Type Inference
Wyn supports Hindley-Milner-style type inference, so in many cases explicit type annotations can be left off. Record field projection cannot in isolation be fully inferred, and may need type annotations where their inputs are bound. The same goes when constructing sum types, as Wyn cannot assume that a given constructor only belongs to a single type. Further, consumed parameters (see In-place updates) must be explicitly annotated.
Type inference processes top-level declared in top-down order, and the type of a top-level function must be completely inferred at its definition site. Specifically, if a top-level function uses overloaded arithmetic operators, the resolution of those overloads cannot be influenced by later uses of the function.
Local bindings made with let are not made polymorphic through let-generalisation unless they are syntactically functions, meaning they have at least one named parameter.