Jun 17, 2024 · Jun 15, 2024 · Jun 15, 2024 · Jun 15, 2024 · Jun 15, 2024 · Jun 15, 2024
diff --git a/mypy/stubgen.py b/mypy/stubgen.py
                return " | ".join([item.accept(self) for item in node.index.items])
            return node.index.accept(self)
        if base_fullname == "typing.Optional":
            if isinstance(node.index, TupleExpr):
                return self.stubgen.add_name("_typeshed.Incomplete")
            return f"{node.index.accept(self)} | None"
        base = node.base.accept(self)
        index = node.index.accept(self)
                else:
                    return False
            return all(self.is_alias_expression(i, top_level=False) for i in indices)
        elif isinstance(expr, OpExpr) and expr.op == "|":
            return self.is_alias_expression(
                expr.left, top_level=False
            ) and self.is_alias_expression(expr.right, top_level=False)
        else:
            return False

diff --git a/mypy/stubutil.py b/mypy/stubutil.py
        if fullname == "typing.Union":
            return " | ".join([item.accept(self) for item in t.args])
        if fullname == "typing.Optional":
            return f"{t.args[0].accept(self)} | None"
            if len(t.args) == 1:
                return f"{t.args[0].accept(self)} | None"
            return self.stubgen.add_name("_typeshed.Incomplete")
        if fullname in TYPING_BUILTIN_REPLACEMENTS:
            s = self.stubgen.add_name(TYPING_BUILTIN_REPLACEMENTS[fullname], require=True)
        if self.known_modules is not None and "." in s:
diff --git a/test-data/unit/stubgen.test b/test-data/unit/stubgen.test
 class Bar(Enum):
    A = ...
    B = ...

 [case testGracefullyHandleInvalidOptionalUsage]
 from typing import Optional

 x: Optional  # invalid
 y: Optional[int]  # valid
 z: Optional[int, str]  # invalid
 w: Optional[int | str]  # valid

 X = Optional
 Y = Optional[int]
 Z = Optional[int, str]
 W = Optional[int | str]

 [out]
 from _typeshed import Incomplete
 from typing import Optional

 x: Incomplete
 y: int | None
 z: Incomplete
 w: int | str | None
 X = Optional
 Y = int | None
 Z = Incomplete
 W = int | str | None
Original file line number	Diff line number	Diff line change
Expand Up		@@ -314,6 +314,8 @@ def visit_index_expr(self, node: IndexExpr) -> str:
		return " \| ".join([item.accept(self) for item in node.index.items])
		return node.index.accept(self)
		if base_fullname == "typing.Optional":
		if isinstance(node.index, TupleExpr):
		return self.stubgen.add_name("_typeshed.Incomplete")
		return f"{node.index.accept(self)} \| None"
		base = node.base.accept(self)
		index = node.index.accept(self)
Expand DownExpand Up		@@ -1060,6 +1062,10 @@ def is_alias_expression(self, expr: Expression, top_level: bool = True) -> bool:
		else:
		return False
		return all(self.is_alias_expression(i, top_level=False) for i in indices)
		elif isinstance(expr, OpExpr) and expr.op == "\|":
		return self.is_alias_expression(
		expr.left, top_level=False
		) and self.is_alias_expression(expr.right, top_level=False)
		else:
		return False

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -257,7 +257,9 @@ def visit_unbound_type(self, t: UnboundType) -> str:
		if fullname == "typing.Union":
		return " \| ".join([item.accept(self) for item in t.args])
		if fullname == "typing.Optional":
		return f"{t.args[0].accept(self)} \| None"
		if len(t.args) == 1:
		return f"{t.args[0].accept(self)} \| None"
		return self.stubgen.add_name("_typeshed.Incomplete")
		if fullname in TYPING_BUILTIN_REPLACEMENTS:
		s = self.stubgen.add_name(TYPING_BUILTIN_REPLACEMENTS[fullname], require=True)
		if self.known_modules is not None and "." in s:
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -4366,3 +4366,29 @@ class Foo(Enum):
		class Bar(Enum):
		A = ...
		B = ...

		[case testGracefullyHandleInvalidOptionalUsage]
		from typing import Optional

		x: Optional # invalid
		y: Optional[int] # valid
		z: Optional[int, str] # invalid
		w: Optional[int \| str] # valid

		X = Optional
		Y = Optional[int]
		Z = Optional[int, str]
		W = Optional[int \| str]

		[out]
		from _typeshed import Incomplete
		from typing import Optional

		x: Incomplete
		y: int \| None
		z: Incomplete
		w: int \| str \| None
		X = Optional
		Y = int \| None
		Z = Incomplete
		W = int \| str \| None