Recognize OpenDaylight's Immutable interface contract

[rovarga]

Aside from recognizing annotations, also treat any class that implements
an interface named Immutable as an immutable class. Fixes #1697.

Signed-off-by: Robert Varga robert.varga@pantheon.tech

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• Added an entry into CHANGELOG.md if you have changed SpotBugs code

[rovarga]

This will be reworked on top of #1704

[rovarga]

This builds on top of #1705

[ThrawnCA]

Please avoid force-pushing; it wrecks the history.

[KengoTODA]

The marker interface has no meaning in the bytecode level; annotated classes still be able to be mutable. Then I suggest not to merge this change but enhance the mutability check algorithm to reduce false positive and false negative.

[rovarga]

Please avoid force-pushing; it wrecks the history.

Ack

[rovarga]

The marker interface has no meaning in the bytecode level; annotated classes still be able to be mutable. Then I suggest not to merge this change but enhance the mutability check algorithm to reduce false positive and false negative.

That depends on what the expectations on MutableClasses are from three perspectives:

• perfomance, i.e. the depth of reasoning we make about the JavaClass
• accuracy of reported boolean
• what assumptions are made about the JavaClass: is it any reference we see? is it something we can load? is it a class that is part of the project being analyzed or is it on classpath? have we already performed bytecode/dataflow analysis on it to conclusively prove it is mutable (or immutable)?

At the end of the day, we are trusting @Immutable annotations here and this just uses a different aspect of what shape the class has.