---
title: LSP Support
description: How the Mist Language Server bridges editor requests through rust-analyzer.
icon: Server
---

The Mist Language Server Protocol implementation runs a headless `rust-analyzer` instance and bridges Mist editor requests to Rust positions.

### Architecture

```
Editor (LSP client)
    │
    ▼
┌─────────────────────┐
│   mist-analyzer     │
│   (Rust + Mist)     │
└─────────────────────┘
    │           ▲
    │  JSON-RPC │
    ▼           │
┌─────────────────────┐
│   rust-analyzer     │
│   (headless child)  │
└─────────────────────┘
```

### Flow

1. Editor sends Mist file edits to `mist-analyzer` via LSP
2. `mist-analyzer` transpiles Mist to Rust
3. The transpiled Rust is forwarded to the headless `rust-analyzer` process
4. For goto-definition, hover, and completion, a unique marker token is injected at the cursor position
5. The transpiled output with the marker is sent to `rust-analyzer`
6. The marker position is located in the response
7. Results are mapped back to Mist positions using the `rev_mapper`

### Key Features

- **Full document sync** — Open, change, save, close
- **Go to definition** — Maps through transpiled Rust positions
- **Completions** — Supports trigger characters `:`, `.`, `'`, `(`
- **Hover** — Type information and docs
- **Diagnostics** — Real-time errors from transpilation failures and Rust compilation
- **Formatting** — Document formatting support
- **Auto-import** — Automatically inserts `pub module <name>;` when new `.mist` files are created
- **File watching** — Monitors `**/*.mist` for new files

### Diagnostic Remapping

When a transpilation error occurs in the `mist-analyzer`:

1. Parse errors are converted to `Diagnostic` with Mist source positions
2. Semantic errors (uninitialized class fields) use the stored line/column
3. Rust compiler errors are remapped via the `Mapping` system back to Mist positions