1 struct X<F> where F: FnOnce() + 'static + Send { 2 field: F, 3 } 4 foo<F>(blk: F) -> X<F> where F: FnOnce() + 'static5 fn foo<F>(blk: F) -> X<F> where F: FnOnce() + 'static { 6 //~^ ERROR `F` cannot be sent between threads safely 7 return X { field: blk }; 8 } 9 main()10 fn main() { 11 } 12