Improve completion of macro_rules partial inputs

rust-analyzer version: rust-analyzer 1.91.0-nightly (040a98a 2025-08-20)

rustc version: rustc 1.91.0-nightly (040a98af7 2025-08-20)

editor or extension: coc-rust-analyzer

code snippet to reproduce:

macro_rules! vec_like {
    ($($e:expr),+ $(,)?) => {
        [$($e),+]
    };
}

fn main() {
    vec_like!("".|);
}

| is cursor

Unable to complete when entering the dot, as it cannot be fully parsed as expr

But there are no other matching branches at this point,
should we try inputting the incomplete expr into the macro_rules?

Start by running the Rust snippet from the issue in rust-analyzer with the cursor after the dot and observe the missing completion. Trace the macro_rules completion path for partially parsed expr inputs; done means completion is offered at this cursor position without requiring the expression to parse fully.