This is possible with statically typed languages with Haskell being one of the examples where it's encouraged to use the REPL to work towards a solution and/or qucikly test ideas without having to write unit tests or full program tests. Ocaml and friends fall within this category too and none require extensive type annotation due to type inference.

I feel that too much focus is on static languages like C/C++ where types become a chore and judging it on that rather than looking at the plenty of languages with type inference brought by ML-style languages.