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

third_party/bazel/rules_haskell/tests/c-compiles/BUILD.bazel

@@ -0,0 +1,26 @@
+load(
+    "@io_tweag_rules_haskell//haskell:haskell.bzl",
+    "haskell_library",
+    "haskell_test",
+)
+
+package(default_testonly = 1)
+
+haskell_library(
+    name = "hs-lib",
+    srcs = ["Lib.hs"],
+    deps = [
+        "//tests/data:ourclibrary",
+        "//tests/hackage:base",
+    ],
+)
+
+haskell_test(
+    name = "c-compiles",
+    srcs = ["Main.hs"],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":hs-lib",
+        "//tests/hackage:base",
+    ],
+)

third_party/bazel/rules_haskell/tests/c-compiles/Lib.hs

@@ -0,0 +1,10 @@
+{-# LANGUAGE ForeignFunctionInterface #-}
+module Lib (ten) where
+
+import Foreign.C.Types (CInt(..))
+
+foreign import ccall "c_add_one"
+  c_add_one :: CInt -> CInt
+
+ten :: Int
+ten = fromIntegral (c_add_one 9)

third_party/bazel/rules_haskell/tests/c-compiles/Main.hs

@@ -0,0 +1,8 @@
+module Main (main) where
+
+import Control.Monad (unless)
+import Lib           (ten)
+
+main :: IO ()
+main = unless (ten == 10)
+    $ error $ "Incorrect lib value. Got " <> show ten

third_party/bazel/rules_haskell/tests/c-compiles/c-compiles.c

@@ -0,0 +1 @@
+int add_five(int x) { return x + 5; }