Update Travis to use Bazel 0.16.0 and also test against HEAD.

RELNOTES: rules_swift now requires Bazel 0.16.0.
PiperOrigin-RevId: 206803918

Author: allevato

.travis.yml

@@ -17,11 +17,20 @@ matrix:
       dist: trusty
       sudo: required
       env:
-        - BAZEL=0.14.1 SWIFT_VERSION=4.1.2 TARGETS="//examples/... -//examples/apple/..."
+        - BAZEL=0.16.0 SWIFT_VERSION=4.1.2 CC=clang TARGETS="//examples/... -//examples/apple/..."
+    - os: linux
+      dist: trusty
+      sudo: required
+      env:
+        - BAZEL=HEAD SWIFT_VERSION=4.1.2 CC=clang TARGETS="//examples/... -//examples/apple/..."
+    - os: osx
+      osx_image: xcode9.3
+      env:
+        - BAZEL=0.16.0 TARGETS=//examples/...
     - os: osx
       osx_image: xcode9.3
       env:
-        - BAZEL=0.14.1 TARGETS=//examples/...
+        - BAZEL=HEAD TARGETS=//examples/...
 
 before_install:
   - .travis/install.sh

swift/internal/swift_protoc_gen_aspect.bzl

@@ -462,7 +462,7 @@ swift_protoc_gen_aspect = aspect(
             "_mkdir_and_run": attr.label(
                 cfg = "host",
                 default = Label(
-                    "@build_bazel_rules_swift@bazel_tools//tools/mkdir_and_run",
+                    "@build_bazel_rules_swift//tools/mkdir_and_run",
                 ),
                 executable = True,
             ),

swift/internal/swift_toolchain.bzl

@@ -28,7 +28,7 @@ load(
     "paths",
     "selects",
 )
-load("//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")
+load("@bazel_tools//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")
 
 def _default_linker_opts(
         cc_toolchain,

swift/repositories.bzl

@@ -20,6 +20,11 @@ def _create_linux_toolchain(repository_ctx):
   Args:
     repository_ctx: The repository rule context.
   """
+  if repository_ctx.os.environ.get("CC") != "clang":
+    fail("ERROR: rules_swift uses Bazel's CROSSTOOL to link, but Swift " +
+         "requires that the driver used is clang. Please set `CC=clang` in " +
+         "your environment before invoking Bazel.")
+
   path_to_swiftc = repository_ctx.which("swiftc")
   path_to_clang = repository_ctx.which("clang")
   root = path_to_swiftc.dirname.dirname
@@ -80,7 +85,7 @@ def _swift_autoconfiguration_impl(repository_ctx):
     _create_linux_toolchain(repository_ctx)
 
 _swift_autoconfiguration = repository_rule(
-    environ = ["PATH"],
+    environ = ["CC", "PATH"],
     implementation=_swift_autoconfiguration_impl,
 )
 

tools/BUILD

@@ -7,7 +7,7 @@ filegroup(
     name = "for_bazel_tests",
     testonly = 1,
     srcs = glob(["**"]) + [
-        "@build_bazel_rules_swift@bazel_tools//tools/mkdir_and_run:for_bazel_tests",
+        "@build_bazel_rules_swift//tools/mkdir_and_run:for_bazel_tests",
     ],
     visibility = [
         "//:__pkg__",