Bug Report: Panic When Using Japanese Function Names in Rust Analyzer(boundary issue)

[nanae772]

rust-analyzer version: 0.3.2257-standalone

rustc version: rustc 1.83.0 (90b35a623 2024-11-26)

editor or extension: VSCode

Code Snippet to Reproduce

fn main() {
    あ // Typing "あ" here causes a panic.
}

fn あい() {}

Expected Behavior

Rust Analyzer should handle the input without errors.

Actual Behavior

Rust Analyzer panics with the following error message:

Panic context:
> 
version: 0.3.2257-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: "/home/kazune/workspace/hoge/src/main.rs",
                query: None,
                fragment: None,
            },
        },
        position: Position {
            line: 1,
            character: 5,
        },
    },
    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,
        },
    ),
}

thread 'Worker' panicked at crates/hir-def/src/import_map.rs:323:41:
byte index 1 is not a char boundary; it is inside 'あ' (bytes 0..3) of `あい`
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::str::slice_error_fail_rt
   3: core::str::slice_error_fail
   4: hir_def::import_map::SearchMode::check
   5: ide_db::symbol_index::Query::search_maps
   6: ide_db::items_locator::items_with_name
   7: ide_db::imports::import_assets::ImportAssets::search_for
   8: ide_db::imports::import_assets::ImportAssets::search_for_imports
   9: ide_completion::completions::flyimport::import_on_the_fly_path
  10: ide_completion::completions::complete_name_ref
  11: ide_completion::completions
  12: ide::Analysis::completions
  13: rust_analyzer::handlers::request::handle_completion
  14: core::ops::function::FnOnce::call_once{{vtable.shim}}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
[Error - 10:10:50 AM] Request textDocument/completion failed.
  Message: request handler panicked: byte index 1 is not a char boundary; it is inside 'あ' (bytes 0..3) of `あい`
  Code: -32603

Additional Information

The error appears to be related to how Rust Analyzer handles Unicode input, specifically in the context of Japanese characters. The error suggests a boundary issue with UTF-8 characters.

Please let me know if further details or logs are needed. Thank you for your support!