added missing test

tests/js/trefbyvar.nim

@@ -0,0 +1,35 @@
+discard """
+  output: '''0
+5
+0
+5'''
+"""
+
+# bug #2476
+
+type A = ref object
+    m: int
+
+proc f(a: var A) =
+    var b: A
+    b.new()
+    b.m = 5
+    a = b
+
+var t: A
+t.new()
+
+echo t.m
+t.f()
+echo t.m
+
+proc main =
+  # now test the same for locals
+  var t: A
+  t.new()
+
+  echo t.m
+  t.f()
+  echo t.m
+
+main()