optimise set(it) into a call to PySet_New(it)

Cython/Compiler/Optimize.py

@@ -1993,25 +1993,39 @@ class OptimizeBuiltinCalls(Visitor.MethodDispatcherTransform):
         exception_value = "((double)-1)",
         exception_check = True)
 
+    PySet_New_func_type = PyrexTypes.CFuncType(
+        Builtin.set_type, [
+            PyrexTypes.CFuncTypeArg("it", PyrexTypes.py_object_type, None)
+        ])
+
     def _handle_simple_function_set(self, node, function, pos_args):
-        if len(pos_args) == 1 and isinstance(pos_args[0], (ExprNodes.ListNode,
-                                                           ExprNodes.TupleNode)):
-            # We can optimise set([x,y,z]) safely into a set literal,
-            # but only if we create all items before adding them -
-            # adding an item may raise an exception if it is not
-            # hashable, but creating the later items may have
-            # side-effects.
-            args = []
-            temps = []
-            for arg in pos_args[0].args:
-                if not arg.is_simple():
-                    arg = UtilNodes.LetRefNode(arg)
-                    temps.append(arg)
-                args.append(arg)
-            result = ExprNodes.SetNode(node.pos, is_temp=1, args=args)
-            for temp in temps[::-1]:
-                result = UtilNodes.EvalWithTempExprNode(temp, result)
-            return result
+        if len(pos_args) == 1:
+            if pos_args[0].is_sequence_constructor:
+                # We can optimise set([x,y,z]) safely into a set literal,
+                # but only if we create all items before adding them -
+                # adding an item may raise an exception if it is not
+                # hashable, but creating the later items may have
+                # side-effects.
+                args = []
+                temps = []
+                for arg in pos_args[0].args:
+                    if not arg.is_simple():
+                        arg = UtilNodes.LetRefNode(arg)
+                        temps.append(arg)
+                    args.append(arg)
+                result = ExprNodes.SetNode(node.pos, is_temp=1, args=args)
+                for temp in temps[::-1]:
+                    result = UtilNodes.EvalWithTempExprNode(temp, result)
+                return result
+            else:
+                # PySet_New(it) is better than a generic Python call to set(it)
+                return ExprNodes.PythonCapiCallNode(
+                    node.pos, "PySet_New",
+                    self.PySet_New_func_type,
+                    args=pos_args,
+                    is_temp=node.is_temp,
+                    utility_code=UtilityCode.load_cached('pyset_compat', 'Builtins.c'),
+                    py_name="set")
         return node
 
     def _handle_simple_function_float(self, node, function, pos_args):