fix if else error info (#19974)

test=develop
test=document_fix

paddle/fluid/operators/merge_lod_tensor_op.cc

@@ -190,9 +190,23 @@ class MergeLoDTensorInferShape : public framework::InferShapeBase {
                    "MergeLoDTensorOp must has output Out");
 
     auto mask_dim = context->GetInputDim("Mask");
-    PADDLE_ENFORCE_EQ(mask_dim.size(), 2);
+    PADDLE_ENFORCE_EQ(mask_dim.size(), 2,
+                      "If you are using IfElse OP:"
+                      "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
+                      "ie.true_block():\n    out_1 = ie.input(x)\n\n"
+                      "Please ensure that the cond should be a 2-D tensor and "
+                      "the second dim size of cond should be 1. "
+                      "But now the cond's shape is [",
+                      *mask_dim.Get(), "].\n");
     if (context->IsRuntime() || mask_dim[1] > 0) {
-      PADDLE_ENFORCE_EQ(mask_dim[1], 1);
+      PADDLE_ENFORCE_EQ(mask_dim[1], 1,
+                        "If you are using IfElse OP:"
+                        "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
+                        "ie.true_block():\n    out_1 = ie.input(x)\n\n"
+                        "Please ensure that the cond should be a 2-D tensor "
+                        "and the second dim size of cond should be 1. "
+                        "But now the cond's shape is [",
+                        *mask_dim.Get(), "].\n");
     }
 
     context->SetOutputDim("Out", context->GetInputDim("InTrue"));

paddle/fluid/operators/split_lod_tensor_op.cc

@@ -156,9 +156,23 @@ class SplitLoDTensorInferShape : public framework::InferShapeBase {
                    "SplitLoDTensorOp must has output OutFalse.");
 
     auto mask_dim = context->GetInputDim("Mask");
-    PADDLE_ENFORCE_EQ(mask_dim.size(), 2);
+    PADDLE_ENFORCE_EQ(mask_dim.size(), 2,
+                      "If you are using IfElse OP:"
+                      "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
+                      "ie.true_block():\n    out_1 = ie.input(x)\n\n"
+                      "Please ensure that the cond should be a 2-D tensor and "
+                      "the second dim size of cond should be 1. "
+                      "But now the cond's shape is [",
+                      *mask_dim.Get(), "].\n");
     if (context->IsRuntime()) {
-      PADDLE_ENFORCE_EQ(mask_dim[1], 1);
+      PADDLE_ENFORCE_EQ(mask_dim[1], 1,
+                        "If you are using IfElse OP:"
+                        "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
+                        "ie.true_block():\n    out_1 = ie.input(x)\n\n"
+                        "Please ensure that the cond should be a 2-D tensor "
+                        "and the second dim size of cond should be 1. "
+                        "But now the cond's shape is [",
+                        *mask_dim.Get(), "].\n");
     }
 
     context->SetOutputDim("OutTrue", context->GetInputDim("X"));