Add getValueOr to llvm::Optional<T>.

This takes a single argument convertible to T, and
- if the Optional has a value, returns the existing value,
- otherwise, constructs a T from the argument and returns that.

Inspired by std::experimental::optional from the "Library Fundamentals" C++ TS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218618 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/Optional.h b/include/llvm/ADT/Optional.h
index cb45c78e2c1fffa1cc3701be61532174ae89f3fc..144367d352d546f131739ec24b9be3ac87830cf7 100644 (file)
--- a/include/llvm/ADT/Optional.h
+++ b/include/llvm/ADT/Optional.h
@@ -119,9 +119,19 @@ public:
   const T& operator*() const LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
   T& operator*() LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
 
+  template <typename U>
+  constexpr T getValueOr(U &&value) const LLVM_LVALUE_FUNCTION {
+    return hasValue() ? getValue() : std::forward<U>(value);
+  }
+
 #if LLVM_HAS_RVALUE_REFERENCE_THIS
   T&& getValue() && { assert(hasVal); return std::move(*getPointer()); }
   T&& operator*() && { assert(hasVal); return std::move(*getPointer()); }
+
+  template <typename U>
+  T getValueOr(U &&value) && {
+    return hasValue() ? std::move(getValue()) : std::forward<U>(value);
+  }
 #endif
 };
 

diff --git a/unittests/ADT/OptionalTest.cpp b/unittests/ADT/OptionalTest.cpp
index 2da408c15e0b054d6604faf7d46ab62a5b87f153..51c54523b88d89356bc92e31ea4048956cd53b6e 100644 (file)
--- a/unittests/ADT/OptionalTest.cpp
+++ b/unittests/ADT/OptionalTest.cpp
@@ -169,6 +169,14 @@ TEST_F(OptionalTest, NullCopyConstructionTest) {
   EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
 }
 
+TEST_F(OptionalTest, GetValueOr) {
+  Optional<int> A;
+  EXPECT_EQ(42, A.getValueOr(42));
+
+  A = 5;
+  EXPECT_EQ(5, A.getValueOr(42));
+}
+
 struct MoveOnly {
   static unsigned MoveConstructions;
   static unsigned Destructions;
@@ -278,5 +286,26 @@ TEST_F(OptionalTest, MoveOnlyAssigningAssignment) {
   EXPECT_EQ(1u, MoveOnly::Destructions);
 }
 
+#if LLVM_HAS_RVALUE_REFERENCE_THIS
+
+TEST_F(OptionalTest, MoveGetValueOr) {
+  Optional<MoveOnly> A;
+
+  MoveOnly::ResetCounts();
+  EXPECT_EQ(42, std::move(A).getValueOr(MoveOnly(42)).val);
+  EXPECT_EQ(1u, MoveOnly::MoveConstructions);
+  EXPECT_EQ(0u, MoveOnly::MoveAssignments);
+  EXPECT_EQ(2u, MoveOnly::Destructions);
+
+  A = MoveOnly(5);
+  MoveOnly::ResetCounts();
+  EXPECT_EQ(5, std::move(A).getValueOr(MoveOnly(42)).val);
+  EXPECT_EQ(1u, MoveOnly::MoveConstructions);
+  EXPECT_EQ(0u, MoveOnly::MoveAssignments);
+  EXPECT_EQ(2u, MoveOnly::Destructions);
+}
+
+#endif // LLVM_HAS_RVALUE_REFERENCE_THIS
+
 } // end anonymous namespace