"An extension or construction, that is,
 anything that can go in an [[extended type|ExtendedType]] or [[class specifier|ClassSpecifier]].
     Point.cartesian(x, y, 0.0)"
shared abstract class ExtensionOrConstruction()
        of Extension | Construction
        extends Node() {
    "The name of the extended class or invoked constructor."
    shared formal NameWithTypeArguments nameAndArgs;
    "The arguments to the extended class or invoked constructor, if any."
    shared formal PositionalArguments? arguments;
    "The qualifier, if any.
     (`QualifiedType` qualifiers are not covered by the specification,
     but supported by some backends.)"
    shared formal SimpleType|PackageQualifier|Super? qualifier;
    shared actual formal <NameWithTypeArguments|PositionalArguments|SimpleType|PackageQualifier|Super>[] children;