RA post 2896 has trouble with completion

[ThomasCartier]

Debian testing, vscode up to date.
Rustc nightly.

When using RA with any version post 0.3.2896, I have some troubles with some completion.

For example

vec.push(MyEnum::MyEnumElement);

Up to 0.3.2896, when asking for the completion vec.push() inside the parentheses it will propose the MyEnum variant.
Past this version, I get in the output panel:

thread 'Worker3' (127983) panicked at crates/hir/src/lib.rs:6590:20:
failed to unify type owners
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::option::expect_failed
   3: hir::TypeOwnerId::must_unify
   4: hir::Type::could_unify_with_deeply
   5: hir::term_search::LookupTable::find
   6: hir::term_search::term_search
   7: ide_completion::completions::complete_name_ref
   8: ide_completion::completions
   9: ide::Analysis::completions
  10: rust_analyzer::handlers::request::handle_completion
  11: core::ops::function::FnOnce::call_once{{vtable.shim}}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
additional context:
   0: 
version: 0.3.2929-standalone
request: textDocument/completion CompletionParams {
    text_document_position: TextDocumentPositionParams {
        text_document: TextDocumentIdentifier {
            uri: Url {
                scheme: "file",
                cannot_be_a_base: false,
                username: "",
                password: None,
                host: None,
                port: None,
                path: "my_path",
                query: None,
                fragment: None,
            },
        },
        position: Position {
            line: 2826,
            character: 41,
        },
    },
    work_done_progress_params: WorkDoneProgressParams {
        work_done_token: None,
    },
    partial_result_params: PartialResultParams {
        partial_result_token: None,
    },
    context: Some(
        CompletionContext {
            trigger_kind: Invoked,
            trigger_character: None,
        },
    ),
}

[Error - 21:37:50] Request textDocument/completion failed.
  Message: request handler panicked: failed to unify type owners
  Code: -32603 

I modified the file path for the bug report.
The only cure is to revert back to 0.3.2896.

[A4-Tacks]

Can't reproduction in 0.4.2930-standalone

enum MuEnum { MyEnumElement }
fn main() {
    let mut vec: Vec<MuEnum> = vec![];
    vec.push(MuEnum::MyEnumElement);
}

Provide complete reproduction code and steps?

[ChayimFriedman2]

As @A4-Tacks said, please provide a complete reproduction.

[ThomasCartier]

I will try multiple versions of rustc and RA to try to minimize where the issue lies. Multiple projects of different size as well. I keep you updated quickly

[ThomasCartier]

It works just fine with very small projects where the enum is in the same file.
Try with a bigger crate.
Malachite for example. Go in the file https://github.com/mhogrefe/malachite/blob/master/malachite-nz/src/natural/mod.rs#L54.

Modify from

fn demote_if_small(&mut self) {
    if let Self(Large(limbs)) = self {
        match limbs.len() {
            0 => *self = Self::ZERO,
            1 => *self = Self(Small(limbs[0])),
            _ => {}
        }
    }
}

to

fn demote_if_small(&mut self) {
    let mut vec: Vec<InnerNatural> = vec![];

    vec.push()

    if let Self(Large(limbs)) = self {
        match limbs.len() {
            0 => *self = Self::ZERO,
            1 => *self = Self(Small(limbs[0])),
            _ => {}
        }
    }
}

Now click in the parentheses of the push method to get the auto complete: past v0.3.2896 (so it's starting with v0.3.2913) there is the error I reported. v0.3.2896 works just fine.

Again, with a very simple test case, it won't reproduce. You have to try on a larger project.
I tried with a previous rustc version, nightly-2026-02-15-x86_64-unknown-linux-gnu, same result as the latest nightly.