Extend CI with all GHC minor versions supported by hls and fix ghc-8.8.3 and ghc-8.8.2 builds (#947)

* Extend CI matrix with all the GHC minor versions supported by HLS
  * Adding a new job for windows: ghc-8.10.2.2

* Use GADTs for all ghc versions in Development.IDE.Plugin.Completions.Logic 
  * Fix ghc-8.8.2 and ghc-8.8.3 builds

Co-authored-by: Pepe Iborra <pepeiborra@gmail.com>

.github/workflows/bench.yml

@@ -1,6 +1,6 @@
 name: Benchmark
 
-on: [push, pull_request]
+on: [pull_request]
 jobs:
   bench:
     runs-on: ${{ matrix.os }}

.github/workflows/nix.yml

@@ -1,6 +1,6 @@
 name: Nix
 
-on: [push, pull_request]
+on: [pull_request]
 jobs:
   nix:
     runs-on: ${{ matrix.os }}

.github/workflows/test.yml

@@ -1,6 +1,6 @@
 name: Testing
 
-on: [push, pull_request]
+on: [pull_request]
 jobs:
   test:
     timeout-minutes: 360
@@ -8,20 +8,47 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macOS-latest, ubuntu-latest, windows-latest]
-        ghc: ['8.10.2', '8.8.4', '8.6.5']
+        # all versions to only build or test for non windows os's
+        # inclusions will modify the major ones to mark them as testables
+        os: [macOS-latest, ubuntu-latest]
+        ghc: ['8.10.2', '8.10.1', '8.8.4', '8.8.3', '8.8.2', '8.6.5', '8.6.4']
         ghc-lib: [false]
-        exclude:
-          - os: windows-latest
-            ghc: '8.10.2' # broken due to https://gitlab.haskell.org/ghc/ghc/-/issues/18550
-          - os: windows-latest
-            ghc: '8.8.4' # also fails due to segfault :(
         include:
-          - os: windows-latest
-            ghc: '8.10.1'
+          # one ghc-lib build
           - os: ubuntu-latest
             ghc: '8.10.1'
             ghc-lib: true
+          # only test supported ghc major versions
+          - os: macOS-latest
+            ghc: '8.10.2'
+            test: true
+          - os: ubuntu-latest
+            ghc: '8.10.2'
+            test: true
+          # specific 8.10.2 version for windows and chocolatey
+          - os: windows-latest
+            ghc: '8.10.2.2'
+            test: true
+          - os: macOS-latest
+            ghc: '8.8.4'
+            test: true
+          - os: ubuntu-latest
+            ghc: '8.8.4'
+            test: true
+          - os: macOS-latest
+            ghc: '8.6.5'
+            test: true
+          - os: ubuntu-latest
+            ghc: '8.6.5'
+            test: true
+          - os: windows-latest
+            ghc: '8.6.5'
+            test: true
+          # only build rest of supported ghc versions for windows
+          - os: windows-latest
+            ghc: '8.10.1'
+          - os: windows-latest
+            ghc: '8.6.4'
 
     steps:
     - uses: actions/checkout@v2
@@ -62,7 +89,7 @@ jobs:
       run: cabal build || cabal build || cabal build
 
     - name: Test
+      if: ${{ !matrix.ghc-lib && matrix.test }}
       shell: bash
       # run the tests without parallelism to avoid running out of memory
       run: cabal test --test-options="-j1 --rerun-update" || cabal test --test-options="-j1 --rerun" || LSP_TEST_LOG_COLOR=0 LSP_TEST_LOG_MESSAGES=true LSP_TEST_LOG_STDERR=true cabal test --test-options="-j1 --rerun"
-      if: ${{ !matrix.ghc-lib}}

src/Development/IDE/Plugin/Completions/Logic.hs

@@ -1,9 +1,8 @@
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE GADTs#-}
 
 #include "ghc-api-version.h"
-#if MIN_GHC_API_VERSION (8,8,4)
-{-# LANGUAGE GADTs#-}
-#endif
+
 -- Mostly taken from "haskell-ide-engine"
 module Development.IDE.Plugin.Completions.Logic (
   CachedCompletions