4 files changed, 9 insertions, 1 deletions
diff --git a/src/tools/rust-installer/combine-installers.sh b/src/tools/rust-installer/combine-installers.sh
index c2de3385a80..01e5a00af4a 100755
--- a/src/tools/rust-installer/combine-installers.sh
+++ b/src/tools/rust-installer/combine-installers.sh
@@ -11,6 +11,8 @@ abs_path() {
     (unset CDPATH && cd "$path" > /dev/null && pwd)
 }
 
+# Running cargo will read the libstd Cargo.toml
+# which uses the unstable `public-dependency` feature.
 export RUSTC_BOOTSTRAP=1
 
 src_dir="$(abs_path $(dirname "$0"))"
diff --git a/src/tools/rust-installer/gen-installer.sh b/src/tools/rust-installer/gen-installer.sh
index 10a69ff5ac5..cc45b5e0803 100755
--- a/src/tools/rust-installer/gen-installer.sh
+++ b/src/tools/rust-installer/gen-installer.sh
@@ -11,6 +11,8 @@ abs_path() {
     (unset CDPATH && cd "$path" > /dev/null && pwd)
 }
 
+# Running cargo will read the libstd Cargo.toml
+# which uses the unstable `public-dependency` feature.
 export RUSTC_BOOTSTRAP=1
 
 src_dir="$(abs_path $(dirname "$0"))"
diff --git a/src/tools/rust-installer/make-tarballs.sh b/src/tools/rust-installer/make-tarballs.sh
index 4aadf078ff1..374e103e89c 100755
--- a/src/tools/rust-installer/make-tarballs.sh
+++ b/src/tools/rust-installer/make-tarballs.sh
@@ -11,6 +11,8 @@ abs_path() {
     (unset CDPATH && cd "$path" > /dev/null && pwd)
 }
 
+# Running cargo will read the libstd Cargo.toml
+# which uses the unstable `public-dependency` feature.
 export RUSTC_BOOTSTRAP=1
 
 src_dir="$(abs_path $(dirname "$0"))"
diff --git a/src/tools/tidy/src/main.rs b/src/tools/tidy/src/main.rs
index 2ad0ae527ac..a9eada22fc0 100644
--- a/src/tools/tidy/src/main.rs
+++ b/src/tools/tidy/src/main.rs
@@ -16,7 +16,9 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::thread::{self, scope, ScopedJoinHandle};
 
 fn main() {
-    // Allow using unstable cargo features in the standard library.
+    // Running Cargo will read the libstd Cargo.toml
+    // which uses the unstable `public-dependency` feature.
+    //
     // `setenv` might not be thread safe, so run it before using multiple threads.
     env::set_var("RUSTC_BOOTSTRAP", "1");