fix bugs in 'LineGap.subRight' (we were not passing nextIdx in recursion properly)

src/line_gap.sml

@@ -2263,42 +2263,32 @@ struct
   end
 
   fun subRight (findIdx, curIdx, hd, tl) =
-    if findIdx > curIdx + String.size hd - 1 then
+    let
-      case tl of
+      val nextIdx = curIdx + String.size hd
-        hd :: tl =>
+    in
-          if findIdx > curIdx + String.size hd - 1 then
+      if findIdx > nextIdx - 1 then
-            subRight (findIdx, curIdx + String.size hd, hd, tl)
+        case tl of
-          else
+          hd :: tl => subRight (findIdx, nextIdx, hd, tl)
-            let val strIdx = findIdx - curIdx
+        | [] => raise Fail "not found"
-            in String.sub (hd, strIdx)
+      else
-            end
+        let val strIdx = findIdx - curIdx
-      | [] => raise Fail "not found"
+        in String.sub (hd, strIdx)
-    else
+        end
-      let val strIdx = findIdx - curIdx
+    end
-      in String.sub (hd, strIdx)
-      end
 
   fun subLeft (findIdx, curIdx, hd, tl) =
-    if findIdx < curIdx - String.size hd then
+    let
-      case tl of
+      val prevIdx = curIdx - String.size hd
-        hd :: tl =>
+    in
-          if findIdx < curIdx - String.size hd then
+      if findIdx < prevIdx then
-            subLeft (findIdx, curIdx - String.size hd, hd, tl)
+        case tl of
-          else
+          hd :: tl => subLeft (findIdx, prevIdx, hd, tl)
-            let
+        | [] => raise Fail "not found"
-              val prevIdx = curIdx - String.size hd
+      else
-              val strIdx = findIdx - prevIdx
+        let val strIdx = findIdx - prevIdx
-            in
+        in String.sub (hd, strIdx)
-              String.sub (hd, strIdx)
+        end
-            end
+    end
-      | [] => raise Fail "not found"
-    else
-      let
-        val prevIdx = curIdx - String.size hd
-        val strIdx = findIdx - prevIdx
-      in
-        String.sub (hd, strIdx)
-      end
 
   fun sub (findIdx, buffer: t) =
     if findIdx >= #idx buffer then