,
-    patch >= 0.0.7 && < 0.1,
-    prim-uniq >= 0.1.0.1 && < 0.3,
-    primitive >= 0.5 && < 0.10,
-    profunctors >= 5.3 && < 5.7,
-    random >= 1.1 && < 1.4,
-    ref-tf >= 0.4 && < 0.6,
-    reflection == 2.1.*,
-    semigroupoids >= 4.0 && < 7,
-    stm >= 2.4 && < 2.6,
-    syb >= 0.5 && < 0.8,
-    time >= 1.4 && < 1.15,
-    transformers >= 0.5 && < 0.7,
-    unbounded-delays >= 0.1.0.0 && < 0.2,
-    witherable >= 0.4 && < 0.6
+    exposed-modules:
+        Control.Monad.ReaderIO
+        Data.AppendMap
+        Data.FastMutableIntMap
+        Data.FastWeakBag
+        Data.Map.Misc
+        Data.WeakBag
+        Reflex
+        Reflex.Class
+        Reflex.Adjustable.Class
+        Reflex.BehaviorWriter.Base
+        Reflex.BehaviorWriter.Class
+        Reflex.Collection
+        Reflex.Dynamic
+        Reflex.Dynamic.TH
+        Reflex.Dynamic.Uniq
+        Reflex.DynamicWriter
+        Reflex.DynamicWriter.Base
+        Reflex.DynamicWriter.Class
+        Reflex.EventWriter
+        Reflex.EventWriter.Base
+        Reflex.EventWriter.Class
+        Reflex.FastWeak
+        Reflex.FunctorMaybe
+        Reflex.Host.Class
+        Reflex.Host.Headless
+        Reflex.Network
+        Reflex.NotReady.Class
+        Reflex.PerformEvent.Base
+        Reflex.PerformEvent.Class
+        Reflex.PostBuild.Base
+        Reflex.PostBuild.Class
+        Reflex.Profiled
+        Reflex.Pure
+        Reflex.Query.Base
+        Reflex.Query.Class
+        Reflex.Requester.Base
+        Reflex.Requester.Base.Internal
+        Reflex.Requester.Class
+        Reflex.Spider
+        Reflex.Spider.Internal
+        Reflex.Time
+        Reflex.TriggerEvent.Base
+        Reflex.TriggerEvent.Class
+        Reflex.Widget.Basic
+        Reflex.Workflow
 
-  if flag(split-these)
-    build-depends:     these >= 1 && <1.3,
-                       semialign >=1 && <1.4,
-                       monoidal-containers >= 0.6.2.0 && < 0.7
-  else
-    build-depends:     these >= 0.4 && <0.9,
-                       monoidal-containers == 0.4.0.0
+    reexported-modules:
+        patch:Data.Functor.Misc
+      , patch:Data.Patch as Reflex.Patch
+      , patch:Data.Patch.Class as Reflex.Patch.Class
+      , patch:Data.Patch.DMap as Reflex.Patch.DMap
+      , patch:Data.Patch.DMapWithMove as Reflex.Patch.DMapWithMove
+      , patch:Data.Patch.IntMap as Reflex.Patch.IntMap
+      , patch:Data.Patch.Map as Reflex.Patch.Map
+      , patch:Data.Patch.MapWithMove as Reflex.Patch.MapWithMove
 
-  exposed-modules:
-    Control.Monad.ReaderIO
-    Data.AppendMap,
-    Data.FastMutableIntMap,
-    Data.FastWeakBag,
-    Data.Map.Misc,
-    Data.WeakBag,
-    Reflex,
-    Reflex.Class,
-    Reflex.Adjustable.Class,
-    Reflex.BehaviorWriter.Base,
-    Reflex.BehaviorWriter.Class,
-    Reflex.Collection,
-    Reflex.Dynamic,
-    Reflex.Dynamic.Uniq,
-    Reflex.DynamicWriter,
-    Reflex.DynamicWriter.Base,
-    Reflex.DynamicWriter.Class,
-    Reflex.EventWriter,
-    Reflex.EventWriter.Base,
-    Reflex.EventWriter.Class,
-    Reflex.FastWeak,
-    Reflex.FunctorMaybe,
-    Reflex.Host.Class,
-    Reflex.Host.Headless,
-    Reflex.Network,
-    Reflex.NotReady.Class,
-    Reflex.PerformEvent.Base,
-    Reflex.PerformEvent.Class,
-    Reflex.PostBuild.Base,
-    Reflex.PostBuild.Class,
-    Reflex.Profiled,
-    Reflex.Pure,
-    Reflex.Query.Base,
-    Reflex.Query.Class,
-    Reflex.Requester.Base,
-    Reflex.Requester.Base.Internal,
-    Reflex.Requester.Class,
-    Reflex.Spider,
-    Reflex.Spider.Internal,
-    Reflex.Time,
-    Reflex.TriggerEvent.Base,
-    Reflex.TriggerEvent.Class,
-    Reflex.Widget.Basic,
-    Reflex.Workflow
+    hs-source-dirs:     src
+    default-language:   Haskell2010
+    ghc-options:
+        -Wall -fwarn-redundant-constraints -fwarn-tabs
+        -funbox-strict-fields -O2 -fspecialise-aggressively
 
-  reexported-modules:
-    patch:Data.Functor.Misc,
-    patch:Data.Patch as Reflex.Patch,
-    patch:Data.Patch.Class as Reflex.Patch.Class,
-    patch:Data.Patch.DMap as Reflex.Patch.DMap,
-    patch:Data.Patch.DMapWithMove as Reflex.Patch.DMapWithMove,
-    patch:Data.Patch.IntMap as Reflex.Patch.IntMap,
-    patch:Data.Patch.Map as Reflex.Patch.Map,
-    patch:Data.Patch.MapWithMove as Reflex.Patch.MapWithMove
+    build-depends:
+        MemoTrie == 0.6.*
+      , base >= 4.11 && < 4.22
+      , bifunctors >= 5.2 && < 5.7
+      , comonad >= 5.0.4 && < 5.1
+      , commutative-semigroups >= 0.1 && <0.3
+      , constraints >= 0.10 && <0.15
+      , constraints-extras >= 0.3 && < 0.5
+      , containers >= 0.6 && < 0.8
+      , data-default >= 0.5 && < 0.9
+      , dependent-map >= 0.3 && < 0.5
+      , dependent-sum >= 0.6 && < 0.8
+      , exceptions >= 0.10 && < 0.11
+      , exception-transformers >= 0.4 && < 0.5
+      , mmorph >= 1.0 && < 1.3
+      , monad-control >= 1.0.1 && < 1.1
+      , mtl >= 2.1 && < 2.4
+      , patch >= 0.0.7 && < 0.1
+      , prim-uniq >= 0.1.0.1 && < 0.3
+      , primitive >= 0.5 && < 0.10
+      , profunctors >= 5.3 && < 5.7
+      , random >= 1.1 && < 1.4
+      , ref-tf >= 0.4 && < 0.6
+      , reflection == 2.1.*
+      , semigroupoids >= 4.0 && < 7
+      , stm >= 2.4 && < 2.6
+      , syb >= 0.5 && < 0.8
+      , time >= 1.4 && < 1.15
+      , transformers >= 0.5 && < 0.7
+      , unbounded-delays >= 0.1.0.0 && < 0.2
+      , witherable >= 0.4 && < 0.6
+      , haskell-src-exts >= 1.16 && < 1.24
+      , haskell-src-meta >= 0.6 && < 0.9
+      , template-haskell >= 2.9 && < 2.24
 
