TC39 General on 2021-09-22

In Chrome:

console.log((new class {
  #id;
  
  test(a,b) {
    return a << #id in b
  }
}).test(0, {}))

Parses without a SyntaxError and results with 'Uncaught TypeError: Cannot convert a Symbol value to a number' when it does (a << #id)
Could someone confirm if this is expected?

14:04

<nicolo-ribaudo>

It should be a parser error, we had the same bug in Babel

14:05

Thanks nicolo-ribaudo - yes Babel emits a parser error as you say

14:06

I've just realized that I'm making the same mistake in the TypeScript parser

14:09

<nicolo-ribaudo>

It looks like JSC has the same bug:

➜ eshost -e "class C { #x; test() { 0 << #x in {} } }" -t
┌────────────────┬──────────────────────────────────────────────────────────┐
│ ChakraCore     │                                                          │
│                │ SyntaxError: Invalid character                           │
├────────────────┼──────────────────────────────────────────────────────────┤
│ Hermes         │                                                          │
│                │ SyntaxError: invalid expression                          │
├────────────────┼──────────────────────────────────────────────────────────┤
│ JavaScriptCore │ class C { #x; test() { 0 << #x in {} } }                 │
├────────────────┼──────────────────────────────────────────────────────────┤
│ Moddable XS    │                                                          │
│                │ SyntaxError: missing expression                          │
├────────────────┼──────────────────────────────────────────────────────────┤
│ SpiderMonkey   │                                                          │
│                │ SyntaxError: private names aren't valid in this context: │
├────────────────┼──────────────────────────────────────────────────────────┤
│ V8             │ class C { #x; test() { 0 << #x in {} } }                 │
└────────────────┴──────────────────────────────────────────────────────────┘