Avoid accidentally enabling unstable features in compilers (take 2)

This allows rustbuild to control whether crates can use nightly features or not.
It also prevents rustbuild from using nightly features itself.

2 files changed, 4 insertions, 1 deletions

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index e38a574ca23..7a684c89fe3 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -1171,7 +1171,6 @@ def bootstrap(help_triggered):
     env = os.environ.copy()
     env["BOOTSTRAP_PARENT_ID"] = str(os.getpid())
     env["BOOTSTRAP_PYTHON"] = sys.executable
-    env["RUSTC_BOOTSTRAP"] = '1'
     if build.rustc_commit is not None:
         env["BOOTSTRAP_DOWNLOAD_RUSTC"] = '1'
     run(args, env=env, verbose=build.verbose, is_bootstrap=True)
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index fcef784d2d1..be6655ddb61 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -881,6 +881,10 @@ impl Step for RustcBook {
         if self.validate {
             cmd.arg("--validate");
         }
+        if !builder.unstable_features() {
+            // We need to validate nightly features, even on the stable channel.
+            cmd.env("RUSTC_BOOTSTRAP", "1");
+        }
         // If the lib directories are in an unusual location (changed in
         // config.toml), then this needs to explicitly update the dylib search
         // path.