Rollup merge of #44396 - joshlf:tls-comment, r=alexcrichton

std::thread::LocalKey: Document limitation with initializers

Document that if a `LocalKey`'s initializer recursively depends on itself, initialization will result in infinite recursion.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs
index 4ee8132f55c..a53c76a333a 100644
--- a/src/libstd/thread/local.rs
+++ b/src/libstd/thread/local.rs
@@ -31,6 +31,10 @@ use mem;
 /// within a thread, and values that implement [`Drop`] get destructed when a
 /// thread exits. Some caveats apply, which are explained below.
 ///
+/// A `LocalKey`'s initializer cannot recursively depend on itself, and using
+/// a `LocalKey` in this way will cause the initializer to infinitely recurse
+/// on the first call to `with`.
+///
 /// # Examples
 ///
 /// ```