#[thread_local] statics shouldn't require Sync

[thestinger]

This was a recent regression.

[brson]

I'm untagging all pre-1.0 regressions to repurpose it for stable regressions.

[brson]

@alexcrichton Do you know if this is still a problem?

[alexcrichton]

Yes this is still a problem:

#![feature(thread_local)]                

use std::cell::Cell;                     

#[thread_local]                          
pub static FOO: Cell<u32> = Cell::new(3);

foo.rs:5:29: 5:41 error: the trait `core::marker::Sync` is not implemented for the type `core::cell::UnsafeCell<u32>` [E0277]
foo.rs:5 pub static FOO: Cell<u32> = Cell::new(3);
                                     ^~~~~~~~~~~~
foo.rs:5:29: 5:41 note: `core::cell::UnsafeCell<u32>` cannot be shared between threads safely
foo.rs:5 pub static FOO: Cell<u32> = Cell::new(3);
                                     ^~~~~~~~~~~~
error: aborting due to previous error

[bltavares]

Triaging: This still fails on rustc 1.9.0-nightly (c9629d61c 2016-03-10)

I've added the const_fn feature as well to reduce the warnings.

#![feature(const_fn)]
#![feature(thread_local)]                

use std::cell::Cell;                     

#[thread_local]                          
pub static FOO: Cell<u32> = Cell::new(3);

fn main() {}

Here is the produced error:

18001.rs:7:29: 7:41 error: the trait `core::marker::Sync` is not implemented for the type `core::cell::Cell<u32>` [E0277]
18001.rs:7 pub static FOO: Cell<u32> = Cell::new(3);
                                       ^~~~~~~~~~~~
18001.rs:7:29: 7:41 help: run `rustc --explain E0277` to see a detailed explanation
18001.rs:7:29: 7:41 note: `core::cell::Cell<u32>` cannot be shared between threads safely
18001.rs:7:29: 7:41 note: shared static variables must have a type that implements `Sync`
error: aborting due to previous error

[sorpaas]

Any update on this?

[Mark-Simulacrum]

Closing in favor of more-recent duplicate #35035.