-  ghc-options: -Wall -fwarn-redundant-constraints -fwarn-tabs -funbox-strict-fields -O2 -fspecialise-aggressively
+    other-extensions:
+      TemplateHaskell
 
-  if flag(debug-trace-events)
-    cpp-options: -DDEBUG_TRACE_EVENTS
-    build-depends:
-      bytestring >= 0.10.8 && < 0.11
+    if flag(split-these)
+        build-depends:
+            these >=1 && <1.3
+          , semialign >=1 && <1.4
+          , monoidal-containers >=0.6.2.0 && <0.7
 
-  if flag(use-reflex-optimizer)
-    cpp-options: -DUSE_REFLEX_OPTIMIZER
-    build-depends: ghc
-    exposed-modules: Reflex.Optimizer
+    else
+        build-depends:
+            these >=0.4 && <0.9
+          , monoidal-containers ==0.4.0.0
 
-  if flag(debug-propagation)
-    cpp-options: -DDEBUG -DDEBUG_TRACE_PROPAGATION -DDEBUG_TRACE_INVALIDATION
+    if flag(debug-trace-events)
+        cpp-options:   -DDEBUG_TRACE_EVENTS
+        build-depends: bytestring >=0.10.8 && <0.11
 
-  if flag(debug-cycles)
-    cpp-options: -DDEBUG_CYCLES
+    if flag(debug-propagation)
+        cpp-options:
+            -DDEBUG -DDEBUG_TRACE_PROPAGATION -DDEBUG_TRACE_INVALIDATION
 
-  if flag(use-template-haskell)
-    cpp-options: -DUSE_TEMPLATE_HASKELL
-    build-depends:
-      haskell-src-exts >= 1.16 && < 1.24,
-      haskell-src-meta >= 0.6 && < 0.9,
-      template-haskell >= 2.9 && < 2.24
-    exposed-modules:
-      Reflex.Dynamic.TH
-    other-extensions: TemplateHaskell
+    if flag(debug-cycles)
+        cpp-options: -DDEBUG_CYCLES
 
-  if flag(fast-weak) && impl(ghcjs)
-    cpp-options: -DGHCJS_FAST_WEAK
+    if flag(fast-weak) && impl(ghcjs >=0)
+        cpp-options: -DGHCJS_FAST_WEAK
 
-  if impl(ghcjs)
-    build-depends:
-      ghcjs-base == 0.2.*
+    if impl(ghcjs)
+        build-depends: ghcjs-base >=0.2 && <0.3
 
 test-suite semantics
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: semantics.hs
-  hs-source-dirs: test
-  ghc-options: -O2 -Wall -rtsopts
-  build-depends:
-    base,
-    bifunctors,
-    containers,
-    deepseq,
-    dependent-map,
-    dependent-sum,
-    mtl,
-    ref-tf,
-    reflex,
-    split,
-    transformers
-  other-modules:
-    Reflex.Bench.Focused
-    Reflex.Plan.Pure
-    Reflex.Plan.Reflex
-    Reflex.Test
-    Reflex.Test.Micro
-    Reflex.TestPlan
+    type:             exitcode-stdio-1.0
+    main-is:          semantics.hs
+    hs-source-dirs:   test
+    other-modules:
+        Reflex.Bench.Focused
+        Reflex.Plan.Pure
+        Reflex.Plan.Reflex
+        Reflex.Test
+        Reflex.Test.Micro
+        Reflex.TestPlan
 
+    default-language: Haskell2010
+    ghc-options:      -O2 -Wall -rtsopts
+    build-depends:
+        base >= 4.11 && < 4.22
+      , bifunctors
+      , containers
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , mtl
+      , ref-tf
+      , reflex
+      , split
+      , transformers
+
 test-suite CrossImpl
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: Reflex/Test/CrossImpl.hs
-  hs-source-dirs: test
-  ghc-options: -O2 -Wall -rtsopts
-  build-depends:
-    base,
-    containers,
-    dependent-map,
-    dependent-sum,
-    deepseq,
-    mtl,
-    transformers,
-    ref-tf,
-    reflex
-  other-modules:
-    Reflex.Test
-    Reflex.TestPlan
-    Reflex.Plan.Reflex
-    Reflex.Plan.Pure
+    type:             exitcode-stdio-1.0
+    main-is:          Reflex/Test/CrossImpl.hs
+    hs-source-dirs:   test
+    other-modules:
+        Reflex.Test
+        Reflex.TestPlan
+        Reflex.Plan.Reflex
+        Reflex.Plan.Pure
 
-test-suite hlint
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: hlint.hs
-  hs-source-dirs: test
-  build-depends: base
-               , directory
-               , filepath
-               , filemanip
-               , reflex
-  if impl(ghc >= 9.6)
-    buildable: False
-  if impl(ghc < 9.2)
-    build-depends: hlint (< 2.1 || >= 2.2.2) && < 3.5
-  else
-    build-depends: hlint >= 3.5 && < 3.6
-  if impl(ghcjs)
-    buildable: False
+    default-language: Haskell2010
+    ghc-options:      -O2 -Wall -rtsopts
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , dependent-map
+      , dependent-sum
+      , deepseq
+      , mtl
+      , transformers
+      , ref-tf
+      , reflex
 
-test-suite EventWriterT
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: EventWriterT.hs
-  hs-source-dirs: test
-  build-depends: base
-               , containers
-               , deepseq
-               , dependent-map
-               , dependent-sum
-               , lens
-               , mtl
-               , these
-               , transformers
-               , reflex
-               , ref-tf
+test-suite hlint
+    type:             exitcode-stdio-1.0
+    main-is:          hlint.hs
+    hs-source-dirs:   test
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , directory
+      , filepath
+      , filemanip
 
-  if flag(split-these)
-    build-depends: these-lens
+    if impl(ghc >=9.6)
+        buildable: False
 
-  other-modules:
-    Test.Run
+    if impl(ghc <9.2)
+        build-depends: hlint (<2.1 || >=2.2.2) && <3.5
 
+    else
+        build-depends: hlint >=3.5 && <3.6
 
-test-suite DebugCycles
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: DebugCycles.hs
-  hs-source-dirs: test
-  ghc-options: -threaded
-  build-depends: base
-               , containers
-               , deepseq
-               , dependent-map
-               , dependent-sum
-               , hspec
-               , lens
-               , mtl
-               , these
-               , transformers
-               , reflex
-               , ref-tf
-               , witherable
+    if impl(ghcjs >=0) || arch(javascript)
+        buildable: False
 
+test-suite EventWriterT
+    type:             exitcode-stdio-1.0
+    main-is:          EventWriterT.hs
+    hs-source-dirs:   test
+    other-modules:    Test.Run
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , lens
+      , mtl
+      , these
+      , transformers
+      , reflex
+      , ref-tf
 
-  if flag(split-these)
-    build-depends: these-lens, semialign
+    if flag(split-these)
+        build-depends: these-lens
 
-  other-modules:
-    Test.Run
+test-suite DebugCycles
+    type:             exitcode-stdio-1.0
+    main-is:          DebugCycles.hs
+    hs-source-dirs:   test
+    other-modules:    Test.Run
+    default-language: Haskell2010
+    ghc-options:      -threaded
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , hspec
+      , lens
+      , mtl
+      , these
+      , transformers
+      , reflex
+      , ref-tf
+      , witherable
 
