Missed those at merge

lark/load_grammar.py

@@ -407,7 +407,7 @@ class TokenTreeToPattern(ChildrenTransformer):
     def value(self, v):
         return v[0]
 
-class PrepareSymbols(Transformer):
+class PrepareSymbols(ChildrenTransformer):
     def value(self, v):
         v ,= v
         if isinstance(v, Tree):
@@ -532,7 +532,8 @@ def options_from_rule(name, *x):
 def symbols_from_strcase(expansion):
     return [Terminal(x, filter_out=x.startswith('_')) if is_terminal(x) else NonTerminal(x) for x in expansion]
 
-class PrepareGrammar(InlineTransformer):
+@inline_args
+class PrepareGrammar(ChildrenTransformer):
     def terminal(self, name):
         return name
     def nonterminal(self, name):

lark/transformers.py

@@ -78,6 +78,8 @@ class Transformer_InPlace(Transformer):
         return self._transform(tree)
 
 class Visitor(Base):
+    "Bottom-up visitor"
+
     def visit(self, tree):
         for subtree in tree.iter_subtrees():
             self._call_userfunc(subtree)
@@ -99,6 +101,31 @@ class Visitor_Recursive(Base):
         return tree
 
 
+from functools import wraps
+def visit_children_decor(func):
+    @wraps(func)
+    def inner(cls, tree):
+        values = cls.visit_children(tree)
+        return func(cls, values)
+    return inner
+
+class Interpreter(object):
+    "Top-down visitor"
+
+    def visit(self, tree):
+        return getattr(self, tree.data)(tree)
+
+    def visit_children(self, tree):
+        return [self.visit(child) if isinstance(child, Tree) else child
+                for child in tree.children]
+
+    def __getattr__(self, name):
+        return self.__default__
+
+    def __default__(self, tree):
+        return self.visit_children(tree)
+
+
 def inline_args(obj):
     if inspect.isclass(obj) and issubclass(obj, ChildrenTransformer):
         class _NewTransformer(ChildrenInlineTransformer, obj):

tests/test_trees.py

@@ -5,7 +5,8 @@ from unittest import TestCase
 import copy
 import pickle
 
-from lark.tree import Tree, Interpreter, visit_children_decor
+from lark.tree import Tree
+from lark.transformers import Interpreter, visit_children_decor
 
 
 class TestTrees(TestCase):