Fix ElementwiseOpInferVarType in elementwise_op to use the default InferVarType to find var recursively

paddle/fluid/operators/elementwise_op.h

@@ -42,6 +42,18 @@ class ElementwiseOp : public framework::OperatorWithKernel {
   }
 };
 
+class ElementwiseOpInferVarType : public framework::VarTypeInference {
+ public:
+  void operator()(const framework::OpDesc& op_desc,
+                  framework::BlockDesc* block) const override {
+    auto x_name = op_desc.Input("X")[0];
+    auto out_name = op_desc.Output("Out")[0];
+    auto& x = block->FindRecursiveOrCreateVar(x_name);
+    auto& out = block->FindRecursiveOrCreateVar(out_name);
+    out.SetType(x.GetType());
+  }
+};
+
 class ElementwiseOpMaker : public framework::OpProtoAndCheckerMaker {
  public:
   void Make() final {
@@ -138,5 +150,6 @@ class ElementwiseOpGrad : public framework::OperatorWithKernel {
   };                                                                    \
   REGISTER_OPERATOR(op_type, ::paddle::operators::ElementwiseOp,        \
                     __ElemwiseOp##op_type##Maker__,                     \
+                    ::paddle::operators::ElementwiseOpInferVarType,     \
                     ::paddle::framework::DefaultGradOpDescMaker<true>); \
   REGISTER_OPERATOR(op_type##_grad, ::paddle::operators::ElementwiseOpGrad)