Auto merge of #43158 - PlasmaPower:thread-local-try-with, r=alexcrichton

Thread local try with

https://github.com/rust-lang/rfcs/pull/2030 was turned into this PR (the RFC was closed, but it looks like just a PR should be good).

See also: state stabilization issue: #27716

`try_with` is used in two places in std: stdio and thread_info. In stdio, it would be better if the result was passed to the closure, but in thread_info, it's better as is where the result is returned from the function call. I'm not sure which is better, but I prefer the current way as it better represents the scope.

1 files changed, 3 insertions, 8 deletions

diff --git a/src/libstd/sys_common/thread_info.rs b/src/libstd/sys_common/thread_info.rs
index 5ed48ee4558..2abb8afa828 100644
--- a/src/libstd/sys_common/thread_info.rs
+++ b/src/libstd/sys_common/thread_info.rs
@@ -12,7 +12,6 @@
 
 use cell::RefCell;
 use thread::Thread;
-use thread::LocalKeyState;
 
 struct ThreadInfo {
     stack_guard: Option<usize>,
@@ -23,19 +22,15 @@ thread_local! { static THREAD_INFO: RefCell<Option<ThreadInfo>> = RefCell::new(N
 
 impl ThreadInfo {
     fn with<R, F>(f: F) -> Option<R> where F: FnOnce(&mut ThreadInfo) -> R {
-        if THREAD_INFO.state() == LocalKeyState::Destroyed {
-            return None
-        }
-
-        THREAD_INFO.with(move |c| {
+        THREAD_INFO.try_with(move |c| {
             if c.borrow().is_none() {
                 *c.borrow_mut() = Some(ThreadInfo {
                     stack_guard: None,
                     thread: Thread::new(None),
                 })
             }
-            Some(f(c.borrow_mut().as_mut().unwrap()))
-        })
+            f(c.borrow_mut().as_mut().unwrap())
+        }).ok()
     }
 }