Set up Bazel rust_repositories with a default edition that is not usable

Author: dtolnay

WORKSPACE

@@ -4,19 +4,23 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(
     name = "rules_rust",
-    sha256 = "3cf493f845837b9c0c44311992a8e387b508a267cb8f261ef97b94c915f292cc",
-    strip_prefix = "rules_rust-55790492aca01b389d208cd1335b9d8c05e28329",
+    sha256 = "29954bced3e0d1a57ff8db816f5cd8a5856179fc657455729f1eb53b39611419",
+    strip_prefix = "rules_rust-6e1cbbfcd0d140baacc8ff1080f885d2a45296a9",
     urls = [
-        # Main branch as of 2022-04-10
-        "https://github.com/bazelbuild/rules_rust/archive/55790492aca01b389d208cd1335b9d8c05e28329.tar.gz",
+        # PR https://github.com/bazelbuild/rules_rust/pull/1254
+        # on top of the main branch as of 2022-04-10
+        "https://github.com/bazelbuild/rules_rust/archive/6e1cbbfcd0d140baacc8ff1080f885d2a45296a9.tar.gz",
     ],
 )
 
 load("@rules_rust//rust:repositories.bzl", "rust_repositories")
 
 RUST_VERSION = "1.60.0"
 
-rust_repositories(version = RUST_VERSION)
+rust_repositories(
+    edition = "required",
+    version = RUST_VERSION,
+)
 
 load("//tools/bazel:vendor.bzl", "vendor")