diff --git a/artiq/transforms/inline.py b/artiq/transforms/inline.py
index abc5a06f1..c3151b54c 100644
--- a/artiq/transforms/inline.py
+++ b/artiq/transforms/inline.py
@@ -6,7 +6,7 @@ import ast
 import builtins
 from copy import deepcopy
 
-from artiq.transforms.tools import eval_ast, value_to_ast
+from artiq.transforms.tools import eval_ast, value_to_ast, NotASTRepresentable
 from artiq.language import core as core_language
 from artiq.language import units
 
@@ -45,7 +45,7 @@ class _ReferenceManager:
         self.kernel_attr_init = []
 
         # (id(obj), func_name, ref_name) or (id(obj), kernel_attr_name)
-        #     -> _UserVariable(name) / ast / constant_object
+        #     -> _UserVariable(name) / complex object
         self._to_inlined = dict()
         # inlined_name -> use_count
         self._use_count = dict()
@@ -57,10 +57,15 @@ class _ReferenceManager:
                      "range"):
             self._use_count[name] = 1
 
-    # node_or_value can be a AST node, used to inline function parameter values
-    # that can be simplified later through constant folding.
-    def register_replace(self, obj, func_name, ref_name, node_or_value):
-        self._to_inlined[(id(obj), func_name, ref_name)] = node_or_value
+    # Complex objects in the namespace of functions can be used in two ways:
+    # 1. Calling a method on them (which gets inlined or RPCd)
+    # 2. Getting or setting attributes (which are turned into local variables)
+    # They are needed to implement "self", which is the only supported use
+    # case.
+    def register_complex_object(self, obj, func_name, ref_name,
+                                complex_object):
+        assert(not isinstance(complex_object, ast.AST))
+        self._to_inlined[(id(obj), func_name, ref_name)] = complex_object
 
     def new_name(self, base_name):
         if base_name[-1].isdigit():
@@ -112,7 +117,7 @@ class _ReferenceManager:
     def resolve_constant(self, obj, func_name, node):
         if isinstance(node, ast.Name):
             c = self.resolve_name(obj, func_name, node.id, False)
-            if isinstance(c, (_UserVariable, ast.AST)):
+            if isinstance(c, _UserVariable):
                 raise ValueError("Not a constant")
             return c
         elif isinstance(node, ast.Attribute):
@@ -192,18 +197,10 @@ class _ReferenceReplacer(ast.NodeVisitor):
         ival = self.rm.resolve_name(self.obj, self.func_name, node.id, store)
         if isinstance(ival, _UserVariable):
             newnode = ast.Name(ival.name, node.ctx)
-        elif isinstance(ival, ast.AST):
-            assert(not store)
-            newnode = deepcopy(ival)
         else:
             if store:
-                raise NotImplementedError(
-                    "Cannot turn object into user variable")
-            else:
-                newnode = value_to_ast(ival)
-                if newnode is None:
-                    raise NotImplementedError(
-                        "Cannot represent inlined value")
+                raise NotImplementedError("Cannot assign to this object")
+            newnode = value_to_ast(ival)
         return ast.copy_location(newnode, node)
 
     def _resolve_attribute(self, node):
@@ -325,40 +322,23 @@ class _ReferenceReplacer(ast.NodeVisitor):
         return node
 
 
-class _ListReadOnlyParams(ast.NodeVisitor):
-    def visit_FunctionDef(self, node):
-        if hasattr(self, "read_only_params"):
-            raise ValueError("More than one function definition")
-        self.read_only_params = {arg.arg for arg in node.args.args}
-        self.generic_visit(node)
-
-    def visit_Name(self, node):
-        if isinstance(node.ctx, ast.Store):
-            try:
-                self.read_only_params.remove(node.id)
-            except KeyError:
-                pass
-
-
-def _list_read_only_params(func_def):
-    lrp = _ListReadOnlyParams()
-    lrp.visit(func_def)
-    return lrp.read_only_params
-
-
 def _initialize_function_params(func_def, k_args, k_kwargs, rm):
     obj = k_args[0]
     func_name = func_def.name
     param_init = []
-    rop = _list_read_only_params(func_def)
     for arg_ast, arg_value in zip(func_def.args.args, k_args):
-        arg_name = arg_ast.arg
-        if arg_name in rop:
-            rm.register_replace(obj, func_name, arg_name, arg_value)
+        if isinstance(arg_value, ast.AST):
+            value = arg_value
         else:
-            uservar = rm.resolve_name(obj, func_name, arg_name, True)
+            try:
+                value = value_to_ast(arg_value)
+            except NotASTRepresentable:
+                value = None
+        if value is None:
+            rm.register_complex_object(obj, func_name, arg_ast.arg, arg_value)
+        else:
+            uservar = rm.resolve_name(obj, func_name, arg_ast.arg, True)
             target = ast.Name(uservar.name, ast.Store())
-            value = value_to_ast(arg_value)
             param_init.append(ast.Assign(targets=[target], value=value))
     return param_init
 
diff --git a/artiq/transforms/tools.py b/artiq/transforms/tools.py
index e6a8baa7e..8a7b4d08e 100644
--- a/artiq/transforms/tools.py
+++ b/artiq/transforms/tools.py
@@ -13,6 +13,10 @@ def eval_ast(expr, symdict=dict()):
     return eval(code, symdict)
 
 
+class NotASTRepresentable(Exception):
+    pass
+
+
 def value_to_ast(value):
     if isinstance(value, core_language.int64):  # must be before int
         return ast.Call(
@@ -41,7 +45,7 @@ def value_to_ast(value):
                 func=ast.Name("Quantity", ast.Load()),
                 args=[value_to_ast(value.amount), ast.Str(value.unit)],
                 keywords=[], starargs=None, kwargs=None)
-        return None
+        raise NotASTRepresentable(str(value))
 
 
 class NotConstant(Exception):