[BugFix]Fix pooling output_size bug if encounter list[Tensor] (#46352)

* [Check]Enhance pooling output_size type check

* add unittest

python/paddle/fluid/tests/unittests/test_unpool_op.py

@@ -436,6 +436,35 @@ class TestZOutputSizeTensor2(unittest.TestCase):
         np.testing.assert_array_equal(unpool_out.shape, [1, 3, 7, 7])
 
 
+class TestZOutputSizeTensor3(unittest.TestCase):
+
+    def setUp(self):
+        paddle.disable_static()
+
+    def tearDown(self):
+        paddle.enable_static()
+
+    def test_dygraph(self):
+        x = paddle.randn([1, 3, 6, 6])
+        pool_out, indices = F.max_pool2d(x,
+                                         kernel_size=2,
+                                         stride=2,
+                                         padding=0,
+                                         return_mask=True)
+        output_size = [
+            paddle.assign([1]),
+            paddle.assign([1]),
+            paddle.assign([7]),
+            paddle.assign([7])
+        ]
+        unpool_out = F.max_unpool2d(pool_out,
+                                    indices,
+                                    kernel_size=2,
+                                    padding=0,
+                                    output_size=output_size)
+        np.testing.assert_array_equal(unpool_out.shape, [1, 3, 7, 7])
+
+
 if __name__ == '__main__':
     paddle.enable_static()
     unittest.main()

python/paddle/nn/functional/pooling.py

@@ -646,6 +646,9 @@ def max_pool1d(x,
 
 
 def _unpool_output_size(x, kernel_size, stride, padding, output_size):
+    assert output_size is None or isinstance(
+        output_size, (list, tuple)
+    ), "Required output_size is None|list|tuple, but received %s" % output_size
     input_size = x.shape
     default_size = []
     for d in range(len(kernel_size)):
@@ -654,7 +657,7 @@ def _unpool_output_size(x, kernel_size, stride, padding, output_size):
 
     has_static_var = False
     if output_size is None:
-        ret = default_size
+        return default_size
     elif utils._contain_var(output_size):
         if not _non_static_mode():
             has_static_var = True
@@ -663,8 +666,7 @@ def _unpool_output_size(x, kernel_size, stride, padding, output_size):
             for i, var in enumerate(output_size):
                 if isinstance(var, Variable):
                     output_size[i] = var.numpy()[0]
-        ret = output_size
-    else:
+
     if len(output_size) == len(kernel_size) + 2:
         output_size = output_size[2:]
     if len(output_size) != len(kernel_size):
@@ -682,8 +684,7 @@ def _unpool_output_size(x, kernel_size, stride, padding, output_size):
                     'invalid output_size "{}" (dim {} must be between {} and {})'
                     .format(output_size, d, min_size, max_size))
 
-        ret = output_size
-    return ret
+    return output_size
 
 
 def max_unpool1d(x,