visitImports

  auto visitor = visitImports(q{
    import cc;
    import ab;
    import aa.cc;
    import aa.bb;

import foo;
import bar, bar2;  // expands to two imports.

    void main() {}
    });
  assert(visitor.declGroups.length == 2);
  assert(visitor.declGroups[0].length == 4);
  assert(visitor.declGroups[1].length == 2);

  assert(visitor.importGroups.length == 2);
  assert(visitor.importGroups[0].length == 4);
  assert(visitor.importGroups[1].length == 3);

  assert(visitor.diff ==
`<<<<unittest:1-5
    import cc;
    import ab;
    import aa.cc;
    import aa.bb;
----
    import aa.bb;
    import aa.cc;
    import ab;
    import cc;
>>>>
<<<<unittest:6-8
import foo;
import bar, bar2;  // expands to two imports.
----
import bar;
import bar2;
import foo;
>>>>
`);