bpo-34822: Simplify AST for subscription. (GH-9605)

* Remove the slice type.
* Make Slice a kind of the expr type instead of the slice type.
* Replace ExtSlice(slices) with Tuple(slices, Load()).
* Replace Index(value) with a value itself.

All non-terminal nodes in AST for expressions are now of the expr type.

1 files changed, 14 insertions, 10 deletions

diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index c1e9f00..0058e93 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -343,6 +343,10 @@ class AST_Tests(unittest.TestCase):
     def test_field_attr_existence(self):
         for name, item in ast.__dict__.items():
             if self._is_ast_node(name, item):
+                if name == 'Index':
+                    # Index(value) just returns value now.
+                    # The argument is required.
+                    continue
                 x = item()
                 if isinstance(x, ast.AST):
                     self.assertEqual(type(x._fields), tuple)
@@ -1308,11 +1312,11 @@ class ASTValidatorTests(unittest.TestCase):
         self.expr(attr, "must have Load context")
 
     def test_subscript(self):
-        sub = ast.Subscript(ast.Name("x", ast.Store()), ast.Index(ast.Num(3)),
+        sub = ast.Subscript(ast.Name("x", ast.Store()), ast.Num(3),
                             ast.Load())
         self.expr(sub, "must have Load context")
         x = ast.Name("x", ast.Load())
-        sub = ast.Subscript(x, ast.Index(ast.Name("y", ast.Store())),
+        sub = ast.Subscript(x, ast.Name("y", ast.Store()),
                             ast.Load())
         self.expr(sub, "must have Load context")
         s = ast.Name("x", ast.Store())
@@ -1320,9 +1324,9 @@ class ASTValidatorTests(unittest.TestCase):
             sl = ast.Slice(*args)
             self.expr(ast.Subscript(x, sl, ast.Load()),
                       "must have Load context")
-        sl = ast.ExtSlice([])
-        self.expr(ast.Subscript(x, sl, ast.Load()), "empty dims on ExtSlice")
-        sl = ast.ExtSlice([ast.Index(s)])
+        sl = ast.Tuple([], ast.Load())
+        self.expr(ast.Subscript(x, sl, ast.Load()))
+        sl = ast.Tuple([s], ast.Load())
         self.expr(ast.Subscript(x, sl, ast.Load()), "must have Load context")
 
     def test_starred(self):
@@ -1664,11 +1668,11 @@ class EndPositionTests(unittest.TestCase):
         ''').strip()
         i1, i2, im = map(self._parse_value, (s1, s2, sm))
         self._check_content(s1, i1.value, 'f()[1, 2]')
-        self._check_content(s1, i1.value.slice.value, '1, 2')
+        self._check_content(s1, i1.value.slice, '1, 2')
         self._check_content(s2, i2.slice.lower, 'a.b')
         self._check_content(s2, i2.slice.upper, 'c.d')
-        self._check_content(sm, im.slice.dims[0].upper, 'f ()')
-        self._check_content(sm, im.slice.dims[1].lower, 'g ()')
+        self._check_content(sm, im.slice.elts[0].upper, 'f ()')
+        self._check_content(sm, im.slice.elts[1].lower, 'g ()')
         self._check_end_pos(im, 3, 3)
 
     def test_binop(self):
@@ -1989,13 +1993,13 @@ eval_results = [
 ('Expression', ('Constant', (1, 0, 1, 2), 10, None)),
 ('Expression', ('Constant', (1, 0, 1, 8), 'string', None)),
 ('Expression', ('Attribute', (1, 0, 1, 3), ('Name', (1, 0, 1, 1), 'a', ('Load',)), 'b', ('Load',))),
-('Expression', ('Subscript', (1, 0, 1, 6), ('Name', (1, 0, 1, 1), 'a', ('Load',)), ('Slice', ('Name', (1, 2, 1, 3), 'b', ('Load',)), ('Name', (1, 4, 1, 5), 'c', ('Load',)), None), ('Load',))),
+('Expression', ('Subscript', (1, 0, 1, 6), ('Name', (1, 0, 1, 1), 'a', ('Load',)), ('Slice', (1, 2, 1, 5), ('Name', (1, 2, 1, 3), 'b', ('Load',)), ('Name', (1, 4, 1, 5), 'c', ('Load',)), None), ('Load',))),
 ('Expression', ('Name', (1, 0, 1, 1), 'v', ('Load',))),
 ('Expression', ('List', (1, 0, 1, 7), [('Constant', (1, 1, 1, 2), 1, None), ('Constant', (1, 3, 1, 4), 2, None), ('Constant', (1, 5, 1, 6), 3, None)], ('Load',))),
 ('Expression', ('List', (1, 0, 1, 2), [], ('Load',))),
 ('Expression', ('Tuple', (1, 0, 1, 5), [('Constant', (1, 0, 1, 1), 1, None), ('Constant', (1, 2, 1, 3), 2, None), ('Constant', (1, 4, 1, 5), 3, None)], ('Load',))),
 ('Expression', ('Tuple', (1, 0, 1, 7), [('Constant', (1, 1, 1, 2), 1, None), ('Constant', (1, 3, 1, 4), 2, None), ('Constant', (1, 5, 1, 6), 3, None)], ('Load',))),
 ('Expression', ('Tuple', (1, 0, 1, 2), [], ('Load',))),
-('Expression', ('Call', (1, 0, 1, 17), ('Attribute', (1, 0, 1, 7), ('Attribute', (1, 0, 1, 5), ('Attribute', (1, 0, 1, 3), ('Name', (1, 0, 1, 1), 'a', ('Load',)), 'b', ('Load',)), 'c', ('Load',)), 'd', ('Load',)), [('Subscript', (1, 8, 1, 16), ('Attribute', (1, 8, 1, 11), ('Name', (1, 8, 1, 9), 'a', ('Load',)), 'b', ('Load',)), ('Slice', ('Constant', (1, 12, 1, 13), 1, None), ('Constant', (1, 14, 1, 15), 2, None), None), ('Load',))], [])),
+('Expression', ('Call', (1, 0, 1, 17), ('Attribute', (1, 0, 1, 7), ('Attribute', (1, 0, 1, 5), ('Attribute', (1, 0, 1, 3), ('Name', (1, 0, 1, 1), 'a', ('Load',)), 'b', ('Load',)), 'c', ('Load',)), 'd', ('Load',)), [('Subscript', (1, 8, 1, 16), ('Attribute', (1, 8, 1, 11), ('Name', (1, 8, 1, 9), 'a', ('Load',)), 'b', ('Load',)), ('Slice', (1, 12, 1, 15), ('Constant', (1, 12, 1, 13), 1, None), ('Constant', (1, 14, 1, 15), 2, None), None), ('Load',))], [])),
 ]
 main()