[Sumarizing from an irc conversation]

Phan can statically detect when an extension calls a non public method, a missing method or a deprecated method.

It would be super cool if we could use this to, on every mediawiki release candidate generate a list of extensions likely (newly) broken by the release (for calling a now missing method) or that need updating as they are now calling a deprecated method. This can provide an extra kick to ext authors that something needs to be done before new mw is released, and also help 3rd parties know which extemsions are likely to have issues.

The biggest issue is probably false positives around method_exists() legacy code and cross ext dependencies.

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