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

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) {