Fix E0794: Invalid discriminant value for enum in Rust

Tue, 21 Jul 2026 22:20:04 +0800

1. Symptoms

When the Rust compiler encounters error E0794, you will see output similar to the following in your terminal:

error[E0794]: invalid discriminant value for enum `EnumName`, valid values are 0..2
  --> src/main.rs:10:17
   |
10 |     let _ = unsafe { transmute::<u8, EnumName>(3u8) };
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^ invalid discriminant value
   |
   = note: values are validated based on the enum discriminant type and defined variants

The error message specifies which discriminant values are considered valid for your enum, helping you understand the range of acceptable values. The compiler indicates the exact location in your source code where the invalid discriminant is being used, and it clarifies the bounds of valid discriminants based on the number of variants defined in your enum.

Fix E0732: #[derive] on Enum with No Variants

Wed, 20 May 2026 17:32:04 +0800

1. Symptoms

When attempting to compile Rust code that uses the #[derive] attribute on an enum with zero variants, the compiler produces the E0732 error:

error[E0732]: #[derive] can't be used with enum that has no data
  --> src/main.rs:3:1
   |
3  | #[derive(Debug, Clone)]
   | ^^^^^^^^^^^^^^^^^^^^^^
4  | enum Void {}
   | ---------- has no variants

The error manifests with any trait in the derive macro, whether it’s Debug, Clone, Default, PartialEq, or any other derive-able trait. The compiler will also highlight the enum definition itself as having no variants.

Enums on ErrorVault — Developer Error Code Dictionary

Fix E0794: Invalid discriminant value for enum in Rust

1. Symptoms

Fix E0732: #[derive] on Enum with No Variants

1. Symptoms