[3.12] gh-108983: Add more PEP 526 tests to test_grammar (GH-108984) (#109000)

gh-108983: Add more PEP 526 tests to `test_grammar` (GH-108984)
(cherry picked from commit 1fb20d4)

Co-authored-by: Nikita Sobolev <[email protected]>

Author: miss-islington

Lib/test/test_grammar.py

@@ -350,6 +350,11 @@ def test_var_annot_syntax_errors(self):
         check_syntax_error(self, "x: int: str")
         check_syntax_error(self, "def f():\n"
                                  "    nonlocal x: int\n")
+        check_syntax_error(self, "def f():\n"
+                                 "    global x: int\n")
+        check_syntax_error(self, "x: int = y = 1")
+        check_syntax_error(self, "z = w: int = 1")
+        check_syntax_error(self, "x: int = y: int = 1")
         # AST pass
         check_syntax_error(self, "[x, 0]: int\n")
         check_syntax_error(self, "f(): int\n")
@@ -363,6 +368,12 @@ def test_var_annot_syntax_errors(self):
         check_syntax_error(self, "def f():\n"
                                  "    global x\n"
                                  "    x: int\n")
+        check_syntax_error(self, "def f():\n"
+                                 "    x: int\n"
+                                 "    nonlocal x\n")
+        check_syntax_error(self, "def f():\n"
+                                 "    nonlocal x\n"
+                                 "    x: int\n")
 
     def test_var_annot_basic_semantics(self):
         # execution order