diff --git a/.travis.yml b/.travis.yml
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,167 +1,179 @@
 # This Travis job script has been generated by a script via
 #
-#   runghc make_travis_yml_2.hs '-o' '.travis.yml' '--ghc-head' '--irc-channel=irc.freenode.org#haskell-lens' '--no-no-tests-no-bench' '--no-unconstrained' 'cabal.project'
+#   haskell-ci '--output=.travis.yml' '--config=cabal.haskell-ci' 'cabal.project'
 #
-# For more information, see https://github.com/hvr/multi-ghc-travis
+# For more information, see https://github.com/haskell-CI/haskell-ci
 #
+# version: 0.3.20190425
+#
 language: c
-sudo: false
-
+dist: xenial
 git:
-  submodules: false  # whether to recursively clone submodules
-
+  # whether to recursively clone submodules
+  submodules: false
 notifications:
   irc:
     channels:
-      - "irc.freenode.org#haskell-lens"
+      - irc.freenode.org#haskell-lens
     skip_join: true
     template:
-      - "\x0313contravariant\x03/\x0306%{branch}\x03 \x0314%{commit}\x03 %{build_url} %{message}"
-
+      - "\"\\x0313contravariant\\x03/\\x0306%{branch}\\x03 \\x0314%{commit}\\x03 %{build_url} %{message}\""
 cache:
   directories:
     - $HOME/.cabal/packages
     - $HOME/.cabal/store
-
 before_cache:
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/build-reports.log
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/build-reports.log
   # remove files that are regenerated by 'cabal update'
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/00-index.*
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/*.json
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.cache
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar
-  - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar.idx
-
-  - rm -rfv $HOME/.cabal/packages/head.hackage
-
-addons:
-  apt:
-    packages: &apt_packages
-      - ghc-ppa-tools
-      - hlint
-
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/00-index.*
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/*.json
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/01-index.cache
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/01-index.tar
+  - rm -fv $CABALHOME/packages/hackage.haskell.org/01-index.tar.idx
+  - rm -rfv $CABALHOME/packages/head.hackage
 matrix:
   include:
-    - compiler: "ghc-8.6.1"
+    - compiler: ghc-8.8.1
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-8.8.1","cabal-install-3.0"]}}
       env: GHCHEAD=true
-      addons: {apt: {packages: [*apt_packages,cabal-install-head,ghc-8.6.1], sources: [hvr-ghc]}}
-    - compiler: "ghc-8.4.3"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-8.4.3], sources: [hvr-ghc]}}
-    - compiler: "ghc-8.2.2"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-8.2.2], sources: [hvr-ghc]}}
-    - compiler: "ghc-8.0.2"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-8.0.2], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.10.3"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.10.3], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.8.4"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.8.4], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.6.3"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.6.3], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.4.2"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.4.2], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.2.2"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.2.2], sources: [hvr-ghc]}}
-    - compiler: "ghc-7.0.4"
-    # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [*apt_packages,cabal-install-2.2,ghc-7.0.4], sources: [hvr-ghc]}}
-    - compiler: "ghc-head"
+    - compiler: ghc-8.6.5
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-8.6.5","cabal-install-2.4"]}}
+    - compiler: ghc-8.4.4
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-8.4.4","cabal-install-2.4"]}}
+    - compiler: ghc-8.2.2
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-8.2.2","cabal-install-2.4"]}}
+    - compiler: ghc-8.0.2
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-8.0.2","cabal-install-2.4"]}}
+    - compiler: ghc-7.10.3
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.10.3","cabal-install-2.4"]}}
+    - compiler: ghc-7.8.4
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.8.4","cabal-install-2.4"]}}
+    - compiler: ghc-7.6.3
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.6.3","cabal-install-2.4"]}}
+    - compiler: ghc-7.4.2
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.4.2","cabal-install-2.4"]}}
+    - compiler: ghc-7.2.2
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.2.2","cabal-install-2.4"]}}
+    - compiler: ghc-7.0.4
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-7.0.4","cabal-install-2.4"]}}
+    - compiler: ghc-head
+      addons: {"apt":{"sources":["hvr-ghc"],"packages":["ghc-head","cabal-install-head"]}}
       env: GHCHEAD=true
-      addons: {apt: {packages: [*apt_packages,cabal-install-head,ghc-head], sources: [hvr-ghc]}}
