fix: provide aliases for all well-known types

Author: alexeagle

protoc/toolchain.bzl

@@ -14,14 +14,18 @@
 
 """Toolchains required to use rules_proto."""
 
-load("//protoc/private:prebuilt_protoc_toolchain.bzl", "prebuilt_protoc_repo")
+load("//protoc/private:prebuilt_protoc_toolchain.bzl", "GOOGLE_PROTOBUF_DEP_EDGES", "prebuilt_protoc_repo")
 load("//protoc/private:protoc_toolchains.bzl", "protoc_toolchains_repo")
 load("//protoc/private:versions.bzl", "PROTOC_PLATFORMS")
 
 def _google_protobuf_alias_repo_impl(rctx):
-    rctx.file("BUILD", """package(default_visibility=["//visibility:public"])
-alias(name = "any_proto", actual = "@{0}//:any_proto")
-""".format(rctx.attr.alias_to))
+    rctx.file("BUILD", """\
+# Generated by @toolchains_protoc//protoc:toolchain.bzl
+package(default_visibility=["//visibility:public"])
+""" + "\n".join([
+        """alias(name = "{1}_proto", actual = "@{0}//:{1}_proto")""".format(rctx.attr.alias_to, wkt)
+        for wkt in GOOGLE_PROTOBUF_DEP_EDGES.keys()
+    ]))
 
 _google_protobuf_alias_repo = repository_rule(_google_protobuf_alias_repo_impl, attrs = {"alias_to": attr.string()})