Remove target vars of gast.For from before_loop_vars or after_loop_vars (#24732)

python/paddle/fluid/dygraph/dygraph_to_static/loop_transformer.py

@@ -166,13 +166,19 @@ class NameVisitor(gast.NodeVisitor):
 
         in_loop_vars = self.in_loop_vars[node]
         in_loop_name_strs = self._var_nodes_to_names(in_loop_vars)
+
         before_loop_body_vars = self.before_loop_body_vars[node]
+        before_loop_body_vars = self._remove_target_vars_of_for(
+            before_loop_body_vars, node)
         before_loop_name_strs = self._var_nodes_to_names(before_loop_body_vars)
+
         after_loop_vars = self.current_seen_vars - before_loop_body_vars - in_loop_vars
+        after_loop_vars = self._remove_target_vars_of_for(after_loop_vars, node)
         after_loop_name_strs = self._var_nodes_to_names(after_loop_vars,
                                                         read_context)
         condition_vars = self.condition_vars[node]
         condition_names = self._var_nodes_to_names(condition_vars)
+
         write_vars = self.write_in_loop[node]
         write_names = self._var_nodes_to_names(write_vars)
 
@@ -203,6 +209,7 @@ class NameVisitor(gast.NodeVisitor):
                 # vars out
                 loop_var_names.add(name)
                 create_var_names.add(name)
+
         return loop_var_names, create_var_names
 
     def visit_Name(self, node):
@@ -309,11 +316,60 @@ class NameVisitor(gast.NodeVisitor):
         return False
 
     def _is_call_func_name_node(self, node):
-        parent_node = self.node_to_wrapper_map[node].parent.node
+        parent_node = self._get_parent_node(node)
         if isinstance(parent_node, gast.Call) and parent_node.func == node:
             return True
         return False
 
+    def _get_parent_node(self, node):
+        wrapper_node = self.node_to_wrapper_map.get(node)
+        if wrapper_node:
+            parent_node = wrapper_node.parent.node
+            return parent_node
+        return None
+
+    def _remove_target_vars_of_for(self, before_or_after_loop_vars, loop_node):
+        """
+        Remove target vars of gast.For from before_loop_vars or after_loop_vars.
+        :param before_or_after_loop_vars: before_loop_vars or after_loop_vars of loop_node.
+        :param loop_node: Current loop node.
+        """
+
+        removed_vars = set()
+        for name_node in before_or_after_loop_vars:
+            if not isinstance(name_node, gast.Name):
+                continue
+
+            parent_node = self._get_parent_node(name_node)
+
+            # NOTE: gast.For.target can be gast.Tuple.
+            #  For example: `for i, j in enumerate(x)` has two target vars: i and j
+            if isinstance(parent_node, gast.Tuple):
+                parent_node = self._get_parent_node(parent_node)
+
+            if isinstance(parent_node,
+                          gast.For) and parent_node is not loop_node:
+                target_node = parent_node.target
+
+                if isinstance(target_node, gast.Tuple):
+                    target_vars = target_node.elts
+                else:
+                    target_vars = [target_node]
+
+                if name_node in target_vars:
+                    removed_vars.add(name_node)
+
+        removed_vars_name_strs = {var.id for var in removed_vars}
+
+        for var in before_or_after_loop_vars:
+            if not isinstance(var, gast.Name):
+                continue
+            if var.id in removed_vars_name_strs and var not in self.condition_vars[
+                    loop_node]:
+                removed_vars.add(var)
+
+        return before_or_after_loop_vars - removed_vars
+
 
 class LoopTransformer(gast.NodeTransformer):
     """

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

@@ -132,6 +132,19 @@ def var_create_in_for_loop(max_len):
     return ret
 
 
+def nested_for_loop_dyfunc():
+    two = fluid.layers.fill_constant(shape=[1], value=2, dtype="int32")
+    three = fluid.layers.fill_constant(shape=[1], value=3, dtype="int32")
+    for j in range(two):
+        for i in range(10):
+            a = 2
+
+    for i in range(three):
+        b = fluid.layers.zeros(shape=[1], dtype='float32')
+
+    return b
+
+
 class TestNameVisitor(unittest.TestCase):
     def setUp(self):
         self.loop_funcs = [
@@ -142,6 +155,8 @@ class TestNameVisitor(unittest.TestCase):
         ]
         self.create_var_names = [set(), set(["ret"]), set()]
 
+        self.nested_for_loop_func = nested_for_loop_dyfunc
+
     def test_loop_vars(self):
         for i in range(len(self.loop_funcs)):
             func = self.loop_funcs[i]
@@ -155,6 +170,28 @@ class TestNameVisitor(unittest.TestCase):
                     self.assertEqual(loop_var_names, self.loop_var_names[i])
                     self.assertEqual(create_var_names, self.create_var_names[i])
 
+    def test_nested_loop_vars(self):
+        func = self.nested_for_loop_func
+        test_func = inspect.getsource(func)
+        gast_root = gast.parse(test_func)
+        name_visitor = NameVisitor(gast_root)
+
+        self.loop_var_names = [
+            set(["j", "two"]),
+            set(["i", "three", "b"]),
+            set(["i"]),
+        ]
+        self.create_var_names = [set(), set(["b"]), set()]
+        i = 0
+        for node in gast.walk(gast_root):
+            if isinstance(node, (gast.While, gast.For)):
+                loop_var_names, create_var_names = name_visitor.get_loop_var_names(
+                    node)
+                # print(loop_var_names)
+                self.assertEqual(loop_var_names, self.loop_var_names[i])
+                self.assertEqual(create_var_names, self.create_var_names[i])
+                i += 1
+
 
 class TestTransformWhileLoop(unittest.TestCase):
     def setUp(self):