Top 9 typechecker open source projects

TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

Optional static typing for Python

Performant type-checking for python.

A static type analyzer for Python code

AlphaSQL provides Integrated Type and Schema Check and Parallelization for SQL file set mainly for BigQuery

Python 2.7 & 3.5+ runtime type-checker

Statically typechecks a common SQL dialect and translates it to various RDBMS backends

Validate Method Arguments & Results in Ruby

Utilities to get and check variable types (isString, isPlainObject, isRegExp, etc)