Test support for GHC 8.4.3

Author: koral

.travis.yml

@@ -65,6 +65,9 @@ matrix:
   - env: BUILD=cabal GHCVER=8.2.2 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
     compiler: ": #GHC 8.2.2"
     addons: {apt: {packages: [cabal-install-1.24,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
+  - env: BUILD=cabal GHCVER=8.4.3 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
+    compiler: ": #GHC 8.4.3"
+    addons: {apt: {packages: [cabal-install-1.24,ghc-8.4.3,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
 
   # Build with the newest GHC and cabal-install. This is an accepted failure,
   # see below.
@@ -106,6 +109,10 @@ matrix:
     compiler: ": #stack 8.2.2"
     addons: {apt: {packages: [libgmp-dev]}}
 
+  - env: BUILD=stack ARGS="--resolver lts-12"
+    compiler: ": #stack 8.4.3"
+    addons: {apt: {packages: [libgmp-dev]}}
+
   # Nightly builds are allowed to fail
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly"