Nullness Checker error message uses incorrect parameter name

Test case:

import org.checkerframework.checker.nullness.qual.Nullable;
class Test {
    interface A<T1 extends @Nullable Object> {
        String fn(T1 o);
    }
    static String foo(Object o) { return o.toString(); }
    static void testPositive() {
        A<@Nullable Object> p = Test::foo;
    }
}

Error output from the Nullness Checker:

/tmp/Test.java:8: error: [methodref.param] Incompatible parameter type for o
        A<@Nullable Object> p = Test::foo;
                                ^
  found   : @Initialized @NonNull Object
  required: @Initialized @Nullable Object
  Consequence: method in @Initialized @NonNull Test
    @Initialized @NonNull String foo(@Initialized @NonNull Object p0)
  is not a valid method reference for method in @UnknownInitialization @Nullable A<@Initialized @Nullable Object>
    @Initialized @NonNull String fn(@Initialized @NonNull A<@Initialized @Nullable Object> this, @Initialized @Nullable Object p0)
1 error

In a couple of places the error message refers to p0 which is not the name of any variable in the program.

I also find the error message somewhat hard to read with all the (irrelevant) initializer annotations, but perhaps that is a separate issue.

Reproduce the diagnostic with the provided Test.java method-reference example and inspect how the Nullness Checker constructs the methodref.param error. Trace where parameter names become p0 instead of the source name o. Done means the diagnostic identifies the correct parameter name and the regression case passes.