Pyrefly

Employs module-level incrementality and parallelism in Rust for rapid type analysis, explicitly designed to prioritize raw speed over fine-grained solving.

Uses flow types to refine static types based on control flow, such as inferring Literal[4] from x: int = 4, enhancing accuracy without extra annotations.

Provides extensions for VSCode, Neovim, Zed, and others, offering semantic highlighting, code navigation, and completion directly within popular editors.

Infers types for variables and return values in most locations, reducing the need for explicit annotations and speeding up adoption in existing codebases.