<bean class="foo.bar.Baz">
  <property name="something" ref="foo"/>
</bean>

Property "something" is of type interface Something.
Reference "foo" is unresolved.

Invoking the "Create new bean 'foo'" quickfix produces:

<bean id="foo" class="foo.bar.Something"/>

...which gets immediately marked as an error ("Interface not allowed").

This is a minor thing, but I think for properties of interface type quickfix should leave "class" blank.
Alternatively, a 'live template' could run, and present a list of concrete implementations.