Why Sigil Uses Explicit Generics Without Hindley-Milner

Sigil now supports explicit parametric polymorphism, but it does not adopt Hindley-Milner as its user model.

What Sigil Wants from Generics

Generic abstractions such as Option[T], Result[T,E], and generic top-level helpers are useful because they reduce vocabulary growth. They let many programs reuse one abstraction instead of multiplying specialized wrappers for each type.

That fits Sigil well.

What Sigil Does Not Want

What Sigil does not want is implicit let-polymorphism on local bindings. That style of inference is compact, but it hides behavior behind checker cleverness in a place where Sigil prefers explicitness.

The language deliberately keeps the rule narrow:

• genericity is declared explicitly
• generic top-level declarations are real
• generic ADTs are real
• local bindings do not silently become polymorphic

Why This Fits Sigil

This split preserves the useful part of generics without importing a broader inference model that makes local reasoning less obvious. For Sigil, that is the important balance: reuse and abstraction are good, but hidden generalization is not.