if trace {
		defer p.trace("paramDeclOrNil")()
	}

	// type set notation is ok in type parameter lists
	typeSetsOk := follow == _Rbrack

	pos := p.pos()
	if name != nil {
		pos = name.pos
	} else if typeSetsOk && p.tok == _Operator && p.op == Tilde {
		// "~" ...
		return p.embeddedElem(nil)
	}

	f := new(Field)
	f.pos = pos