-
   allow_failures:
-    - compiler: "ghc-head"
-    - compiler: "ghc-7.0.4"
-    - compiler: "ghc-7.2.2"
-    - compiler: "ghc-8.6.1"
-
+    - compiler: ghc-head
+    - compiler: ghc-7.0.4
+    - compiler: ghc-7.2.2
+    - compiler: ghc-8.8.1
 before_install:
-  - HC=${CC}
-  - HCPKG=${HC/ghc/ghc-pkg}
+  - HC=$(echo "/opt/$CC/bin/ghc" | sed 's/-/\//')
+  - HCPKG="$HC-pkg"
   - unset CC
-  - ROOTDIR=$(pwd)
-  - mkdir -p $HOME/.local/bin
-  - "PATH=/opt/ghc/bin:/opt/ghc-ppa-tools/bin:$HOME/local/bin:$PATH"
+  - CABAL=/opt/ghc/bin/cabal
+  - CABALHOME=$HOME/.cabal
+  - export PATH="$CABALHOME/bin:$PATH"
+  - TOP=$(pwd)
   - HCNUMVER=$(( $(${HC} --numeric-version|sed -E 's/([0-9]+)\.([0-9]+)\.([0-9]+).*/\1 * 10000 + \2 * 100 + \3/') ))
   - echo $HCNUMVER
-
+  - CABAL="$CABAL -vnormal+nowrap+markoutput"
+  - set -o pipefail
+  - |
+    echo 'function blue(s) { printf "\033[0;34m" s "\033[0m " }'           >> .colorful.awk
+    echo 'BEGIN { state = "output"; }'                                     >> .colorful.awk
+    echo '/^-----BEGIN CABAL OUTPUT-----$/ { state = "cabal" }'            >> .colorful.awk
+    echo '/^-----END CABAL OUTPUT-----$/ { state = "output" }'             >> .colorful.awk
+    echo '!/^(-----BEGIN CABAL OUTPUT-----|-----END CABAL OUTPUT-----)/ {' >> .colorful.awk
+    echo '  if (state == "cabal") {'                                       >> .colorful.awk
+    echo '    print blue($0)'                                              >> .colorful.awk
+    echo '  } else {'                                                      >> .colorful.awk
+    echo '    print $0'                                                    >> .colorful.awk
+    echo '  }'                                                             >> .colorful.awk
+    echo '}'                                                               >> .colorful.awk
+  - cat .colorful.awk
+  - |
+    color_cabal_output () {
+      awk -f $TOP/.colorful.awk
+    }
+  - echo text | color_cabal_output
 install:
-  - cabal --version
+  - ${CABAL} --version
   - echo "$(${HC} --version) [$(${HC} --print-project-git-commit-id 2> /dev/null || echo '?')]"
-  - BENCH=${BENCH---enable-benchmarks}
-  - TEST=${TEST---enable-tests}
-  - HADDOCK=${HADDOCK-true}
-  - UNCONSTRAINED=${UNCONSTRAINED-true}
-  - NOINSTALLEDCONSTRAINTS=${NOINSTALLEDCONSTRAINTS-false}
+  - TEST=--enable-tests
+  - BENCH=--enable-benchmarks
   - GHCHEAD=${GHCHEAD-false}
-  - travis_retry cabal update -v
-  - "sed -i.bak 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config"
-  - rm -fv cabal.project cabal.project.local
-  # Overlay Hackage Package Index for GHC HEAD: https://github.com/hvr/head.hackage
+  - rm -f $CABALHOME/config
   - |
+    echo "verbose: normal +nowrap +markoutput"          >> $CABALHOME/config
+    echo "remote-build-reporting: anonymous"            >> $CABALHOME/config
+    echo "remote-repo-cache: $CABALHOME/packages"       >> $CABALHOME/config
+    echo "logs-dir:          $CABALHOME/logs"           >> $CABALHOME/config
+    echo "world-file:        $CABALHOME/world"          >> $CABALHOME/config
+    echo "extra-prog-path:   $CABALHOME/bin"            >> $CABALHOME/config
+    echo "symlink-bindir:    $CABALHOME/bin"            >> $CABALHOME/config
+    echo "installdir:        $CABALHOME/bin"            >> $CABALHOME/config
+    echo "build-summary:     $CABALHOME/logs/build.log" >> $CABALHOME/config
+    echo "store-dir:         $CABALHOME/store"          >> $CABALHOME/config
+    echo "install-dirs user"                            >> $CABALHOME/config
+    echo "  prefix: $CABALHOME"                         >> $CABALHOME/config
+    echo "repository hackage.haskell.org"               >> $CABALHOME/config
+    echo "  url: http://hackage.haskell.org/"           >> $CABALHOME/config
+  - |
     if $GHCHEAD; then
-      sed -i 's/-- allow-newer: .*/allow-newer: *:base/' ${HOME}/.cabal/config
-      for pkg in $($HCPKG list --simple-output); do pkg=$(echo $pkg | sed 's/-[^-]*$//'); sed -i "s/allow-newer: /allow-newer: *:$pkg, /" ${HOME}/.cabal/config; done
-
-      echo 'repository head.hackage'                                                        >> ${HOME}/.cabal/config
-      echo '   url: http://head.hackage.haskell.org/'                                       >> ${HOME}/.cabal/config
-      echo '   secure: True'                                                                >> ${HOME}/.cabal/config
-      echo '   root-keys: 07c59cb65787dedfaef5bd5f987ceb5f7e5ebf88b904bbd4c5cbdeb2ff71b740' >> ${HOME}/.cabal/config
-      echo '              2e8555dde16ebd8df076f1a8ef13b8f14c66bad8eafefd7d9e37d0ed711821fb' >> ${HOME}/.cabal/config
-      echo '              8f79fd2389ab2967354407ec852cbe73f2e8635793ac446d09461ffb99527f6e' >> ${HOME}/.cabal/config
-      echo '   key-threshold: 3'                                                            >> ${HOME}/.cabal.config
