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

third_party/bazel/rules_haskell/haskell/platforms/BUILD.bazel

@@ -0,0 +1,39 @@
+# This file declares constraint values for each platform supported by
+# GHC. These rules follow the GHC naming convention, for example,
+# //haskell/platform:linux and //haskell/platform:x86_64. See the
+# config.guess in any GHC source distribution for possible platforms.
+#
+# These can be used in select expressions to choose platform-specifc
+# sources and dependencies.
+
+load(":list.bzl", "declare_config_settings")
+
+declare_config_settings()
+
+constraint_value(
+    name = "nixpkgs",
+    constraint_setting = "@bazel_tools//tools/cpp:cc_compiler",
+    visibility = ["//visibility:public"],
+)
+
+platform(
+    name = "linux_x86_64_nixpkgs",
+    constraint_values = [
+        # XXX using the platform names defined here results in a graph
+        # cycle for some reason.
+        "@bazel_tools//platforms:x86_64",
+        "@bazel_tools//platforms:linux",
+        ":nixpkgs",
+    ],
+    visibility = ["//visibility:public"],
+)
+
+platform(
+    name = "darwin_x86_64_nixpkgs",
+    constraint_values = [
+        "@bazel_tools//platforms:x86_64",
+        "@bazel_tools//platforms:osx",
+        ":nixpkgs",
+    ],
+    visibility = ["//visibility:public"],
+)

third_party/bazel/rules_haskell/haskell/platforms/list.bzl

@@ -0,0 +1,44 @@
+OS = {
+    "aix": None,
+    "darwin": "@bazel_tools//platforms:osx",
+    "dragonfly": None,
+    "freebsd": "@bazel_tools//platforms:freebsd",
+    "haiku": None,
+    "hpux": None,
+    "ios": "@bazel_tools//platforms:ios",
+    "linux_android": "@bazel_tools//platforms:android",
+    "linux": "@bazel_tools//platforms:linux",
+    "mingw32": "@bazel_tools//platforms:windows",
+    "netbsd": None,
+    "openbsd": None,
+    "solaris2": None,
+}
+
+ARCH = {
+    "aarch64": None,
+    "alpha": None,
+    "arm64": "@bazel_tools//platforms:aarch64",
+    "arm": "@bazel_tools//platforms:arm",
+    "i386": "@bazel_tools//platforms:x86_32",
+    "ia64": None,
+    "powerpc64": None,
+    "powerpc64le": None,
+    "powerpc": "@bazel_tools//platforms:ppc",
+    "rs6000": None,
+    "sparc": None,
+    "x86_64": "@bazel_tools//platforms:x86_64",
+}
+
+def declare_config_settings():
+    for os, constraint_value in OS.items():
+        if constraint_value:
+            native.config_setting(
+                name = os,
+                constraint_values = [constraint_value],
+            )
+    for arch, constraint_value in ARCH.items():
+        if constraint_value:
+            native.config_setting(
+                name = arch,
+                constraint_values = [constraint_value],
+            )