Expression visit(IdentifierExpression e) {
        return IdentifierVisitor!(delegate Expression(identified) {
            static if(is(typeof(identified) : Expression)) {
                return identified;
            } else {
                static if(is(typeof(identified) : Symbol)) {
                    if(auto s = cast(OverloadSet) identified) {
                        return buildPolysemous(e.location, s);
                    }
                }

                return pass.raiseCondition!Expression(e.location, e.identifier.name ~ " isn't an expression.");
            }
        })(pass).visit(e.identifier);
    }