-
-      grep -Ev -- '^\s*--' ${HOME}/.cabal/config | grep -Ev '^\s*$'
-
-      cabal new-update head.hackage -v
+    echo "allow-newer: $($HCPKG list --simple-output | sed -E 's/([a-zA-Z-]+)-[0-9.]+/*:\1/g')" >> $CABALHOME/config
+    
+    echo "repository head.hackage"                                                        >> $CABALHOME/config
+    echo "   url: http://head.hackage.haskell.org/"                                       >> $CABALHOME/config
+    echo "   secure: True"                                                                >> $CABALHOME/config
+    echo "   root-keys: 07c59cb65787dedfaef5bd5f987ceb5f7e5ebf88b904bbd4c5cbdeb2ff71b740" >> $CABALHOME/config
+    echo "              2e8555dde16ebd8df076f1a8ef13b8f14c66bad8eafefd7d9e37d0ed711821fb" >> $CABALHOME/config
+    echo "              8f79fd2389ab2967354407ec852cbe73f2e8635793ac446d09461ffb99527f6e" >> $CABALHOME/config
+    echo "   key-threshold: 3"                                                            >> $CABALHOME/config
     fi
-  - grep -Ev -- '^\s*--' ${HOME}/.cabal/config | grep -Ev '^\s*$'
-  - "printf 'packages: \".\"\\n' > cabal.project"
-  - touch cabal.project.local
-  - "if ! $NOINSTALLEDCONSTRAINTS; then for pkg in $($HCPKG list --simple-output); do echo $pkg | sed 's/^/constraints: /' | sed 's/-[^-]*$/ installed/' >> cabal.project.local; done; fi"
+  - cat $CABALHOME/config
+  - rm -fv cabal.project cabal.project.local cabal.project.freeze
+  - travis_retry ${CABAL} v2-update -v
+  - if [ $HCNUMVER -eq 80801 ] ; then ${CABAL} v2-install -w ${HC} -j2 hlint --constraint='hlint ==2.1.*' | color_cabal_output ; fi
+  # Generate cabal.project
+  - rm -rf cabal.project cabal.project.local cabal.project.freeze
+  - touch cabal.project
+  - |
+    echo 'packages: "."' >> cabal.project
+  - |
+    echo "write-ghc-environment-files: always" >> cabal.project
+  - "for pkg in $($HCPKG list --simple-output); do echo $pkg | sed 's/-[^-]*$//' | grep -vE -- '^(contravariant)$' | sed 's/^/constraints: /' | sed 's/$/ installed/' >> cabal.project.local; done"
   - cat cabal.project || true
   - cat cabal.project.local || true
-  - if [ -f "./configure.ac" ]; then
-      (cd "." && autoreconf -i);
-    fi
-  - rm -f cabal.project.freeze
-  - cabal new-build -w ${HC} ${TEST} ${BENCH} --project-file="cabal.project" --dep -j2 all
-  - rm -rf .ghc.environment.* "."/dist
-  - DISTDIR=$(mktemp -d /tmp/dist-test.XXXX)
-
-# Here starts the actual work to be performed for the package under test;
-# any command which exits with a non-zero exit code causes the build to fail.
+  - if [ -f "./configure.ac" ]; then (cd "." && autoreconf -i); fi
+  - ${CABAL} v2-freeze -w ${HC} ${TEST} ${BENCH} | color_cabal_output
+  - "cat cabal.project.freeze | sed -E 's/^(constraints: *| *)//' | sed 's/any.//'"
+  - rm  cabal.project.freeze
+  - ${CABAL} v2-build -w ${HC} ${TEST} ${BENCH} --dep -j2 all | color_cabal_output
 script:
-  # test that source-distributions can be generated
-  - (cd "." && cabal sdist)
-  - mv "."/dist/contravariant-*.tar.gz ${DISTDIR}/
+  - DISTDIR=$(mktemp -d /tmp/dist-test.XXXX)
+  # Packaging...
+  - ${CABAL} v2-sdist all | color_cabal_output
+  # Unpacking...
+  - mv dist-newstyle/sdist/*.tar.gz ${DISTDIR}/
   - cd ${DISTDIR} || false
   - find . -maxdepth 1 -name '*.tar.gz' -exec tar -xvf '{}' \;
-  - "printf 'packages: contravariant-*/*.cabal\\n' > cabal.project"
-  - touch cabal.project.local
-  - "if ! $NOINSTALLEDCONSTRAINTS; then for pkg in $($HCPKG list --simple-output); do echo $pkg | sed 's/^/constraints: /' | sed 's/-[^-]*$/ installed/' >> cabal.project.local; done; fi"
+  # Generate cabal.project
+  - rm -rf cabal.project cabal.project.local cabal.project.freeze
+  - touch cabal.project
+  - |
+    echo 'packages: "contravariant-*/*.cabal"' >> cabal.project
+  - |
+    echo "write-ghc-environment-files: always" >> cabal.project
+  - "for pkg in $($HCPKG list --simple-output); do echo $pkg | sed 's/-[^-]*$//' | grep -vE -- '^(contravariant)$' | sed 's/^/constraints: /' | sed 's/$/ installed/' >> cabal.project.local; done"
   - cat cabal.project || true
   - cat cabal.project.local || true
-
+  # Building with tests and benchmarks...
   # build & run tests, build benchmarks
-  - cabal new-build -w ${HC} ${TEST} ${BENCH} all
-
-  # cabal check
-  - (cd contravariant-* && cabal check)
-
-  # haddock
-  - rm -rf ./dist-newstyle
-  - if $HADDOCK; then cabal new-haddock -w ${HC} ${TEST} ${BENCH} all; else echo "Skipping haddock generation";fi
-
-  # hlint
-  - (cd contravariant-* && hlint src --cpp-define=HLINT)
+  - ${CABAL} v2-build -w ${HC} ${TEST} ${BENCH} all | color_cabal_output
+  # HLint..
+  - if [ $HCNUMVER -eq 80801 ] ; then (cd contravariant-* && hlint --cpp-ansi --cpp-define=HLINT src old-src) ; fi
+  # cabal check...
+  - (cd contravariant-* && ${CABAL} -vnormal check)
+  # haddock...
+  - ${CABAL} v2-haddock -w ${HC} ${TEST} ${BENCH} all | color_cabal_output
 
