What would Your_Favorite_Compiler do?
gaius:     # let x = 10;;
    val x : int = 10
    # let y = x + ++x;;
    Error: Syntax error


Hmm. Let's try that again:    # let x = ref 10;;
    val x : int ref = {contents = 10}
    # let y = !x + incr x;;
    Error: This expression has type unit but an expression was expected of type int


So nothing, I guess!