Template files cannot identify each other, unless all of them are compiled by saving (or reconciling)

[amirsh]

In order to force template files know each other, they should be compiled. If they are not compiled, they cannot know each other.

For example, suppose the code for a.scala.html is like this:
@(number: Int)
and the code for b.scala.html is:
@()
@A(1)

When you open b.scala.html, it will have compile error in the second line. That's because a.scala.html is not loaded. If you open a.scala.html, and make it to be loaded (by making some changes and saving), the errors in b.scala.html will be disappeared!