Dupliate AST nodes in Go

[fwendland]

I've identified the following test case resources, where duplicate AST nodes occur:

• src/test/resources/golang/branch.go
  Default[location=branch.go(19:3-20:12),type=UNKNOWN] -> 2
• src/test/resources/golang/type_assert.go
  Reference[name=f,location=type_assert.go(23:14-23:15),type=ObjectType[name=main.MyInterface],refersTo=Variable[name=f,location=type_assert.go(14:6-14:32),initializer=InitializerList[location=type_assert.go(14:22-14:32),type=ObjectType[name=main.MyStruct],initializers=[]],modifiers=[]]] -> 4

Initial analysis:

• In the case with the Reference it seems that the reference node is reused in each case of the switch.