-# REGENDATA ["-o",".travis.yml","--ghc-head","--irc-channel=irc.freenode.org#haskell-lens","--no-no-tests-no-bench","--no-unconstrained","cabal.project"]
+# REGENDATA ["--output=.travis.yml","--config=cabal.haskell-ci","cabal.project"]
 # EOF
diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,8 @@
+1.5.1 [2019.05.02]
+------------------
+* Remove the use of `unsafeCoerce` in `Data.Functor.Contravariant.Generic`. As
+  a result, the `safe` flag has been removed, as it is no longer used.
+
 1.5 [2018.07.01]
 ----------------
 * Support building with GHC 8.6, where `Data.Functor.Contravariant` has been
diff --git a/contravariant.cabal b/contravariant.cabal
--- a/contravariant.cabal
+++ b/contravariant.cabal
@@ -1,6 +1,6 @@
 name:          contravariant
 category:      Control, Data
-version:       1.5
+version:       1.5.1
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
@@ -21,8 +21,9 @@
              , GHC == 7.10.3
              , GHC == 8.0.2
              , GHC == 8.2.2
-             , GHC == 8.4.3
-             , GHC == 8.6.1
+             , GHC == 8.4.4
+             , GHC == 8.6.5
+             , GHC == 8.8.1
 extra-source-files:
   .travis.yml
   CHANGELOG.markdown
@@ -49,11 +50,6 @@
   default: True
   manual: True
 
