You've always been able to have type holes at the ghci prompt - wrap your expression in a lambda and see what's inferred as the first argument.
That's not to say the ability to do it in the middle of a program isn't huge - it is! - but just a technique I have occasionally found quite useful that's available to those stuck on older versions of ghc.
That's not to say the ability to do it in the middle of a program isn't huge - it is! - but just a technique I have occasionally found quite useful that's available to those stuck on older versions of ghc.