fix reference leak in closure when reassigning to "*args" argument

Cython/Compiler/Nodes.py

@@ -1915,7 +1915,7 @@ class FuncDefNode(StatNode, BlockNode):
             elif is_cdef and entry.type.is_memoryviewslice and len(entry.cf_assignments) > 1:
                 code.put_incref_memoryviewslice(entry.cname, have_gil=code.funcstate.gil_owned)
         for entry in lenv.var_entries:
-            if entry.is_arg and len(entry.cf_assignments) > 1:
+            if entry.is_arg and len(entry.cf_assignments) > 1 and not entry.in_closure:
                 if entry.xdecref_cleanup:
                     code.put_var_xincref(entry)
                 else:

tests/run/closure_leak_1.pyx

+# mode: run
+# tag: closure
+
+def reassign_args(x, *args):
+    """
+    >>> reassign_args(1, [1,2,3,4])
+    """
+    a,args = args[0], args[1:]
+    b = False
+    if b:
+        c = x.map_coefficients(lambda c: c(*args))