This is a declaration annotation that applies to type declarations and packages. On a type, it means that the class conceptually takes a type qualifier parameter, though there is nowhere to write it because the class hard-codes a Java basetype rather than taking a type parameter. Writing HasQualifierParameter on a package is the same as writing it on each class in that package.

Writing @HasQualifierParameter on a type declaration has two effects.

1. Invariant subtyping is used for occurrences of the type: no two occurrences of the type with different qualifiers have a subtyping relationship.
2. The polymorphic qualifier is the default for all occurrences of that type in its own compilation unit, including as the receiver, as another formal parameter, or as a return type.

Here is an example of the effect of invariant subtyping. Suppose we have the following declaration:

 @HasQualifierParameter
  class StringBuffer { ... }

Then @Tainted StringBuffer is unrelated to @Untainted StringBuffer.

The type hierarchy looks like this:

                      @Tainted Object
                     /       |       \
                    /        |       @Tainted Date
                  /          |               |
                 /           |               |
                /   @Untainted Object       |
               /             |       \       |
 @Tainted StringBuffer      |      @Untainted Date
            |                |
            |      @Untainted StringBuffer
            |                |
 @Tainted MyStringBuffer    |
                             |
                   @Untainted MyStringBuffer

When a class is @HasQualifierParameter, all its subclasses are as well.

When @HasQualifierParameter is written on a package, it is equivalent to writing that annotation on each class in the package or in a sub-package. It can be disabled on a specific class and its subclasses by writing @NoQualifierParameter on that class. This annotation may not be written on the same class as NoQualifierParameter for the same hierarchy.