chrome IDE error with a let in a switch case

Hello,

i find a strange behaviour of the chrome ide with a pico with v2.00 firmware
If i use a let in a switch case block, IDE generate an error

Error: Line 15: Unexpected token let

i'm not not sure why it's wrong?
in an html page with the code it does not generate error
and for my point of view i could legaly use a let in the block
if i upload the code in the espruino, it works.
in a more complexe prog, it generate error in the code and nothing works (i've took some time to understand the prob)
if i change the let for a var
no error anymore and code run on the espruino

let phrase= "";
function test() {
  let tire = 7;  
  switch (tire) {
    case 7:
      // try a let
      let vTemp = Math.random(); 
      console.log(vTemp);
      break;
    default:
      break;
  }
}

function onInit() {
  setInterval(test,1000);
}

is it an error?

regards