Emit warning when an unknown GHC version is encountered

Forward-ported from 5339b36 Addresses #415
haskell · Feb 23, 2018 · c01d92f · c01d92f
1 parent 6f50672
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diff --git a/Cabal/Distribution/Simple/GHC.hs b/Cabal/Distribution/Simple/GHC.hs
@@ -131,6 +131,13 @@ configure verbosity hcPath hcPkgPath conf0 = do
       (userMaybeSpecifyPath "ghc" hcPath conf0)
   let implInfo = ghcVersionImplInfo ghcVersion
 
+  -- Cabal currently supports ghc >= 6.11 && < 8.7
+  unless (ghcVersion < mkVersion [8,7]) $
+    warn verbosity $
+         "Unknown/unsupported 'ghc' version detected "
+      ++ "(Cabal " ++ display cabalVersion ++ " supports 'ghc' version < 8.7): "
+      ++ programPath ghcProg ++ " is version " ++ display ghcVersion
+
   -- This is slightly tricky, we have to configure ghc first, then we use the
   -- location of ghc to help find ghc-pkg in the case that the user did not
   -- specify the location of ghc-pkg directly:

diff --git a/Cabal/changelog b/Cabal/changelog
@@ -70,6 +70,7 @@
 	  `D.S.findHookedPackageDesc` (#4874).
 	* `D.S.getHookedBuildInfo` now takes an additional parameter
 	  specifying the build directory path (#4874).
+	* Emit warning when encountering unknown GHC versions (#415).
 	* TODO
 
 2.0.1.1 Mikhail Glushenkov <[email protected]> December 2017