Macros on ErrorVault — Developer Error Code Dictionary

Fix E0615: Attempted to Derive an Impl of a Trait That Is Not Derivable

Sun, 26 Jul 2026 10:20:04 +0800

1. Symptoms

When you encounter Rust error E0615, the compiler produces output similar to the following:

error[E0615]: attempted to derive an impl of a trait that is not marked `#[derivable]`
  --> src/main.rs:5:12
   |
5  | #[derive(MyCustomTrait)]
   |            ^^^^^^^^^^^^^
   |
   = note: only traits marked with `#[derivable]` can be derived

The error manifests at the specific line where the #[derive(...)] attribute is applied to a struct or enum definition. The compiler rejects the derivation request because the specified trait is not recognized as derivable by the Rust compiler’s built-in derive mechanism. This error typically surfaces during the compilation phase when the compiler attempts to expand the derive macro and discovers that the target trait lacks the necessary metadata to support automatic implementation generation.

Fix E0666: Malformed Macro Invocation

Sun, 26 Jul 2026 07:56:04 +0800

1. Symptoms

When Rust’s macro expansion engine encounters a macro invocation that does not match the macro definition’s pattern, the compiler emits error E0666. This error manifests with a clear diagnostic message indicating the specific mismatch between what the macro expected and what was provided in the invocation.

The compiler output typically includes the macro name, the pattern that failed to match, and the tokens that were actually supplied. The error message structure varies slightly depending on the complexity of the mismatch, but the core diagnostic remains consistent across Rust versions.

Fix E0367: Malformed Attribute Syntax in Rust

Wed, 22 Jul 2026 03:08:04 +0800

1. Symptoms

When the Rust compiler encounters a malformed attribute, it halts compilation and emits error E0367. This error manifests with several observable indicators that help developers identify the problematic code location.

The compiler output typically includes the error code, a descriptive message, and a span pointing to the offending attribute. The error message generally reads “malformed attribute attribute, expected (” or a similar variant indicating the expected syntax structure.

Fix E0466: Imported Macros Cannot Have Unused Lifetimes

Sat, 30 May 2026 17:32:04 +0800

1. Symptoms

When the Rust compiler encounters error E0466, you will see output similar to:

error[E0466]: imported macro `macro_name` cannot have unused lifetimes
  --> src/main.rs:5:1
   |
5  | use crate_name::macro_name;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^

This error appears during the compilation phase, specifically during macro import resolution. The error indicates that Rust has successfully located the macro you’re trying to import, but detected that the macro definition itself contains lifetime parameters that are not actually used anywhere in the macro body.