Hi! This is my first contribution to rust-analyzer - I hope I'm following the right approach.

Problem

When rust-analyzer encounters "unknown literal prefix" errors, they can sometimes be caused by unterminated string literals earlier in the code. This makes debugging confusing because the error points to a distant location rather than the actual missing quote.

For example:

fn main() {
    hello("world);
    // a bunch of code was here
    env("FLAGS", "-help")
}

Solution

Added simple quote balance detection to provide helpful hints when this situation occurs:

• When an "unknown literal prefix" error happens, check for unbalanced quotes in the preceding 500 characters
• If odd number of quotes found, add a note suggesting to check for unterminated string literals
• If even number, show normal error message

Before:

error: unknown literal prefix `help`

After:

error: unknown literal prefix `help` (note: check for unterminated string literal)

Implementation

• File: crates/parser/src/lexed_str.rs
• Lines added: 8 (very minimal change)
• Performance: Only checks recent text when error occurs
• Safety: Non-breaking, only enhances existing error messages

The implementation follows rust-analyzer's style of simple, reliable improvements. I tried to keep it as minimal as possible while still being helpful.

I'd really appreciate any feedback on the approach or implementation! Thank you for considering this contribution.