Implement type inference for stared unpacking targets as list.

2 files changed, 34 insertions, 2 deletions

diff --git a/Cython/Compiler/FlowControl.py b/Cython/Compiler/FlowControl.py
index 30301f91a..81d013529 100644
--- a/Cython/Compiler/FlowControl.py
+++ b/Cython/Compiler/FlowControl.py
@@ -778,8 +778,11 @@ class ControlFlowAnalysis(CythonTransform):
             self.flow.mark_assignment(lhs, rhs, entry)
         elif lhs.is_sequence_constructor:
             for i, arg in enumerate(lhs.args):
-                if not rhs or arg.is_starred:
-                    item_node = None
+                if arg.is_starred:
+                    # "a, *b = x" assigns a list to "b"
+                    item_node = TypedExprNode(Builtin.list_type, may_be_none=False, pos=arg.pos)
+                elif rhs is self.object_expr:
+                    item_node = rhs
                 else:
                     item_node = rhs.inferable_item_node(i)
                 self.mark_assignment(arg, item_node)
diff --git a/tests/run/type_inference.pyx b/tests/run/type_inference.pyx
index 76a16c3b8..eb9016b00 100644
--- a/tests/run/type_inference.pyx
+++ b/tests/run/type_inference.pyx
@@ -287,6 +287,35 @@ def cascaded_assignment():
     e = a + b + c + d
     assert typeof(e) == "double"
 
+
+def unpacking(x):
+    """
+    >>> unpacking(0)
+    """
+    a, b, c, d = x, 1, 2.0, [3]
+    assert typeof(a) == "Python object", typeof(a)
+    assert typeof(b) == "long", typeof(b)
+    assert typeof(c) == "double", typeof(c)
+    assert typeof(d) == "list object", typeof(d)
+
+
+def star_unpacking(*x):
+    """
+    >>> star_unpacking(1, 2)
+    """
+    a, b = x
+    c, *d = x
+    *e, f = x
+    *g, g = x  # re-assignment
+    assert typeof(a) == "Python object", typeof(a)
+    assert typeof(b) == "Python object", typeof(b)
+    assert typeof(c) == "Python object", typeof(c)
+    assert typeof(d) == "list object", typeof(d)
+    assert typeof(e) == "list object", typeof(e)
+    assert typeof(f) == "Python object", typeof(f)
+    assert typeof(g) == "Python object", typeof(f)
+
+
 def increment():
     """
     >>> increment()