--- a/python/ir/instruction.py	Sat Jun 15 19:13:05 2013 +0200
+++ b/python/ir/instruction.py	Fri Jun 21 15:01:08 2013 +0200
@@ -16,6 +16,7 @@
 class Use:
    def __init__(self, user, val):
       self.user = user
+      assert type(val) is Value
       self.val = val
       self.val.used_by.append(self.user)
    def delete(self):
@@ -99,6 +100,7 @@
 class ImmLoad(Instruction):
    def __init__(self, target, value):
       super().__init__()
+      assert type(target) is Value
       self.target = target
       self.value = value
       self.addDef(target)
@@ -111,6 +113,8 @@
       super().__init__()
       #print('operation is in binops:', operation in BinOps)
       # Check types of the two operands:
+      assert type(value1) is Value
+      assert type(value2) is Value
       self.result = result
       self.addDef(result)
       self.value1 = value1