Closed
Description
#![feature(type_alias_impl_trait)]
type Alias<T: Send> = (impl Send,);
pub fn foo<T: Send>(x: T) -> Alias<T> {
(x,)
}Compiling this code (Playground) produces the following diagnostics:
warning: bounds on generic parameters are not enforced in type aliases
--> src/lib.rs:3:15
|
3 | type Alias<T: Send> = (impl Send,);
| ^^^^
|
= note: `#[warn(type_alias_bounds)]` on by default
help: the bound will not be checked when the type alias is used, and should be removed
|
3 - type Alias<T: Send> = (impl Send,);
3 + type Alias<T> = (impl Send,);
|
I expected to see this happen: The compiler should not have suggested removing : Send from the type alias.
Instead, this happened: Removing : Send as per the compiler's suggestion breaks the code.
error[E0277]: `T` cannot be sent between threads safely
--> src/lib.rs:3:18
|
3 | type Alias<T> = (impl Send,);
| ^^^^^^^^^ `T` cannot be sent between threads safely
|
help: consider restricting type parameter `T`
|
3 | type Alias<T: std::marker::Send> = (impl Send,);
| +++++++++++++++++++
For more information about this error, try `rustc --explain E0277`.
error: could not compile `playground` due to previous error
Meta
rustc --version --verbose:
rustc 1.61.0-nightly (532d3cda9 2022-02-23)
binary: rustc
commit-hash: 532d3cda90b8a729cd982548649d32803d265052
commit-date: 2022-02-23
host: aarch64-apple-darwin
release: 1.61.0-nightly
LLVM version: 14.0.0