+    if flag(split-these)
+        build-depends:
+            these-lens
+          , semialign
 
 test-suite RequesterT
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: RequesterT.hs
-  hs-source-dirs: test
-  build-depends: base
-               , constraints
-               , constraints-extras
-               , containers
-               , deepseq
-               , dependent-map
-               , dependent-sum
-               , lens
-               , mtl
-               , ref-tf
-               , reflex
-               , text
-               , these
-               , transformers
+    type:             exitcode-stdio-1.0
+    main-is:          RequesterT.hs
+    hs-source-dirs:   test
+    other-modules:
+        Reflex.TestPlan
+        Reflex.Plan.Pure
+        Test.Run
 
-  if flag(split-these)
-    build-depends: these-lens
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , constraints
+      , constraints-extras
+      , containers
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , lens
+      , mtl
+      , ref-tf
+      , reflex
+      , text
+      , these
+      , transformers
 
-  other-modules:
-    Reflex.TestPlan
-    Reflex.Plan.Pure
-    Test.Run
+    if flag(split-these)
+        build-depends: these-lens
 
 test-suite Headless
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: Headless.hs
-  hs-source-dirs: test
-  build-depends: base
-               , reflex
+    type:             exitcode-stdio-1.0
+    main-is:          Headless.hs
+    hs-source-dirs:   test
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , reflex
 
 test-suite Adjustable
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: Adjustable.hs
-  hs-source-dirs: test
-  build-depends: base
-               , containers
-               , dependent-sum
-               , reflex
-               , ref-tf
-               , these
-
-  other-modules:
-    Test.Run
+    type:             exitcode-stdio-1.0
+    main-is:          Adjustable.hs
+    hs-source-dirs:   test
+    other-modules:    Test.Run
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , dependent-sum
+      , reflex
+      , ref-tf
+      , these
 
 test-suite QueryT
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: QueryT.hs
-  hs-source-dirs: test
-  build-depends: base
-               , commutative-semigroups
-               , containers
-               , dependent-map
-               , dependent-sum
-               , deepseq
-               , lens
-               , monoidal-containers
-               , mtl
-               , patch
-               , ref-tf
-               , reflex
-               , these
-               , transformers
+    type:             exitcode-stdio-1.0
+    main-is:          QueryT.hs
+    hs-source-dirs:   test
+    other-modules:
+        Test.Run
+        Reflex.TestPlan
+        Reflex.Plan.Reflex
+        Reflex.Plan.Pure
 
-  if flag(split-these)
-    build-depends: semialign, these-lens
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , commutative-semigroups
+      , containers
+      , dependent-map
+      , dependent-sum
+      , deepseq
+      , lens
+      , monoidal-containers
+      , mtl
+      , patch
+      , ref-tf
+      , reflex
+      , these
+      , transformers
 
-  other-modules:
-    Test.Run
-    Reflex.TestPlan
-    Reflex.Plan.Reflex
-    Reflex.Plan.Pure
+    if flag(split-these)
+        build-depends:
+            semialign
+          , these-lens
 
 test-suite GC-Semantics
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: GC.hs
-  hs-source-dirs: test
-  build-depends: base
-               , containers
-               , dependent-sum
-               , dependent-map
-               , deepseq
-               , mtl
-               , patch
-               , these
-               , transformers
-               , reflex
-               , ref-tf
+    type:             exitcode-stdio-1.0
+    main-is:          GC.hs
+    hs-source-dirs:   test
+    other-modules:
+        Reflex.Plan.Pure
+        Reflex.Plan.Reflex
+        Reflex.TestPlan
+        Test.Run
 
-  if flag(split-these)
-    build-depends: semialign
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , dependent-sum
+      , dependent-map
+      , deepseq
+      , mtl
+      , patch
+      , these
+      , transformers
+      , reflex
+      , ref-tf
 
-  other-modules:
-    Reflex.Plan.Pure
-    Reflex.Plan.Reflex
-    Reflex.TestPlan
-    Test.Run
+    if flag(split-these)
+        build-depends: semialign
 
 test-suite rootCleanup
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  main-is: rootCleanup.hs
-  hs-source-dirs: test
-  build-depends: base
-               , containers
-               , deepseq
-               , dependent-sum
-               , mtl
-               , reflex
-               , ref-tf
-               , these
-  other-modules:
-    Reflex.Plan.Pure
-    Reflex.TestPlan
-    Test.Run
+    type:             exitcode-stdio-1.0
+    main-is:          rootCleanup.hs
+    hs-source-dirs:   test
+    other-modules:
+        Reflex.Plan.Pure
+        Reflex.TestPlan
+        Test.Run
 
+    default-language: Haskell2010
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , deepseq
+      , dependent-sum
+      , mtl
+      , reflex
+      , ref-tf
+      , these
+
 benchmark spider-bench
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  hs-source-dirs: bench test
-  main-is: Main.hs
-  ghc-options: -Wall -O2 -rtsopts
-  build-depends:
-    base,
-    containers,
-    criterion,
-    deepseq,
-    dependent-map,
-    dependent-sum,
-    ref-tf,
-    mtl,
-    primitive,
-    reflex,
-    split,
-    stm,
-    transformers
-  other-modules:
-    Reflex.TestPlan
-    Reflex.Plan.Reflex
-    Reflex.Bench.Focused
+    type:             exitcode-stdio-1.0
+    main-is:          Main.hs
+    hs-source-dirs:   bench test
+    other-modules:
+        Reflex.TestPlan
+        Reflex.Plan.Reflex
+        Reflex.Bench.Focused
 
+    default-language: Haskell2010
+    ghc-options:      -Wall -O2 -rtsopts
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , criterion
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , ref-tf
+      , mtl
+      , primitive
+      , reflex
+      , split
+      , stm
+      , transformers
+
+    if arch(javascript)
+        buildable: False
+
 benchmark saulzar-bench
-  default-language: Haskell2010
-  type: exitcode-stdio-1.0
-  hs-source-dirs: bench test
-  c-sources: bench-cbits/checkCapability.c
-  main-is: RunAll.hs
-  ghc-options: -Wall -O2 -rtsopts -threaded
-  build-depends:
-    base,
-    containers,
-    criterion,
-    deepseq,
-    dependent-map,
-    dependent-sum,
-    loch-th,
-    mtl,
-    primitive,
-    process,
-    ref-tf,
-    reflex,
-    split,
-    stm,
-    time,
-    transformers
-  other-modules:
-    Reflex.TestPlan
-    Reflex.Plan.Reflex
-    Reflex.Bench.Focused
+    type:             exitcode-stdio-1.0
+    main-is:          RunAll.hs
+    c-sources:        bench-cbits/checkCapability.c
+    hs-source-dirs:   bench test
+    other-modules:
+        Reflex.TestPlan
+        Reflex.Plan.Reflex
+        Reflex.Bench.Focused
 
