Covariant methods and Join Point matching
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## Covariant methods and Join Point matching

The join point matching rules for `call` and `execution` pointcut designators are extended to match against covariant methods.

Given the classes `A` and `B` as defined in the previous section, and the program fragment

    		A a = new A();
    		B b = new B();
    		a.whoAreYou();
    		b.whoAreYou();

The signatures for the call join point `a.whoAreYou()` are simply:

    		A A.whoAreYou()

The signatures for the call join point `b.whoAreYou()` are:

    		A A.whoAreYou()
    		B B.whoAreYou()

Following the join point matching rules given in Join Point Signatures,

call(* whoAreYou())

  Matches both calls, (since each call join point has at least one matching signature).

call(* A.whoAreYou())

  Matches both calls, (since each call join point has at least one matching signature).

call(A whoAreYou())

  Matches both calls, (since each call join point has at least one matching signature).

call(A B.whoAreYou())

  Does not match anything - neither of the call join points has a signature matched by this pattern. A lint warning is given for the call `a.whoAreYou()` ("does not match because declaring type is A, if match required use target(B)").

call(A+ B.whoAreYou())

  Matches the call to `b.whoAreYou()` since the signature pattern matches the signature `B B.whoAreYou()`. A lint warning is given for the call `a.whoAreYou()` ("does not match because declaring type is A, if match required use target(B)").

call(B A.whoAreYou())

  Does not match anything since neither join point has a signature matched by this pattern.

call(B whoAreYou())

  Matches the call to `b.whoAreYou()` only.

call(B B.whoAreYou())

  Matches the call to `b.whoAreYou()` only.

The rule for signature matching at call and execution join points is unchanged from AspectJ 1.2: a call or execution pointcut matches if the signature pattern matches at least one of the signatures of the join point, and if the modifiers of the method or constructor are matched by any modifier pattern or annotation pattern that may be present.

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