Fix E0640: Self-referential struct definition

Wed, 15 Jul 2026 05:32:04 +0800

1. Symptoms

When you attempt to compile a Rust program containing a struct definition where one field directly references the struct type itself (outside of pointer wrappers), the compiler emits error E0640. The error message clearly indicates that the struct definition contains an unsupported self-referential pattern.

Shell output demonstrating the error looks like the following:

error[E0640]: self-referential struct
  --> src/main.rs:5:5
   |
5  |     name: String,
6  |     // ERROR: next points back to the containing struct
7  |     next: Option<Node>,
   |           ^^^^^^^^^^^^^^ self-referential struct
   |
   = note: this error indicates that the struct is self-referential
   = help: consider using `Box<Self>`, `Arc<Self>`, `Rc<Self>`, or a reference type
   = help: for more information, see https://doc.rust-lang.org/reference/structures.html

A slightly different manifestation occurs when attempting to embed the struct directly within itself as a field rather than behind a smart pointer wrapper:

Self-Referential on ErrorVault — Developer Error Code Dictionary

Fix E0640: Self-referential struct definition

1. Symptoms