rust-analyzer

Provides symbol-based code completion by analyzing the current file and workspace through LSP, automatically resolving and inserting necessary imports. Uses Rust's type system and symbol table to rank suggestions contextually, enabling developers to complete code with full namespace awareness rather than simple text matching.

Performs real-time type inference using Hindley-Milner algorithm and displays inferred types as inline hints (parameter names, return types, closure captures) without requiring explicit annotations. Leverages LSP's inlay hint protocol to render non-intrusive overlays in the editor, updating incrementally as code changes.

Analyzes Cargo.toml and Cargo.lock to provide information about project dependencies, including version constraints, available updates, and dependency tree visualization. Displays dependency metadata on hover and provides quick actions to update or add dependencies.

Displays lifetime parameters and borrow checker information through inlay hints and hover tooltips, helping developers understand ownership and borrowing rules. Shows lifetime annotations, mutable/immutable borrow status, and move semantics through semantic highlighting and inline annotations.

Discovers Rust tests (functions marked with #[test] or in test modules) and provides UI elements (CodeLens) to run individual tests or test suites directly from the editor. Integrates with cargo test to execute tests and display results inline.

Integrates with rustfmt (Rust's standard code formatter) to automatically format code on save or on demand. Applies rustfmt's formatting rules to ensure consistent code style across the project. Respects rustfmt.toml configuration files.

Indexes all Rust symbols (functions, types, traits, modules) across the workspace and provides fast fuzzy search via LSP workspace symbol queries. Enables go-to-definition, go-to-implementation, and go-to-type-definition navigation by resolving symbol references through the project's dependency graph and module hierarchy.

Performs semantic tokenization (not just regex-based syntax highlighting) to color code Rust constructs based on their semantic role: traits, lifetimes, mutable bindings, unsafe blocks, and macro invocations. Uses LSP semantic tokens protocol to send fine-grained token information to the editor, enabling theme-aware coloring that reflects code semantics.

Performs real-time compilation-like analysis (without full compilation) to detect errors, warnings, and hints, displaying them as inline squiggles with quick-fix suggestions. Code assists (refactoring actions) are provided via LSP code action protocol, allowing one-click application of compiler suggestions like adding missing imports, fixing type mismatches, or applying lint suggestions.

Enables safe renaming of Rust symbols (functions, types, variables, modules) across the entire workspace by analyzing scope and visibility rules. Uses LSP rename protocol to compute all affected locations, respecting Rust's module system and visibility modifiers to avoid breaking changes or creating shadowing issues.

Locates all usages of a symbol (function, type, variable, trait) across the workspace and displays them in a structured list with code context. Uses LSP references protocol to compute all locations where a symbol is read, written, or referenced, filtering by scope and visibility to avoid false positives.

Displays comprehensive information on hover, including inferred types, function signatures, documentation comments, and trait bounds. Fetches documentation from Cargo dependencies and renders it with syntax highlighting, enabling developers to understand APIs without leaving the editor or consulting external documentation.

Provides limited visibility into macro expansions by showing the expanded code in a preview panel, enabling developers to understand what code a macro generates. Uses Rust's macro expansion engine (via rustc) to compute expansions, but does not provide semantic analysis of expanded code (type checking, completion, etc.).

Discovers Rust test functions (marked with #[test] or #[tokio::test]) across the workspace and provides inline UI to run, debug, or profile individual tests or test suites. Integrates with VSCode's test explorer and provides real-time test results with pass/fail status and execution time.