FFI type for handles in return values or out parameters, where `NULL` is used as a sentry value to indicate errors, such as in the return value of `CreateThread`. This uses `repr(transparent)` and has the representation of a host handle, so that it can be used in such FFI declarations.

A simple wrapper around a type to assert that it is unwind safe.

The metadata for a `Dyn = dyn SomeTrait` trait object type.

RAII structure used to release the shared read access of a lock when dropped, which can point to a subfield of the protected data.

`Weak` is a version of `Arc` that holds a non-owning reference to the managed allocation. The allocation is accessed by calling `upgrade` on the `Weak` pointer, which returns an Option<Arc<T>>.

The current status of a backtrace, indicating whether it was captured or whether it is empty for some other reason.

Performs bounds-checking of a range.

A captured OS thread stack backtrace.

A builder for computing where in a HashMap a key-value pair would be stored.

A view into an occupied entry in a `HashMap`. It is part of the `RawEntryMut` enum.