Throw an error if there are duplicate rules in ebnf

diff --git a/extra/peg/ebnf/ebnf.factor b/extra/peg/ebnf/ebnf.factor
index 2aec8b9aea09ccd5cb573a0d9941135aa5da5094..e78757be34d3c051bdb533cf36f16158988203f8 100644 (file)
--- a/extra/peg/ebnf/ebnf.factor
+++ b/extra/peg/ebnf/ebnf.factor
@@ -305,7 +305,7 @@ M: ebnf (transform) ( ast -- parser )
 M: ebnf-rule (transform) ( ast -- parser )\r
   dup elements>> \r
   (transform) [\r
-    swap symbol>> set\r
+    swap symbol>> dup get [ "Rule '" over append "' defined more than once" append throw ] [ set ] if\r
   ] keep ;\r
 \r
 M: ebnf-sequence (transform) ( ast -- parser )\r