rust-analyzer - Finally, a Rust Language Server That Doesn't Suck

If you tried Rust before 2020, you probably remember the pain. RLS was so fucking slow that you'd hit Ctrl+S, go make coffee, and come back to see if your errors had loaded yet. VS Code would freeze, autocomplete would time out, and "restart language server" became muscle memory. I literally had a teammate quit a Rust project in 2019 because RLS kept crashing during a demo to the CEO.

rust-analyzer fixed all of that. Instead of waiting for rustc to compile your entire project just to tell you there's a missing semicolon, it analyzes your code incrementally. Changes show up instantly. Autocomplete actually works. The official LSP implementation that should have existed from day one.

The RFC that made rust-analyzer the official Rust LSP explains why the old tooling was insufficient. The first release announcement details the architectural improvements that make rust-analyzer so much faster than RLS.

The difference is night and day. RLS made Rust feel broken in editors. rust-analyzer makes it feel like a real programming language with proper tooling. No more 30-second compile cycles just to see if your function signature is right.

Architecture and Performance

Here's the technical bit that actually matters: rust-analyzer uses salsa for incremental computation. Instead of re-analyzing your entire codebase every time you add a semicolon, it caches results and only recomputes what changed. The Salsa algorithm explanation dives deep into how incremental computation works. This query-based system is why you get instant feedback instead of waiting for rustc.

The durable incrementality blog post explains recent optimizations that make rust-analyzer even faster. The architecture documentation shows how all the pieces fit together.

Performance is dramatically better than RLS. There's ongoing community discussion about optimizations, but rust-analyzer already kicks ass compared to the old tooling.

Yeah, it uses 200-500MB of RAM for medium projects (community benchmarks), but that's a fair trade for millisecond response times instead of the multi-second delays RLS inflicted on us. Your laptop can handle it, and the productivity gain is worth every megabyte.

It's got different modes depending on your project size:

• Full workspace analysis: Analyzes everything upfront - great for small to medium projects
• Lazy analysis: Only analyzes what you're actually looking at - saves your sanity on massive codebases
• Experimental flycheck: Shows errors as you type without full compilation - like having a compiler that doesn't hate you

Works in Your Actual Editor

The beauty of Language Server Protocol is that rust-analyzer works everywhere. Unlike IntelliJ's proprietary plugin that locks you into their ecosystem, LSP means you get the same features whether you're in VS Code, Neovim, Emacs, or whatever editor you prefer.

You get all the good stuff:

• Smart syntax highlighting: Colors that actually mean something, not just keyword matching
• Instant refactoring: Rename variables across your entire project without breaking anything
• Symbol search: Find that function you wrote last week anywhere in your workspace
• Go-to everything: Click on a type and actually land on its definition
• Call hierarchy: See where your functions are used without grep

Because it uses LSP, you're not stuck with one editor's half-baked Rust support. Works in VS Code, Neovim, whatever you use. The LSP server implementation is open source and well-documented. When shit breaks, the community support forums actually help. The GitHub discussions are active with both users and maintainers.

Forget the marketing bullshit - here's what rust-analyzer does that will save your ass during development.

Autocomplete That Doesn't Suck

The autocomplete engine actually understands Rust's type system instead of just matching strings like a drunk regex. Type Vec:: and it shows you the methods that actually exist on Vec, not every function in your codebase that starts with "v".

When you're deep in generic hell and need to call .into() for the fifteenth time, rust-analyzer knows what types are expected and only suggests conversions that will actually compile. This isn't magic - it's just a language server that actually parses your code instead of giving up.

The import suggestions are smart too. Hit Ctrl+Space on an undefined struct and rust-analyzer adds the use statement automatically. No more scrolling to the top of the file to figure out which crate exports what.

// Type this
Result<String, E>
// Get suggestions for actual error types, not random bullshit

Best part? It works inside macros. Try using autocomplete in a serde derive macro - rust-analyzer knows the field names and suggests the right attributes. RLS would just give up and show you nothing.

Refactoring Without Breaking Everything

The refactoring tools don't just move text around like sed scripts. They understand Rust's ownership rules and won't suggest changes that'll make the borrow checker shit itself.

Extract a function? rust-analyzer figures out the right parameter types and return values. No more "expected &str, found String" errors because your IDE doesn't understand lifetimes. The extract function assist actually works:

// Select this mess
let data = expensive_computation(input);
let processed = data.transform();
let result = processed.finalize();

// Hit Ctrl+. and pick "Extract into function" (finally, an IDE feature that works)
// Get working code with correct types and lifetimes
// Note: this broke in v0.3.2540 and got fixed in v0.3.2545 - typical week in Rust land

Variable renaming works across your entire workspace, including inside macro expansions. Try renaming a struct field that's used in derive macros - rust-analyzer finds all the generated code too.

The "inline variable" assist is clutch when refactoring. It removes one-use variables and inlines them at call sites, but only when it won't break lifetimes or move semantics.

Error Detection That's Not Useless

rust-analyzer shows you errors as you type, not after you wait 30 seconds for compilation. The real-time diagnostics catch the obvious shit immediately:

• Missing semicolons (before you save)
• Type mismatches (before you compile)
• Dead code warnings (before you push)
• Clippy lints (before your teammates mock your code)

When you hover over an error, you get actual explanations and fix suggestions, not just "mismatched types" with no context. The error messages link to rustc's detailed explanations so you can understand why the borrow checker is pissed at you this time.

The unused code detection is aggressive but smart. It'll gray out dead functions but won't complain about #[allow(dead_code)] items or things that are only used in tests.

Macro Expansion That Actually Works

This is where rust-analyzer shines and other IDEs eat shit. Procedural macros are notoriously difficult for static analysis, but rust-analyzer handles them better than anything else.

Hit "Expand macro" on a serde derive and see exactly what code gets generated. No more guessing what field names the macro creates or why your Serialize implementation is broken.

The macro-aware autocomplete works inside format!, println!, and custom macros. Try typing inside a tokio::main macro - rust-analyzer knows you're in an async context and suggests .await on futures.

When proc macros fail to expand (because proc macros are cursed), rust-analyzer degrades gracefully instead of showing you nothing. You still get basic completion and error detection even if the macro expansion is broken. Learned this the hard way when syn 2.0 broke half our custom derives and took me 3 hours to figure out why rust-analyzer was only showing basic completions.

Turn on rust-analyzer.procMacro.enable and watch previously dark magic become visible. Your serde-heavy codebases suddenly make sense again.

Performance Tuning and Configuration

If rust-analyzer is being slow or eating too much RAM, there are tons of config options to tune it. Memory settings, cargo check tweaks, whatever you need. When things break, check Stack Overflow for the common fixes.