Add back split-these from Reflex to support older GHCs

Author: Ericson2314

ChangeLog.md

@@ -1,5 +1,9 @@
 # Revision history for patch
 
+## Unreleased
+
+* Support older GHCs with `split-these` flag.
+
 ## 0.0.0.1
 
 * Remove unneeded dependencies

cabal.haskell-ci

@@ -5,3 +5,10 @@ installed:     -all
 
 -- https://github.com/haskell/cabal/issues/6106
 install-dependencies: False
+
+constraint-set old-these
+  ghc: <8.8
+  constraints: these <1
+
+constraint-set old-witherable
+  constraints: witherable <0.3.2

patch.cabal

@@ -23,17 +23,19 @@ tested-with:
   GHC  ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.1
   GHCJS ==8.4
 
+flag split-these
+  description: Use split these/semialign packages
+  manual:      False
+  default:     True
+
 library
   hs-source-dirs: src
   build-depends: base >= 4.9 && < 4.14
                , constraints-extras >= 0.3 && < 0.4
                , containers >= 0.6 && < 0.7
                , dependent-map >= 0.3 && < 0.4
                , dependent-sum >= 0.6 && < 0.7
-               , monoidal-containers >= 0.6 && < 0.7
-               , semialign >=1 && <1.2
                , semigroupoids >= 4.0 && < 6
-               , these >= 1 && <1.1
                , transformers >= 0.5.6.0 && < 0.6
                , witherable >= 0.3 && < 0.3.2
 
@@ -48,6 +50,14 @@ library
 
   ghc-options: -Wall -fwarn-redundant-constraints -fwarn-tabs
 
+  if flag(split-these)
+    build-depends: these >= 1 && <1.1
+                 , semialign >=1 && <1.2
+                 , monoidal-containers >= 0.6 && < 0.7
+  else
+    build-depends: these >= 0.4 && <0.9
+                 , monoidal-containers == 0.4.0.0
+
 test-suite hlint
   type: exitcode-stdio-1.0
   main-is: hlint.hs