formatjs: defaultMessage does not handle statically evaluate-able variables

[cuyl]

Describe the bug

formatjs leaves empty when there is a variable in the defaultMessage

Example Input:

import { FormattedMessage, defineMessage, formatMessage } from "react-intl";

const hello = "Hello, ";
const world = "world!";

const helloWorldWithVariableConcatenation = defineMessage({
  defaultMessage: hello + world,
});
console.log(
  formatMessage(helloWorldWithVariableConcatenation),
);

function HelloWorldComponent() {
  return (
    <>
      <FormattedMessage defaultMessage={`${hello}${world}`} />
      <FormattedMessage defaultMessage={hello + world} />
    </>
  );
}

export default HelloWorldComponent;

Current Output:

import { FormattedMessage, defineMessage, formatMessage } from "react-intl";
const hello = "Hello, ";
const world = "world!";
const helloWorldWithVariableConcatenation = defineMessage({
    id: "FZQkTV",
    defaultMessage: [
        {
            "type": 0,
            "value": "helloworld"
        }
    ]
});
console.log(formatMessage(helloWorldWithVariableConcatenation));
function HelloWorldComponent() {
    return React.createElement(React.Fragment, null, React.createElement(FormattedMessage, {
        defaultMessage: []
    }), React.createElement(FormattedMessage, {
        id: "FZQkTV",
        defaultMessage: [
            {
                "type": 0,
                "value": "helloworld"
            }
        ]
    }));
}
export default HelloWorldComponent;

Expected Output:

import { FormattedMessage, defineMessage, formatMessage } from "react-intl";
const hello = "Hello, ";
const world = "world!";
const helloWorldWithVariableConcatenation = defineMessage({
    id: "wVJ82J",
    defaultMessage: [
        {
            "type": 0,
            "value": "Hello, world!"
        }
    ]
});
console.log(formatMessage(helloWorldWithVariableConcatenation));
function HelloWorldComponent() {
    return React.createElement(React.Fragment, null, React.createElement(FormattedMessage, {
        id: "wVJ82J",
        defaultMessage: [
            {
                "type": 0,
                "value": "Hello, world!"
            }
        ]
    }), React.createElement(FormattedMessage, {
        id: "wVJ82J",
        defaultMessage: [
            {
                "type": 0,
                "value": "Hello, world!"
            }
        ]
    }));
}
export default HelloWorldComponent;