evalf dtype runtime checker

nutils/evaluable.py

@@ -757,10 +757,26 @@ def _assparse(self):
       return chunks
     return _assparse
 
+  class _evalf_checker:
+    def __init__(self, orig):
+      self.evalf_obj = getattr(orig, '__get__', lambda *args: orig)
+    def __get__(self, instance, owner):
+      evalf = self.evalf_obj(instance, owner)
+      @functools.wraps(evalf)
+      def evalf_with_check(*args, **kwargs):
+        res = evalf(*args, **kwargs)
+        assert not hasattr(instance, 'dtype') or asdtype(res.dtype) == instance.dtype, ((instance.dtype, res.dtype), instance, res)
+        assert not hasattr(instance, 'ndim') or res.ndim == instance.ndim
+        assert not hasattr(instance, 'shape') or all(m == n for m, n in zip(res.shape, instance.shape) if isinstance(n, int)), 'shape mismatch'
+        return res
+      return evalf_with_check
+
   class _ArrayMeta(type(Evaluable)):
     def __new__(mcls, name, bases, namespace):
       if '_assparse' in namespace:
         namespace['_assparse'] = _chunked_assparse_checker(namespace['_assparse'])
+      if 'evalf' in namespace:
+        namespace['evalf'] = _evalf_checker(namespace['evalf'])
       return super().__new__(mcls, name, bases, namespace)
 
 else: