C++ API parity: at::Tensor::set_data

Summary: Pull Request resolved: pytorch#26647

Test Plan: Imported from OSS

Differential Revision: D17542604

Pulled By: pbelevich

fbshipit-source-id: 37d5d67ebdb9348b5561d983f9bd26d310210983

Author: pbelevich

test/cpp/api/tensor.cpp

@@ -489,3 +489,18 @@ TEST(TensorTest, DetachInplace) {
   ASSERT_THROWS_WITH(x.detach_(), message);
   ASSERT_THROWS_WITH(y.detach_(), message);
 }
+
+TEST(TensorTest, SetData) {
+  auto x = torch::randn({5});
+  auto y = torch::randn({5});
+  ASSERT_FALSE(torch::equal(x, y));
+  ASSERT_NE(x.data_ptr<float>(), y.data_ptr<float>());
+
+  x.set_data(y);
+  ASSERT_TRUE(torch::equal(x, y));
+  ASSERT_EQ(x.data_ptr<float>(), y.data_ptr<float>());
+
+  x = at::tensor({5});
+  y = at::tensor({5});
+  ASSERT_THROWS_WITH(x.set_data(y), "set_data is not implemented for Tensor");
+}