Ergonomic Clone Support

The following code errors with rust analyzer, but builds and runs with cargo:

#![feature(ergonomic_clones)]
// ...
let mut y = use || {
    // ...
};

specifically:

1. Syntax Error: expected expression [syntax-error] (on the 'u' in 'use')
2. Syntax Error: expected SEMICOLON [syntax-error] (on the space after 'use')

with nightly (2025-08-24) rust analyzer using rustup and rustaceanvim.

The other x.use syntax also fails as well, but the UseCloned trait works as expected.

It's an incomplete feature, so sorry if this is too early. I have no clue if those are supported or if it makes more sense to wait (couldn't find clear info on this). I thought I'd make this issue anyways in case someone else comes across this.

Start by reproducing the reported snippet with rust-analyzer nightly 2025-08-24, rustup, and rustaceanvim, then compare diagnostics for the use || and x.use forms with the working UseCloned trait. Trace the syntax handling for the incomplete ergonomic_clones feature; done means supported forms no longer produce syntax errors, or their unsupported status is clearly established.