Add reproduction from issue ocaml#1848

tests/test-dirs/locate/issue1848.t

@@ -0,0 +1,71 @@
+Create a module with an mli file
+  $ cat > foo.ml << EOF
+  > type t = Foo
+  > module Bar = struct
+  >   type t = Bar
+  > end
+  > EOF
+
+  $ cat > foo.mli << EOF
+  > module Bar : sig
+  >   type t
+  > end
+  > type t
+  > EOF
+
+  $ $OCAMLC -c -bin-annot foo.mli
+  $ $OCAMLC -c -bin-annot foo.ml
+
+Locate the Bar on line 4
+  $ cat > test1.ml << EOF
+  > module type Foo = sig
+  >   include module type of Foo
+  >   module Bar : sig
+  >     include module type of Bar
+  >   end
+  > end
+  > EOF
+
+The expected location is 2:7 of foo.ml, but it instead goes to 1:9, which is the
+constructor Foo
+  $ $MERLIN single locate -position 4:28 -look-for ml \
+  > -filename test1.ml < test1.ml | jq .value
+  {
+    "file": "$TESTCASE_ROOT/foo.ml",
+    "pos": {
+      "line": 1,
+      "col": 9
+    }
+  }
+
+Locate the Bar on line 3
+  $ cat > test2.ml << EOF
+  > include Foo
+  > module Bar = struct
+  >   include Bar
+  > end
+  > EOF
+
+Correctly returns 2:7
+  $ $MERLIN single locate -position 3:12 -look-for ml -filename test2.ml < test2.ml | jq .value
+  {
+    "file": "$TESTCASE_ROOT/foo.ml",
+    "pos": {
+      "line": 2,
+      "col": 7
+    }
+  }
+
+Locate the Foo.Bar on line 1
+  $ cat > test3.ml << EOF
+  > include module type of Foo.Bar
+  > EOF
+Correctly returns 2:7
+  $ $MERLIN single locate -position 1:28 -look-for ml -filename test3.ml < test3.ml | jq .value
+  {
+    "file": "$TESTCASE_ROOT/foo.ml",
+    "pos": {
+      "line": 2,
+      "col": 7
+    }
+  }