Thankfully that would be a simple compile-time error. The message might even be readable.
If you type var and mean val - would there be any error?
(I'm sure that this is just something you need to get used to, I'm merely trying to point out that this could be a silent typo/mistake)
In actuality it will be extremely obvious in the IDE and the developer would not make this error.
if "val" is a constant, and you try to mutate it later, the compiler will tell you, "That ain't gonna happen."
In many cases, you would get warnings when accessing a var that you don't get when accessing a val. Also, IntelliJ suggests converting to val if a var is never reassigned.
As others said, not a problem if you are using an IDE (and a specific one.)
Considering who authored the language, I am not surprised at all.
It's even worse when your primary keyboard is Dvorak!