Rust syntax highlighting stopped working after upgrade to 25.07

[oyvind-ege]

Summary

After upgrading to 25.07, syntax highlighting for Rust stopped working, and the logs contain errors related to rust-analyzer. Downgrading to version 25.01.1 solves the problem.

Context

• Rust version 1.88, rust-analyzer 1.88
• Single rust-analyzer binary located in .cargo
• Reinstalled both Helix and Rust/rust-analyzer, to no avail
• Ran hx -g fetch && hx -g build

Reproduction Steps

Rust-version 1.88

I tried this:

1. Upgrade to 25.07
2. Open a Rust project in helix

I expected this to happen:

Syntax highlighting to work as intended, and rust-analyzer to run without fatal errors.

Instead, this happened:

Syntax highlighting does not work, and helix logs contains multiple rust-analyzer errors. Downgrading to 25.01.1 solves the issue.

Helix log

~/.cache/helix/helix.log

...
2025-07-16T11:55:55.799 helix_lsp::transport [ERROR] rust-analyzer err <- "\n"
2025-07-16T11:55:55.799 helix_lsp::transport [ERROR] rust-analyzer err <- "thread 'PrimeCaches#2' panicked at /rust/deps/thin-vec-0.2.14/src/lib.rs:1061:51:\n"
2025-07-16T11:55:55.799 helix_lsp::transport [ERROR] rust-analyzer err <- "capacity overflow\n"
2025-07-16T11:55:55.799 helix_lsp::transport [ERROR] rust-analyzer err <- "stack backtrace:\n"
2025-07-16T11:55:55.993 helix_lsp::transport [ERROR] rust-analyzer err <- "   0: __rustc::rust_begin_unwind\n"
2025-07-16T11:55:55.993 helix_lsp::transport [ERROR] rust-analyzer err <- "   1: core::panicking::panic_fmt\n"
2025-07-16T11:55:55.994 helix_lsp::transport [ERROR] rust-analyzer err <- "   2: core::option::expect_failed\n"
2025-07-16T11:55:55.994 helix_lsp::transport [ERROR] rust-analyzer err <- "   3: <thin_vec::ThinVec<salsa::table::memo::MemoEntry>>::reserve\n"
2025-07-16T11:55:55.994 helix_lsp::transport [ERROR] rust-analyzer err <- "   4: <salsa::function::IngredientImpl<<_ as hir_def::db::DefDatabase>::impl_signature_with_source_map::impl_signature_with_source_map_shim::Configuration_>>::execute\n"
2025-07-16T11:55:55.995 helix_lsp::transport [ERROR] rust-analyzer err <- "   5: <salsa::function::IngredientImpl<<_ as hir_def::db::DefDatabase>::impl_signature_with_source_map::impl_signature_with_source_map_shim::Configuration_>>::fetch_cold\n"
2025-07-16T11:55:55.995 helix_lsp::transport [ERROR] rust-analyzer err <- "   6: <_ as hir_def::db::DefDatabase>::impl_signature_with_source_map::impl_signature_with_source_map_shim\n"
2025-07-16T11:55:55.995 helix_lsp::transport [ERROR] rust-analyzer err <- "   7: <salsa::function::IngredientImpl<<_ as hir_def::db::DefDatabase>::impl_signature::impl_signature_shim::Configuration_>>::execute\n"
2025-07-16T11:55:55.996 helix_lsp::transport [ERROR] rust-analyzer err <- "   8: <salsa::function::IngredientImpl<<_ as hir_def::db::DefDatabase>::impl_signature::impl_signature_shim::Configuration_>>::fetch_cold\n"
2025-07-16T11:55:55.996 helix_lsp::transport [ERROR] rust-analyzer err <- "   9: <_ as hir_def::db::DefDatabase>::impl_signature::impl_signature_shim\n"
2025-07-16T11:55:55.996 helix_lsp::transport [ERROR] rust-analyzer err <- "  10: <hir::symbols::SymbolCollector>::do_work::{closure#1}\n"
2025-07-16T11:55:55.996 helix_lsp::transport [ERROR] rust-analyzer err <- "  11: <hir::symbols::SymbolCollector>::collect\n"
2025-07-16T11:55:55.997 helix_lsp::transport [ERROR] rust-analyzer err <- "  12: <<_ as ide_db::symbol_index::SymbolsDatabase>::module_symbols::module_symbols_shim::Configuration_ as salsa::function::Configuration>::execute\n"
2025-07-16T11:55:55.998 helix_lsp::transport [ERROR] rust-analyzer err <- "  13: <salsa::function::IngredientImpl<<_ as ide_db::symbol_index::SymbolsDatabase>::module_symbols::module_symbols_shim::Configuration_>>::execute\n"
2025-07-16T11:55:55.998 helix_lsp::transport [ERROR] rust-analyzer err <- "  14: <salsa::function::IngredientImpl<<_ as ide_db::symbol_index::SymbolsDatabase>::module_symbols::module_symbols_shim::Configuration_>>::fetch_cold\n"
2025-07-16T11:55:55.998 helix_lsp::transport [ERROR] rust-analyzer err <- "  15: <_ as ide_db::symbol_index::SymbolsDatabase>::module_symbols::module_symbols_shim\n"
2025-07-16T11:55:55.999 helix_lsp::transport [ERROR] rust-analyzer err <- "  16: ide_db::symbol_index::crate_symbols\n"
2025-07-16T11:55:56.000 helix_lsp::transport [ERROR] rust-analyzer err <- "note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "query stacktrace:\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "   0: impl_signature_shim(Id(3f0b3)) -> (R1, Durability::HIGH)\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "             at src/tools/rust-analyzer/crates/hir-def/src/db.rs:101\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "   1: module_symbols_shim(Id(7800)) -> (R4099, Durability::MEDIUM)\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "             at src/tools/rust-analyzer/crates/ide-db/src/symbol_index.rs:99\n"
2025-07-16T11:55:56.001 helix_lsp::transport [ERROR] rust-analyzer err <- "\n"
2025-07-16T12:02:57.900 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:06:39.965 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:06:55.456 helix_lsp::transport [ERROR] rust-analyzer err: <- StreamClosed
2025-07-16T12:07:07.514 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:10:06.485 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:13:35.405 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:13:46.980 helix_lsp::transport [ERROR] rust-analyzer err: <- StreamClosed
2025-07-16T12:13:53.094 helix_lsp::transport [ERROR] rust-analyzer <- ServerError(-32801): content modified
2025-07-16T12:13:53.097 helix_term::handlers::signature_help [ERROR] signature help request failed: protocol error: ServerError(-32801): content modified
2025-07-16T12:13:53.996 helix_view::document [ERROR] Formatter error: error[E0670]: `async fn` is not permitted in Rust 2015
  --> <stdin>:65:1
   |
65 | async fn main() -> Result<(), AppError> {
   | ^^^^^ to use `async fn`, switch to Rust 2018 or later
   |
   = help: pass `--edition 2024` to `rustc`
   = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:106:1
    |
106 | async fn setup_db(State(state): State<SharedState>) -> Result<(), AppError> {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:114:1
    |
114 | async fn get_all_projects(State(state): State<SharedState>) -> APIResponse {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:119:1
    |
119 | async fn get_single_project(State(state): State<SharedState>, Path(id): Path<usize>) -> APIResponse {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:130:1
    |
130 | async fn add_project(State(state): State<SharedState>, Json(payload): Json<CreateProject>) -> Result<APIResponse, StatusCode> {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide


