(This came up while reviewing the nestmates stuff. I'm sending it in its own thread, FTR.)
Here's a question to mull over for the future. It belongs in the "strict VM" bucket of ideas, which I have occasionally spoken about. There is a lot of (IMO needless) complexity in the JVM dealing with a symbolic reference from a class D to a protected member C.m/I.m of a super C/I outside of D's package. I think such references can and should be normalized specifically to D's immediate super, whether that is C or not. Could we do this? I think it would simplify JVMS 5.4.4, at a point where it is rather opaque. This is the language I'm talking about: > • R is protected and is declared in a class C, and D is either a subclass of > C or C itself. Furthermore, if R is not static, then the symbolic reference > to R must contain a symbolic reference to a class T, such that T is either a > subclass of D, a superclass of D, or D itself. > > During verification, it was also required that, even if T is a superclass of > D, the target reference of a protected instance field access or method > invocation must be an instance of D or a subclass of D (4.10.1.8). We could replace it by this: > • R is protected and is declared in a class C *not in the same run-time > package as D*, and D is *a subclass of C*. Furthermore the symbolic reference > to R must contain a symbolic reference to *the immediate superclass of D*. > > During verification, it was also required that the target reference of a > protected instance field access or method invocation must be an instance of D > or a subclass of D (4.10.1.8). The existing complexities are due IMO to historical mis-steps (as recognized in hindsight) in the way symbolic references were formulated. This is the ancient 1.0 time frame, before we invented ACC_SUPER and when miranda methods were a new thing. We've come a ways since then; perhaps we can make use of our knowledge. — John
