Swift 6.2: Unavailable Sendable conformance emits an undesired warning for types that conform to SendableMetatype

[groue]

Description

It should be possible to conform to SendableMetatype via a protocol, and prevent Sendable conformance, without compiler warning.

Reproduction

protocol MyProtocol: SendableMetatype { }

class MyClass: MyProtocol { }

// Warning: Redundant conformance of 'MyClass' to protocol 'SendableMetatype'
@available(*, unavailable)
extension MyClass: Sendable { }

Expected behavior

protocol MyProtocol: SendableMetatype { }

class MyClass: MyProtocol { }

// No warning
@available(*, unavailable)
extension MyClass: Sendable { }

Environment

Swift 6.2, Xcode Version 26.0 beta (17A5241e)

Additional information

This code does not emit any warning, so it looks like the protocol is needed for the bug to express itself.

class MyClass: SendableMetatype { }

// No warning
@available(*, unavailable)
extension MyClass: Sendable { }