Require Send + Sync for object types

Without this, it is possible to send types that contain non-threadsafe
constructs like `RefCell` over FFI, and call methods that use them from
multiple threads.

Both Send and Sync are required on the inner type for Arc to implement
Send itself, which is what we must guarantee to be able to move an Arc
over FFI, since we can't guarantee it is kept on the same thread inside
the calling code.

fixtures/uitests/tests/ui/interface_not_sync_and_send.stderr

@@ -11,12 +11,11 @@ note: required because it appears within the type `Counter`
   |
 9 | pub struct Counter {
   |            ^^^^^^^
-note: required by a bound in `_::{closure#0}::assert_impl_all`
- --> $OUT_DIR[uniffi_uitests]/counter.uniffi.rs
+note: required by a bound in `FfiConverterArc`
+ --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
   |
-  | #[::uniffi::expand_interface_support(tag = crate::UniFfiTag)]
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
-  = note: this error originates in the macro `uniffi::deps::static_assertions::assert_impl_all` which comes from the expansion of the attribute macro `::uniffi::expand_interface_support` (in Nightly builds, run with -Z macro-backtrace for more info)
+  | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+  |                                              ^^^^ required by this bound in `FfiConverterArc`
 
 error[E0277]: `Cell<u32>` cannot be shared between threads safely
   --> tests/ui/interface_not_sync_and_send.rs:27:12
@@ -31,9 +30,8 @@ note: required because it appears within the type `ProcMacroCounter`
    |
 27 | pub struct ProcMacroCounter {
    |            ^^^^^^^^^^^^^^^^
-note: required by a bound in `_::{closure#0}::assert_impl_all`
-  --> tests/ui/interface_not_sync_and_send.rs:26:10
+note: required by a bound in `FfiConverterArc`
+  --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
    |
-26 | #[derive(uniffi::Object)]
-   |          ^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
-   = note: this error originates in the macro `uniffi::deps::static_assertions::assert_impl_all` which comes from the expansion of the derive macro `uniffi::Object` (in Nightly builds, run with -Z macro-backtrace for more info)
+   | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+   |                                              ^^^^ required by this bound in `FfiConverterArc`

fixtures/uitests/tests/ui/interface_trait_not_sync_and_send.stderr

@@ -1,55 +1,55 @@
-error[E0277]: `dyn Trait` cannot be shared between threads safely
+error[E0277]: `(dyn Trait + 'static)` cannot be shared between threads safely
  --> $OUT_DIR[uniffi_uitests]/trait.uniffi.rs
   |
   | ::uniffi::expand_trait_interface_support!(r#Trait);
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Trait` cannot be shared between threads safely
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Trait + 'static)` cannot be shared between threads safely
   |
-  = help: the trait `Sync` is not implemented for `dyn Trait`
-note: required by a bound in `_::{closure#0}::assert_impl_all`
- --> $OUT_DIR[uniffi_uitests]/trait.uniffi.rs
+  = help: the trait `Sync` is not implemented for `(dyn Trait + 'static)`
+note: required by a bound in `FfiConverterArc`
+ --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
   |
-  | ::uniffi::expand_trait_interface_support!(r#Trait);
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
+  | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+  |                                              ^^^^ required by this bound in `FfiConverterArc`
   = note: this error originates in the macro `::uniffi::expand_trait_interface_support` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: `dyn Trait` cannot be sent between threads safely
+error[E0277]: `(dyn Trait + 'static)` cannot be sent between threads safely
  --> $OUT_DIR[uniffi_uitests]/trait.uniffi.rs
   |
   | ::uniffi::expand_trait_interface_support!(r#Trait);
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Trait` cannot be sent between threads safely
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Trait + 'static)` cannot be sent between threads safely
   |
-  = help: the trait `Send` is not implemented for `dyn Trait`
-note: required by a bound in `_::{closure#0}::assert_impl_all`
- --> $OUT_DIR[uniffi_uitests]/trait.uniffi.rs
+  = help: the trait `Send` is not implemented for `(dyn Trait + 'static)`
+note: required by a bound in `FfiConverterArc`
+ --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
   |
-  | ::uniffi::expand_trait_interface_support!(r#Trait);
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
+  | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+  |                                       ^^^^ required by this bound in `FfiConverterArc`
   = note: this error originates in the macro `::uniffi::expand_trait_interface_support` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: `dyn ProcMacroTrait` cannot be shared between threads safely
+error[E0277]: `(dyn ProcMacroTrait + 'static)` cannot be shared between threads safely
   --> tests/ui/interface_trait_not_sync_and_send.rs:11:1
    |
 11 | #[uniffi::export]
-   | ^^^^^^^^^^^^^^^^^ `dyn ProcMacroTrait` cannot be shared between threads safely
+   | ^^^^^^^^^^^^^^^^^ `(dyn ProcMacroTrait + 'static)` cannot be shared between threads safely
    |
-   = help: the trait `Sync` is not implemented for `dyn ProcMacroTrait`
-note: required by a bound in `_::{closure#0}::assert_impl_all`
-  --> tests/ui/interface_trait_not_sync_and_send.rs:11:1
+   = help: the trait `Sync` is not implemented for `(dyn ProcMacroTrait + 'static)`
+note: required by a bound in `FfiConverterArc`
+  --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
    |
-11 | #[uniffi::export]
-   | ^^^^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
+   | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+   |                                              ^^^^ required by this bound in `FfiConverterArc`
    = note: this error originates in the attribute macro `uniffi::export` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: `dyn ProcMacroTrait` cannot be sent between threads safely
+error[E0277]: `(dyn ProcMacroTrait + 'static)` cannot be sent between threads safely
   --> tests/ui/interface_trait_not_sync_and_send.rs:11:1
    |
 11 | #[uniffi::export]
-   | ^^^^^^^^^^^^^^^^^ `dyn ProcMacroTrait` cannot be sent between threads safely
+   | ^^^^^^^^^^^^^^^^^ `(dyn ProcMacroTrait + 'static)` cannot be sent between threads safely
    |
-   = help: the trait `Send` is not implemented for `dyn ProcMacroTrait`
-note: required by a bound in `_::{closure#0}::assert_impl_all`
-  --> tests/ui/interface_trait_not_sync_and_send.rs:11:1
+   = help: the trait `Send` is not implemented for `(dyn ProcMacroTrait + 'static)`
+note: required by a bound in `FfiConverterArc`
+  --> $WORKSPACE/uniffi_core/src/ffi_converter_traits.rs
    |
-11 | #[uniffi::export]
-   | ^^^^^^^^^^^^^^^^^ required by this bound in `assert_impl_all`
+   | pub unsafe trait FfiConverterArc<UT>: Send + Sync {
+   |                                       ^^^^ required by this bound in `FfiConverterArc`
    = note: this error originates in the attribute macro `uniffi::export` (in Nightly builds, run with -Z macro-backtrace for more info)

uniffi_core/src/ffi_converter_traits.rs

@@ -174,7 +174,7 @@ pub unsafe trait FfiConverter<UT>: Sized {
 /// ## Safety
 ///
 /// This has the same safety considerations as FfiConverter
-pub unsafe trait FfiConverterArc<UT> {
+pub unsafe trait FfiConverterArc<UT>: Send + Sync {
     type FfiType;
     type ReturnType: FfiDefault;
     type FutureCallback: Copy;