bpo-42737: annotations with complex targets no longer causes any runtime effects (GH-23952)

Author: isidentical

Doc/whatsnew/3.10.rst

@@ -791,6 +791,10 @@ Other Language Changes
   Moreover, static methods are now callable as regular functions.
   (Contributed by Victor Stinner in :issue:`43682`.)
 
+* Annotations for complex targets (everything beside ``simple name`` targets
+  defined by :pep:`526`) no longer cause any runtime effects with ``from __future__ import annotations``.
+  (Contributed by Batuhan Taskaya in :issue:`42737`.)
+
 
 New Modules
 ===========

Lib/test/test_future.py

@@ -134,8 +134,12 @@ async def f2() -> {ann}:
             ...
         async def g2(arg: {ann}) -> None:
             ...
+        class H:
+            var: {ann}
+            object.attr: {ann}
         var: {ann}
         var2: {ann} = None
+        object.attr: {ann}
         """
     )
 
@@ -343,6 +347,13 @@ def test_infinity_numbers(self):
         self.assertAnnotationEqual("('inf', 1e1000, 'infxxx', 1e1000j)", expected=f"('inf', {inf}, 'infxxx', {infj})")
         self.assertAnnotationEqual("(1e1000, (1e1000j,))", expected=f"({inf}, ({infj},))")
 
+    def test_annotation_with_complex_target(self):
+        with self.assertRaises(SyntaxError):
+            exec(
+                "from __future__ import annotations\n"
+                "object.__debug__: int"
+            )
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core and Builtins/2021-04-22-22-48-30.bpo-42737.lsJ7pD.rst

@@ -0,0 +1,2 @@
+Annotations for complex targets (everything beside simple names) no longer
+cause any runtime effects with ``from __future__ import annotations``.

Python/compile.c

@@ -5356,6 +5356,12 @@ check_ann_expr(struct compiler *c, expr_ty e)
 static int
 check_annotation(struct compiler *c, stmt_ty s)
 {
+    /* Annotations of complex targets does not produce anything
+       under annotations future */
+    if (c->c_future->ff_features & CO_FUTURE_ANNOTATIONS) {
+        return 1;
+    }
+
     /* Annotations are only evaluated in a module or class. */
     if (c->u->u_scope_type == COMPILER_SCOPE_MODULE ||
         c->u->u_scope_type == COMPILER_SCOPE_CLASS) {