diff --git a/tool/playground/UWalker.g b/tool/playground/UWalker.g
deleted file mode 100644
index fbfa194cd..000000000
--- a/tool/playground/UWalker.g
+++ /dev/null
@@ -1,4 +0,0 @@
-tree grammar UWalker;
-options {tokenVocab=U;}
-
-a : ^(DECL x+=ID y=INT) ;