Method parse

assert-struct-macros/src/pattern/field.rs:55–75

Parses a field name, which can be either an identifier or a numeric index. # Examples - `name` → `FieldName::Ident("name")` - `0` → `FieldName::Index(0)` - `42` → `FieldName::Index(42)` # Note on consecutive indices Due to proc macro tokenization, consecutive numeric indices like `.0.0` are tokenized as a float literal after the first dot is consumed. This is a known limitation - use tuple destr

(input: syn::parse::ParseStream)

    /// are tokenized as a float literal after the first dot is consumed.
    /// This is a known limitation - use tuple destructuring syntax instead.
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        // Try to parse as a numeric literal first using fork
        let fork = input.fork();
        if let Ok(lit) = fork.parse::<syn::LitInt>() {
            // Successfully parsed as number, consume from real input
            let _: syn::LitInt = input.parse()?;
            let index = lit.base10_parse()?;
            Ok(FieldName::Index(index))
        } else {
            // Try parsing as identifier
            input
                .parse::<syn::Ident>()
                .map(FieldName::Ident)
                .map_err(|_| {
                    syn::Error::new(
                        input.span(),
                        "expected field name (identifier or numeric index)",
                    )
                })
        }
    }
}

/// Field assertion - field operations paired with an expected pattern