FyroxEngine / Fyrox

Hi,
I found a memory-safety/soundness issue in this crate while scanning Rust code for potential vulnerabilities. This PR contains a fix for the issue.

Issue Description

Handle<T> unconditionally implements Sync. This allows users to create data races on T: !Sync. Such data races can lead to undefined behavior.

Fyrox/fyrox-core/src/pool.rs

Lines 203 to 204 in 7f91449

    
           unsafe impl<T> Send for Handle<T> {} 
        
           unsafe impl<T> Sync for Handle<T> {}

This may not cause a direct data race. But making changes can be useful.

#480

It is impossible to get data races in Handle struct, because its fields are just both u32 which both Send + Sync. This unsafe impl is needed just to implement Send + Sync for PhantomData<T>. Any objections?

	unsafe impl<T> Send for Handle<T> {}
	unsafe impl<T> Sync for Handle<T> {}

Handle<T>unconditionally implements Send/Sync

Issue Description