The programming language I want but doesn’t exist yet would be statically-typed. Ada, Scala, and Rust showed me all the advantages of programming with types. To simplify, these annotations are invaluable when designing interfaces and even deriving implementation from the type signatures! Also, I must stress I don’t think types are a replacement for tests.
Robert C. Martin wrote a blog explaining how dynamic typing can still be every bit as safe as static typing. The key is to approach software development in a different way: using TDD.