Module unification 

Type unification for Seq

Implements Hindley-Milner style unification with support for:

• Type variables (T, U, V)
• Row variables (..a, ..rest)
• Concrete types (Int, Bool, String)

Structs

Subst

Combined substitution environment

Functions

unify_stacks

Unify two stack types, returning a substitution or an error

unify_types

Unify two types, returning a substitution or an error

Type Aliases

RowSubst

Substitutions for row variables (stack type variables)

TypeSubst

Substitutions for type variables