Open-source alternatives to Pytype

Sorbet is a static analysis tool and type checker designed for Ruby codebases. It identifies type inconsistencies, potential bugs, and logic errors by examining source code without execution, helping to improve software reliability and maintainability in large-scale projects. The system employs a constraint-based type inference engine that evaluates expressions against defined annotations to validate data structures. To support rapid development, it utilizes incremental analysis and caching to provide feedback by processing only modified files and their dependencies. Beyond static analysis,

MonkeyType is a runtime type inferencer and analysis tool for Python. It collects actual argument and return types from function calls during program execution to automate the production of static type annotations and compatible stub files. The system converts captured execution traces into static type hints, which can be inserted directly into source code function definitions or used to generate external type stubs. This process allows for the addition of type safety to existing codebases by analyzing real-world data types rather than through manual auditing. The tool's capabilities cover r

lua-language-server is a static analysis tool and type checker for the Lua language that implements the Language Server Protocol. It provides a system for detecting type mismatches, unused code, and logic errors in source files. The project features an inference-based type system that deduces variable types and supports optional annotations and meta files to enforce type safety. It allows for the definition of custom types and function signatures, including support for overloads and member visibility controls. The server provides a broad set of IDE capabilities, including real-time code auto

This project is a comprehensive guide and educational resource for the TypeScript language. It covers the fundamental principles of the language, including its structural type system, static type analysis, and the process of transpiling typed source files into JavaScript. The material details how to model complex data and reusable type logic using generics, conditional types, and mapped types. It also explains the use of declaration files to provide type safety for external JavaScript libraries and the integration of type checking into existing JavaScript projects via JSDoc annotations. The

Pyre is a high-performance static type checker and analysis tool for Python. It identifies type errors and ensures type safety without executing the program, utilizing a static type inference engine to maintain consistency across functions. The project is distinguished by an incremental type analysis engine that operates as a background daemon. This system monitors filesystem changes to re-validate only modified parts of a project, reducing the time required for repeated analysis. It also includes a static analysis security tool that uses taint analysis to track untrusted data flows and ident

This project is a high-performance static type checker and comprehensive development toolkit for Python. It functions as a core analysis engine that identifies type inconsistencies and enforces code correctness, while simultaneously providing a language server implementation to deliver real-time diagnostics and intelligence directly within development environments. The tool distinguishes itself through a parallelized execution engine that maximizes performance across large-scale codebases and monorepo structures. It supports gradual type adoption, allowing developers to integrate type checkin

The Concise TypeScript Book: A Concise Guide to Effective Development in TypeScript. Free and Open Source.

Phan is a static analyzer and type checker for PHP that identifies bugs and type incompatibilities without executing the code. It serves as a quality gate for continuous integration pipelines and a tool for verifying type safety, specifically checking union types, generics, and array shapes. The project is distinguished by its use of a background daemon and Language Server Protocol implementation, which provide real-time diagnostics and navigation within editors. It also features a baseline-based suppression system that allows developers to record existing errors in a snapshot file to focus e

Pyright is a static type checker for Python designed to validate type hints and identify potential errors within large codebases. It functions as a command-line utility that integrates into local development environments and continuous integration pipelines to ensure code quality and consistency. The tool distinguishes itself through a high-performance analysis engine that utilizes incremental dependency graph analysis and persistent state caching to re-evaluate only the affected portions of a project. By implementing the Language Server Protocol, it provides real-time feedback, including err

F# is a strongly typed, functional programming language and compiler for the .NET ecosystem. It transforms functional source code into Common Intermediate Language for execution on the .NET runtime and provides a foundational core library of primitive types and functions. The language emphasizes immutability and uses a static, constraint-based type inference system to automatically determine variable types without requiring explicit user annotations. It also functions as a Language Server Protocol provider, exposing compiler logic through a service-based API to deliver real-time code analysis

Frege is a purely functional programming language that compiles to JVM bytecode, providing Haskell-like semantics for the Java platform. It is built around a Haskell-inspired compiler that implements non-strict evaluation and a static type inference system to ensure data immutability and prevent side effects. The project distinguishes itself through a sophisticated type system featuring rank polymorphism, type-class based dispatch, and static purity enforcement. It includes a JVM language bridge and a foreign function interface that map Java classes and interfaces into functional types, allow

This project is a static analysis engine and type checker designed for PHP codebases. It evaluates source code structure and type annotations to identify potential bugs, type mismatches, and logic errors without executing the application. By parsing code into an abstract syntax tree and applying a rule-based validation framework, it enforces code quality and safety standards across a project. What distinguishes this tool is its sophisticated type inference engine, which models dynamic language features, magic methods, and conditional types to maintain accuracy even in unconventional code. It

flow-typed is a type definition manager, repository, and library designed to enable static type checking for third-party JavaScript libraries. It provides a curated collection of external type declarations that allow Flow projects to maintain type safety and error detection for non-typed dependencies. The project centers on a command-line interface used to install and update library type definitions from a remote source. This manager resolves compatible type versions based on a project's dependencies and maps them to local directories for use by a static type checker. Beyond type checking, t

cel-go is a Go implementation of the Common Expression Language, providing a type-safe engine for the evaluation of non-Turing complete, side-effect-free expressions. It functions as an embedded expression engine that converts human-readable strings into type-checked abstract syntax trees to ensure safe execution. The system utilizes a compile-once evaluate-many model, parsing and validating expressions into cached programs for repeated execution across different datasets. It further distinguishes itself as a partial state evaluator, using commutative logic to compute results and return resid

Flow is a JavaScript static type checker and AST parser that identifies type errors and prevents runtime failures through static annotations. It functions as a code intelligence engine and a static analysis linter to identify unsafe coding patterns and enforce consistency across a codebase. The project includes a type annotation stripper that removes static type signatures from source code, ensuring the resulting JavaScript is compatible with any runtime environment. It also provides a parser that converts typed JavaScript into an abstract syntax tree conforming to the ESTree specification.