-source-repository head
-  type: git
-  location: https://github.com/reflex-frp/reflex
+    default-language: Haskell2010
+    ghc-options:      -Wall -O2 -rtsopts -threaded
+    build-depends:
+        base >= 4.11 && < 4.22
+      , containers
+      , criterion
+      , deepseq
+      , dependent-map
+      , dependent-sum
+      , loch-th
+      , mtl
+      , primitive
+      , process
+      , ref-tf
+      , reflex
+      , split
+      , stm
+      , time
+      , transformers
+
+    if arch(javascript)
+        buildable: False
diff --git a/src/Control/Monad/ReaderIO.hs b/src/Control/Monad/ReaderIO.hs
--- a/src/Control/Monad/ReaderIO.hs
+++ b/src/Control/Monad/ReaderIO.hs
@@ -2,14 +2,12 @@
 {-# language MultiParamTypeClasses #-}
 {-# language FlexibleInstances #-}
 {-# language CPP #-}
+
 module Control.Monad.ReaderIO
-  (
-    ReaderIO (..)
-  )
-  where
+  ( ReaderIO (..)
+  ) where
 
 import Control.Monad.Fix
-import Control.Applicative
 import Control.Monad
 import Control.Monad.Reader.Class
 import Control.Monad.IO.Class
@@ -32,8 +30,10 @@
   {-# INLINE pure #-}
   (<*>) = ap
   {-# INLINE (<*>) #-}
+#if MIN_VERSION_base(4,18,0)
   liftA2 = liftM2
   {-# INLINE liftA2 #-}
+#endif
 
 instance Monad (ReaderIO e) where
   ReaderIO q >>= f = ReaderIO $ \e -> q e >>= \a -> runReaderIO (f a) e
diff --git a/src/Data/AppendMap.hs b/src/Data/AppendMap.hs
--- a/src/Data/AppendMap.hs
+++ b/src/Data/AppendMap.hs
@@ -7,6 +7,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
+
 -- |
 -- Module:
 --   Data.AppendMap
@@ -26,7 +27,6 @@
 import Data.Default
 import Data.Map (Map)
 import qualified Data.Map.Internal.Debug as Map (showTree, showTreeWith)
-
 import Data.Map.Monoidal
 
 
diff --git a/src/Data/FastMutableIntMap.hs b/src/Data/FastMutableIntMap.hs
--- a/src/Data/FastMutableIntMap.hs
+++ b/src/Data/FastMutableIntMap.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TypeFamilies #-}
+
 -- |
 -- Module:
 --   Data.FastMutableIntMap
diff --git a/src/Data/FastWeakBag.hs b/src/Data/FastWeakBag.hs
--- a/src/Data/FastWeakBag.hs
+++ b/src/Data/FastWeakBag.hs
@@ -1,12 +1,10 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE ExistentialQuantification #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
 #ifdef GHCJS_FAST_WEAK
 {-# LANGUAGE ForeignFunctionInterface #-}
 {-# LANGUAGE JavaScriptFFI #-}
 #endif
+
 -- | This module defines the 'FastWeakBag' type, which represents a mutable
 -- collection of items that does not cause the items to be retained in memory.
 -- This is useful for situations where a value needs to be inspected or modified
diff --git a/src/Data/Map/Misc.hs b/src/Data/Map/Misc.hs
--- a/src/Data/Map/Misc.hs
+++ b/src/Data/Map/Misc.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE LambdaCase #-}
+
 -- | Additional functions for manipulating 'Map's.
 module Data.Map.Misc
   (
diff --git a/src/Data/WeakBag.hs b/src/Data/WeakBag.hs
--- a/src/Data/WeakBag.hs
+++ b/src/Data/WeakBag.hs
@@ -1,9 +1,7 @@
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE ExistentialQuantification #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- | This module defines the 'WeakBag' type, which represents a mutable
 -- collection of items that does not cause the items to be retained in memory.
 -- This is useful for situations where a value needs to be inspected or modified
diff --git a/src/Reflex.hs b/src/Reflex.hs
--- a/src/Reflex.hs
+++ b/src/Reflex.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE CPP #-}
+
 -- | This module exports all of the commonly-used functionality of Reflex; if
 -- you are just getting started with Reflex, this is probably what you want.
 module Reflex
@@ -13,9 +14,7 @@
 import Reflex.Dynamic as X
 import Reflex.EventWriter.Base as X
 import Reflex.EventWriter.Class as X
-#ifdef USE_TEMPLATE_HASKELL
 import Reflex.Dynamic.TH as X
-#endif
 import Reflex.Dynamic.Uniq as X
 import Reflex.DynamicWriter.Base as X
 import Reflex.DynamicWriter.Class as X
diff --git a/src/Reflex/Adjustable/Class.hs b/src/Reflex/Adjustable/Class.hs
--- a/src/Reflex/Adjustable/Class.hs
+++ b/src/Reflex/Adjustable/Class.hs
@@ -7,9 +7,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- |
 -- Module:
 --   Reflex.Adjustable.Class
diff --git a/src/Reflex/BehaviorWriter/Base.hs b/src/Reflex/BehaviorWriter/Base.hs
--- a/src/Reflex/BehaviorWriter/Base.hs
+++ b/src/Reflex/BehaviorWriter/Base.hs
@@ -13,9 +13,7 @@
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE StandaloneDeriving #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.BehaviorWriter.Base
   ( BehaviorWriterT (..)
   , runBehaviorWriterT
@@ -39,6 +37,10 @@
 import Data.Map (Map)
 import qualified Data.Map as Map
 import Data.Some (Some)
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad.Identity
+#endif
 
 import Reflex.Class
 import Reflex.Adjustable.Class
diff --git a/src/Reflex/BehaviorWriter/Class.hs b/src/Reflex/BehaviorWriter/Class.hs
--- a/src/Reflex/BehaviorWriter/Class.hs
+++ b/src/Reflex/BehaviorWriter/Class.hs
@@ -7,9 +7,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.BehaviorWriter.Class
   ( MonadBehaviorWriter
   , BehaviorWriter(..)
diff --git a/src/Reflex/Class.hs b/src/Reflex/Class.hs
--- a/src/Reflex/Class.hs
+++ b/src/Reflex/Class.hs
@@ -17,9 +17,6 @@
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE Trustworthy #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
 
 -- |
 -- Module:
diff --git a/src/Reflex/Collection.hs b/src/Reflex/Collection.hs
--- a/src/Reflex/Collection.hs
+++ b/src/Reflex/Collection.hs
@@ -7,9 +7,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- |
 -- Module:
 --   Reflex.Collection
@@ -42,6 +40,10 @@
 import qualified Data.Map as Map
 import Data.Map.Misc
 import Data.These
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad.Identity
+#endif
 
 import Reflex.Class
 import Reflex.Adjustable.Class
diff --git a/src/Reflex/Dynamic.hs b/src/Reflex/Dynamic.hs
--- a/src/Reflex/Dynamic.hs
+++ b/src/Reflex/Dynamic.hs
@@ -14,9 +14,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- |
 -- Module:
 --   Reflex.Dynamic
@@ -78,16 +76,14 @@
   , unsafeDynamic
   ) where
 
-import Data.Functor.Compose
-import Data.Functor.Misc
-import Reflex.Class
-
 import Control.Monad.Fix
 import Control.Monad.Identity
 import Data.Align
 import Data.Dependent.Map (DMap)
 import qualified Data.Dependent.Map as DMap
 import Data.Dependent.Sum (DSum (..))
+import Data.Functor.Compose
+import Data.Functor.Misc
 import Data.GADT.Compare (GCompare (..), GEq (..), GOrdering (..))
 import Data.IntMap (IntMap)
 import Data.Kind (Type)
@@ -97,6 +93,13 @@
 import Data.Type.Equality ((:~:) (..))
 
 import Debug.Trace (trace)
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad
+import Data.Monoid ((<>))
+#endif
+
+import Reflex.Class
 
