error: generator cannot be sent between threads safely --> $DIR/generator-print-verbose-1.rs:40:18 | LL | require_send(send_gen); | ^^^^^^^^ generator is not `Send` | = help: the trait `Sync` is not implemented for `RefCell` = note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead note: generator is not `Send` as this value is used across a yield --> $DIR/generator-print-verbose-1.rs:38:9 | LL | let _non_send_gen = make_non_send_generator(); | ------------- has type `Opaque(DefId(0:34 ~ generator_print_verbose_1[7d1d]::make_non_send_generator::{opaque#0}), [])` which is not `Send` LL | yield; | ^^^^^ yield occurs here, with `_non_send_gen` maybe used later LL | }; | - `_non_send_gen` is later dropped here note: required by a bound in `require_send` --> $DIR/generator-print-verbose-1.rs:29:25 | LL | fn require_send(_: impl Send) {} | ^^^^ required by this bound in `require_send` error[E0277]: `RefCell` cannot be shared between threads safely --> $DIR/generator-print-verbose-1.rs:59:18 | LL | require_send(send_gen); | ------------ ^^^^^^^^ `RefCell` cannot be shared between threads safely | | | required by a bound introduced by this call | = help: the trait `Sync` is not implemented for `RefCell` = note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead = note: required for `Arc>` to implement `Send` note: required because it's used within this generator --> $DIR/generator-print-verbose-1.rs:45:5 | LL | || { | ^^ note: required because it appears within the type `Opaque(DefId(0:35 ~ generator_print_verbose_1[7d1d]::make_gen2::{opaque#0}), [Arc>])` --> $DIR/generator-print-verbose-1.rs:44:30 | LL | pub fn make_gen2(t: T) -> impl Generator { | ^^^^^^^^^^^^^^^^^^^^^^^^^^ note: required because it appears within the type `Opaque(DefId(0:36 ~ generator_print_verbose_1[7d1d]::make_non_send_generator2::{opaque#0}), [])` --> $DIR/generator-print-verbose-1.rs:50:34 | LL | fn make_non_send_generator2() -> impl Generator>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = note: required because it captures the following types: `Opaque(DefId(0:36 ~ generator_print_verbose_1[7d1d]::make_non_send_generator2::{opaque#0}), [])`, `()` note: required because it's used within this generator --> $DIR/generator-print-verbose-1.rs:55:20 | LL | let send_gen = || { | ^^ note: required by a bound in `require_send` --> $DIR/generator-print-verbose-1.rs:29:25 | LL | fn require_send(_: impl Send) {} | ^^^^ required by this bound in `require_send` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.