add testcase for #5926 (#14965)

tests/generics/t5926.nim

@@ -0,0 +1,22 @@
+discard """
+action: compile
+"""
+
+type
+  SomeObj[T] = object
+
+template useSomeObj[T]() =
+  var retObj: SomeObj[T]
+
+useSomeObj[void]()
+useSomeObj[int]()
+
+
+type
+  Data*[T] = object
+    x: T
+
+template test*[T](xxx: T) =
+  let data = Data[T](x: xxx)
+
+test(1)