Fix walrus assignment type propagation across call arguments

mypy/checkexpr.py

@@ -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(

test-data/unit/check-expressions.test

@@ -2538,3 +2538,36 @@ 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"