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matthiaskrgrmatthiaskrgr
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Rollup merge of #106944 - Nilstrieb:there-once-was-a-diagnostic, r=WaffleLapkin
Suggest using a lock for `*Cell: Sync` bounds I mostly did this for `OnceCell<T>` at first because users will be confused to see that the `OnceCell<T>` in `std` isn't `Sync` but then extended it to `Cell<T>` and `RefCell<T>` as well.
2 parents 9e3f330 + 6d0c91f commit 22e62a4

19 files changed

+233
-5
lines changed

‎library/core/src/cell/once.rs‎

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@@ -298,3 +298,7 @@ impl<T> const From<T> for OnceCell<T> {
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OnceCell { inner: UnsafeCell::new(Some(value)) }
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}
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}
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// Just like for `Cell<T>` this isn't needed, but results in nicer error messages.
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T> !Sync for OnceCell<T> {}

‎library/core/src/marker.rs‎

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@@ -469,6 +469,62 @@ pub macro Copy($item:item) {
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#[cfg_attr(not(test), rustc_diagnostic_item = "Sync")]
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#[lang = "sync"]
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#[rustc_on_unimplemented(
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on(
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_Self = "std::cell::OnceCell<T>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::OnceLock` instead"
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),
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on(
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_Self = "std::cell::Cell<u8>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU8` instead",
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),
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on(
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_Self = "std::cell::Cell<u16>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU16` instead",
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),
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on(
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_Self = "std::cell::Cell<u32>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU32` instead",
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),
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on(
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_Self = "std::cell::Cell<u64>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU64` instead",
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),
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on(
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_Self = "std::cell::Cell<usize>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicUsize` instead",
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),
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on(
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_Self = "std::cell::Cell<i8>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI8` instead",
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),
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on(
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_Self = "std::cell::Cell<i16>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI16` instead",
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),
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on(
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_Self = "std::cell::Cell<i32>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead",
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),
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on(
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_Self = "std::cell::Cell<i64>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI64` instead",
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),
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on(
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_Self = "std::cell::Cell<isize>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicIsize` instead",
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),
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on(
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_Self = "std::cell::Cell<bool>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicBool` instead",
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),
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on(
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_Self = "std::cell::Cell<T>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock`",
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),
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on(
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_Self = "std::cell::RefCell<T>",
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note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead",
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),
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message = "`{Self}` cannot be shared between threads safely",
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label = "`{Self}` cannot be shared between threads safely"
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)]

‎tests/ui/async-await/issue-68112.drop_tracking.stderr‎

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@@ -5,6 +5,7 @@ LL | require_send(send_fut);
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| ^^^^^^^^ future created by async block is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: future is not `Send` as it awaits another future which is not `Send`
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--> $DIR/issue-68112.rs:34:17
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|
@@ -23,6 +24,7 @@ LL | require_send(send_fut);
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| ^^^^^^^^ future created by async block is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: future is not `Send` as it awaits another future which is not `Send`
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--> $DIR/issue-68112.rs:43:17
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|
@@ -43,6 +45,7 @@ LL | require_send(send_fut);
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| required by a bound introduced by this call
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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= note: required for `Arc<RefCell<i32>>` to implement `Send`
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note: required because it's used within this `async fn` body
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--> $DIR/issue-68112.rs:50:31

‎tests/ui/async-await/issue-68112.no_drop_tracking.stderr‎

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@@ -5,6 +5,7 @@ LL | require_send(send_fut);
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| ^^^^^^^^ future created by async block is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: future is not `Send` as it awaits another future which is not `Send`
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--> $DIR/issue-68112.rs:34:17
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|
@@ -23,6 +24,7 @@ LL | require_send(send_fut);
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| ^^^^^^^^ future created by async block is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: future is not `Send` as it awaits another future which is not `Send`
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--> $DIR/issue-68112.rs:43:17
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|
@@ -43,6 +45,7 @@ LL | require_send(send_fut);
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| required by a bound introduced by this call
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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= note: required for `Arc<RefCell<i32>>` to implement `Send`
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note: required because it's used within this `async fn` body
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--> $DIR/issue-68112.rs:50:31

‎tests/ui/generator/issue-68112.rs‎

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@@ -40,6 +40,7 @@ fn test1() {
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require_send(send_gen);
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//~^ ERROR generator cannot be sent between threads
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//~| NOTE not `Send`
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//~| NOTE use `std::sync::RwLock` instead
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}
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pub fn make_gen2<T>(t: T) -> impl Generator<Return = T> {
@@ -66,6 +67,7 @@ fn test2() {
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//~| NOTE required for
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//~| NOTE required by a bound introduced by this call
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//~| NOTE captures the following types
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//~| NOTE use `std::sync::RwLock` instead
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}
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fn main() {}

