svoid test_structure_shouldIncludeField() {
  new structure_Data d;
  d.shouldIncludeField = field -> {
    S c = shortClassName(field.getDeclaringClass());
    S f = field.getName();
    bool shouldInclude = !(eq(c, "Pair") && eq(f, "a"));
    printVars("shouldIncludeField", +c, +f, +shouldInclude);
    ret shouldInclude;
  };
  
  S s = structure(pair(1, 2), d);
  assertEqualsVerbose("Pair(b=2)", s);
}

Began life as a copy of #1034647