E0722 - Error codes index
Description: Book listing all Rust error codes

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# Error code E0722

#### Note: this error code is no longer emitted by the compiler

This is because it was too specific to the `optimize` attribute. Similar diagnostics occur for other attributes too. The example here will now emit `E0539`

The `optimize` attribute was malformed.

Erroneous code example:

    #![allow(unused)]
    #![feature(optimize_attribute)]

    fn main() {
    #[optimize(something)] // error: invalid argument
    pub fn something() {}
    }

The `#[optimize]` attribute should be used as follows:

- `#[optimize(size)]` – instructs the optimization pipeline to generate code that’s smaller rather than faster

- `#[optimize(speed)]` – instructs the optimization pipeline to generate code that’s faster rather than smaller

For example:

    #![allow(unused)]
    #![feature(optimize_attribute)]

    fn main() {
    #[optimize(size)]
    pub fn something() {}
    }

See RFC 2412 for more details.