 -- | Map a sampling function over a 'Dynamic'.
 mapDynM :: forall t m a b. (Reflex t, MonadHold t m) => (forall m'. MonadSample t m' => a -> m' b) -> Dynamic t a -> m (Dynamic t b)
diff --git a/src/Reflex/Dynamic/TH.hs b/src/Reflex/Dynamic/TH.hs
--- a/src/Reflex/Dynamic/TH.hs
+++ b/src/Reflex/Dynamic/TH.hs
@@ -5,9 +5,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TypeOperators #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- | Template Haskell helper functions for building complex 'Dynamic' values.
 module Reflex.Dynamic.TH
   ( qDynPure
@@ -15,8 +13,6 @@
   , mkDynPure
   ) where
 
-import Reflex.Dynamic
-
 import Control.Monad.State
 import Data.Data
 import Data.Generics
@@ -25,6 +21,12 @@
 import Language.Haskell.TH
 import Language.Haskell.TH.Quote
 import qualified Language.Haskell.TH.Syntax as TH
+
+#if !MIN_VERSION_base(4,18,0)
+import Data.Monoid ((<>))
+#endif
+
+import Reflex.Dynamic
 
 -- | Quote a 'Dynamic' expression.  Within the quoted expression, you can use
 -- @$(unqDyn [| x |])@ to refer to any expression @x@ of type @Dynamic t a@; the
diff --git a/src/Reflex/Dynamic/Uniq.hs b/src/Reflex/Dynamic/Uniq.hs
--- a/src/Reflex/Dynamic/Uniq.hs
+++ b/src/Reflex/Dynamic/Uniq.hs
@@ -2,9 +2,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- | This module provides a variation of 'Dynamic' values that uses cheap
 -- pointer equality checks to reduce the amount of signal propagation needed.
 module Reflex.Dynamic.Uniq
@@ -15,6 +13,11 @@
   ) where
 
 import GHC.Exts
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (Applicative(..))
+#endif
+
 import Reflex.Class
 
 -- | A 'Dynamic' whose 'updated' 'Event' will never fire with the same value as
diff --git a/src/Reflex/DynamicWriter/Base.hs b/src/Reflex/DynamicWriter/Base.hs
--- a/src/Reflex/DynamicWriter/Base.hs
+++ b/src/Reflex/DynamicWriter/Base.hs
@@ -11,9 +11,7 @@
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE StandaloneDeriving #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.DynamicWriter.Base
   ( DynamicWriterT (..)
   , runDynamicWriterT
@@ -41,6 +39,11 @@
 import qualified Data.Map as Map
 import Data.Some (Some)
 import Data.These
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad.Identity
+import Data.Semigroup (Semigroup(..))
+#endif
 
 import Reflex.Adjustable.Class
 import Reflex.Class
diff --git a/src/Reflex/DynamicWriter/Class.hs b/src/Reflex/DynamicWriter/Class.hs
--- a/src/Reflex/DynamicWriter/Class.hs
+++ b/src/Reflex/DynamicWriter/Class.hs
@@ -4,9 +4,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.DynamicWriter.Class
   ( MonadDynamicWriter
   , DynamicWriter(..)
diff --git a/src/Reflex/EventWriter/Base.hs b/src/Reflex/EventWriter/Base.hs
--- a/src/Reflex/EventWriter/Base.hs
+++ b/src/Reflex/EventWriter/Base.hs
@@ -10,9 +10,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.EventWriter.Base
   ( EventWriterT (..)
   , runEventWriterT
diff --git a/src/Reflex/EventWriter/Class.hs b/src/Reflex/EventWriter/Class.hs
--- a/src/Reflex/EventWriter/Class.hs
+++ b/src/Reflex/EventWriter/Class.hs
@@ -3,14 +3,16 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.EventWriter.Class
   ( EventWriter (..)
   ) where
 
 import Control.Monad.Reader (ReaderT, lift)
+
+#if !MIN_VERSION_base(4,18,0)
+import Data.Semigroup (Semigroup)
+#endif
 
 import Reflex.Class (Event)
 
diff --git a/src/Reflex/Host/Class.hs b/src/Reflex/Host/Class.hs
--- a/src/Reflex/Host/Class.hs
+++ b/src/Reflex/Host/Class.hs
@@ -10,9 +10,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- | This module provides the interface for hosting 'Reflex' engines.  This
 -- should only be necessary if you're writing a binding or some other library
 -- that provides a core event loop.
diff --git a/src/Reflex/Host/Headless.hs b/src/Reflex/Host/Headless.hs
--- a/src/Reflex/Host/Headless.hs
+++ b/src/Reflex/Host/Headless.hs
@@ -39,6 +39,7 @@
   , MonadSample t (Performable m)
   , MonadSample t m
   , MonadThrow m
+  , MonadThrow (Performable m)
   , NotReady t m
   , PerformEvent t m
   , PostBuild t m
diff --git a/src/Reflex/Network.hs b/src/Reflex/Network.hs
--- a/src/Reflex/Network.hs
+++ b/src/Reflex/Network.hs
@@ -1,8 +1,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 -- |
 -- Module:
 --   Reflex.Network
diff --git a/src/Reflex/NotReady/Class.hs b/src/Reflex/NotReady/Class.hs
--- a/src/Reflex/NotReady/Class.hs
+++ b/src/Reflex/NotReady/Class.hs
@@ -6,9 +6,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.NotReady.Class
   ( NotReady(..)
   ) where
diff --git a/src/Reflex/Optimizer.hs b/src/Reflex/Optimizer.hs
deleted file mode 100644
--- a/src/Reflex/Optimizer.hs
+++ /dev/null
@@ -1,63 +0,0 @@
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE OverloadedStrings #-}
--- |
--- Module:
---   Reflex.Optimizer
--- Description:
---   This module provides a GHC plugin designed to improve code that uses
---   Reflex.  Currently, it just adds an INLINABLE pragma to any top-level
---   definition that doesn't have an explicit inlining pragma.  In the future,
---   additional optimizations are likely to be added.
-module Reflex.Optimizer
-  ( plugin
-  ) where
-
-#ifdef ghcjs_HOST_OS
-import Plugins
-#else
-import Control.Arrow
-import CoreMonad
-import Data.String
-import GhcPlugins
-
-import Prelude hiding ((<>))
-
-#endif
-
-#ifdef ghcjs_HOST_OS
-
--- | The GHCJS build of Reflex.Optimizer just throws an error; instead, the version built with GHC should be used.
-plugin :: Plugin
-plugin = error "The GHCJS build of Reflex.Optimizer cannot be used.  Instead, build with GHC and use the result with GHCJS."
-
-#else
-
--- | The GHC plugin itself.  See "GhcPlugins" for more details.
-plugin :: Plugin
-plugin = defaultPlugin { installCoreToDos = install }
-
-install :: [CommandLineOption] -> [CoreToDo] -> CoreM [CoreToDo]
-install [] p = do
-  liftIO $ putStrLn $ showSDocUnsafe $ ppr p
-  let f = \case
-        simpl@(CoreDoSimplify _ _) -> [CoreDoSpecialising, simpl]
-        x -> [x]
-  return $ makeInlinable : concatMap f p
-install options@(_:_) p = do
-  warnMsg $ "Reflex.Optimizer: ignoring " <> fromString (show $ length options) <> " command-line options"
-  install [] p
-
-makeInlinable :: CoreToDo
-makeInlinable = CoreDoPluginPass "MakeInlinable" $ \modGuts -> do
-  let f v = setIdInfo v $ let i = idInfo v in
-        setInlinePragInfo i $ let p = inlinePragInfo i in
-        if isDefaultInlinePragma p
-        then defaultInlinePragma { inl_inline = Inlinable }
-        else p
-      newBinds = flip map (mg_binds modGuts) $ \case
-        NonRec b e -> NonRec (f b) e
-        Rec bes -> Rec $ map (first f) bes
-  return $ modGuts { mg_binds = newBinds }
-
-#endif
diff --git a/src/Reflex/PerformEvent/Base.hs b/src/Reflex/PerformEvent/Base.hs
--- a/src/Reflex/PerformEvent/Base.hs
+++ b/src/Reflex/PerformEvent/Base.hs
@@ -15,24 +15,21 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.PerformEvent.Base
   ( PerformEventT (..)
   , FireCommand (..)
   , hostPerformEventT
   ) where
 
