Support nullptr:

Author: kuhar

llvm/include/llvm/ADT/TypeSwitch.h

@@ -119,6 +119,14 @@ class TypeSwitch : public detail::TypeSwitchBase<TypeSwitch<T, ResultT>, T> {
     return defaultResult;
   }
 
+  /// Default for pointer-like results types that accept `nullptr`.
+  template <typename ArgT = ResultT,
+            typename =
+                std::enable_if_t<std::is_constructible_v<ArgT, std::nullptr_t>>>
+  [[nodiscard]] ResultT Default(std::nullptr_t) {
+    return Default(ResultT(nullptr));
+  }
+
   /// Default for optional results types that accept `std::nullopt`.
   template <typename ArgT = ResultT,
             typename =

llvm/unittests/ADT/TypeSwitchTest.cpp

@@ -152,3 +152,34 @@ TEST(TypeSwitchTest, DefaultNullopt) {
   EXPECT_EQ(0, translate(DerivedA()));
   EXPECT_EQ(std::nullopt, translate(DerivedD()));
 }
+
+TEST(TypeSwitchTest, DefaultNullptr) {
+  float foo = 0.0f;
+  auto translate = [&](auto value) {
+    return TypeSwitch<Base *, float *>(&value)
+        .Case([&](DerivedA *) { return &foo; })
+        .Default(nullptr);
+  };
+  EXPECT_EQ(&foo, translate(DerivedA()));
+  EXPECT_EQ(nullptr, translate(DerivedD()));
+}
+
+TEST(TypeSwitchTest, DefaultNullptrForPointerLike) {
+  struct Value {
+    void *ptr;
+    Value(const Value &other) : ptr(other.ptr) {}
+    Value(std::nullptr_t) : ptr(nullptr) {}
+    Value() : Value(nullptr) {}
+  };
+
+  float foo = 0.0f;
+  Value fooVal;
+  fooVal.ptr = &foo;
+  auto translate = [&](auto value) {
+    return TypeSwitch<Base *, Value>(&value)
+        .Case([&](DerivedA *) { return fooVal; })
+        .Default(nullptr);
+  };
+  EXPECT_EQ(&foo, translate(DerivedA()).ptr);
+  EXPECT_EQ(nullptr, translate(DerivedD()).ptr);
+}