API breakage tool fails to detect default protocol implementations

[0xTim]

Description

When adding a new function to a protocol in an API, the API Diff tool doesn't handle default implementations correctly. New requirements satisfied with a default implementation should not be marked as an API breaking change

Expected behavior

Default function implementations are handled correctly, no error reported

Actual behavior

Error reported saying API has breaking changes

Steps to reproduce

• Have a public protocol on main
• Switch to a new branch add-api
• Add a new function to the protocol and a default implementation in an extension
• Run swift package diagnose-api-breaking-changes main

Swift Package Manager version/commit hash

5.6.1

Swift & OS version (output of swift --version && uname -a)

swift-driver version: 1.45.2 Apple Swift version 5.6.1 (swiftlang-5.6.0.323.66 clang-1316.0.20.12) Target: arm64-apple-macosx12.0 Darwin Tims-MBP-2021.brokenhands.net 21.6.0 Darwin Kernel Version 21.6.0: Sat Jun 18 17:07:22 PDT 2022; root:xnu-8020.140.41~1/RELEASE_ARM64_T6000 arm64

[tomerd]

@akyrtzi I assume this belongs with api-digester, which SwiftPM shells out for this purpose. where should this be reported?

[akyrtzi]

\cc @nkcsgexi