Const Generics on ErrorVault — Developer Error Code Dictionary

Fix E0589: Type Parameter Bound Not Satisfied for Const Generic

Sun, 26 Jul 2026 00:44:04 +0800

1. Symptoms

When Rust code triggers error E0589, the compiler produces output that clearly indicates a const generic bound mismatch. The diagnostic message typically follows this pattern:

error[E0589]: the trait bound `SomeType: Trait` is not satisfied
  --> src/main.rs:10:5
   |
10 |     fn generic_function<const N: usize where T: SomeTrait<N>>() {}
   |                                                       ^^^^^ required by this bound in `SomeTrait`

The error manifests in several common scenarios. First, when defining a function with const generic parameters that require trait bounds, the compiler rejects calls where the const value doesn’t satisfy those bounds. Second, struct definitions with const generic fields that impose trait constraints will fail compilation when instantiated incorrectly. Third, impl blocks for generic types may trigger E0589 when attempting to implement methods for type combinations that violate the declared constraints.

Fix E0643: Generic Const Parameters Cannot Be Used in Function Body

Sat, 25 Jul 2026 00:44:04 +0800

Fix E0643: Generic Const Parameters Cannot Be Used in Function Body

Rust’s const generics feature enables writing code that is generic over constant values, allowing types like Vec<N> where N is a compile-time integer. However, the compiler imposes strict restrictions on what operations can be performed on const generic parameters inside function bodies. Error E0643 is emitted when a const generic parameter is used in a way that the compiler cannot evaluate at compile time, making it impossible to monomorphize the function for a given set of generic arguments.

Fix E0208: Invalid Constraint in Const Generic Default

Mon, 20 Jul 2026 12:44:04 +0800

1. Symptoms

When you encounter error E0208, the Rust compiler produces output similar to the following:

error[E0208]: constraints in const generic parameters must be satisfied by every concrete value
  --> src/main.rs:5:12
   |
5  | struct Wrapper<const N: usize = K, const K: usize = 4>();
   |                     ^^^^^^^^

The compiler is telling you that the constraint specified on a const generic parameter cannot be verified against the default value provided for that parameter. This typically manifests when you attempt to use a const generic parameter in the constraint of another const generic parameter with a default.

Fix E0207: Const Parameter Type Must Be Copy in Rust

Fri, 17 Jul 2026 07:56:04 +0800

Fix E0207: Const Parameter Type Must Be Copy in Rust

Rust’s const generics provide powerful compile-time computation capabilities, but they come with strict requirements on what types can be used as const parameters. Error code E0207 specifically indicates that a const generic parameter has been declared with a type that does not implement the Copy trait. This limitation exists because const parameters must be evaluable at compile time, and only Copy types guarantee deterministic, repeatable evaluation without side effects.