[llvm] 2a47485 - [ADT] Implement Optional::transform

[Kazu Hirata via llvm-commits]

Author: Kazu Hirata
Date: 2022-08-13T11:48:25-07:00
New Revision: 2a4748576e4f734a15c9b0553eec602dd6f03633

URL: https://github.com/llvm/llvm-project/commit/2a4748576e4f734a15c9b0553eec602dd6f03633
DIFF: https://github.com/llvm/llvm-project/commit/2a4748576e4f734a15c9b0553eec602dd6f03633.diff

LOG: [ADT] Implement Optional::transform

This patch implements Optional::transform for consistency with
std::optional::transform in C++23.

Note that the new function is identical to Optional::map.  My plan is
to deprecate Optional::map after migrating all of its uses to
Optional::transform.

Differential Revision: https://reviews.llvm.org/D131829

Added: 
    

Modified: 
    llvm/include/llvm/ADT/Optional.h
    llvm/unittests/ADT/OptionalTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/Optional.h b/llvm/include/llvm/ADT/Optional.h
index 1862a2d703aad..874183ce190e5 100644
--- a/llvm/include/llvm/ADT/Optional.h
+++ b/llvm/include/llvm/ADT/Optional.h
@@ -342,6 +342,12 @@ template <typename T> class Optional {
 
   /// Apply a function to the value if present; otherwise return None.
   template <class Function>
+  auto transform(const Function &F) const & -> Optional<decltype(F(value()))> {
+    if (*this)
+      return F(value());
+    return None;
+  }
+  template <class Function>
   auto map(const Function &F) const & -> Optional<decltype(F(value()))> {
     if (*this)
       return F(value());
@@ -365,6 +371,13 @@ template <typename T> class Optional {
 
   /// Apply a function to the value if present; otherwise return None.
   template <class Function>
+  auto transform(
+      const Function &F) && -> Optional<decltype(F(std::move(*this).value()))> {
+    if (*this)
+      return F(std::move(*this).value());
+    return None;
+  }
+  template <class Function>
   auto map(const Function &F)
       && -> Optional<decltype(F(std::move(*this).value()))> {
     if (*this)

diff  --git a/llvm/unittests/ADT/OptionalTest.cpp b/llvm/unittests/ADT/OptionalTest.cpp
index 3db84ed4c3306..c583ff0df9af1 100644
--- a/llvm/unittests/ADT/OptionalTest.cpp
+++ b/llvm/unittests/ADT/OptionalTest.cpp
@@ -603,6 +603,40 @@ TEST(OptionalTest, MoveValueOr) {
   EXPECT_EQ(2u, MoveOnly::Destructions);
 }
 
+TEST(OptionalTest, Transform) {
+  Optional<int> A;
+
+  Optional<int> B = A.transform([&](int N) { return N + 1; });
+  EXPECT_FALSE(B.has_value());
+
+  A = 3;
+  Optional<int> C = A.transform([&](int N) { return N + 1; });
+  EXPECT_TRUE(C.has_value());
+  EXPECT_EQ(4, C.value());
+}
+
+TEST(OptionalTest, MoveTransform) {
+  Optional<MoveOnly> A;
+
+  MoveOnly::ResetCounts();
+  Optional<int> B =
+      std::move(A).transform([&](const MoveOnly &M) { return M.val + 2; });
+  EXPECT_FALSE(B.has_value());
+  EXPECT_EQ(0u, MoveOnly::MoveConstructions);
+  EXPECT_EQ(0u, MoveOnly::MoveAssignments);
+  EXPECT_EQ(0u, MoveOnly::Destructions);
+
+  A = MoveOnly(5);
+  MoveOnly::ResetCounts();
+  Optional<int> C =
+      std::move(A).transform([&](const MoveOnly &M) { return M.val + 2; });
+  EXPECT_TRUE(C.has_value());
+  EXPECT_EQ(7, C.value());
+  EXPECT_EQ(0u, MoveOnly::MoveConstructions);
+  EXPECT_EQ(0u, MoveOnly::MoveAssignments);
+  EXPECT_EQ(0u, MoveOnly::Destructions);
+}
+
 struct EqualTo {
   template <typename T, typename U> static bool apply(const T &X, const U &Y) {
     return X == Y;