Dec 16, 2025 · Dec 16, 2025 · Dec 16, 2025 · Dec 17, 2025 · Dec 18, 2025
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
                e.callee.arg_names,
                lambda i: self.accept(e.args[i]),
            )
            checked_args = []
            for arg in e.args:
                checked_args.append(self.accept(arg))

            arg_types = [
                join.join_type_list([self.accept(e.args[j]) for j in formal_to_actual[i]])
                join.join_type_list([checked_args[j] for j in formal_to_actual[i]])
                for i in range(len(e.callee.arg_kinds))
            ]
            type_context = CallableType(
diff --git a/test-data/unit/check-expressions.test b/test-data/unit/check-expressions.test
    x, y, z = xy  # E: Unpacking a string is disallowed
    reveal_type(z)  # N: Revealed type is "builtins.str"
 [builtins fixtures/primitives.pyi]

 [case testWalrusAssignmentInCallArguments]
 # Ensure that assignment expressions (:=) in earlier call arguments
 # propagate type information to later arguments in the same call.

 from dataclasses import dataclass

 @dataclass
 class Notification:
    request_reference: str

 @dataclass
 class Case:
    title: str
    notifications: list[Notification]
    initial_reference: str = ""

 cases = [
    *[
        Case(
            title="example",
            initial_reference=(request_reference := "abc"),
            notifications=[
                Notification(
                    request_reference=request_reference,
                ),
            ],
        )
        for _ in (1, 2)
    ],
 ]

 reveal_type(request_reference)  # N: Revealed type is "builtins.str"
 [builtins fixtures/tuple.pyi]
Original file line number	Diff line number	Diff line change
Expand Up		@@ -585,9 +585,12 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
		e.callee.arg_names,
		lambda i: self.accept(e.args[i]),
		)
		checked_args = []
		for arg in e.args:
		checked_args.append(self.accept(arg))

		arg_types = [
		join.join_type_list([self.accept(e.args[j]) for j in formal_to_actual[i]])
		join.join_type_list([checked_args[j] for j in formal_to_actual[i]])
		for i in range(len(e.callee.arg_kinds))
		]
		type_context = CallableType(
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2538,3 +2538,37 @@ def last_known_value() -> None:
		x, y, z = xy # E: Unpacking a string is disallowed
		reveal_type(z) # N: Revealed type is "builtins.str"
		[builtins fixtures/primitives.pyi]

		[case testWalrusAssignmentInCallArguments]
		# Ensure that assignment expressions (:=) in earlier call arguments
		# propagate type information to later arguments in the same call.

		from dataclasses import dataclass

		@dataclass
		class Notification:
		request_reference: str

		@dataclass
		class Case:
		title: str
		notifications: list[Notification]
		initial_reference: str = ""

		cases = [
		*[
		Case(
		title="example",
		initial_reference=(request_reference := "abc"),
		notifications=[
		Notification(
		request_reference=request_reference,
		),
		],
		)
		for _ in (1, 2)
		],
		]

		reveal_type(request_reference) # N: Revealed type is "builtins.str"
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		[builtins fixtures/tuple.pyi]