Understanding Rust Error E0516: 'typeof' Unimplemented

Rust Error E0516: typeof Reserved but Unimplemented

In Rust, when you try to use the 'typeof' keyword, it raises the error E0516. It occurs because the 'typeof' keyword is reserved in Rust's syntax but is not currently implemented.

Erroneous Code Example:

fn main() {
    let x: typeof(92) = 92;

Fixing Rust Error E0516

To fix the error, you should use type inference instead of 'typeof'. Rust's type inference system is robust and will be able to determine the data type without explicitly specifying it.

Corrected Code Example:

fn main() {
    let x = 92;

Using type annotations

In situations where you would like to explicitly specify the data type, you can use type annotations. For example:

fn main() {
    let x: i32 = 92;

Type annotations can aid in making the code more readable and help prevent possible type-related errors. However, they are unnecessary if the compiler can infer the correct type on its own.


Rust Error E0516 occurs when attempting to use the reserved but unimplemented 'typeof' keyword. To resolve the error, use Rust's type inference mechanism or explicitly specify the data type using type annotations.