Add tests for assignment expression in class scope

Author: dhood

test-data/unit/check-python38.test

@@ -338,6 +338,28 @@ def check_narrow(x: Optional[int], s: List[int]) -> None:
     if isinstance((y := x), int):
         reveal_type(y)  # N: Revealed type is 'builtins.int'
 
+class AssignmentExpressionsClass:
+    x = (y := 1) + (z := 2)
+    reveal_type(z)  # N: Revealed type is 'builtins.int'
+
+    l = [x2 := 1, 2, 3]
+    reveal_type(x2)  # N: Revealed type is 'builtins.int'
+
+    def __init__(self) -> None:
+        reveal_type(self.z)  # N: Revealed type is 'builtins.int'
+
+        l = [z2 := 1, z2 + 2, z2 + 3]
+        reveal_type(z2)  # N: Revealed type is 'builtins.int'
+        reveal_type(l)  # N: Revealed type is 'builtins.list[builtins.int*]'
+
+        filtered_data = [z3 for x in l if (z3 := 1) is not None]
+        reveal_type(filtered_data)  # N: Revealed type is 'builtins.list[builtins.int*]'
+        reveal_type(z3)  # N: Revealed type is 'builtins.int'
+
+# Assignment expressions from inside the class should not escape the class scope.
+reveal_type(x2)  # E: Name 'x2' is not defined  # N: Revealed type is 'Any'
+reveal_type(z2)  # E: Name 'z2' is not defined  # N: Revealed type is 'Any'
+
 [builtins fixtures/isinstancelist.pyi]
 
 [case testWalrusPartialTypes]