Haxe: how to expand arbitrary interpolated strings in macros

MoreLiteral.hx

import haxe.macro.Expr;
import haxe.macro.MacroStringTools;
import haxe.macro.Printer;

class MoreLiteral {
    static function main() {
        var x = 2;
        trace(Util.xpand(34));
    }

    static function otherFunction() return 43;
}

class Util {
    macro static public function xpand(e:Expr) {
        // This is cool. We can expand arbitrary expressions in other
        // contexts.
        var result = MacroStringTools.formatString("${x * 3 + otherFunction()}", e.pos);
        trace(result);
        trace(new Printer().printExpr(result));
        return result;
    }
}

output.txt

$ haxe --run MoreLiteral
MoreLiteral.hx:19: { expr => EBinop(OpAdd,{ expr => EConst(CString()), pos => #pos(MoreLiteral.hx:8: character 26) },{ expr => EBinop(OpAdd,{ expr => EBinop(OpMult,{ expr => EConst(CIdent(x)), pos => #pos(MoreLiteral.hx:8: characters 28-29) },{ expr => EConst(CInt(3)), pos => #pos(MoreLiteral.hx:9: characters 0-1) }), pos => #pos(MoreLiteral.hx:8: lines 8-9) },{ expr => ECall({ expr => EConst(CIdent(otherFunction)), pos => #pos(MoreLiteral.hx:9: lines 9-11) },[]), pos => #pos(MoreLiteral.hx:9: lines 9-11) }), pos => #pos(MoreLiteral.hx:8: lines 8-11) }), pos => #pos(MoreLiteral.hx:8: lines 8-11) }
MoreLiteral.hx:20: "" + x * 3 + otherFunction()
MoreLiteral.hx:8: 49