global x: int is not tested

[sobolevn]

While reading https://peps.python.org/pep-0526/#where-annotations-aren-t-allowed I've noticed that not all corner-cases are covered:

cpython/Lib/test/test_grammar.py

Lines 347 to 365 in 6f8411c

	def test_var_annot_syntax_errors(self):
	# parser pass
	check_syntax_error(self, "def f: int")
	check_syntax_error(self, "x: int: str")
	check_syntax_error(self, "def f():\n"
	" nonlocal x: int\n")
	# AST pass
	check_syntax_error(self, "[x, 0]: int\n")
	check_syntax_error(self, "f(): int\n")
	check_syntax_error(self, "(x,): int")
	check_syntax_error(self, "def f():\n"
	" (x, y): int = (1, 2)\n")
	# symtable pass
	check_syntax_error(self, "def f():\n"
	" x: int\n"
	" global x\n")
	check_syntax_error(self, "def f():\n"
	" global x\n"
	" x: int\n")

For example, explicit PEP's example:

def f():
    global x: int  # SyntaxError

def g():
    x: int  # Also a SyntaxError
    global x

Two problems:

1. global x: int is not tested, only nonlocal x: int is
2. x: int; nonlocal x is not tested

There's also an interesting corner-case from the rejected ideas:

x: int = y = 1
z = w: int = 1

Since, we have this test check_syntax_error(self, "def f: int"), I assume that we also test rejected ideas here. So, let's add this one as well.

I propose adding these three cases.

Linked PRs

• gh-108983: Add more PEP 526 tests to test_grammar #108984
• [3.12] gh-108983: Add more PEP 526 tests to test_grammar (GH-108984) #109000
• [3.11] gh-108983: Add more PEP 526 tests to test_grammar (GH-108984) #109001

[hugovk]

Thank you!