Make base::Optional constructor constexpr.

base/optional_unittest.cc

Index: base/optional_unittest.cc
diff --git a/base/optional_unittest.cc b/base/optional_unittest.cc
index 565b6cd6c74cad6679c02c68953176b0dce11c6f..15dc62e8243c4ad2da50399fcfa35c019036fcba 100644
--- a/base/optional_unittest.cc
+++ b/base/optional_unittest.cc
@@ -98,7 +98,7 @@ static_assert(
 
 TEST(OptionalTest, DefaultConstructor) {
   {
-    Optional<float> o;
+    constexpr Optional<float> o;
     EXPECT_FALSE(o);
   }
 
@@ -144,7 +144,7 @@ TEST(OptionalTest, CopyConstructor) {
 
 TEST(OptionalTest, ValueConstructor) {
   {
-    Optional<float> o(0.1f);
+    constexpr Optional<float> o(0.1f);
     EXPECT_TRUE(o);
     EXPECT_EQ(o.value(), 0.1f);
   }
@@ -198,13 +198,11 @@ TEST(OptionalTest, MoveConstructor) {
 
 TEST(OptionalTest, MoveValueConstructor) {
   {
-    Optional<float> first(0.1f);
-    Optional<float> second(std::move(first.value()));
-
-    EXPECT_TRUE(second);
-    EXPECT_EQ(second.value(), 0.1f);
+    constexpr float value = 0.1f;

[danakj, 2016/10/21 23:12:08]

Can you make all 3 cases in this test look alike? None of them need a first
Optional instance to call value() on really.

[alshabalin, 2016/10/22 07:47:52]

Done.

+    constexpr Optional<float> a(std::move(value));
 
-    EXPECT_TRUE(first);
+    EXPECT_TRUE(a);
+    EXPECT_EQ(0.1f, a.value());
   }
 
   {
@@ -232,7 +230,7 @@ TEST(OptionalTest, MoveValueConstructor) {
 
 TEST(OptionalTest, ConstructorForwardArguments) {
   {
-    Optional<float> a(base::in_place, 0.1f);
+    constexpr Optional<float> a(base::in_place, 0.1f);
     EXPECT_TRUE(a);
     EXPECT_EQ(0.1f, a.value());
   }
@@ -251,7 +249,7 @@ TEST(OptionalTest, ConstructorForwardArguments) {
 }
 
 TEST(OptionalTest, NulloptConstructor) {
-  Optional<int> a = base::nullopt;
+  constexpr Optional<int> a(base::nullopt);
   EXPECT_FALSE(a);
 }