2 files changed, 13 insertions, 1 deletions

diff --git a/lpcode.c b/lpcode.c
index 1ee6ed1..70a8d3c 100644
--- a/lpcode.c
+++ b/lpcode.c
@@ -192,10 +192,13 @@ int checkaux (TTree *tree, int pred) {
       if (!checkaux(sib1(tree), pred)) return 0;
       /* else return checkaux(sib2(tree), pred); */
       tree = sib2(tree); goto tailcall;
-    case TChoice: case TLabChoice: /* labeled failure */
+    case TChoice: 
       if (checkaux(sib2(tree), pred)) return 1;
       /* else return checkaux(sib1(tree), pred); */
       tree = sib1(tree); goto tailcall;
+                case TLabChoice: /* labeled failure */
+     /* in a labeled ordered choice we do not know whether sib2 will be evaluated */
+     tree = sib1(tree); goto tailcall;
     case TCapture: case TGrammar: case TRule:
       /* return checkaux(sib1(tree), pred); */
       tree = sib1(tree); goto tailcall;
diff --git a/testlabel.lua b/testlabel.lua
index d4cc815..1962fbf 100644
--- a/testlabel.lua
+++ b/testlabel.lua
@@ -101,6 +101,15 @@ assert(p:match("aa") == nil)
 p = (m.P"a" + m.T(0))^0
 assert(p:match("aa") == 3)
 
+-- Bug reported by Matthew Allen
+-- some optmizations performed by LPeg should not be
+-- applied in case of labeled choices
+p = m.Lc(m.P"A", m.P(true), 1) + m.P("B")
+assert(p:match("B") == 2)
+
+p = m.Lc(m.P"A", m.P(false), 1) + m.P("B")
+assert(p:match("B") == 2)
+
 
 --[[
 S -> A /{1} 'a'