‎tests/ui/generator/issue-68112.stderr‎

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@@ -5,6 +5,7 @@ LL | require_send(send_gen);
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| ^^^^^^^^ generator is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: generator is not `Send` as this value is used across a yield
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--> $DIR/issue-68112.rs:36:9
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|
@@ -23,33 +24,34 @@ LL | fn require_send(_: impl Send) {}
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| ^^^^ required by this bound in `require_send`
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error[E0277]: `RefCell<i32>` cannot be shared between threads safely
26-
--> $DIR/issue-68112.rs:63:18
27+
--> $DIR/issue-68112.rs:64:18
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|
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LL | require_send(send_gen);
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| ------------ ^^^^^^^^ `RefCell<i32>` cannot be shared between threads safely
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| |
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| required by a bound introduced by this call
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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= note: required for `Arc<RefCell<i32>>` to implement `Send`
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note: required because it's used within this generator
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--> $DIR/issue-68112.rs:48:5
38+
--> $DIR/issue-68112.rs:49:5
3739
|
3840
LL | || {
3941
| ^^
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note: required because it appears within the type `impl Generator<Return = Arc<RefCell<i32>>>`
41-
--> $DIR/issue-68112.rs:45:30
43+
--> $DIR/issue-68112.rs:46:30
4244
|
4345
LL | pub fn make_gen2<T>(t: T) -> impl Generator<Return = T> {
4446
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
4547
note: required because it appears within the type `impl Generator<Return = Arc<RefCell<i32>>>`
46-
--> $DIR/issue-68112.rs:53:34
48+
--> $DIR/issue-68112.rs:54:34
4749
|
4850
LL | fn make_non_send_generator2() -> impl Generator<Return = Arc<RefCell<i32>>> {
4951
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
5052
= note: required because it captures the following types: `impl Generator<Return = Arc<RefCell<i32>>>`, `()`
5153
note: required because it's used within this generator
52-
--> $DIR/issue-68112.rs:59:20
54+
--> $DIR/issue-68112.rs:60:20
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|
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LL | let send_gen = || {
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| ^^

‎tests/ui/generator/not-send-sync.stderr‎

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@@ -12,6 +12,7 @@ LL | | });
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| |_____^ `Cell<i32>` cannot be shared between threads safely
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|
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= help: the trait `Sync` is not implemented for `Cell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead
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= note: required for `&Cell<i32>` to implement `Send`
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note: required because it's used within this generator
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--> $DIR/not-send-sync.rs:16:17
@@ -36,6 +37,7 @@ LL | | });
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| |_____^ generator is not `Sync`
3738
|
3839
= help: within `[generator@$DIR/not-send-sync.rs:9:17: 9:19]`, the trait `Sync` is not implemented for `Cell<i32>`
40+
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead
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note: generator is not `Sync` as this value is used across a yield
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--> $DIR/not-send-sync.rs:12:9
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|

‎tests/ui/generator/print/generator-print-verbose-1.stderr‎

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@@ -5,6 +5,7 @@ LL | require_send(send_gen);
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| ^^^^^^^^ generator is not `Send`
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
8+
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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note: generator is not `Send` as this value is used across a yield
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--> $DIR/generator-print-verbose-1.rs:35:9
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|
@@ -29,6 +30,7 @@ LL | require_send(send_gen);
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| required by a bound introduced by this call
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|
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= help: the trait `Sync` is not implemented for `RefCell<i32>`
33+
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
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= note: required for `Arc<RefCell<i32>>` to implement `Send`
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note: required because it's used within this generator
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--> $DIR/generator-print-verbose-1.rs:42:5

‎tests/ui/generator/print/generator-print-verbose-2.stderr‎

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@@ -12,6 +12,7 @@ LL | | });
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| |_____^ `Cell<i32>` cannot be shared between threads safely
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|
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= help: the trait `Sync` is not implemented for `Cell<i32>`
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= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead
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= note: required for `&'_#4r Cell<i32>` to implement `Send`
1617
note: required because it's used within this generator
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--> $DIR/generator-print-verbose-2.rs:19:17
@@ -36,6 +37,7 @@ LL | | });
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| |_____^ generator is not `Sync`
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|
3839
= help: within `[main::{closure#0} upvar_tys=() {Cell<i32>, ()}]`, the trait `Sync` is not implemented for `Cell<i32>`
40+
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead
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note: generator is not `Sync` as this value is used across a yield
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--> $DIR/generator-print-verbose-2.rs:15:9
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|

‎tests/ui/issues/issue-7364.stderr‎

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@@ -5,6 +5,7 @@ LL | static boxed: Box<RefCell<isize>> = Box::new(RefCell::new(0));
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| ^^^^^^^^^^^^^^^^^^^ `RefCell<isize>` cannot be shared between threads safely
66
|
77
= help: the trait `Sync` is not implemented for `RefCell<isize>`
8+
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead
89
= note: required for `Unique<RefCell<isize>>` to implement `Sync`
910
= note: required because it appears within the type `Box<RefCell<isize>>`
1011
= note: shared static variables must have a type that implements `Sync`

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