in packages/babel-plugin-fbt/src/FbtUtil.js [152:159]
function isTextualNode(node: mixed): boolean {
if (isStringLiteral(node) || isJSXText(node)) {
return true;
} else if (isBinaryExpression(node) && node.operator === '+') {
return isTextualNode(node.left) && isTextualNode(node.right);
}
return false;
}