error[E0277]: `Foo` cannot be shared between threads safely
  --> $DIR/issue-17718-static-sync.rs:9:1
   |
LL | static BAR: Foo = Foo;
   | ^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be shared between threads safely
   |
   = help: the trait `std::marker::Sync` is not implemented for `Foo`
   = note: shared static variables must have a type that implements `Sync`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.