code: @Override
      protected void propagateAcrossPhiNode(TypeQualifierValueSet fact, ValueNumber sourceVN, ValueNumber targetVN) {
          // Backwards analysis - propagate value from target to source
          fact.propagateAcrossPhiNode(targetVN, sourceVN);
      }
docs: /*
  (non-Javadoc)
  
  @see edu.umd.cs.findbugs.ba.jsr305.TypeQualifierDataflowAnalysis#
  propagateAcrossPhiNode
  (edu.umd.cs.findbugs.ba.jsr305.TypeQualifierValueSet,
  edu.umd.cs.findbugs.ba.vna.ValueNumber,
  edu.umd.cs.findbugs.ba.vna.ValueNumber)