#7 misleading error message when "override" is missing

[Karl Matthias Hamel]

A message like the following occurs instad of a message
"override is missing".

error:Method "Edge
graphcollaboration/ColoredGraph_Impl$Vertex_Impl.getEdges()"
cannot redefine method with different return type
[JLS 8.4.6.3] ColoredGraph.java course scheduling
2/graphcollaboration line 14