stubgen: Fix valid type detection to allow pipe unions (#18726)

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`stubgen` has a regex which it uses to reject invalid types that are
extracted from docstrings. It needed to be updated to support union
shorthand: `str | int`.

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Author: chadrik

mypy/stubdoc.py

@@ -21,7 +21,7 @@
 Sig: _TypeAlias = tuple[str, str]
 
 
-_TYPE_RE: Final = re.compile(r"^[a-zA-Z_][\w\[\], .\"\']*(\.[a-zA-Z_][\w\[\], ]*)*$")
+_TYPE_RE: Final = re.compile(r"^[a-zA-Z_][\w\[\], .\"\'|]*(\.[a-zA-Z_][\w\[\], ]*)*$")
 _ARG_NAME_RE: Final = re.compile(r"\**[A-Za-z_][A-Za-z0-9_]*$")
 
 

mypy/test/teststubgen.py

@@ -1405,6 +1405,9 @@ def test_is_valid_type(self) -> None:
         assert is_valid_type("Literal[True]")
         assert is_valid_type("Literal[Color.RED]")
         assert is_valid_type("Literal[None]")
+        assert is_valid_type("str | int")
+        assert is_valid_type("dict[str, int] | int")
+        assert is_valid_type("tuple[str, ...]")
         assert is_valid_type(
             'Literal[26, 0x1A, "hello world", b"hello world", u"hello world", True, Color.RED, None]'
         )