1module A { header "a.h" export * }
2module B { header "b.h" export * }
3module C {
4  module C2 { header "c2.h" export * }
5  module C1 { header "c1.h" export * }
6}
7module X { header "x.h" export * }
8module Y { header "y.h" export * }
9module na { header "na.h" export * }
10module nb { header "nb.h" export * }
11