Closed
Description
openedon Feb 26, 2022
#![feature(generic_const_exprs)]
trait Trait {
const N: usize;
}
struct Struct<const N: usize>;
type Alias<T: Trait> = Struct<{<T as Trait>::N}>;Compiling this code (Playground) produces the following diagnostics:
warning: bounds on generic parameters are not enforced in type aliases
--> src/lib.rs:9:19
|
9 | pub type Alias<T: Trait> = Struct<{<T as Trait>::N}>;
| ^^^^^
|
= 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
|
9 - pub type Alias<T: Trait> = Struct<{<T as Trait>::N}>;
9 + pub type Alias<T> = Struct<{<T as Trait>::N}>;
|
I expected to see this happen: The compiler should not have suggested removing : Trait from the type alias.
Instead, this happened: Removing : Trait as per the compiler's suggestion breaks the code.
error[E0277]: the trait bound `T: Trait` is not satisfied
--> src/lib.rs:9:29
|
9 | pub type Alias<T> = Struct<{<T as Trait>::N}>;
| ^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
|
help: consider restricting type parameter `T`
|
9 | pub type Alias<T: Trait> = Struct<{<T as Trait>::N}>;
| +++++++
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
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
