Redundant trait bound

What it does

Warn about a trait definition or a generic variable being redundantly bound by the same trait multiple times.

Lint Name

redundant_trait_bound

Category

suspicious

Advantage

• Redundant code takes extra space and is confusing.
• It may be an error: the author may have intended to write a different trait.
• It can be autofixed.

Drawbacks

No response

Example

trait Foo: Send + Send {}

fn foo<T: Send + Send>(x: T) {}

type MyFuture = dyn std::future::Future + Send;
trait Foo: MyFuture + Send + Sync;

Could be written as:

trait Foo: Send {}

fn foo<T: Send>(x: T) {}

type MyFuture = dyn std::future::Future + Send;
trait Foo: MyFuture + Sync;

Use the redundant_trait_bound lint name and suspicious category as the entry point; begin by finding how Clippy implements and registers comparable redundant-bound lints. Define done as detecting repeated trait bounds in the trait and generic examples, handling the shown MyFuture case correctly, and supporting the stated autofix. The issue names no files or tests, so those must be located in the repository.