2025-07-16T12:14:07.420 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:15:05.311 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:18:50.760 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:21:37.965 helix_lsp::transport [ERROR] rust-analyzer err: <- StreamClosed
2025-07-16T12:22:47.602 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:27:06.002 helix_lsp::transport [ERROR] rust-analyzer err: <- StreamClosed
2025-07-16T12:27:10.757 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:27:33.082 helix_view::document [ERROR] Formatter error: error[E0670]: `async fn` is not permitted in Rust 2015
  --> <stdin>:65:1
   |
65 | async fn main() -> Result<(), AppError> {
   | ^^^^^ to use `async fn`, switch to Rust 2018 or later
   |
   = help: pass `--edition 2024` to `rustc`
   = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:106:1
    |
106 | async fn setup_db(State(state): State<SharedState>) -> Result<(), AppError> {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:114:1
    |
114 | async fn get_all_projects(State(state): State<SharedState>) -> APIResponse {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:119:1
    |
119 | async fn get_single_project(State(state): State<SharedState>, Path(id): Path<usize>) -> APIResponse {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0670]: `async fn` is not permitted in Rust 2015
   --> <stdin>:130:1
    |
130 | async fn add_project(State(state): State<SharedState>, Json(payload): Json<CreateProject>) -> Result<APIResponse, StatusCode> {
    | ^^^^^ to use `async fn`, switch to Rust 2018 or later
    |
    = help: pass `--edition 2024` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide


2025-07-16T12:30:50.230 helix_view::document [WARN] Error building syntax for '~/.cache/helix/helix.log': configured timeout was exceeded
2025-07-16T12:30:55.489 helix_lsp::transport [ERROR] rust-analyzer err: <- StreamClosed

Platform

macOS

Terminal Emulator

rio

Installation Method

brew

Helix Version

helix 25.07

[the-mikedavis]

Syntax highlighting is provided by tree-sitter rather than the language server. If you aren't seeing any highlights at all then try uninstalling and reinstalling the runtime directory https://docs.helix-editor.com/building-from-source.html#configuring-helixs-runtime-files

[oyvind-ege]

I did. I deleted the runtime directory and reinstalled, and I kept the same runtime directory when downgrading from 25.07 to 25.01.1. Syntax highlighting only works with 25.01.1.

[dessalines]

Thx. I also had this problem, and it was fixed by force removing that dir and reinstalling. For arch-based:

rm -rf ~/.config/helix/runtime
yay -S helix

[RuairidhWilliamson]

As recommended above rm -rf ~/.config/helix/runtime helps but I am documenting my mistake in case it helps anyone else.

I had also overridden the rust language grammar commit in my ~/.config/helix/languages.toml:

[[grammar]]
name = "rust"
source = { git = "https://github.com/tree-sitter/tree-sitter-rust", rev = "9c84af007b0f144954adb26b3f336495cbb320a7" }

This means it fetches and rebuilds an old version of the grammar that does not support gen_block which was added to the rust highlight.scm in helix between 25.07 and 25.01.1. You get this in the helix log:

2025-07-16T18:26:33.056 helix_core::syntax [ERROR] Failed to compile highlights for 'rust': invalid node type "gen_block"
  --> 215:2
     |
 214 |   "for" @keyword.control.repeat)
 215 | (gen_block "gen" @keyword.control)
     |  ^^^^^^^^^
     |

Simply removing the rust grammar config from my languages.toml, fetching and rebuilding the grammars fixed it.

[oyvind-ege]

Thanks a lot for your patience. I must have done something wrong the first time around, because deleting the runtime directory and reinstalling 25.07 with homebrew solved the issue.

[MeiramSh]

What about 25.07 compiled from source?

Could you provide minimal example?

Try to reproduce the issue with boilerplate cargo init hello world project. If the lsp won't crash, try to add snippet which will crash it.

Also, Rust-analyzer version would be pretty helpful