May 3, 2023 · Apr 24, 2023 · Apr 24, 2023 · Apr 24, 2023 · Apr 24, 2023 · Apr 24, 2023
diff --git a/mypy/checker.py b/mypy/checker.py
    def visit_name_expr(self, e: NameExpr) -> None:
        if self.lvalue and e.node is self.var_node:
            self.last_line = max(self.last_line, e.line)

    def visit_with_stmt(self, s: WithStmt) -> None:
        self.lvalue = True
        for lv in s.target:
            if lv is not None:
                lv.accept(self)
        self.lvalue = False
        s.body.accept(self)

    def visit_for_stmt(self, s: ForStmt) -> None:
        self.lvalue = True
        s.index.accept(self)
        self.lvalue = False
        s.body.accept(self)
        if s.else_body:
            s.else_body.accept(self)
diff --git a/test-data/unit/check-optional.test b/test-data/unit/check-optional.test
 if 3 in x:
    pass

 [casetestNarrowedVariableInNestedFunction]
 [casetestNarrowedVariableInNestedFunctionBasic]
 from typing import Optional

 def can_narrow(x: Optional[str]) -> None:

 def cannot_narrow_top_level() -> None:
    reveal_type(x)  # N: Revealed type is "Union[builtins.str, None]"

 [case testNarrowedVariableInNestedFunction2]
 from typing import Optional

 class C:
    a: Optional[str]

 def attribute_narrowing(c: C) -> None:
    # This case is not supported at the moment.
    c.a = "x"
    def nested() -> str:
        return c.a  # E: Incompatible return value type (got "Optional[str]", expected "str")
    nested()

 def assignment_in_for(x: Optional[str]) -> None:
    if x is None:
        x = "e"
    def nested() -> str:
        return x  # E: Incompatible return value type (got "Optional[str]", expected "str")
    for x in ["x"]:
        pass

 def foo(): pass

 def assignment_in_with(x: Optional[str]) -> None:
    if x is None:
        x = "e"
    def nested() -> str:
        return x  # E: Incompatible return value type (got "Optional[str]", expected "str")
    with foo() as x:
        pass
Original file line number	Diff line number	Diff line change
Expand Up		@@ -7672,3 +7672,19 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
		def visit_name_expr(self, e: NameExpr) -> None:
		if self.lvalue and e.node is self.var_node:
		self.last_line = max(self.last_line, e.line)

		def visit_with_stmt(self, s: WithStmt) -> None:
		self.lvalue = True
		for lv in s.target:
		if lv is not None:
		lv.accept(self)
		self.lvalue = False
		s.body.accept(self)

		def visit_for_stmt(self, s: ForStmt) -> None:
		self.lvalue = True
		s.index.accept(self)
		self.lvalue = False
		s.body.accept(self)
		if s.else_body:
		s.else_body.accept(self)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1040,7 +1040,7 @@ x: Optional[List[int]]
		if 3 in x:
		pass

		[casetestNarrowedVariableInNestedFunction]
		[casetestNarrowedVariableInNestedFunctionBasic]
		from typing import Optional

		def can_narrow(x: Optional[str]) -> None:
Expand DownExpand Up		@@ -1069,3 +1069,34 @@ x: Optional[str] = "x"

		def cannot_narrow_top_level() -> None:
Copy link Member ilevkivskyiApr 27, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. The actual narrowing is missing here. Until#2008 is fixed this would be optional despite r.h.s. So you need to write x:Optional[str]ifxisNone:x="x" here as well. Copy link CollaboratorAuthor JukkaLMay 3, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Yeah this was an incomplete test case.
		reveal_type(x) # N: Revealed type is "Union[builtins.str, None]"

		[case testNarrowedVariableInNestedFunction2]
		from typing import Optional

		class C:
		a: Optional[str]

		def attribute_narrowing(c: C) -> None:
		# This case is not supported at the moment.
		c.a = "x"
		def nested() -> str:
		return c.a # E: Incompatible return value type (got "Optional[str]", expected "str")
		nested()

		def assignment_in_for(x: Optional[str]) -> None:
		if x is None:
		x = "e"
		def nested() -> str:
		return x # E: Incompatible return value type (got "Optional[str]", expected "str")
		for x in ["x"]:
		pass

		def foo(): pass

		def assignment_in_with(x: Optional[str]) -> None:
		if x is None:
		x = "e"
		def nested() -> str:
		return x # E: Incompatible return value type (got "Optional[str]", expected "str")
		with foo() as x:
		pass