Macro aml::make_parser_concrete

macro_rules! make_parser_concrete {
    ($parser: expr) => { ... };
}

This encapsulates an unfortunate hack we sometimes need to use, where the type checker gets caught in an infinite loop of parser types. This occurs when an object can indirectly contain itself, and so the parser type will contain its own type. This works by breaking the cycle of impl Parser chains that build up, by effectively creating a "concrete" closure type.

You can try using this hack if you are writing a parser and end up with an error of the form: error[E0275]: overflow evaluating the requirement 'impl Parser<{a type}>' help: consider adding a a '#![recursion_limit="128"] attribute to your crate Note: Increasing the recursion limit will not fix the issue, as the cycle will just continue until you either hit the new recursion limit or rustc overflows its stack.