Macro konst::parse_with

macro_rules! parse_with {
    ($parser:expr, $type:ty $(,)*) => { ... };
}

Available on crate feature parsing only.

Parses a type that impls HasParser with the passed in Parser.

Example

This example demonstrates how you can use this macro to parse both standard library and user-defined types.

use konst::{parse_with, try_rebind, unwrap_ctx};

use konst::parsing::{HasParser, Parser, ParseValueResult};

const PAIR: (u32, Foo) = unwrap_ctx!(parse_pair(Parser::new("100,Baz"))).0;

assert_eq!(PAIR.0, 100);
assert_eq!(PAIR.1, Foo::Baz);

const fn parse_pair(mut parser: Parser<'_>) -> ParseValueResult<'_, (u32, Foo)> {
    try_rebind!{(let left, parser) = parse_with!(parser, u32)}
    try_rebind!{parser = parser.strip_prefix(',')}
    try_rebind!{(let right, parser) = parse_with!(parser, Foo)}
     
    Ok(((left, right), parser))
}


#[derive(Debug, PartialEq)]
enum Foo {
    Bar,
    Baz,
    Qux,
}

impl HasParser for Foo {
    type Parser = Self;
}

impl Foo {
    const fn parse_with(parser: Parser<'_>) -> ParseValueResult<'_, Self> {
        // You can use the `parser_method` macro instead of this chain of if elses
        if let Ok(parser) = parser.strip_prefix("Bar") {
            Ok((Foo::Bar, parser))
        } else if let Ok(parser) = parser.strip_prefix("Baz") {
            Ok((Foo::Baz, parser))
        } else if let Ok(parser) = parser.strip_prefix("Qux") {
            Ok((Foo::Qux, parser))
        } else {
            Err(parser.into_other_error(&"expected one of `Bar`, `Baz`, or `Qux`"))
        }
    }
}