I'm confused about operator overloading. say I've ...

# getting-started

[y]

I'm confused about operator overloading. say I've got a class Foo and I'd like to override Foo + String and String + Foo, such that both return a Foo.
the first part is easy enough, just implement operator fun plus(s: String): Foo inside the definition of class Foo.
for the second part, attempting to add an extension function operator fun String.plus(foo: Foo): Foo makes kotlin complain that I'm shadowing operator fun plus(other: Any?): String
is there a way around this (and should I even go that way)?

[Vampire]

It does not tell that you are shadowing that function, it tells you that function is shadowing your extension method as member functions always have precedence over extensions functions, so your extension function would never be used, so no.

[Robert Williams]

Just to add some context on why this would be a bad idea even if it were possible: it's a very common pattern (especially in Java so you may see it in converted code) to do something like

log("error in foo: " + myFoo);

with the expectation this would call myFoo.toString and add to the log message.
If what you propose were possible, it'd instead construct a new Foo and then call toString on that, which would be a completely unexpected and confusing log message.
There's probably even more serious things it would also break but this alone would be reason to avoid it.

[Daniel Pitts]

As an alternative, you could consider creating an infix function instead of operator overloading. This would allow similar reading of the code, but avoid operators

[y]

thanks everyone.