equals.kt

class A()
class B<T>()

fun <T> A.f(b: B<T>) {
    val eq = this == b // Error: Operator '==' cannot be applied to 'A' and 'B<T>'
}

class A2<T>()
class B2<T>()

fun <T> A2<T>.f(b: B2<T>) {
    val eq = this == b // No error here
}