For languages that do not have REPLs I usually just write unit tests.
This works particularly well for Java as the Eclipse compiler iteratively compiles and most IDEs will let you run a single method.
I imagine a similar stopgap could be used for Rust. I know its not the same but in some ways I have sort of disliked REPLs because its is very easy to accidentally delete or loose what you have type and you might as well make your playing around a test (just my 2 cents).
This works particularly well for Java as the Eclipse compiler iteratively compiles and most IDEs will let you run a single method.
I imagine a similar stopgap could be used for Rust. I know its not the same but in some ways I have sort of disliked REPLs because its is very easy to accidentally delete or loose what you have type and you might as well make your playing around a test (just my 2 cents).