Choose() returns the expected message from the alternative that made the furthest progress, if any did.

peg.js

@@ -90,15 +90,17 @@ Peg.Choose = function (...patterns) {
   const expected = patterns.map((pattern) => pattern.expectLabel).join(" | ");
   return Peg.WrapPattern(function (source, index) {
     let furthest = index;
+    let furthestExpected = expected;
     for (const pattern of patterns) {
       const match = pattern(source, index);
       if (match[0]) {
         return match;
       } else if (match[1] > furthest) {
         furthest = match[1];
+        furthestExpected = match[2];
       }
     }
-    return [false, furthest, expected];
+    return [false, furthest, furthestExpected];
   }).expects(expected);
 };