-flag safe
-  description: Get Safe guarantees rather than merely Trustworthy, but with worse constant factors.
-  default: False
-  manual: True
-
 flag StateVar
   description:
     You can disable the use of the `StateVar` package using `-f-StateVar`.
@@ -85,9 +81,6 @@
 
   if impl(ghc >= 7.2 && < 7.6)
     build-depends: ghc-prim
-
-  if flag(safe)
-    cpp-options: -DSAFE
 
   exposed-modules:
     Data.Functor.Contravariant.Compose
diff --git a/src/Data/Functor/Contravariant/Divisible.hs b/src/Data/Functor/Contravariant/Divisible.hs
--- a/src/Data/Functor/Contravariant/Divisible.hs
+++ b/src/Data/Functor/Contravariant/Divisible.hs
@@ -108,7 +108,7 @@
 -- parts of a structure. If we postulate the existance of two primitive
 -- serializers - @string :: Serializer String@ and @int :: Serializer Int@, we
 -- would like to be able to combine these into a serializer for pairs of
--- @String@s and @Int@s. How can we do this? Simply run both serializer and
+-- @String@s and @Int@s. How can we do this? Simply run both serializers and
 -- combine their output!
 --
 -- @
@@ -146,6 +146,7 @@
 -- @
 --
 class Contravariant f => Divisible f where
+  --- | If one can handle split `a` into `(b, c)`, as well as handle `b`s and `c`s, then one can handle `a`s
   divide  :: (a -> (b, c)) -> f b -> f c -> f a
 
