Merge branch 'main' into gh-25949

smontanaro · web-flow · commit 8fec43c87ce6 · 2022-11-01T10:21:29.000-05:00
diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst
@@ -122,7 +122,7 @@ An example that uses most of the list methods::
 
 You might have noticed that methods like ``insert``, ``remove`` or ``sort`` that
 only modify the list have no return value printed -- they return the default
-``None``. [1]_  This is a design principle for all mutable data structures in
+``None``. [#]_  This is a design principle for all mutable data structures in
 Python.
 
 Another thing you might notice is that not all data can be sorted or
@@ -731,5 +731,5 @@ interpreter will raise a :exc:`TypeError` exception.
 
 .. rubric:: Footnotes
 
-.. [1] Other languages may return the mutated object, which allows method
+.. [#] Other languages may return the mutated object, which allows method
        chaining, such as ``d->insert("a")->remove("b")->sort();``.
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
@@ -70,6 +70,18 @@ Important deprecations, removals or restrictions:
 
 * :pep:`623`, Remove wstr from Unicode
 
+Improved Error Messages
+=======================
+
+* Improve the :exc:`SyntaxError` error message when the user types ``import x
+  from y`` instead of ``from y import x``. Contributed by Pablo Galindo in :gh:`98931`.
+
+    >>> import a.y.z from b.y.z
+    Traceback (most recent call last):
+      File "<stdin>", line 1
+        import a.y.z from b.y.z
+        ^^^^^^^^^^^^^^^^^^^^^^^
+    SyntaxError: Did you mean to use 'from ... import ...' instead?
 
 New Features
 ============
diff --git a/Grammar/python.gram b/Grammar/python.gram
@@ -194,7 +194,10 @@ yield_stmt[stmt_ty]: y=yield_expr { _PyAST_Expr(y, EXTRA) }
 
 assert_stmt[stmt_ty]: 'assert' a=expression b=[',' z=expression { z }] { _PyAST_Assert(a, b, EXTRA) }
 
-import_stmt[stmt_ty]: import_name | import_from
+import_stmt[stmt_ty]: 
+    | invalid_import
+    | import_name
+    | import_from
 
 # Import statements
 # -----------------
@@ -1230,6 +1233,10 @@ invalid_group:
         RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot use starred expression here") }
     | '(' a='**' expression ')' {
         RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot use double starred expression here") }
+invalid_import:
+    | a='import' dotted_name 'from' dotted_name {
+        RAISE_SYNTAX_ERROR_STARTING_FROM(a, "Did you mean to use 'from ... import ...' instead?") }
+ 
 invalid_import_from_targets:
     | import_from_as_names ',' NEWLINE {
         RAISE_SYNTAX_ERROR("trailing comma not allowed without surrounding parentheses") }
diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
@@ -1011,8 +1011,8 @@ def __len__(self):
 
     def __iter__(self):
         d = {}
-        for mapping in reversed(self.maps):
-            d.update(dict.fromkeys(mapping))    # reuses stored hash values if possible
+        for mapping in map(dict.fromkeys, reversed(self.maps)):
+            d |= mapping                        # reuses stored hash values if possible
         return iter(d)
 
     def __contains__(self, key):
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
@@ -1584,6 +1584,22 @@
 Traceback (most recent call last):
 SyntaxError: trailing comma not allowed without surrounding parentheses
 
+>>> import a from b
+Traceback (most recent call last):
+SyntaxError: Did you mean to use 'from ... import ...' instead?
+
+>>> import a.y.z from b.y.z
+Traceback (most recent call last):
+SyntaxError: Did you mean to use 'from ... import ...' instead?
+
+>>> import a from b as bar
+Traceback (most recent call last):
+SyntaxError: Did you mean to use 'from ... import ...' instead?
+
+>>> import a.y.z from b.y.z as bar
+Traceback (most recent call last):
+SyntaxError: Did you mean to use 'from ... import ...' instead?
+
 # Check that we dont raise the "trailing comma" error if there is more
 # input to the left of the valid part that we parsed.
 
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
@@ -3916,6 +3916,34 @@ class A:
         # C version of GenericAlias
         self.assertEqual(list[A()].__parameters__, (T,))
 
+    def test_non_generic_subscript(self):
+        T = TypeVar('T')
+        class G(Generic[T]):
+            pass
+        class A:
+            __parameters__ = (T,)
+
+        for s in (int, G, A, List, list,
+                  TypeVar, TypeVarTuple, ParamSpec,
+                  types.GenericAlias, types.UnionType):
+
+            for t in Tuple, tuple:
+                with self.subTest(tuple=t, sub=s):
+                    self.assertEqual(t[s, T][int], t[s, int])
+                    self.assertEqual(t[T, s][int], t[int, s])
+                    a = t[s]
+                    with self.assertRaises(TypeError):
+                        a[int]
+
+            for c in Callable, collections.abc.Callable:
+                with self.subTest(callable=c, sub=s):
+                    self.assertEqual(c[[s], T][int], c[[s], int])
+                    self.assertEqual(c[[T], s][int], c[[int], s])
+                    a = c[[s], s]
+                    with self.assertRaises(TypeError):
+                        a[int]
+
+
 class ClassVarTests(BaseTestCase):
 
     def test_basics(self):
diff --git a/Lib/typing.py b/Lib/typing.py
@@ -1437,6 +1437,10 @@ def _determine_new_args(self, args):
         new_args = []
         for old_arg in self.__args__:
 
+            if isinstance(old_arg, type):
+                new_args.append(old_arg)
+                continue
+
             substfunc = getattr(old_arg, '__typing_subst__', None)
             if substfunc:
                 new_arg = substfunc(new_arg_by_param[old_arg])
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-10-31-21-01-35.gh-issue-98852.MYaRN6.rst b/Misc/NEWS.d/next/Core and Builtins/2022-10-31-21-01-35.gh-issue-98852.MYaRN6.rst
@@ -0,0 +1,4 @@
+Fix subscription of type aliases containing bare generic types or types like
+:class:`~typing.TypeVar`: for example ``tuple[A, T][int]`` and
+``tuple[TypeVar, T][int]``, where ``A`` is a generic type, and ``T`` is a
+type variable.
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-10-31-22-55-34.gh-issue-98931.AoWZ-4.rst b/Misc/NEWS.d/next/Core and Builtins/2022-10-31-22-55-34.gh-issue-98931.AoWZ-4.rst
@@ -0,0 +1,2 @@
+Improve the :exc:`SyntaxError` error message when the user types ``import x
+from y`` instead of ``from y import x``. Patch by Pablo Galindo
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
@@ -458,6 +458,13 @@ _Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObje
     }
     for (Py_ssize_t iarg = 0, jarg = 0; iarg < nargs; iarg++) {
         PyObject *arg = PyTuple_GET_ITEM(args, iarg);
+        if (PyType_Check(arg)) {
+            Py_INCREF(arg);
+            PyTuple_SET_ITEM(newargs, jarg, arg);
+            jarg++;
+            continue;
+        }
+
         int unpack = _is_unpacked_typevartuple(arg);
         if (unpack < 0) {
             Py_DECREF(newargs);
diff --git a/Parser/parser.c b/Parser/parser.c

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Improve the :exc:`SyntaxError` error message when the user types ``import x
	`2`	+from y`` instead of ``from y import x``. Patch by Pablo Galindo