Top 7 sum-types open source projects

A code generator enabling sum-types in Dart

ftor enables ML-like type-directed, functional programming with Javascript including reasonable debugging.

ADT sum type in typescript

A type-safe and space-efficient sum type for C# (comparable to discriminated unions in C or C++)

A namedtuple-style library for defining immutable sum types in Python.

Recursive Variant: A simple library for Recursive Variant Types

Elm Either