-import Reflex.Class
 import Reflex.Adjustable.Class
+import Reflex.Class
 import Reflex.Host.Class
 import Reflex.PerformEvent.Class
 import Reflex.Requester.Base
 import Reflex.Requester.Class
 
-import Control.Lens
-import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
+import Control.Monad.Catch (MonadCatch, MonadMask, MonadThrow)
 import Control.Monad.Exception
 import Control.Monad.Fix
 import Control.Monad.Primitive
@@ -42,9 +39,14 @@
 import Data.Dependent.Map (DMap)
 import qualified Data.Dependent.Map as DMap
 import Data.Dependent.Sum
+import Data.Functor.Identity
 import Data.IntMap.Strict (IntMap)
 import qualified Data.IntMap.Strict as IntMap
 import qualified Data.Semigroup as S
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad.Identity
+#endif
 
 -- | A function that fires events for the given 'EventTrigger's and then runs
 -- any followup actions provided via 'PerformEvent'.  The given 'ReadPhase'
diff --git a/src/Reflex/PerformEvent/Class.hs b/src/Reflex/PerformEvent/Class.hs
--- a/src/Reflex/PerformEvent/Class.hs
+++ b/src/Reflex/PerformEvent/Class.hs
@@ -9,9 +9,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.PerformEvent.Class
   ( PerformEvent (..)
   , performEventAsync
@@ -20,8 +18,11 @@
 import Control.Monad
 import Control.Monad.Reader
 import Control.Monad.Trans.Maybe (MaybeT (..))
-
 import Data.Kind (Type)
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Monad.Fix
+#endif
 
 import Reflex.Class
 import Reflex.TriggerEvent.Class
diff --git a/src/Reflex/PostBuild/Base.hs b/src/Reflex/PostBuild/Base.hs
--- a/src/Reflex/PostBuild/Base.hs
+++ b/src/Reflex/PostBuild/Base.hs
@@ -10,9 +10,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.PostBuild.Base
   ( PostBuildT (..)
   , runPostBuildT
@@ -21,14 +19,6 @@
   , mapDMapWithAdjustImpl
   ) where
 
-import Reflex.Class
-import Reflex.Adjustable.Class
-import Reflex.Host.Class
-import Reflex.PerformEvent.Class
-import Reflex.PostBuild.Class
-import Reflex.TriggerEvent.Class
-
-import Control.Applicative (liftA2)
 import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
 import Control.Monad.Exception
 import Control.Monad.Fix
@@ -42,6 +32,18 @@
 import Data.IntMap.Strict (IntMap)
 import qualified Data.IntMap.Strict as IntMap
 import qualified Data.Semigroup as S
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+import Control.Monad.Identity
+#endif
+
+import Reflex.Class
+import Reflex.Adjustable.Class
+import Reflex.Host.Class
+import Reflex.PerformEvent.Class
+import Reflex.PostBuild.Class
+import Reflex.TriggerEvent.Class
 
 -- | Provides a basic implementation of 'PostBuild'.
 newtype PostBuildT t m a = PostBuildT { unPostBuildT :: ReaderT (Event t ()) m a }
diff --git a/src/Reflex/PostBuild/Class.hs b/src/Reflex/PostBuild/Class.hs
--- a/src/Reflex/PostBuild/Class.hs
+++ b/src/Reflex/PostBuild/Class.hs
@@ -7,9 +7,7 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.PostBuild.Class
   ( PostBuild (..)
   ) where
diff --git a/src/Reflex/Profiled.hs b/src/Reflex/Profiled.hs
--- a/src/Reflex/Profiled.hs
+++ b/src/Reflex/Profiled.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE EmptyDataDecls #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
@@ -11,6 +12,7 @@
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE RankNTypes #-}
+
 -- |
 -- Module:
 --   Reflex.Profiled
@@ -44,6 +46,12 @@
 import GHC.Foreign
 import GHC.IO.Encoding
 import GHC.Stack
+import System.IO.Unsafe
+
+#if !MIN_VERSION_base(4,18,0)
+import Data.Monoid ((<>))
+#endif
+
 import Reflex.Adjustable.Class
 import Reflex.BehaviorWriter.Class
 import Reflex.Class
@@ -56,8 +64,6 @@
 import Reflex.Query.Class
 import Reflex.Requester.Class
 import Reflex.TriggerEvent.Class
-
-import System.IO.Unsafe
 
 data ProfiledTimeline t
 
diff --git a/src/Reflex/Pure.hs b/src/Reflex/Pure.hs
--- a/src/Reflex/Pure.hs
+++ b/src/Reflex/Pure.hs
@@ -8,15 +8,11 @@
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE PolyKinds #-}
-
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
-
 -- There are two expected orphan instances in this module:
 --   * MonadSample (Pure t) ((->) t)
 --   * MonadHold (Pure t) ((->) t)
 {-# OPTIONS_GHC -fno-warn-orphans #-}
+
 -- |
 -- Module: Reflex.Pure
 -- Description:
diff --git a/src/Reflex/Query/Base.hs b/src/Reflex/Query/Base.hs
--- a/src/Reflex/Query/Base.hs
+++ b/src/Reflex/Query/Base.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE InstanceSigs #-}
@@ -19,7 +20,6 @@
   , mapQueryT
   ) where
 
-import Control.Applicative (liftA2)
 import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
 import Control.Monad.Exception
 import Control.Monad.Fix
@@ -45,6 +45,11 @@
 import Data.Semigroup.Commutative
 import Data.Some (Some(Some))
 import Data.These
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+import Data.Monoid ((<>))
+#endif
 
 import Reflex.Class
 import Reflex.Adjustable.Class
diff --git a/src/Reflex/Query/Class.hs b/src/Reflex/Query/Class.hs
--- a/src/Reflex/Query/Class.hs
+++ b/src/Reflex/Query/Class.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
+
 -- |
 -- Module:
 --   Reflex.Query.Class
@@ -27,7 +28,6 @@
   , mapQueryResult
   ) where
 
-import Control.Applicative
 import Control.Category (Category)
 import qualified Control.Category as Cat
 import Control.Monad.Reader
@@ -41,6 +41,11 @@
 import Data.Void
 import Data.Monoid hiding ((<>))
 import Foreign.Storable
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative
+import Data.Semigroup (Semigroup(..))
+#endif
 
 import Reflex.Class
 
diff --git a/src/Reflex/Requester/Base/Internal.hs b/src/Reflex/Requester/Base/Internal.hs
--- a/src/Reflex/Requester/Base/Internal.hs
+++ b/src/Reflex/Requester/Base/Internal.hs
@@ -16,22 +16,9 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
-module Reflex.Requester.Base.Internal where
 
-import Reflex.Class
-import Reflex.Adjustable.Class
-import Reflex.Dynamic
-import Reflex.EventWriter.Class
-import Reflex.Host.Class
-import Reflex.PerformEvent.Class
-import Reflex.PostBuild.Class
-import Reflex.Requester.Class
-import Reflex.TriggerEvent.Class
+module Reflex.Requester.Base.Internal where
 
