add _make to our NamedTuple stub, add test for bug found implementing it

from_cpython/Lib/collections.py

@@ -422,6 +422,13 @@ def namedtuple(name, fields):
             for i in xrange(len(fields)):
                 setattr(self, fields[i], args[i])
 
+        @classmethod
+        def _make(cls, iterable):
+            t = tuple(iterable)
+            if len(t) != len(fields):
+                raise TypeError('Expected %d arguments, got %d' % (len(fields), len(t)))
+            return cls(*t)
+
         def __getitem__(self, idx):
             assert 0 <= idx < len(fields)
             return getattr(self, fields[idx])

src/codegen/irgen/irgenerator.cpp

@@ -1832,6 +1832,7 @@ private:
 
         endBlock(DEAD);
 
+        // This is tripping in test/tests/return_selfreferential.py
         ASSERT(rtn->getVrefs() == 1, "%d", rtn->getVrefs());
         assert(rtn->getValue());
         emitter.getBuilder()->CreateRet(rtn->getValue());

test/tests/return_selfreferential.py

+# fail-if: ('-n' in EXTRA_JIT_ARGS) or ('-O' in EXTRA_JIT_ARGS)
+# trips an assert about vref counts in irgenerator.cpp: IrGeneratorImpl::doReturn()
+def f1():
+    def bar(x):
+        print 'bar(%s)' % x
+        if x:
+            return bar(0)
+        return x
+    return bar
+
+g = f1()
+print g(2)
+
+def makeA():
+    class A(object):
+        def __init__(self, *args):
+            self.args = args
+
+        @classmethod
+        def _make(cls, *args):
+            tmp = A
+            return cls(*args)
+    return A
+
+def f2():
+    A = makeA()
+    return A(1,2,3)
+a = f2()
+print a.args