[benchmark-set] Add benchmark for set copy

perf/benchmark-set.cc

@@ -120,4 +120,27 @@ BENCHMARK(BM_SetIteration)
         {{1 << 10, 1 << 16}, // Set Size
          {2, 512}});          // Density
 
+/* Set copy. */
+static void BM_SetCopy(benchmark::State& state) {
+  unsigned set_size = state.range(0);
+  unsigned max_value = state.range(0) * state.range(1);
+
+  hb_set_t* original = hb_set_create ();
+  RandomSet(set_size, max_value, original);
+  assert(hb_set_get_population(original) == set_size);
+
+  for (auto _ : state) {
+    hb_set_t *s = hb_set_create ();
+    hb_set_set (s, original);
+    hb_set_destroy (s);
+  }
+
+  hb_set_destroy(original);
+}
+BENCHMARK(BM_SetCopy)
+    ->Unit(benchmark::kMicrosecond)
+    ->Ranges(
+        {{1 << 10, 1 << 16}, // Set Size
+         {2, 512}});          // Density
+
 BENCHMARK_MAIN();

src/hb-set.hh

@@ -43,8 +43,8 @@ struct hb_sparseset_t
 
   hb_sparseset_t (const hb_sparseset_t& other) : hb_sparseset_t () { set (other); }
   hb_sparseset_t (hb_sparseset_t&& other) : hb_sparseset_t () { s = std::move (other.s); }
-  hb_sparseset_t& operator= (const hb_sparseset_t& other) { set (other); return *this; }
+  hb_sparseset_t& operator = (const hb_sparseset_t& other) { set (other); return *this; }
-  hb_sparseset_t& operator= (hb_sparseset_t&& other) { s = std::move (other.s); return *this; }
+  hb_sparseset_t& operator = (hb_sparseset_t&& other) { s = std::move (other.s); return *this; }
   friend void swap (hb_sparseset_t& a, hb_sparseset_t& b) { hb_swap (a.s, b.s); }
 
   hb_sparseset_t (std::initializer_list<hb_codepoint_t> lst) : hb_sparseset_t ()
@@ -169,8 +169,8 @@ struct hb_set_t : hb_sparseset_t<hb_bit_set_invertible_t>
   hb_set_t (std::nullptr_t) : hb_set_t () {};
   hb_set_t (const hb_set_t &o) : sparseset ((sparseset &) o) {};
   hb_set_t (hb_set_t&& o) : sparseset (std::move ((sparseset &) o)) {}
-  hb_set_t& operator= (const hb_set_t&) = default;
+  hb_set_t& operator = (const hb_set_t&) = default;
-  hb_set_t& operator= (hb_set_t&&) = default;
+  hb_set_t& operator = (hb_set_t&&) = default;
   hb_set_t (std::initializer_list<hb_codepoint_t> lst) : sparseset (lst) {}
   template <typename Iterable,
 	    hb_requires (hb_is_iterable (Iterable))>