Issue a warning for receiver-dependent qualifiers on fields or parameters when receiver is invariant

[wmdietl]

Summary

When a field, method return type, or parameter is declared with @ReceiverDependentQual (or another receiver-dependent / polymorphic qualifier) in a context where the enclosing class or receiver is invariant (e.g., the class declaration is annotated with a fixed concrete qualifier like @A class C or @A final class C), the receiver-dependent qualifier will always adapt to that fixed qualifier.

Allowing @ReceiverDependentQual in such contexts can be misleading to developers, as it suggests the member varies dynamically with the receiver when it is effectively constant.

Example

@A class InvariantContainer {
    // Misleading: field always viewpoint-adapts to @A Object for instances of InvariantContainer
    @ReceiverDependentQual Object field;

    // Misleading: method return type and parameter always adapt to @A
    @ReceiverDependentQual Object get() { return field; }
    void set(@ReceiverDependentQual Object o) { this.field = o; }
}

Proposed Enhancement

Consider issuing a warning (e.g., under -AwarnRedundantAnnotations or a viewpoint-specific lint):

1. Static members: When @ReceiverDependentQual is placed on static fields or static methods (where there is no receiver to adapt against).
2. Fixed final classes: When @ReceiverDependentQual is used in a final class whose qualifier is fixed at class declaration time (e.g. @A final class C).
3. Monomorphic/Invariant class hierarchies: When a class fixes its qualifier and cannot be subclassed with different qualifiers.