Monty is a sandboxed execution environment designed primarily for running Python code generated by AI models. It provides a secure, isolated runtime that blocks host access, enforces resource limits, and supports pre-execution type checking against built-in type hints to catch signature mismatches before code runs. The sandbox can persist its interpreter state at external function calls, allowing execution sessions to be serialized, stored, and later resumed from a file or database. What distinguishes Monty is its combination of stateful, resumable execution with multi-language native embeddi

Roc is a statically typed, functional programming language built around immutable-by-default semantics, exhaustive pattern matching on tag unions, and a type system that combines optional explicit annotations with full compile-time type inference. Its core identity centers on correctness and expressiveness, using tagged unions for error handling with a question-mark operator for early error propagation, and a trailing-bang naming convention that makes side-effect boundaries syntactically visible at every call site. The language distinguishes itself through a platform-based I/O abstraction tha

jscamp is a full-stack web development and education project focused on mastering JavaScript, TypeScript, and AI integration. It provides a structured curriculum and interactive exercises covering language fundamentals, frontend engineering, and backend API development. The project distinguishes itself through the implementation of autonomous AI agents capable of complex task automation, such as modifying files, managing servers, and executing API calls. It includes advanced AI development tools for conversational querying, real-time code suggestions, and automated repository analysis to gene

pysheeet is a technical reference library providing a curated collection of code snippets and implementation patterns for advanced Python development, system integration, and high-performance computing. It serves as a comprehensive guide for implementing low-level network programming, native C extensions, and asynchronous and concurrent programming. The project provides specialized frameworks for the development and deployment of large language models, including tools for distributed GPU inference and high-performance serving. It also includes detailed patterns for high-performance computing

This project is a comprehensive, curated directory of static analysis, linting, and security scanning utilities. It serves as a central resource for developers to discover, compare, and select tools based on specific programming languages, licensing models, and integration requirements. The directory distinguishes itself by providing deep metadata for each listed utility, including community-driven popularity rankings, maintenance status, and deployment methods. By aggregating these tools into a single searchable index, it enables teams to identify solutions for enforcing coding standards, ma

flow-typed is a collection of curated type definitions for external JavaScript libraries and a manager for installing these definitions into Flow projects. It serves as a centralized repository of type declarations that enable static type checking and autocomplete for third-party dependencies that do not ship with their own types. The project provides a command line interface to fetch, inject, and update specific type definitions within a local project directory. This process ensures that external library imports are resolved by the Flow type checker through version-matched type mapping.

Awesome autocompletion, static analysis and refactoring library for python

Checkstyle is a Java static analysis tool and linter designed to identify and enforce coding standards and best practices. It functions as a code quality auditor and Javadoc validation tool, checking source code against configurable rulesets to ensure structural and stylistic consistency. The project allows for the creation of custom linting rules by extending a core API to inspect the abstract syntax tree. It further enables specialized validation through the use of XPath expressions to query the syntax tree for specific code patterns and violations. Capability areas include the enforcement

p3c is a Java static analysis tool and code quality linter designed to enforce professional coding guidelines and quality standards. It utilizes a set of custom rules based on the PMD engine to scan source code for style violations, performance bottlenecks, and potential bugs. The project is distributed as an IDE linting plugin that provides real-time feedback and warnings during development. It also includes functionality for pre-commit code quality gates, allowing modified files to be scanned and blocked if they violate defined rules before being committed to version control. The analysis

Pylint is a static code analyzer for Python that scans source code for errors, coding standard violations, code smells, and type-related issues without executing the program. It functions as a plugin-based linter framework, allowing users to extend its analysis capabilities with custom or third-party checks for project-specific rules and framework support. The tool also includes a duplicate code detector that identifies identical or near-identical code blocks across a project to help reduce redundancy. Beyond its core linting functionality, Pylint can generate UML class and package diagrams f

NullAway is a Java static analysis tool and build-time detector designed to identify null pointer risks. It functions as a nullability checker that uses annotations to verify that references are not null before they are dereferenced, preventing runtime crashes. The analyzer implements the JSpecify standard to ensure consistent nullability annotations across different Java libraries. It distinguishes itself through the use of a service provider interface to model the nullability behavior of third-party libraries that lack source annotations and by providing specialized support for Lombok-gener

SpotBugs is a static analysis tool and bytecode analyzer for Java applications. It scans compiled class files to identify bugs, security vulnerabilities, and performance issues without executing the code. The system functions as both a bug detector and a static application security testing tool to locate logical errors and API misuse. The project distinguishes itself through a plugin-based detector architecture that allows the integration of external libraries to add custom detection rules. It provides specialized security auditing for vulnerabilities such as SQL injection, cross-site scripti