docs: function isTraceryExpr (node, makeSymbolName) {
    makeSymbolName = makeSymbolName || defaultMakeSymbolName
    return typeof(node) === 'object' && node.type === 'cond'
      && node.test.length === 1 && typeof(node.test[0]) === 'object' && node.test[0].type === 'lookup'
      && node.t.length === 1 && isEvalVar (node.t[0])
      && node.f.length === 1 && isPlainSymExpr (node.f[0])
      && node.test[0].varname.toLowerCase() === node.t[0].args[0].varname.toLowerCase()
      && node.test[0].varname.toLowerCase() === makeSymbolName (node.f[0]).toLowerCase()
  }