Send trait的源码

https://github.com/rust-lang/rust/blob/master/library/core/src/marker.rs

#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "send_trait")]
#[rustc_on_unimplemented(
    message = "`{Self}` cannot be sent between threads safely",
    label = "`{Self}` cannot be sent between threads safely"
)]
pub unsafe auto trait Send {
    // empty.
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> !Send for *const T {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> !Send for *mut T {}