assert dataclass_array_container fields are not strings

Author: alexfikl

arraycontext/container/dataclass.py

@@ -48,6 +48,8 @@ def dataclass_array_container(cls: type) -> type:
     """
     from dataclasses import is_dataclass
     assert is_dataclass(cls)
+    assert all(not isinstance(f.type, str) for f in fields(cls)), \
+            "dataclass cannot have string-based type annotations"
 
     array_fields = [
             f for f in fields(cls) if is_array_container_type(f.type)]