Rename refactoring produce syntactically incorrect code

[bazhenov]

rust-analyzer version: rust-analyzer version: 0.3.1394-standalone (0b32b65 2023-02-05)

rustc version: rustc 1.67.1 (d5a82bbd2 2023-02-07)

relevant settings: N/A

Consider following code:

struct Value {
    inner: u8,
}

#[tokio::main]
async fn main() {
    let value = Value { inner: 1 };
    let Value { inner } = value;
    println!("{}", inner);
}

If I'm trying to rename inner local variable on last line (println!("{}", inner);) I get broken code:

struct Value {
    inner: u8,
}

#[tokio::main]
async fninner: value() {
    let value = Value { inner: 1 };
    let Value { inner } = value;
    println!("{}", inner);
}

This happens wherever I use struct unpack syntax or match-statement. In both cases rust-analyzer reports incorrect TextEdit offsets back to IDE (vscode).

The problem seems to be related to #9403 and #13388 because manifest itself only in presence of #[tokio::main] or #[tokio::test] proc macro.

[bazhenov]

If surrounding function is not annotated with [tokio::main] everything work correctly and ide_db::rename::rename_reference() creates two TextEdits – one from source_edit_from_references() another one from source_edit_from_def(). It makes sense. When renaming such a trivial case we need to change two places in sources files.

But in presence of [tokio::main] some basic mechanism is broken. Like for example rust-analyzer can't rename even local variable in following code:

#[tokio::main]
async fn main() {
    let f = 2;
    println!("{}", f);
}

In this example when trying rename variable f, rust-analyzer correctly rename definition (source_edit_from_def()), but unable to find reference to a variables (source_edit_from_references()). This line produce empty usages –

rust-analyzer/crates/ide-db/src/rename.rs

Line 288 in a6603fc

let usages = def.usages(sema).all();

Later in FindUsages::search() I see that search_scope is pointing not to a function body (as in normal case) but to the macro mention before function definition (eg. #[tokio::main]). I suspect this has something to do with how tokio::main implemented.

[Veykril]

This is a known bug with proc-macros for r-a. r-a currently fails to properly handle macros re-using spans.

[bazhenov]

I wonder if there is a practical way it can be solved in general case? Proc macro can rewrite a TokenStream in any way. But r-a should somehow map tokens in the source file to tokens after proc-macro expansion. Is this even possible?

[Veykril]

This will be fixed once #9403 is implemented.
For now you can set

    "rust-analyzer.procMacro.ignored": {
        "tokio-macros": [
            "main"
        ]
    },

in your settings to get around this mostly

[Veykril]

This works now