At which situations does implicit conversion happen?

[Wasabi375]

@jazzinpark

What I have understood from above section of the documentation is:

• For assignments = , implicit type conversion happens

No, it doesn’t. Kotlin doesn’t have implicit type conversion. There is one exception with number literals.
So val foo: Long = 1 is ok even though 1 as a literal generally is of type Int.

@jazzinpark

The documentation says this has to do with the operator overloading.
How is this operator overloading implemented under the hood?
I tried to find the source code at Github https://github.com/JetBrains/kotlin/blob/master/core/builtins/native/kotlin/Primitives.kt ,
but here the functions are only declared but not implemented. Where can I find the implementations?

This is indeed done by operator overloading. The reason you can’t find the implementations is that they are directly translated into the specific jvm bytecode instructions. I don’t know the compiler well enough to point to a specific file (if this is even possible).

@jazzinpark

It seems that operation overloading does not actually perform type conversion. Do we just implementing all possible functions with same name but different parameter type signatures, so that the type is inferred, then the function with the matching signature is selected?

Yes. The standard library contains a plus method for each combination of Number types. If you were to add a new class extending Number you would need to provide your own implementations of those functions or you couldn’t use mathmatical operators.