Check that nested statics in thread locals are duplicated per thread.

tests/ui/statics/nested_thread_local.rs

@@ -0,0 +1,24 @@
+// Check that nested statics in thread locals are
+// duplicated per thread.
+
+#![feature(const_refs_to_cell)]
+#![feature(thread_local)]
+
+//@run-pass
+
+#[thread_local]
+static mut FOO: &mut u32 = &mut 42;
+
+fn main() {
+    unsafe {
+        *FOO = 1;
+
+        let _ = std::thread::spawn(|| {
+            assert_eq!(*FOO, 42);
+            *FOO = 99;
+        })
+        .join();
+
+        assert_eq!(*FOO, 1);
+    }
+}