Async SyntaxErrors omit which line the error occurs on

[broofa]

• Version: v11.6.0
• Platform: Darwin RWK-Mac-2017.local 17.7.0 Darwin Kernel Version 17.7.0: Fri Nov 2 20:43:16 PDT 2018; root:xnu-4570.71.17~1/RELEASE_X86_64 x86_64
• Subsystem:

Notice in the following two examples, where state is erroneously redeclared, the "Sync Example", provides this (very useful!) information, which is not present in the Async Example:

/Users/kieffer/work/sync_test.js:4
  let state = 123;
      ^

The "first" line of the stack shown in the async example is not the line on which the error occurred. Rather, it is the line that calls the function containing the error. Unfortunately this can be anywhere, so is completely unhelpful in fixing the problem.

Sync Example:

sync_test.js

'use strict';

function foo(state = {}) {
  let state = 123;
}

(function main() {
  foo();
}())

$ node sync_test.js
/Users/kieffer/work/sync_test.js:4
  let state = 123;
      ^

SyntaxError: Identifier 'state' has already been declared
    at main (/Users/kieffer/work/sync_test.js:8:3)
    at Object.<anonymous> (/Users/kieffer/work/sync_test.js:9:2)
(etc...)

Async Example

async_test.js

'use strict';

async function foo(state = {}) {
  let state = 123;
}

(async function main() {
  foo();
}())

$ node async_test.js
(node:89392) UnhandledPromiseRejectionWarning: SyntaxError: Identifier 'state' has already been declared
    at main (/Users/kieffer/work/async_test.js:8:3)
    at Object.<anonymous> (/Users/kieffer/work/async_test.js:9:2)
(etc...)

[devsnek]

Duplicate of #11865

[vsemozhetbyt]

It seems improved in V8 7.3:

>node.12.0.0.v8-7.3.2019-01-02.v8-canary.exe test.js
test.js:4
  let state = 123;
      ^^^^^

SyntaxError: Identifier 'state' has already been declared
    at new Script (vm.js:84:7)
    at createScript (vm.js:264:10)
    at Object.runInThisContext (vm.js:312:10)
    at Module._compile (internal/modules/cjs/loader.js:681:28)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:729:10)
    at Module.load (internal/modules/cjs/loader.js:617:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:560:12)
    at Function.Module._load (internal/modules/cjs/loader.js:552:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:771:12)
    at executeUserCode (internal/bootstrap/node.js:434:15)