-import Control.Applicative (liftA2)
 import Control.Monad
 import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
 import Control.Monad.Exception
@@ -62,6 +49,21 @@
 
 import GHC.Exts (Any)
 import Unsafe.Coerce
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+import Data.Monoid ((<>))
+#endif
+
+import Reflex.Class
+import Reflex.Adjustable.Class
+import Reflex.Dynamic
+import Reflex.EventWriter.Class
+import Reflex.Host.Class
+import Reflex.PerformEvent.Class
+import Reflex.PostBuild.Class
+import Reflex.Requester.Class
+import Reflex.TriggerEvent.Class
 
 --TODO: Make this module type-safe
 
diff --git a/src/Reflex/Requester/Class.hs b/src/Reflex/Requester/Class.hs
--- a/src/Reflex/Requester/Class.hs
+++ b/src/Reflex/Requester/Class.hs
@@ -10,9 +10,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
+
 module Reflex.Requester.Class
  ( Requester (..)
  , withRequesting
@@ -40,6 +38,8 @@
   type Response m :: Type -> Type
   -- | Emit a request whenever the given 'Event' fires, and return responses in
   -- the resulting 'Event'.
+  --
+  -- Semantically, the response event occurs at a later time than the request event.
   requesting :: Event t (Request m a) -> m (Event t (Response m a))
   -- | Emit a request whenever the given 'Event' fires, and ignore all responses.
   requesting_ :: Event t (Request m a) -> m ()
diff --git a/src/Reflex/Spider.hs b/src/Reflex/Spider.hs
--- a/src/Reflex/Spider.hs
+++ b/src/Reflex/Spider.hs
@@ -1,20 +1,21 @@
 {-# LANGUAGE CPP #-}
+
 -- |
 -- Module:
 --   Reflex.Spider
 -- Description:
 --   This module exports all of the user-facing functionality of the 'Spider' 'Reflex' engine
 module Reflex.Spider
-       ( Spider
-       , SpiderTimeline
-       , Global
-       , SpiderHost
-       , runSpiderHost
-       , runSpiderHostForTimeline
-       , newSpiderTimeline
-       , withSpiderTimeline
-         -- * Deprecated
-       , SpiderEnv
-       ) where
+  ( Spider
+  , SpiderTimeline
+  , Global
+  , SpiderHost
+  , runSpiderHost
+  , runSpiderHostForTimeline
+  , newSpiderTimeline
+  , withSpiderTimeline
+    -- * Deprecated
+  , SpiderEnv
+  ) where
 
 import Reflex.Spider.Internal
diff --git a/src/Reflex/Spider/Internal.hs b/src/Reflex/Spider/Internal.hs
--- a/src/Reflex/Spider/Internal.hs
+++ b/src/Reflex/Spider/Internal.hs
@@ -20,31 +20,25 @@
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE InstanceSigs #-}
 {-# LANGUAGE MultiWayIf #-}
-
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
 {-# OPTIONS_GHC -Wunused-binds #-}
+
 -- | This module is the implementation of the 'Spider' 'Reflex' engine.  It uses
 -- a graph traversal algorithm to propagate 'Event's and 'Behavior's.
-module Reflex.Spider.Internal (module Reflex.Spider.Internal) where
+module Reflex.Spider.Internal
+  ( module Reflex.Spider.Internal
+  ) where
 
-import Control.Applicative (liftA2)
 import Control.Concurrent
 import Control.Exception
 import Control.Monad hiding (forM, forM_, mapM, mapM_)
 import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
 import Control.Monad.Exception
 import Control.Monad.Fix
-import Control.Monad.Identity
 import Control.Monad.Primitive
 import Control.Monad.Reader.Class
 import Control.Monad.IO.Class
 import Control.Monad.ReaderIO
 import Control.Monad.Ref
-#if !MIN_VERSION_base(4,13,0)
-import Control.Monad.Fail (MonadFail)
-#endif
 import qualified Control.Monad.Fail as MonadFail
 import Data.Align
 import Data.Coerce
@@ -76,6 +70,16 @@
 import Unsafe.Coerce
 import Witherable (Filterable, mapMaybe)
 
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+import Control.Monad.Identity hiding (forM, forM_, mapM, mapM_)
+import Control.Monad.Fail (MonadFail)
+import Data.List (isPrefixOf)
+import Data.Monoid (mempty, (<>))
+#else
+import Control.Monad.Identity
+#endif
+
 #ifdef MIN_VERSION_semialign
 #if MIN_VERSION_these(0,8,0)
 import Data.These.Combinators (justThese)
@@ -290,7 +294,7 @@
   return (subscription, occ)
 
 --TODO: Make this lazy in its input event
-headE :: (Defer (SomeMergeInit x) m) => Event x a -> m (Event x a)
+headE :: Defer (SomeMergeInit x) m => Event x a -> m (Event x a)
 headE originalE = do
   parent <- liftIO $ newIORef $ Just originalE
   defer $ SomeMergeInit $ do --TODO: Rename SomeMergeInit appropriately
@@ -311,11 +315,10 @@
 #endif
                      }
 
-nowSpiderEventM :: (HasSpiderTimeline x) => EventM x (R.Event (SpiderTimeline x) ())
-nowSpiderEventM =
-  SpiderEvent <$> now
+nowSpiderEventM :: HasSpiderTimeline x => EventM x (R.Event (SpiderTimeline x) ())
+nowSpiderEventM = SpiderEvent <$> now
 
-now :: (Defer (Some Clear) m) => m (Event x ())
+now :: Defer (Some Clear) m => m (Event x ())
 now = do
   nowOrNot <- liftIO $ newIORef $ Just ()
   scheduleClear nowOrNot
@@ -536,10 +539,12 @@
 newSubscriberCoincidenceInner :: forall x a. HasSpiderTimeline x => CoincidenceSubscribed x a -> IO (Subscriber x a)
 newSubscriberCoincidenceInner subscribed = debugSubscriber ("SubscriberCoincidenceInner" <> showNodeId subscribed) $ Subscriber
   { subscriberPropagate = \a -> {-# SCC "traverseCoincidenceInner" #-} do
+#ifdef DEBUG
       occ <- liftIO $ readIORef $ coincidenceSubscribedOccurrence subscribed
       case occ of
-        Just _ -> return () -- SubscriberCoincidenceOuter must have already propagated this event
+        Just _ -> error "Coincidence inner is propagating, but coincidence occurrence is already known?"
         Nothing -> do
+#endif          
           liftIO $ writeIORef (coincidenceSubscribedOccurrence subscribed) $ Just a
           scheduleClear $ coincidenceSubscribedOccurrence subscribed
           propagate a $ coincidenceSubscribedSubscribers subscribed
@@ -1158,9 +1163,7 @@
             , switchSubscribed :: !(IORef (Maybe (SwitchSubscribed x a)))
             }
 
-#ifdef USE_TEMPLATE_HASKELL
 {-# ANN CoincidenceSubscribed "HLint: ignore Redundant bracket" #-}
-#endif
 data CoincidenceSubscribed x a
    = CoincidenceSubscribed { coincidenceSubscribedCachedSubscribed :: !(IORef (Maybe (CoincidenceSubscribed x a)))
                            , coincidenceSubscribedOccurrence :: !(IORef (Maybe a))
@@ -1609,9 +1612,7 @@
       occ <- getOcc
       return (sln, subscribed, occ)
 
