Error with `rowan 0.15.16`: `protocol error: InternalError: request handler panicked: tree is mutable` when asking for documentation in big crate graphs

rust-analyzer version: 07659783fdfd4ec0a0bffa93017e33e31e567e42

rustc version: rustc 1.80.1 (3f5fd8dd4 2024-08-06)

editor or extension: hx

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTC, RUSTUP_HOME or CARGO_HOME) none of those

code snippet to reproduce:

cd /tmp
cargo new --bin repro
cd repro
cargo add bevy
hx src/main.rs

fn main() {
    println!("Hello, world!");
}

Asking for documentation on println! fails with protocol error: InternalError: request handler panicked: tree is mutable, which comes from here I think: https://github.com/rust-lang/rust-analyzer/blob/07659783fdfd4ec0a0bffa93017e33e31e567e42/crates/rust-analyzer/src/handlers/dispatch.rs#L268

I haven't found the string tree is mutable either in Helix or R-A nor in the vendored dependencies of either

Reproduce the failure with the provided cargo and Helix commands, using the bevy dependency and a documentation request on println!. Start at crates/rust-analyzer/src/handlers/dispatch.rs around line 268 and trace the request path that produces the “tree is mutable” panic. Done means the documentation request no longer returns the internal handler-panic error for the reproduction.