Add bool operator vs. implicit cast unit test

Bug: 1073933
Change-Id: I12c279457aa360cbb0cd9ea53a4ae54db4d4d051
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2226003
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774051}

base/memory/checked_ptr_unittest.cc

@@ -167,6 +167,45 @@ TEST_F(CheckedPtrTest, NullCmpBool) {
   EXPECT_EQ(g_get_for_dereference_cnt, 0);
 }
 
+bool IsValidNoCast(CountingCheckedPtr<int> ptr) {
+  return !!ptr;  // !! to avoid implicit cast
+}
+bool IsValidNoCast2(CountingCheckedPtr<int> ptr) {
+  return ptr && true;
+}
+
+TEST_F(CheckedPtrTest, BoolOpNotCast) {
+  CountingCheckedPtr<int> ptr = nullptr;
+  volatile bool is_valid = !!ptr;  // !! to avoid implicit cast
+  is_valid = ptr || is_valid;      // volatile, so won't be optimized
+  if (ptr)
+    is_valid = true;
+  bool is_not_valid = !ptr;
+  if (!ptr)
+    is_not_valid = true;
+  std::ignore = IsValidNoCast(ptr);
+  std::ignore = IsValidNoCast2(ptr);
+  // No need to unwrap pointer, just compare against 0.
+  EXPECT_EQ(g_get_for_comparison_cnt, 0);
+  EXPECT_EQ(g_get_for_extraction_cnt, 0);
+  EXPECT_EQ(g_get_for_dereference_cnt, 0);
+}
+
+bool IsValidWithCast(CountingCheckedPtr<int> ptr) {
+  return ptr;
+}
+
+// This test is mostly for documentation purposes, demonstrating that a more
+// costly cast can be invoked if we aren't careful.
+TEST_F(CheckedPtrTest, CastNotBoolOp) {
+  CountingCheckedPtr<int> ptr = nullptr;
+  bool is_valid = ptr;
+  is_valid = IsValidWithCast(ptr);
+  EXPECT_EQ(g_get_for_comparison_cnt, 0);
+  EXPECT_EQ(g_get_for_extraction_cnt, 2);
+  EXPECT_EQ(g_get_for_dereference_cnt, 0);
+}
+
 TEST_F(CheckedPtrTest, StarDereference) {
   int foo = 42;
   CountingCheckedPtr<int> ptr = &foo;