Fix E0364: Trait Bounds on Self Cannot Be Repeated in Where Clause

Wed, 15 Jul 2026 10:20:04 +0800

1. Symptoms

When the Rust compiler encounters duplicate trait bounds referencing Self in a where clause, it halts compilation and reports error E0364. The compiler produces diagnostic output that clearly identifies the problematic where clause and explains the constraint violation.

The typical error message from rustc reads:

error[E0364]: trait bounds that refer to `Self` may not be repeated in the where clause
 --> src/lib.rs:3:29
  |
3 |     fn method() where Self: Clone, Self: Clone { }
  |                             ^^^^^^^^ second `Self` bound here

In more complex scenarios involving generic parameters, you might see additional context about the trait definition itself:

E0364 on ErrorVault — Developer Error Code Dictionary

Fix E0364: Trait Bounds on Self Cannot Be Repeated in Where Clause

1. Symptoms