   -- | Conquer acts as an identity for combining @Divisible@ functors.
@@ -342,7 +343,7 @@
 -- functor has the ability to "fan out" input, under the intuition that contravariant
 -- functors consume input.
 --
--- In the dicussion for @Divisible@, an example was demonstrated with @Serializer@s,
+-- In the discussion for @Divisible@, an example was demonstrated with @Serializer@s,
 -- that turn @a@s into @ByteString@s. @Divisible@ allowed us to serialize the /product/
 -- of multiple values by concatenation. By making our @Serializer@ also @Decidable@-
 -- we now have the ability to serialize the /sum/ of multiple values - for example
diff --git a/src/Data/Functor/Contravariant/Generic.hs b/src/Data/Functor/Contravariant/Generic.hs
--- a/src/Data/Functor/Contravariant/Generic.hs
+++ b/src/Data/Functor/Contravariant/Generic.hs
@@ -1,8 +1,6 @@
 {-# LANGUAGE CPP #-}
-#ifdef SAFE
-{-# LANGUAGE BangPatterns #-}
-#elif __GLASGOW_HASKELL__ >= 704
-{-# LANGUAGE Trustworthy #-}
+#if __GLASGOW_HASKELL__ >= 704
+{-# LANGUAGE Safe #-}
 #endif
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE ConstraintKinds #-}
@@ -14,6 +12,10 @@
 #if __GLASGOW_HASKELL__ >= 706
 {-# LANGUAGE PolyKinds #-}
 #endif
+{-# LANGUAGE TypeFamilies #-}
+#if __GLASGOW_HASKELL__ >= 708
+{-# LANGUAGE EmptyCase #-}
+#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Functor.Contravariant.Generic
@@ -36,9 +38,6 @@
 import Data.Functor.Contravariant
 import Data.Functor.Contravariant.Divisible
 import GHC.Generics
-#ifndef SAFE
-import Unsafe.Coerce
-#endif
 
 -- | This provides machinery for deconstructing an arbitrary 'Generic' instance using a 'Decidable' 'Contravariant' functor.
 --
@@ -53,14 +52,53 @@
 -- geq :: 'Deciding' 'Eq' a => a -> a -> 'Bool'
 -- geq = 'getEquivalence' $ 'deciding' (Proxy :: Proxy 'Eq') ('Equivalence' ('=='))
 -- @
-class (Generic a, GDeciding q (Rep a)) => Deciding q a where
+class (Generic a, GDeciding q (Rep' a)) => Deciding q a where
 #ifndef HLINT
   deciding :: Decidable f => p q -> (forall b. q b => f b) -> f a
 #endif
 
-instance (Generic a, GDeciding q (Rep a)) => Deciding q a  where
-  deciding p q = contramap from $ gdeciding p q
+instance (Generic a, GG (Rep a), GDeciding q (Rep' a)) => Deciding q a  where
+  deciding p q = contramap (swizzle . from) $ gdeciding p q
 
+type Rep' a = Swizzle (Rep a)
+type Rep1' f = Swizzle (Rep1 f)
+type family Swizzle (r :: * -> *) :: * -> *
+type instance Swizzle (M1 i c f) = M1 i c (Swizzle f)
+type instance Swizzle V1 = V1
+type instance Swizzle U1 = U1
+type instance Swizzle Par1 = Par1
+type instance Swizzle (Rec1 f) = Rec1 f
+type instance Swizzle (K1 i c) = K1 i c
+type instance Swizzle (f :+: g) = Swizzle f ::+: Swizzle g
+type instance Swizzle (f :*: g) = Swizzle f ::*: Swizzle g
+type instance Swizzle (f :.: g) = f :.: Swizzle g
+
+newtype (::+:) f g a = Sum {unSum :: Either (f a) (g a)}
+newtype (::*:) f g a = Prod {unProd :: (f a, g a)}
+
+class GG r where
+  swizzle :: r p -> Swizzle r p
+instance GG f => GG (M1 i c f) where
+  swizzle (M1 a) = M1 (swizzle a)
+instance GG V1 where swizzle v = v
+instance GG U1 where swizzle v = v
+instance GG (K1 i c) where swizzle v = v
+instance GG Par1 where swizzle v = v
+instance GG (Rec1 f) where swizzle v = v
+instance (GG f, GG g) => GG (f :+: g) where
+  {-# INLINE swizzle #-}
+  swizzle (L1 x) = Sum (Left (swizzle x))
+  swizzle (R1 x) = Sum (Right (swizzle x))
+instance (GG f, GG g) => GG (f :*: g) where
+  {-# INLINE swizzle #-}
+  swizzle (x :*: y) = Prod (swizzle x, swizzle y)
+{-
+-- This instance wouldn't be that efficient. But we don't
+-- offer instances for compositions anyway.
+instance (Functor f, GG g) => GG (f :.: g) where
+  swizzle (Comp1 x) = Comp1 (fmap swizzle x)
+-}
+
 -- | This provides machinery for deconstructing an arbitrary 'Generic1' instance using a 'Decidable' 'Contravariant' functor.
 --
 -- /Examples:/
@@ -74,13 +112,13 @@
 -- geq1 :: 'Deciding1' 'Eq' f => (a -> a -> 'Bool') -> f a -> f a -> 'Bool'
 -- geq1 f = 'getEquivalence' $ 'deciding1' (Proxy :: Proxy 'Eq') ('Equivalence' ('==')) ('Equivalence' f)
 -- @
-class (Generic1 t, GDeciding1 q (Rep1 t)) => Deciding1 q t where
+class (Generic1 t, GDeciding1 q (Rep1' t)) => Deciding1 q t where
 #ifndef HLINT
   deciding1 :: Decidable f => p q -> (forall b. q b => f b) -> f a -> f (t a)
 #endif
 
