ccls/tests/usage/func_usage_forward_decl_func.cc

void foo();

void usage() {
  foo();
}
/*
OUTPUT:
{
  "funcs": [{
      "id": 0,
      "usr": "c:@F@foo#",
      "short_name": "foo",
      "qualified_name": "void foo()",
      "declarations": ["1:6-1:9"],
      "callers": ["1@4:3-4:6"]
    }, {
      "id": 1,
      "usr": "c:@F@usage#",
      "short_name": "usage",
      "qualified_name": "void usage()",
      "definition_spelling": "3:6-3:11",
      "definition_extent": "3:1-5:2",
      "callees": ["0@4:3-4:6"]
    }]
}
*/