Redundant conformance error message Swift 2

You’ll get that error message in Xcode 7 (Swift 2) if a subclass declares conformance
to a protocol which is already inherited from a superclass. Example:

class MyClass : CustomStringConvertible {
    var description: String { return "MyClass" }
}

class Subclass : MyClass, CustomStringConvertible {
    override var description: String { return "Subclass" }
}

The error log shows:

main.swift:10:27: error: redundant conformance of 'Subclass' to protocol 'CustomStringConvertible'
class Subclass : MyClass, CustomStringConvertible {
                          ^
main.swift:10:7: note: 'Subclass' inherits conformance to protocol 'CustomStringConvertible' from superclass here
class Subclass : MyClass, CustomStringConvertible {
      ^

Removing the protocol conformance from the subclass declaration
solves the problem:

class Subclass : MyClass {
    override var description: String { return "Subclass" }
}

But the superclass must declare the conformance explicitly, it is
not automatically inferred from the existence of the description
property.