fix error that tuple with star expr

Author: LiuYuHui

mypy/checker.py

@@ -2483,8 +2483,17 @@ def check_assignment_to_multiple_lvalues(self, lvalues: List[Lvalue], rvalue: Ex
             # control in cases like: a, b = [int, str] where rhs would get
             # type List[object]
 
-            rvalues = rvalue.items
-
+            rvalues = [] # type: List[Expression]
+            for rval in rvalue.items:
+                if isinstance(rval, StarExpr):
+                    typs = self.expr_checker.visit_star_expr(rval)
+                    typs = get_proper_type(typs.type)
+                    if isinstance(typs, TupleType):
+                        rvalues.extend([TempNode(typ) for typ in typs.items])
+                    else:
+                        rvalues.append(TempNode(typ))
+                else:
+                    rvalues.append(rval)
             if self.check_rvalue_count_in_assignment(lvalues, len(rvalues), context):
                 star_index = next((i for i, lv in enumerate(lvalues) if
                                    isinstance(lv, StarExpr)), len(lvalues))

test-data/unit/check-tuples.test

@@ -1421,3 +1421,10 @@ t6: Tuple[int, int, int, int, int, int, int, int, int, int, int, int] = (1, 2, 3
                                                                     # E: Incompatible types in assignment (expression has type Tuple[int, int, ... <15 more items>], variable has type Tuple[int, int, ... <10 more items>])
 
 [builtins fixtures/tuple.pyi]
+
+[case testTupleWithStarExpr]
+from typing import Tuple
+points1 = (1, 2)  # type: Tuple[int, int]
+x, y, z = *points1, 0
+
+[builtins fixtures/tuple.pyi]