How to make a proc with a default genetic type that can be inferred at compile time?

[ElegantBeef]

This problem might be better handled with a static enum, as it gives you a 
typeclass and also language specific dispatch. 
    
    
    type
      Locale = enum
        Unknown, English, French
      Language[T: static Locale] = distinct string
    
    proc readFile(path: string; locale: static Locale = Unknown): 
Language[locale] =
        echo "Lang: ", locale, ", path: ", path
        Language[locale]("") # dummy
    
    proc `$`(lang: Language): string = string(lang) # Devel has a fix for 
borrowing typeclasses like this, but before needs this.
    
    discard readFile("english.txt", English)
    discard readFile("french.txt", French)
    discard readFile("we_dont_know_what_language_at_compile_time.txt", Unknown)
    
    discard readFile("we_dont_know_what_language_at_compile_time.txt")
    
    
    Run