Autocomplete of enum variants does not work in `vec![Enum_::|]` context

[enomado]

enum En {
    Foo,
    Bar,
}

fn yolo() {
    // autocomplete works
    let p = En::Foo;

    // autocomplete do not works
    let p = vec![En::|];
}

rust-analyzer version: latest master 0.0.0 (f64c956 2022-09-12)

[jonas-schievink]

The reason is that the macro is just expanded to $e. Apparently we're having trouble recovering from the syntax error (but there's no macro error?).

[jonas-schievink]

Reduced to:

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

enum En {
    Foo,
    Bar,
}

fn test() {
    let p = mac![En::$0];
}

Seems like we swallow the content of the repetition if it doesn't parse correctly.

[ChayimFriedman2]

Don't we insert a dummy identifier at the cursor position?

[jonas-schievink]

We expand macros in both the original file and the one with the fake ident, and stop when either of them fails, or if the fake ident does not appear in the output (and also on other conditions):

rust-analyzer/crates/ide-completion/src/context/analysis.rs

Lines 22 to 25 in 2b61be2

	/// Expand attributes and macro calls at the current cursor position for both the original file
	/// and fake file repeatedly. As soon as one of the two expansions fail we stop so the original
	/// and speculative states stay in sync.
	pub(super) fn expand_and_analyze(

[flodiebold]

(The reason for that being that we can't do things like name resolution in the fake expansion yet, so we can only expand macros there if the same macro call is also present in the real expansion)

[DasLixou]

Any updates on this?