Invalid production rule?

[danecek]

trait Showable[A]:
  extension (a: A) def show: String

case class Person(firstName: String, lastName: String)

//StructuralInstance ::=  ConstrApp {‘with’ ConstrApp} [‘with’ TemplateBody]
//TemplateBody      ::=  :<<< [SelfType] TemplateStat {semi TemplateStat} >>>
given Showable[Person] with : // ################ an identifier expected, but ':' found
  extension (p: Person) def show: String =
    s"${p.firstName} ${p.lastName}"

[SethTisue]

what page is this in reference to?

[xuwei-k]

• https://github.com/scala/docs.scala-lang/blob/c127f922f070e5a851fded3073c1c83e41587163/_overviews/scala3-book/ca-type-classes.md
• https://github.com/scala/docs.scala-lang/blob/c127f922f070e5a851fded3073c1c83e41587163/_scala3-reference/syntax.md

🤔