Mismatched virtual on property getter/setter

[jpobst]

What should happen if the getter & setter differ in their "virtual-ness"?

This has actually happened in Android, via Activity's getTitle() and setTitle() methods:

<class abstract="false" deprecated="not deprecated" extends="android.view.ContextThemeWrapper" extends-generic-aware="android.view.ContextThemeWrapper" jni-extends="Landroid/view/ContextThemeWrapper;" final="false" name="Activity" static="false" visibility="public" jni-signature="Landroid/app/Activity;">
  <method abstract="false" deprecated="not deprecated" final="true" name="getTitle" jni-signature="()Ljava/lang/CharSequence;" bridge="false" native="false" return="java.lang.CharSequence" jni-return="Ljava/lang/CharSequence;" static="false" synchronized="false" synthetic="false" visibility="public" />
  <method abstract="false" deprecated="not deprecated" final="false" name="setTitle" jni-signature="(Ljava/lang/CharSequence;)V" bridge="false" native="false" return="void" jni-return="V" static="false" synchronized="false" synthetic="false" visibility="public">
    <parameter name="title" type="java.lang.CharSequence" jni-type="Ljava/lang/CharSequence;" />
  </method>
</class>

(Above XML fragments from xamarin-android/bin/BuildDebug/api/api-28.xml.in.)

Which is to say, consider:

public class Activity {
    public final CharSequence getTitle() {return null;}
    public void setTitle(CharSequence value) {}
}

Currently -- arguably a bug! -- we remove the "virtual-ness", and emit:

partial class Activity {
  public unsafe Java.Lang.ICharSequence TitleFormatted {
    get { /*performs non-virtual dispatch */}
    set { /* performs virtual dispatch! */ }
  }
}

Which is admittedly "wonky", but... that's what we've done.

Rephrased: maybe perhaps we should reconsider this code idiom?

That said, in "reconsidering" we also need to maintain ABI compatibility with existing Mono.Android.dll, but there are various ways to work around that...