feat(third_party/bazel): Check in rules_haskell from Tweag

third_party/bazel/rules_haskell/tests/binary-with-compiler-flags/BUILD.bazel

@@ -0,0 +1,18 @@
+load(
+    "@io_tweag_rules_haskell//haskell:haskell.bzl",
+    "haskell_test",
+)
+
+package(default_testonly = 1)
+
+haskell_test(
+    name = "binary-with-compiler-flags",
+    srcs = ["Main.hs"],
+    # Flags that require -threaded, which we should get from the toolchain's
+    # compiler_flags. Include spaces to validate proper quoting:
+    compiler_flags = [
+        "-with-rtsopts=-N2 -qg -I0 -n2m -A128m",
+        "-XLambdaCase",
+    ],
+    deps = ["//tests/hackage:base"],
+)

third_party/bazel/rules_haskell/tests/binary-with-compiler-flags/Main.hs

@@ -0,0 +1,13 @@
+-- Expects to pull -XStandaloneDeriving from the default compiler flags.
+module Main (main) where
+
+data Foo = Foo
+deriving instance Show Foo
+
+-- Expects -XLambdaCase to be passed via the 'compiler_flags' rule attribute.
+dummyId :: Foo -> Foo
+dummyId = \case
+  Foo -> Foo
+
+main :: IO ()
+main = print $ dummyId Foo