Compiler crash with #[thread_local]

[Amanieu]

#![feature(thread_local)]

#[thread_local]
static mut X: ::std::sync::atomic::AtomicUsize = ::std::sync::atomic::ATOMIC_USIZE_INIT;

fn main() {
    unsafe {
        let mut x = X;
        let _y = x.get_mut();
    }
}

produces the following error:

thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: (MoveData { move_paths: [MovePath { place: _0 }, MovePath { place: _1 }, MovePath { place: _2 }, MovePath { place: _3 }, MovePath { place: _4 }], moves: [mp2@bb0[3], mp2@bb0[4], mp4@bb0[8], mp4@bb1[0], mp3@bb1[2], mp1@bb1[3], mp0@bb1[4]], loc_map: LocationMap { map: [[[], [], [], [mo0], [mo1], [], [], [], [mo2]], [[mo3], [], [mo4], [mo5], [mo6]]] }, path_map: [[mo6], [mo5], [mo0, mo1], [mo4], [mo2, mo3]], rev_lookup: MovePathLookup { locals: [mp0, mp1, mp2, mp3, mp4], projections: {} }, inits: [mp2@src/main.rs:8:21: 8:22 (Deep), mp1@src/main.rs:8:21: 8:22 (Deep), mp4@src/main.rs:9:18: 9:19 (Deep), mp3@src/main.rs:9:18: 9:29 (NonPanicPathOnly), mp0@src/main.rs:7:5: 10:6 (Deep)], init_loc_map: LocationMap { map: [[[], [], [in0], [in1], [], [], [], [in2], [in3]], [[], [in4], [], [], []]] }, init_path_map: [[in4], [in1], [in0], [in3], [in2]] }, [IllegalMove { cannot_move_out_of: IllegalMoveOrigin { span: src/main.rs:8:21: 8:22, kind: Static } }])', /checkout/src/libcore/result.rs:916:5

Also, the following code fails to compile due to a lifetime error, but doesn't crash the compiler:

#![feature(thread_local)]

#[thread_local]
static mut X: ::std::sync::atomic::AtomicUsize = ::std::sync::atomic::ATOMIC_USIZE_INIT;

fn main() {
    unsafe {
        let mut _x = X.get_mut();
    }
}

Output:

error[E0597]: borrowed value does not live long enough
 --> src/main.rs:8:22
  |
8 |         let mut _x = X.get_mut();
  |                      ^          - temporary value dropped here while still borrowed
  |                      |
  |                      temporary value does not live long enough
9 |     }
  |     - temporary value needs to live until here
  |
  = note: consider using a `let` binding to increase its lifetime

[matthewjasper]

Both are solved by mir borrowck/nll.
It looks like ast borrowck incorrectly thinks that thread locals are temporaries, so can be moved from, and drop elaboration doesn't.

rust/src/librustc/middle/mem_categorization.rs

Lines 681 to 687 in b98fd52

	Def::Static(def_id, mutbl) => {
	// `#[thread_local]` statics may not outlive the current function.
	for attr in &self.tcx.get_attrs(def_id)[..] {
	if attr.check_name("thread_local") {
	return Ok(self.cat_rvalue_node(id, span, expr_ty));
	}
	}

[pnkfelix]

In addition to being fixed by NLL, this is also fixed by #55150. (The NLL-fixed-by-NLL is intended for issues that are only fixed when NLL is enabled...)

[pnkfelix]

(assigning medium priority; the PR is approved that fixes this, #55150, is approved, and this ICE is only exposed by a feature that is currently nightly-only.)