Annotating types with #[must-use] - The bindgen User Guide
Description: `bindgen` automatically generates Rust FFI bindings to C and C++ libraries.

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# Annotating types with `#[must-use]`

`bindgen` can be instructed to annotate certain types with `#[must_use]`.

Some libraries have a common error type, returned by lots of their functions, which needs to be checked after every call. In these cases it’s useful to add `#[must_use]` to this type, so the Rust compiler emits a warning when the check is missing.

### Library

- `bindgen::Builder::must_use_type`

### Command Line

- `--must-use-type <regex>`

### Annotations

    /** <div rustbindgen mustusetype></div> */
    struct ErrorType {
        // ...
    };

    ...