Warn if @DefaultQualifier is used where @DefaultQualifierInHierarchy should be used

The @DefaultQualifier and @DefaultQualifierInHierarchy annotations have very
similar names, so it is easy to misuse one where the other is necessary.

It would be good for the Checker Framework to issue an error message if
@DefaultQualifier is written on an annotation definition.

Here are two ways this could be done:

• when compiling an annotation (@interface) definition, issue a warning if it is meta-annotated with @DefaultQualifier. This is the most direct approach, but an annotation definition is not necessarily compiled using a pluggable type-checker.

• when using a pluggable type-checker, whenever an annotation is used, determine its meta-annotations and issue a warning if those include @DefaultQualifier.

Original issue reported on code.google.com by mer...@cs.washington.edu on 24 Mar 2014 at 4:50

No files, tests, or entry points are named. Start by tracing how the Checker Framework handles annotation definitions and annotation meta-annotations, then compare the two warning approaches described in the issue; done means a misuse of @DefaultQualifier where @DefaultQualifierInHierarchy is required produces an error or warning.