Issues to resolve before merge PICO into EISOP

[aosen-xiong]

This issue tracks the remaining work needed before PICO can be merged into EISOP.

Required Work

Status	Item	Notes
In review	#1032	Viewpoint-adapted type-use validity check.
In review	#1049	Cast logic; also coordinates with eisop/guava#10.
In review	#1068	Forbid annotations on supertypes.
Needs issue	Viewpoint-adapted method override check	Create after #1032 if test interactions depend on that PR.
In review	#799	Fix viewpoint adaptation of type variables. Clarify whether required for PICO merge.
Draft	#865	Varargs/viewpoint adaptor fix. Clarify whether required for PICO merge.

Design Questions

• Is Fix requalifying type variable uses during viewpoint adaptation #799 required for the initial PICO merge, or can it be follow-up work?
• Is Compute Varargs before calling setParameterTypes in viewpointadaptor #865 required for the initial PICO merge, or can it be follow-up work?

Nice To Have

• Flow refinement for PICO after s.getClass() == ImmutableClass.class.
  See comment: Issues to resolve before merge PICO into EISOP #1071 (comment)
  Update: implemented as part of c416281

[aosen-xiong]

Features nice to have:

// TODO: Implement flow refinement for PICO
public @Immutable BaseClass testFlow(@Readonly BaseClass s) {
    if (s.getClass() == ImmutableClass.class) {
        return s;
    }
    return new ImmutableClass();
}

@ReceiverDependentMutable class BaseClass {}

@Immutable class ImmutableClass extends BaseClass {}