-#ifdef USE_TEMPLATE_HASKELL
 {-# ANN cleanupRootSubscribed "HLint: ignore Redundant bracket" #-}
-#endif
 cleanupRootSubscribed :: RootSubscribed x a -> IO ()
 cleanupRootSubscribed self@RootSubscribed { rootSubscribedKey = k, rootSubscribedCachedSubscribed = cached } = do
   rootSubscribedUninit self
@@ -2106,7 +2107,7 @@
 {-# INLINE mergeGCheap' #-}
 mergeGCheap' :: forall k v x p s q. (HasSpiderTimeline x, GCompare k, PatchTarget p ~ DMap k q)
   => MergeGetSubscription x s -> MergeInitFunc k v q x s -> MergeUpdateFunc k v x p s -> MergeDestroyFunc k s -> DynamicS x p -> Event x (DMap k v)
-mergeGCheap' getParent getInitialSubscribers updateFunc destroy d = Event $ \sub -> do
+mergeGCheap' _ getInitialSubscribers updateFunc destroy d = Event $ \sub -> do
   initialParents <- readBehaviorUntracked $ dynamicCurrent d
   accumRef <- liftIO $ newIORef $ error "merge: accumRef not yet initialized"
   heightRef <- liftIO $ newIORef $ error "merge: heightRef not yet initialized"
diff --git a/src/Reflex/Time.hs b/src/Reflex/Time.hs
--- a/src/Reflex/Time.hs
+++ b/src/Reflex/Time.hs
@@ -4,13 +4,11 @@
 {-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE RecursiveDo #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections #-}
 {-# LANGUAGE TypeFamilies #-}
-#ifdef USE_TEMPLATE_HASKELL
-{-# LANGUAGE TemplateHaskell #-}
-#endif
 -- |
 -- Module:
 --   Reflex.Time
@@ -18,15 +16,8 @@
 --   Clocks, timers, and other time-related functions.
 module Reflex.Time where
 
-import Reflex.Class
-import Reflex.Dynamic
-import Reflex.PerformEvent.Class
-import Reflex.PostBuild.Class
-import Reflex.TriggerEvent.Class
-
 import Control.Concurrent
 import qualified Control.Concurrent.Thread.Delay as Concurrent
-import Control.Lens hiding ((|>))
 import Control.Monad
 import Control.Monad.Fix
 import Control.Monad.IO.Class
@@ -40,6 +31,16 @@
 import GHC.Generics (Generic)
 import System.Random
 
+#if !MIN_VERSION_base(4,18,0)
+import Data.Semigroup (Semigroup(..))
+#endif
+
+import Reflex.Class
+import Reflex.Dynamic
+import Reflex.PerformEvent.Class
+import Reflex.PostBuild.Class
+import Reflex.TriggerEvent.Class
+
 -- | Metadata associated with a timer "tick"
 data TickInfo
   = TickInfo { _tickInfo_lastUTC :: UTCTime
@@ -365,18 +366,14 @@
       delayed <- lag (void outE)
   return outE
 
-#ifdef USE_TEMPLATE_HASKELL
-makeLensesWith (lensRules & simpleLenses .~ True) ''TickInfo
-#else
-tickInfo_lastUTC :: Lens' TickInfo UTCTime
+tickInfo_lastUTC :: Functor f => (UTCTime -> f UTCTime) -> TickInfo -> f TickInfo
 tickInfo_lastUTC f (TickInfo x1 x2 x3) = (\y -> TickInfo y x2 x3) <$> f x1
 {-# INLINE tickInfo_lastUTC #-}
 
-tickInfo_n :: Lens' TickInfo Integer
+tickInfo_n :: Functor f => (Integer  -> f Integer ) -> TickInfo -> f TickInfo
 tickInfo_n f (TickInfo x1 x2 x3) = (\y -> TickInfo x1 y x3) <$> f x2
 {-# INLINE tickInfo_n #-}
 
-tickInfo_alreadyElapsed :: Lens' TickInfo NominalDiffTime
-tickInfo_alreadyElapsed f (TickInfo x1 x2 x3) = (\y -> TickInfo x1 x2 y) <$> f x3
+tickInfo_alreadyElapsed :: Functor f => (NominalDiffTime -> f NominalDiffTime) -> TickInfo -> f TickInfo
+tickInfo_alreadyElapsed f (TickInfo x1 x2 x3) = TickInfo x1 x2 <$> f x3
 {-# INLINE tickInfo_alreadyElapsed #-}
-#endif
diff --git a/src/Reflex/TriggerEvent/Base.hs b/src/Reflex/TriggerEvent/Base.hs
--- a/src/Reflex/TriggerEvent/Base.hs
+++ b/src/Reflex/TriggerEvent/Base.hs
@@ -1,11 +1,13 @@
 -- | This module defines 'TriggerEventT', the standard implementation of
 -- 'TriggerEvent'.
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
+
 module Reflex.TriggerEvent.Base
   ( TriggerEventT (..)
   , runTriggerEventT
@@ -14,7 +16,6 @@
   , EventTriggerRef (..)
   ) where
 
-import Control.Applicative (liftA2)
 import Control.Concurrent
 import Control.Monad.Catch (MonadMask, MonadThrow, MonadCatch)
 import Control.Monad.Exception
@@ -26,6 +27,12 @@
 import Data.Dependent.Sum
 import Data.IORef
 import qualified Data.Semigroup as S
+
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+import Data.Monoid ((<>))
+#endif
+
 import Reflex.Class
 import Reflex.Adjustable.Class
 import Reflex.Host.Class
diff --git a/src/Reflex/TriggerEvent/Class.hs b/src/Reflex/TriggerEvent/Class.hs
--- a/src/Reflex/TriggerEvent/Class.hs
+++ b/src/Reflex/TriggerEvent/Class.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE UndecidableInstances #-}
+
 module Reflex.TriggerEvent.Class
   ( TriggerEvent (..)
   ) where
diff --git a/src/Reflex/Widget/Basic.hs b/src/Reflex/Widget/Basic.hs
--- a/src/Reflex/Widget/Basic.hs
+++ b/src/Reflex/Widget/Basic.hs
@@ -2,9 +2,6 @@
 {-# LANGUAGE ExplicitForAll #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RecursiveDo #-}
-#ifdef USE_REFLEX_OPTIMIZER
-{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
-#endif
 
 module Reflex.Widget.Basic where
 
diff --git a/src/Reflex/Workflow.hs b/src/Reflex/Workflow.hs
--- a/src/Reflex/Workflow.hs
+++ b/src/Reflex/Workflow.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE RecursiveDo #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+
 -- |
 -- Module:
 --   Reflex.Workflow
@@ -7,8 +8,8 @@
 --   Provides a convenient way to describe a series of interrelated widgets that
 --   can send data to, invoke, and replace one another. Useful for modeling user interface
 --   "workflows."
-module Reflex.Workflow (
-    Workflow (..)
+module Reflex.Workflow
+  ( Workflow (..)
   , workflow
   , workflowView
   , mapWorkflow
diff --git a/test/hlint.hs b/test/hlint.hs
--- a/test/hlint.hs
+++ b/test/hlint.hs
@@ -22,7 +22,6 @@
         , "--ignore=Use unless"
         , "--ignore=Reduce duplication"
         , "--ignore=Replace case with maybe"
-        , "--cpp-define=USE_TEMPLATE_HASKELL"
         , "--cpp-define=DEBUG"
         , "--ignore=Use tuple-section"
         ]