fixes #4625

tests/cpp/tempty_generic_obj.nim

@@ -0,0 +1,22 @@
+discard """
+  cmd: "nim cpp $file"
+  output: '''int
+float'''
+"""
+
+import typetraits
+
+# bug #4625
+type
+  Vector {.importcpp: "std::vector<'0 >", header: "vector".} [T] = object
+
+proc initVector[T](): Vector[T] {.importcpp: "'0(@)", header: "vector", constructor.}
+
+proc doSomething[T](v: var Vector[T]) =
+  echo T.name
+
+var v = initVector[int]()
+v.doSomething()
+
+var vf = initVector[float]()
+vf.doSomething() # Nim uses doSomething[int] here in C++