Type inference for generators

[DustinByfuglien]

#![feature(generators)]

fn main() {
    let x = || { yield 3 };
}

When using VSCode with this code I notice that:

1. It seems a yield with argument is reported by analyzer as error.
2. Also helping hint about x type displays that x have closure type || -> i32 instead of generator trait type.

[DustinByfuglien]

I can illustrate by screenshot.

1. Rust analyzer red underscored a error but no error is.
2. Hint shows that x have closure type || -> i32 but really it have generator type

[ExoticMatter]

Interestingly, despite the bogus syntax error for no.1, rust-analyzer seems to typecheck yield arguments properly.

fn foo() {
    let bar = || {
        yield "baz";
        yield 0i32;     // E0308: expected `&str`, found `i32`
        yield;          // E0308: expected `&str`, found `()`
    };
}

[flodiebold]

Any such error is coming from cargo check, not rust-analyzer's analysis.

[DustinByfuglien]

Cargo check passed without errors. Program compiled and executed without errors.

[flodiebold]

Sorry, I meant the E308 type checker errors.

[Veykril]

Parsing has been implemented in #7209, type inference is yet to be implemented.

[yuhr]

Type inference for the parameter should also be covered:

fn wrapper(mut generator: impl Generator<i32, Yield = i32> + Unpin) {
    while let Yielded(x) = Pin::new(&mut generator).resume(42) {
        println!("{}", x);
    }
}

fn main() {
    wrapper(|i| { // i: {unknown}
        yield i + 1;
        yield i + 2;
        yield i + 3;
    });
}