typemodule

Typemodule is a term used in some programming language ecosystems to describe a module whose primary purpose is to declare and organize type information rather than runtime values. A typemodule typically contains abstract type declarations, type aliases, and interfaces or signatures that constrain what types can be used in other parts of the program. It may also define type-level constructs such as type classes or traits in languages that support them. In contrast to modules that primarily export data constructors, functions, or values, a typemodule focuses on the shape and constraints of data rather than on concrete implementations.

Typemodules are used to encapsulate and hide implementations behind an abstract type, enabling a stable surface for clients while allowing the internal representation to change. They support separation of concerns by isolating type ambiguities, enabling safer refactoring and stronger guarantees about how data can be manipulated. In many languages, typemodules support abstraction boundaries that make it possible to evolve the underlying implementation without affecting users of the module.

In languages with strong module systems, typemodules may align with concepts such as module signatures, interfaces, or type-only namespaces. They often pair with value modules that provide concrete implementations, allowing a clear division between type-level contracts and runtime code. While the exact syntax and guarantees vary by language, the core idea remains: to organize and enforce type information independently of concrete values, improving modularity and type safety.