refine GetExpectedKernelType in conat op, test=develop (#17934)

paddle/fluid/operators/concat_op.cc

@@ -23,7 +23,7 @@ limitations under the License. */
 
 namespace paddle {
 namespace operators {
-using framework::Tensor;
+using Tensor = framework::Tensor;
 
 class ConcatOp : public framework::OperatorWithKernel {
  public:
@@ -80,12 +80,12 @@ class ConcatOp : public framework::OperatorWithKernel {
  protected:
   framework::OpKernelType GetExpectedKernelType(
       const framework::ExecutionContext &ctx) const override {
-    auto vars = ctx.MultiInputVar("X");
+    auto inputs = ctx.MultiInput<Tensor>("X");
     auto input_data_type = framework::proto::VarType::Type(0);
     bool flag = 0;
-    for (auto *var : vars) {
-      if (var->IsInitialized()) {
-        input_data_type = framework::GetDataTypeOfVar(var);
+    for (auto *input : inputs) {
+      if (input->IsInitialized() && input->numel() > 0) {
+        input_data_type = input->type();
         flag = 1;
         break;
       }