Code completion not working in #[tokio::main]

[chanced]

rust-analyzer version: rust-analyzer version: 0.4.1232-standalone (476d043 2022-10-04)
rustc version: rustc 1.64.0 (a55dd71d5 2022-09-19)
relevant settings:

---

I'm not getting code completion in #[tokio::main] but it seems based on old issues that it should work?

Screen.Recording.2022-10-05.at.8.00.43.PM.mov

This is happening in a fresh project with the following Cargo.toml:

[package]
name = "example"
version = "0.1.0"
edition = "2021"

[dependencies]
tokio = { version = "1.21.2", features = ["full"] }

Sorry if I should have resurrected an old issue instead of starting a new one.

[fasterthanlime]

I can reproduce this with 0.3.1229-standalone on rustc 1.64 (and rustc 2022-10-08), even though rust-analyzer is able to expand the main! macro successfully, there's no completions in there, cf. #13373 (comment)

[fasterthanlime]

I've travelled to the past (through VSCode's "Install another version" menu) to confirm completions in tokio::main used to work:

That's with 0.3.1123 - so it broke sometime between 0.3.1123 and 0.3.1162 - will try to narrow it down further.

edit: 0.3.1131 still works.

edit: 0.3.1140 still works.

[fasterthanlime]

I've narrowed it down to:

• 0.3.1140-standalone (7e2b983fd 2022-07-24) (still works), and
• 0.3.1148-standalone (2b472f668 2022-07-31) (doesn't work)

Here's the relevant diff: 7e2b983...2b472f6

I'm going to try and bisect this.

Edit: while bisecting, I encountered "Broken pipe (os error 32)" at dadb832, so I'm going to try and switch to 1.63.0 for the rest of the bisection and hope it still tells us what we want to know.

[Veykril]

From a quick look (inserting a dbg!) it seems that our completion "analysis"(the part figuring out where we are completing things) is returning None (that is it fails to analyse the current position). A lot of things changed in that code path so its most likely a faulty ? placed somewhere

[fasterthanlime]

My bisection pointed to fba6adf, so I must've messed something up, unless doc comments are somehow load-bearing. Starting again... (with 1.63.0 the whole time).

[Veykril]

We are hitting this early return which disables completions

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

Line 421 in 61504c8

return None;

Which is kind of weird, because I don't think any code regarding this has changed there?

[Veykril]

Okay this seems to be a problem with the token mapping again, for some reason we are looking at the offset of the let keyword in this expansion instead of the s in the async block

[fasterthanlime]

New bisect result:

The merge base 977e12a is bad.
This means the bug has been fixed between 977e12a and [7e2b983].

Not sure what's going on with my git bisect usage today lol, it thinks I'm looking for a commit that fixed a bug?

[Veykril]

Ye those commits are not related I'm failry certain, so from what I've checked, the problem is that we map the token we are completing to the let keyword, because the tokio proc-macro re-uses the function body spans for the new output body and we just pick the first token there (not a lot we can do there better really I believe). What surprises me is why this only fails now, this behavior should've been the same even before ...

[fasterthanlime]

• 0.3.1140-standalone (7e2b983fd 2022-07-24) (still works), and

Upon closer inspection, it doesn't work with this version either (at least, with rustc 1.63.0). I'm going to stop posting comments until I can pinpoint it to one commit.

edit: I'm keeping track of my bisect work here https://gist.github.com/fasterthanlime/43142d7bb3bcae4869441852bcee830b

edit: latest bisect points to ebfbb31 (but that's for rustc 1.63.0, it seems that broke at a different place)

git bisect bad
ebfbb314c03cd8e70198eebf5a96ece8a2f79e51 is the first bad commit
commit ebfbb314c03cd8e70198eebf5a96ece8a2f79e51
Author: Jonas Schievink <jonas.schievink@ferrous-systems.com>
Date:   Tue Jul 12 15:13:04 2022 +0200

    Update 1.63 proc macro ABI to match rustc

 .../src/abis/abi_1_63/proc_macro/bridge/client.rs  |   8 --
 .../src/abis/abi_1_63/proc_macro/bridge/handle.rs  |  22 +++-
 .../src/abis/abi_1_63/proc_macro/bridge/mod.rs     | 136 ++++++++++++---------
 .../src/abis/abi_1_63/proc_macro/bridge/rpc.rs     |  53 ++++----
 .../src/abis/abi_1_63/proc_macro/bridge/server.rs  |  22 ++--
 .../src/abis/abi_1_63/proc_macro/mod.rs            |  96 ++++++++++++---
 .../src/abis/abi_1_63/rustc_server.rs              |  87 +++++++------
 7 files changed, 264 insertions(+), 160 deletions(-)

I can confirm that caf23f2 works, but ebfbb31 doesn't.