astral-sh/ruff · error · syn::Error

unexpected suffix `{suffix}` on string literal

Error message

unexpected suffix `{suffix}` on string literal

What it means

A syn compile error from get_string_literal in the option macros: a value passed to default/value_type/scope/example is a string literal with a suffix attached after the closing quote. The macros require plain string literals.

Source

Thrown at crates/ruff_macros/src/config.rs:343

fn get_string_literal(
    meta: &ParseNestedMeta,
    meta_name: &str,
    attribute_name: &str,
) -> syn::Result<syn::LitStr> {
    let expr: syn::Expr = meta.value()?.parse()?;

    let mut value = &expr;
    while let syn::Expr::Group(e) = value {
        value = &e.expr;
    }

    if let syn::Expr::Lit(ExprLit {
        lit: Lit::Str(lit), ..
    }) = value
    {
        let suffix = lit.suffix();
        if !suffix.is_empty() {
            return Err(syn::Error::new(
                lit.span(),
                format!("unexpected suffix `{suffix}` on string literal"),
            ));
        }

        Ok(lit.clone())
    } else {
        Err(syn::Error::new(
            expr.span(),
            format!("expected {attribute_name} attribute to be a string: `{meta_name} = \"...\"`"),
        ))
    }
}

#[derive(Default, Debug)]
struct DeprecatedAttribute {
    since: Option<String>,
    note: Option<String>,

View on GitHub (pinned to 26f38c119c)

Solutions

1. Remove the suffix so the value is a plain string literal
2. Quote the whole value correctly, e.g. default = "true"

When it happens

Trigger: Thrown at crates/ruff_macros/src/config.rs:343 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of astral-sh/ruff@26f38c119c (2026-09-05). Data as JSON: /api/errors/59332c71ac8e3e84. Report an issue: GitHub.