-instance (Generic1 t, GDeciding1 q (Rep1 t)) => Deciding1 q t where
-  deciding1 p q r = contramap from1 $ gdeciding1 p q r
+instance (Generic1 t, GDeciding1 q (Rep1' t), GG (Rep1 t)) => Deciding1 q t where
+  deciding1 p q r = contramap (swizzle . from1) $ gdeciding1 p q r
 
 class GDeciding q t where
 #ifndef HLINT
@@ -93,10 +131,10 @@
 instance GDeciding q V1 where
   gdeciding _ _ = glose
 
-instance (GDeciding q f, GDeciding q g) => GDeciding q (f :*: g) where
+instance (GDeciding q f, GDeciding q g) => GDeciding q (f ::*: g) where
   gdeciding p q = gdivide (gdeciding p q) (gdeciding p q)
 
-instance (GDeciding q f, GDeciding q g) => GDeciding q (f :+: g) where
+instance (GDeciding q f, GDeciding q g) => GDeciding q (f ::+: g) where
   gdeciding p q = gchoose (gdeciding p q) (gdeciding p q)
 
 #ifndef HLINT
@@ -118,36 +156,29 @@
 instance GDeciding1 q V1 where
   gdeciding1 _ _ _ = glose
 
-instance (GDeciding1 q f, GDeciding1 q g) => GDeciding1 q (f :*: g) where
+instance (GDeciding1 q f, GDeciding1 q g) => GDeciding1 q (f ::*: g) where
   gdeciding1 p q r = gdivide (gdeciding1 p q r) (gdeciding1 p q r)
 
-instance (GDeciding1 q f, GDeciding1 q g) => GDeciding1 q (f :+: g) where
+instance (GDeciding1 q f, GDeciding1 q g) => GDeciding1 q (f ::+: g) where
   gdeciding1 p q r = gchoose (gdeciding1 p q r) (gdeciding1 p q r)
 
-
-
-glose :: Decidable f => f (V1 a)
-#ifdef SAFE
-glose = lose (\ !_ -> error "impossible")
+absurd1 :: V1 a -> b
+#if defined(HLINT) || (__GLASGOW_HASKELL__ < 708)
+absurd1 x = x `seq` error "impossible"
 #else
-glose = lose unsafeCoerce
+absurd1 x = case x of
 #endif
+
+glose :: Decidable f => f (V1 a)
+glose = lose absurd1
 {-# INLINE glose #-}
 
-gdivide :: Divisible f => f (g a) -> f (h a) -> f ((g:*:h) a)
-#ifdef SAFE
-gdivide = divide (\(f:*:g) -> (f,g))
-#else
-gdivide = divide unsafeCoerce
-#endif
+gdivide :: Divisible f => f (g a) -> f (h a) -> f ((g::*:h) a)
+gdivide = divide unProd
 {-# INLINE gdivide #-}
 
-gchoose :: Decidable f => f (g a) -> f (h a) -> f ((g:+:h) a)
-#ifdef SAFE
-gchoose = choose (\xs -> case xs of L1 a -> Left a; R1 b -> Right b)
-#else
-gchoose = choose unsafeCoerce
-#endif
+gchoose :: Decidable f => f (g a) -> f (h a) -> f ((g::+:h) a)
+gchoose = choose unSum
 {-# INLINE gchoose #-}
 
 #ifndef HLINT