Hacker news had a link to Zuo recently:

• https://news.ycombinator.com/item?id=33560492

That has support for "struct", which seems to do a bunch of things. Given the following code:

   (struct person name age)

Generates a bunch of things:

• Generates a constructor
  • (set! person (fn* (name age))
• Generates a type check
  • `(set! person? (fn* (x) ... is x an instance of person)"
• Generates accessors for each field
  • (set! person-name (fn* (strct) (return strct.name)
  • (set! person-age (fn* (strct) (return strct.age)

More stuff wasn't immediately obvious, but I guess there are setters to match the getters. I guess the complication for implementation would be the creation of the methods, dynamically.