always implement unwind safe

Author: matklad

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Increase minimal supported Rust version to 1.56.0.
+- Implement `UnwindSafe` even if the `std` feature is disabled.
 
 ## 1.14.0
 

src/lib.rs

@@ -348,11 +348,9 @@ pub mod unsync {
         cell::{Cell, UnsafeCell},
         fmt, hint, mem,
         ops::{Deref, DerefMut},
+        panic::{RefUnwindSafe, UnwindSafe},
     };
 
-    #[cfg(feature = "std")]
-    use std::panic::{RefUnwindSafe, UnwindSafe};
-
     /// A cell which can be written to only once. It is not thread safe.
     ///
     /// Unlike [`std::cell::RefCell`], a `OnceCell` provides simple `&`
@@ -382,9 +380,7 @@ pub mod unsync {
     // `&unsync::OnceCell` to sneak a `T` through `catch_unwind`,
     // by initializing the cell in closure and extracting the value in the
     // `Drop`.
-    #[cfg(feature = "std")]
     impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for OnceCell<T> {}
-    #[cfg(feature = "std")]
     impl<T: UnwindSafe> UnwindSafe for OnceCell<T> {}
 
     impl<T> Default for OnceCell<T> {
@@ -680,7 +676,6 @@ pub mod unsync {
         init: Cell<Option<F>>,
     }
 
-    #[cfg(feature = "std")]
     impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where OnceCell<T>: RefUnwindSafe {}
 
     impl<T: fmt::Debug, F> fmt::Debug for Lazy<T, F> {
@@ -1225,7 +1220,6 @@ pub mod sync {
     unsafe impl<T, F: Send> Sync for Lazy<T, F> where OnceCell<T>: Sync {}
     // auto-derived `Send` impl is OK.
 
-    #[cfg(feature = "std")]
     impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where OnceCell<T>: RefUnwindSafe {}
 
     impl<T, F> Lazy<T, F> {