Weird warning in NullnessChecker with code have Generic Type,Type Cast and EqualTo statement

Test Version of checker framework: javac 1.8.0-jsr308-2.0.0

NullnessChecker will give a weird warning of below code:

public class Test {
    @SuppressWarnings("unchecked")
    public <T> T incompatibleTypes(Object o) {
        final T x = (T) o;
        if (x != null) {
        }
        return x;
    }
}

The warning is:

Error: [return.type.incompatible] incompatible types in return.
        return x;
               ^
  found : T extends @Initialized @Nullable Object
  required: T extends @Initialized @Nullable Object

And the more detail warning of above code with printVerboseGenerics is:

error: [return.type.incompatible] incompatible types in return.
        return x;
               ^
  found   : T[ extends @Initialized @Nullable Object super @Initialized @Nullable Void]
  required: T[ extends @Initialized @Nullable Object super @Initialized @NonNull Void]

This wired error will appear when the code has a TypeCast first and then has a NotEqualTo against with null literal.

The same problem also appears in EqualTo against with null literal:
code:

public class Test {
    @SuppressWarnings("unchecked")
    public <T> T incompatibleTypes(Object o) {
        final T x = (T) o;
        if (x == null) {
        }
        return x;
    }
}

warning with printVerboseGenerics:

error: [return.type.incompatible] incompatible types in return.
        return x;
               ^
  found   : T[ extends @Initialized @Nullable Object super @Initialized @Nullable Void]
  required: T[ extends @Initialized @Nullable Object super @Initialized @NonNull Void]

Start by compiling the two provided Java reproductions with NullnessChecker and printVerboseGenerics enabled, comparing the cast followed by each null comparison. Trace how the checker reports the inferred generic bounds at the return statement. Done means both examples no longer produce the spurious return.type.incompatible warning.