Large index alwways show the last type.

src/frontend/query_commands.ml

@@ -278,6 +278,15 @@ let dispatch pipeline (type a) : a Query_protocol.t -> a = function
       in
       concat_dedup [] small_enclosings enclosing_nodes
     in
+    let index =
+      (* Clamp the index to [0; number_of_results[ *)
+      let number_of_results = List.length all_results in
+      match index with
+      | Some index when index < 0 -> Some 0
+      | Some index when index >= number_of_results ->
+        Some (number_of_results - 1)
+      | index -> index
+    in
     List.mapi all_results ~f:(fun i (loc, text, tail) ->
         let print =
           match index with

tests/test-dirs/type-enclosing/generic-types.t

@@ -157,8 +157,7 @@ FIXME? We don't see the generic version
   > let _ = List.map Fun.id [3]
   > EOF
 
-FIXME With index 0 only the first type is shown but deduplication failed becauser the
-next type was not rendered.
+With index 0 only the first type is shown and deduplication id working
   $ $MERLIN single type-enclosing -position 2:14 -index 0 \
   > -filename ./main.ml < ./main.ml 
   {
@@ -192,8 +191,7 @@ next type was not rendered.
     "notifications": []
   }
 
-FIXME With index 1 the list is shorter and the numbering is wrong ! In fact, it
-should have been shorter earlier.
+And with index=1 the correct type is shown
   $ $MERLIN single type-enclosing -position 2:14 -index 1 \
   > -filename ./main.ml < ./main.ml 
   {
@@ -226,3 +224,37 @@ should have been shorter earlier.
     ],
     "notifications": []
   }
+
+And with index>=2 Merlin sticks to the last item
+  $ $MERLIN single type-enclosing -position 2:14 -index 2 \
+  > -filename ./main.ml < ./main.ml 
+  {
+    "class": "return",
+    "value": [
+      {
+        "start": {
+          "line": 2,
+          "col": 8
+        },
+        "end": {
+          "line": 2,
+          "col": 16
+        },
+        "type": "(int -> int) -> int list -> int list",
+        "tail": "no"
+      },
+      {
+        "start": {
+          "line": 2,
+          "col": 8
+        },
+        "end": {
+          "line": 2,
+          "col": 27
+        },
+        "type": "int list",
+        "tail": "no"
+      }
+    ],
+    "notifications": []
+  }