parse error on static blocks containing await accessor param

[jdalton]

@rwaldron (who runs test262 for fun) found this bit of code that is technically valid (its function is beyond me) but found that acorn throws a parse error trying to process it. Reporting as a heads up:

    class C {
      static {
        ({set accessor(await) {}});
      }
    }

[cool-little-fish]

see https://262.ecma-international.org/12.0/#prod-MethodDefinition, I believe it's invalide syntax.

[jdalton]

It seems to parse in Chrome, Firefox, but not Safari:
https://jsbin.com/dunaqiz/1/edit?html,js,console,output

Update:

Here's the test262 test:
https://github.com/tc39/test262/blob/afe217b318df5f197e64b30a8b5a4b391c777359/test/language/expressions/object/method-definition/static-init-await-binding-accessor.js

Update:

Ah I see it's part of

"[Add tests for "Class Static Init. Blocks" proposal]

Looks like it's part of the static blocks proposal which hit stage 4 in August 2021 and is now supported by Chrome/Firefox:
tc39/proposal-class-static-block#48 (comment)

Spec link:
https://tc39.es/ecma262/#sec-classstaticblockdefinition-record-specification-type

[marijnh]

I'm not actually seeing a parse error for this code in the current version of Acorn. How are you testing this?

[cool-little-fish]

I used accorn v8.5.0 to reproduce this problem.

[marijnh]

What did you set ecmaVersion to? Does the problem go away when you upgrade to 8.7.0?

[cool-little-fish]

still can reproduce after upgrade to 8.7.0, with ecma 2022

[cool-little-fish]

let acorn = require("acorn");
const fs = require('fs');

// const tplToRead = fs.readFileSync('./src/acorn/parse-str.txt', { encoding: 'utf-8' });
const parseRes = acorn.parse(`
class C {
  static {
    ({set accessor(await) {}});
  }
}`, {ecmaVersion: 2022,  locations: true, sourceType: 'module' });

The error message: Uncaught SyntaxError: Cannot use keyword 'await' outside an async function (4:19)

[marijnh]

Right, if you add sourceType: 'module' you can't use await as an identifier, but I'm pretty sure that's the appropriate behavior and I don't think the error has much to do with this specific code (just function foo(await){} also gives that parse error).

[jdalton]

@marijnh Ah yes, as "module" it does error as expected.

module example:
https://jsbin.com/nemagif/1/edit?html,js,console,output

Thanks!