tests: refactor and complete test for #949

 about locating infix operators

tests/test-dirs/locate/issue949.t

@@ -0,0 +1,27 @@
+This test is for testing the behavior of identifiers with a . in them:
+
+  $ cat >main.ml <<EOF
+  > module A = struct let (+.) a b = a +. b end
+  > let f x = A.(x +. 1.)
+  > let g x = A.(+.) x 1.
+  > EOF
+
+  $ $MERLIN single locate -look-for ml -position 2:16 \
+  > -filename ./main.ml < ./main.ml | jq '.value'
+  {
+    "file": "$TESTCASE_ROOT/main.ml",
+    "pos": {
+      "line": 1,
+      "col": 22
+    }
+  }
+
+  $ $MERLIN single locate -look-for ml -position 3:14 \
+  > -filename ./main.ml < ./main.ml | jq '.value'
+  {
+    "file": "$TESTCASE_ROOT/main.ml",
+    "pos": {
+      "line": 1,
+      "col": 22
+    }
+  }