1error[E0277]: `F` cannot be sent between threads safely 2 --> $DIR/closure-bounds-cant-promote-superkind-in-struct.rs:5:22 3 | 4LL | fn foo<F>(blk: F) -> X<F> where F: FnOnce() + 'static { 5 | ^^^^ `F` cannot be sent between threads safely 6 | 7note: required by a bound in `X` 8 --> $DIR/closure-bounds-cant-promote-superkind-in-struct.rs:1:43 9 | 10LL | struct X<F> where F: FnOnce() + 'static + Send { 11 | ^^^^ required by this bound in `X` 12help: consider further restricting this bound 13 | 14LL | fn foo<F>(blk: F) -> X<F> where F: FnOnce() + 'static + std::marker::Send { 15 | +++++++++++++++++++ 16 17error: aborting due to previous error 18 19For more information about this error, try `rustc --explain E0277`. 20