More determinism in fused types.

Cython/Compiler/FusedNode.py

@@ -6,6 +6,7 @@ from . import (ExprNodes, PyrexTypes, MemoryView,
                ParseTreeTransforms, StringEncoding, Errors)
 from .ExprNodes import CloneNode, ProxyNode, TupleNode
 from .Nodes import FuncDefNode, CFuncDefNode, StatListNode, DefNode
+from ..Utils import OrderedSet
 
 
 class FusedCFuncDefNode(StatListNode):
@@ -576,7 +577,7 @@ class FusedCFuncDefNode(StatListNode):
 
         fused_index = 0
         default_idx = 0
-        all_buffer_types = set()
+        all_buffer_types = OrderedSet()
         seen_fused_types = set()
         for i, arg in enumerate(self.node.args):
             if arg.type.is_fused:

Cython/Utils.py

@@ -449,6 +449,22 @@ class LazyStr:
         return left + self.callback()
 
 
+class OrderedSet(object):
+  def __init__(self, elements=()):
+    self._list = []
+    self._set = set()
+    self.update(elements)
+  def __iter__(self):
+    return iter(self._list)
+  def update(self, elements):
+    for e in elements:
+      self.add(e)
+  def add(self, e):
+    if e not in self._set:
+      self._list.append(e)
+      self._set.add(e)
+
+
 # Class decorator that adds a metaclass and recreates the class with it.
 # Copied from 'six'.
 def add_metaclass(metaclass):