Use new information from uids to jump to the correct file.

src/analysis/locate.ml

@@ -510,9 +510,15 @@ let find_loc_of_uid ~config ~local_defs uid comp_unit =
   end
   else begin
     log ~title "Loading the cmt file for unit %S" comp_unit;
+    let ml_or_mli =
+      match uid with
+      | Item { from = Intf; _ } -> `MLI
+      | _ -> config.ml_or_mli
+    in
+    let config = { config with ml_or_mli } in
     match load_cmt ~config comp_unit with
     | Ok (_pos_fname, cmt) ->
-      log ~title "Shapes successfully loaded, looking for %a" Logger.fmt
+      log ~title "Cmt successfully loaded, looking for %a" Logger.fmt
         (fun fmt -> Shape.Uid.print fmt uid);
       begin
         match Shape.Uid.Tbl.find_opt cmt.cmt_uid_to_decl uid with

tests/test-dirs/locate/issue1848.t

@@ -26,15 +26,15 @@ Locate the Bar on line 4
   > end
   > EOF
 
-The expected location is 2:7 of foo.ml, but it instead goes to 1:9, which is the
-constructor Foo
+FIXME Module type Bar in foo.mli is a correct answer, but since there is only
+one corresponding implementation we could jump there instead.
   $ $MERLIN single locate -position 4:28 -look-for ml \
   > -filename test1.ml < test1.ml | jq .value
   {
-    "file": "$TESTCASE_ROOT/foo.ml",
+    "file": "$TESTCASE_ROOT/foo.mli",
     "pos": {
       "line": 1,
-      "col": 9
+      "col": 7
     }
   }