Corresponding Source of the work from the predecessor in interest, if
the predecessor has it or can get it with reasonable efforts.

  You may not impose any further restrictions on the exercise of the
rights granted or affirmed under this License.  For example, you may
not impose a license fee, royalty, or other charge for exercise of
rights granted under this License, and you may not initiate litigation

pkg go/ast, type File struct
pkg go/ast, type File struct, Comments []*CommentGroup
pkg go/ast, type File struct, Decls []Decl
pkg go/ast, type File struct, Doc *CommentGroup
pkg go/ast, type File struct, Imports []*ImportSpec
pkg go/ast, type File struct, Name *Ident
pkg go/ast, type File struct, Package token.Pos
pkg go/ast, type File struct, Scope *Scope
pkg go/ast, type File struct, Unresolved []*Ident