add tests for 'df<char>' motion, uncover bug found by test where new match was not recognised after deletion if match involved last character in buffer, and fix that bug by checking (in fcore/search-list/search-list.sm) if we are at a dead state before we check if we are in the last index of the buffer

shf/fcore/search-list/search-list.sml

@@ -131,20 +131,7 @@ struct
 
   fun insertUntilMatch
     (idx, buffer, searchList, dfa, curState, startPos, prevFinalPos) =
-    if idx = #textLength buffer then
-      if prevFinalPos < 0 then
-        (buffer, searchList)
-      else if PersistentVector.isInRange (prevFinalPos, searchList) then
-        (buffer, searchList)
-      else
-        let
-          val searchList =
-            PersistentVector.insertMatchKeepingAbsoluteInddices
-              (startPos, prevFinalPos, searchList)
-        in
-          (buffer, searchList)
-        end
-    else if Dfa.isDead curState then
+    if Dfa.isDead curState then
       if prevFinalPos = ~1 then
         (* no match found: restart search from `startPos + 1` *)
         insertUntilMatch
@@ -161,6 +148,19 @@ struct
         in
           insertUntilMatch (newStart, buffer, searchList, dfa, 0, newStart, ~1)
         end
+    else if idx = #textLength buffer then
+      if prevFinalPos < 0 then
+        (buffer, searchList)
+      else if PersistentVector.isInRange (prevFinalPos, searchList) then
+        (buffer, searchList)
+      else
+        let
+          val searchList =
+            PersistentVector.insertMatchKeepingAbsoluteInddices
+              (startPos, prevFinalPos, searchList)
+        in
+          (buffer, searchList)
+        end
     else
       let
         val buffer = LineGap.goToIdx (idx, buffer)
@@ -176,14 +176,7 @@ struct
 
   fun tryExtendingPrevMatch
     (idx, buffer, searchList, dfa, finalPos, curState, start) =
-    if idx = #textLength buffer then
-      let
-        val searchList =
-          PersistentVector.extendExistingMatch (start, finalPos, searchList)
-      in
-        (buffer, searchList)
-      end
-    else if Dfa.isDead curState then
+    if Dfa.isDead curState then
       let
         val searchList =
           PersistentVector.extendExistingMatch (start, finalPos, searchList)
@@ -191,6 +184,13 @@ struct
         insertUntilMatch
           (finalPos + 1, buffer, searchList, dfa, 0, finalPos + 1, ~1)
       end
+    else if idx = #textLength buffer then
+      let
+        val searchList =
+          PersistentVector.extendExistingMatch (start, finalPos, searchList)
+      in
+        (buffer, searchList)
+      end
     else
       let
         val buffer = LineGap.goToIdx (idx, buffer)