honest swan
I'm just asking why can't I do this :
use once_cell::unsync::Lazy; // 1.18.0
pub static STATIC_TEST: Lazy<fn(usize) -> bool> = new(|| {
|a| a > 5
});
I get the error :
Compiling playground v0.0.1 (/playground)
error[E0425]: cannot find function `new` in this scope
--> src/lib.rs:3:51
|
3 | pub static STATIC_TEST: Lazy<fn(usize) -> bool> = new(|| {
| ^^^ not found in this scope
|
help: consider importing one of these items
|
1 + use autocfg::new;
|
1 + use mio::unix::pipe::new;
|
1 + use want::new;
|
error[E0277]: `Cell<Option<fn() -> fn(usize) -> bool>>` cannot be shared between threads safely
--> src/lib.rs:3:25
|
3 | pub static STATIC_TEST: Lazy<fn(usize) -> bool> = new(|| {
| ^^^^^^^^^^^^^^^^^^^^^^^ `Cell<Option<fn() -> fn(usize) -> bool>>` cannot be shared between threads safely
|
= help: within `once_cell::unsync::Lazy<fn(usize) -> bool>`, the trait `Sync` is not implemented for `Cell<Option<fn() -> fn(usize) -> bool>>`
= note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock`
note: required because it appears within the type `Lazy<fn(usize) -> bool>`
--> /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/once_cell-1.18.0/src/lib.rs:716:16
|
716 | pub struct Lazy<T, F = fn() -> T> {
| ^^^^
= note: shared static variables must have a type that implements `Sync`
error[E0277]: `UnsafeCell<Option<fn(usize) -> bool>>` cannot be shared between threads safely
--> src/lib.rs:3:25
|
3 | pub static STATIC_TEST: Lazy<fn(usize) -> bool> = new(|| {
| ^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<Option<fn(usize) -> bool>>` cannot be shared between threads safely
|
= help: within `once_cell::unsync::Lazy<fn(usize) -> bool>`, the trait `Sync` is not implemented for `UnsafeCell<Option<fn(usize) -> bool>>`
note: required because it appears within the type `OnceCell<fn(usize) -> bool>`
--> /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/once_cell-1.18.0/src/lib.rs:413:16
|
413 | pub struct OnceCell<T> {
| ^^^^^^^^
note: required because it appears within the type `Lazy<fn(usize) -> bool>`
--> /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/once_cell-1.18.0/src/lib.rs:716:16
|
716 | pub struct Lazy<T, F = fn() -> T> {
| ^^^^
= note: shared static variables must have a type that implements `Sync`
But I am using once_cell::unsync and not the sync version
link to playground
gentle robin