Pyrefly

Pyrefly is a fast type checker and language server for Python, developed by Meta and written in Rust. It provides lightning-fast static type checking along with powerful IDE features such as code navigation, semantic highlighting, and code completion. Pyrefly aims to catch type-related errors before runtime, improve code quality, and enhance the developer experience. It is available as a command-line tool and an IDE extension, with new releases typically every Monday and more frequent updates for new features and bug fixes.