Don't do any tricky inference in deferred nodes (#7134)

ilevkivskyi · web-flow · commit b279f4c46311 · 2019-07-02T20:23:04.000+01:00
Fixes #7126
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -2410,6 +2410,9 @@ def check_multi_assignment_from_tuple(self, lvalues: List[Lvalue], rvalue: Expre
                                                            reinferred_rvalue_type, context,
                                                            infer_lvalue_type)
                     return
+                if isinstance(reinferred_rvalue_type, AnyType) and self.current_node_deferred:
+                    # Doing more inference in deferred nodes can be hard, so give up for now.
+                    return
                 assert isinstance(reinferred_rvalue_type, TupleType)
                 rvalue_type = reinferred_rvalue_type
 
diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
@@ -2749,3 +2749,15 @@ def g() -> None:
         x + 'no way'  # E: Unsupported operand types for + ("int" and "str")
     x = int()
     f()
+
+[case testDeferralOfMemberNested]
+from typing import Tuple
+
+def f() -> None:
+    c: C
+    t: Tuple[str, Tuple[str, str]]
+    x, (y, c.a) = t  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+
+class C:
+    def __init__(self, a: int) -> None:
+        self.a = a
