Structure
Semantic.Analyses.HasExactlyOneOf
Checks a parent directive for the presence of exactly one of two child directives—but not both—to be converted to a type Result. If so, return that child and the remainder.
struct HasExactlyOneOf<Parent, Child1, Child2> where Parent : Semantic, Parent : DirectiveConvertible, Child1 : Semantic, Child1 : DirectiveConvertible, Child2 : Semantic, Child2 : DirectiveConvertible