[Dy2static] Add for iterate or enumerate variable list unittest (#25100)

* add for iter var list, test=develop

* add enumerate unittest, test=develop

python/paddle/fluid/tests/unittests/dygraph_to_static/test_for_enumerate.py

@@ -176,6 +176,40 @@ def for_enumerate_var(x_array):
     return y, z
 
 
+# 13. for iter list[var]
+@declarative
+def for_iter_var_list(x):
+    # 1. prepare data, ref test_list.py
+    x = fluid.dygraph.to_variable(x)
+    iter_num = fluid.layers.fill_constant(shape=[1], value=5, dtype="int32")
+    a = []
+    for i in range(iter_num):
+        a.append(x + i)
+    # 2. iter list[var]
+    y = fluid.layers.fill_constant([1], 'int32', 0)
+    for x in a:
+        y = y + x
+    return y
+
+
+# 14. for enumerate list[var]
+@declarative
+def for_enumerate_var_list(x):
+    # 1. prepare data, ref test_list.py
+    x = fluid.dygraph.to_variable(x)
+    iter_num = fluid.layers.fill_constant(shape=[1], value=5, dtype="int32")
+    a = []
+    for i in range(iter_num):
+        a.append(x + i)
+    # 2. iter list[var]
+    y = fluid.layers.fill_constant([1], 'int32', 0)
+    z = fluid.layers.fill_constant([1], 'int32', 0)
+    for i, x in enumerate(a):
+        y = y + i
+        z = z + x
+    return y, z
+
+
 class TestTransformBase(unittest.TestCase):
     def setUp(self):
         self.place = fluid.CUDAPlace(0) if fluid.is_compiled_with_cuda(
@@ -303,5 +337,15 @@ class TestForEnumerateVar(TestForIterVarNumpy):
         self.dygraph_func = for_enumerate_var
 
 
+class TestForIterVarList(TestForInRange):
+    def set_test_func(self):
+        self.dygraph_func = for_iter_var_list
+
+
+class TestForEnumerateVarList(TestForInRange):
+    def set_test_func(self):
+        self.dygraph_func = for_enumerate_var_list
+
+
 if __name__ == '__main__':
     unittest.main()