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//! Checked strings containing Rust identifiers.
//!
//! Raw identifiers are unsupported.
//!
//! # Examples
//!
//! ```rust
//! use strck_ident::{IntoCk, rust::RustIdent};
//!
//! assert!("foo".ck::<RustIdent>().is_ok());
//! assert!("_identifier".ck::<RustIdent>().is_ok());
//! assert!("Москва".ck::<RustIdent>().is_ok());
//! assert!("東京".ck::<RustIdent>().is_ok());
//!
//! assert!("struct".ck::<RustIdent>().is_err());
//! assert!("r#try".ck::<RustIdent>().is_err());
//! assert!("👍".ck::<RustIdent>().is_err());
//! ```
//!
//! # Aliases
//!
//! This module exposes [`Ident`] and [`IdentBuf`], which alias `Ck<RustIdent>`
//! and `Check<RustIdent>` respectively. These aliases are preferred to keep
//! type signatures succinct.
//!
//! # Requirements
//!
//! This module is only available when the `rust` feature flag is enabled.
use crate::unicode;
use core::fmt;
use strck::{Check, Ck, Invariant};
/// An [`Invariant`] for Rust identifiers.
///
/// Raw identifiers are unsupported.
///
/// # Invariants
///
/// * The string is nonempty.
/// * The first character is `_` or XID_Start.
/// * Any following characters are XID_Continue.
/// * The string isn't a single underscore, e.g. `"_"`.
/// * The string isn't a [strict] or [reserved] keyword.
///
#[derive(Clone, Debug)]
pub struct RustIdent;
/// Borrowed checked string containing a Rust identifier.
///
/// See [`RustIdent`] for more details.
pub type Ident = Ck<RustIdent>;
/// Owned checked string containing a Rust identifier.
///
/// See [`RustIdent`] for more details.
pub type IdentBuf<B = String> = Check<RustIdent, B>;
/// The error type returned from checking the invariants of [`RustIdent`].
#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub enum Error {
/// An invalid unicode identifier.
Unicode(unicode::Error),
/// A [strict] or [reserved] keyword.
///
Keyword(&'static str),
/// A single underscore.
Wildcard,
}
impl std::error::Error for Error {}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Error::Unicode(err) => err.fmt(f),
Error::Keyword(keyword) => {
write!(f, "Rust keyword: '{keyword}'")
}
Error::Wildcard => f.pad("wildcard '_' isn't a valid Rust ident"),
}
}
}
impl Invariant for RustIdent {
type Error = Error;
fn check(slice: &str) -> Result<(), Self::Error> {
match unicode::UnicodeIdent::check(slice) {
Ok(()) => match KEYWORDS.binary_search(&slice) {
Ok(index) => Err(Error::Keyword(KEYWORDS[index])),
Err(_) => Ok(()),
},
Err(unicode::Error::Start('_')) => match slice.len() {
1 => Err(Error::Wildcard), // `_` isn't ok
_ => Ok(()), // `_x` is ok
},
Err(e) => Err(Error::Unicode(e)),
}
}
}
static KEYWORDS: [&str; 51] = [
"Self", "abstract", "as", "async", "await", "become", "box", "break", "const", "continue",
"crate", "do", "dyn", "else", "enum", "extern", "false", "final", "fn", "for", "if", "impl",
"in", "let", "loop", "macro", "match", "mod", "move", "mut", "override", "priv", "pub", "ref",
"return", "self", "static", "struct", "super", "trait", "true", "try", "type", "typeof",
"unsafe", "unsized", "use", "virtual", "where", "while", "yield",
];
#[cfg(test)]
mod tests {
use super::{Error, RustIdent};
use strck::IntoCk;
#[test]
fn test_underscore() {
assert_eq!("_".ck::<RustIdent>().unwrap_err(), Error::Wildcard);
assert!("_unused".ck::<RustIdent>().is_ok());
assert!("__private".ck::<RustIdent>().is_ok());
assert!("snake_case".ck::<RustIdent>().is_ok());
}
#[test]
fn test_rust_reference() {
assert!("foo".ck::<RustIdent>().is_ok());
assert!("_identifier".ck::<RustIdent>().is_ok());
assert!("Москва".ck::<RustIdent>().is_ok());
assert!("東京".ck::<RustIdent>().is_ok());
}
}