This uses [lalrpop](https://github.com/lalrpop/lalrpop) under the hood I believe, which is a pretty awesome parser generator library for Rust.
I love the AST in XML approach.
Seems overkill for a language whose grammar is LL(1)?
Just curious, how did you know this?
> Python 3.9 uses a new parser, based on PEG instead of LL(1). The new parser’s performance is roughly comparable to that of the old parser, but the PEG formalism is more flexible than LL(1) when it comes to designing new language features. We’ll start using this flexibility in Python 3.10 and later.
More specifically, the grammar [0] is in EBNF form and is ELL(1). That means that if each EBNF production is converted to a set of BNF productions in an LL(1)-compliant way, the BNF grammar as a whole is LL(1). It seems that the Python tools themselves do not check this [1], but I have verified it myself.
However, as another commenter mentioned, the grammar doesn't exactly describe Python, but a superset of it. The compiler needs to perform further checks after parsing that "should" be part of the parser itself. A more advanced parser would allow these checks to be performed in the correct place - this is probably what RustPython does when using LR(1), and was one reason why CPython recently replaced its LL(1) parser with one based on PEG.
[0] https://docs.python.org/3.8/reference/grammar.html
[1] https://discuss.python.org/t/should-there-be-a-check-whether...
Solution?
async fn foo() {
}
fn main() {
let x = async { await foo() };
}
error: incorrect use of `await`
--> src/main.rs:6:13
|
6 | let x = async { await foo() };
| ^^^^^^^^^^^ help: `await` is a postfix operation: `foo().await`