Confusing error when using await in non-async function

[anishkny]

Prettier 2.2.1
Playground link

--parser babel

Input:

function foo () {
  await bar();
}

Output:

SyntaxError: Unexpected token, expected ";" (2:9)
  1 | function foo () {
> 2 |   await bar();
    |         ^
  3 | }

Expected behavior:
Honestly, this error message makes no sense.

Perhaps a more relevant message would be:

SyntaxError: await is only valid in async function

[thorn0]

This comment might help with improving this: #9084 (comment)

[fisker]

All parsers throw similar errors

espree SyntaxError: Unexpected token bar
meriyah [1:23]: Unexpected token: 'identifier'
flow Unexpected identifier, expected the end of an expression statement (`;`)

I think there is nothing we can do, unless parsers improve it.

[thorn0]

Specifically Babel can throw "'await' is only allowed within async functions", but it somehow trickily depends on its configuration.

[fisker]

You are right

require('@babel/parser').parse('function foo () {await bar();}', {sourceType: 'module'})
Uncaught [SyntaxError: 'await' is only allowed within async functions (1:17)
] {
  loc: Position { line: 1, column: 17 },
  pos: 17
}

[fisker]

require('@babel/parser').parse('function foo () {await bar();}', {sourceType: 'module', errorRecovery: true})
Uncaught [SyntaxError: Unexpected token, expected ";" (1:23)
] {
  loc: Position { line: 1, column: 23 },
  pos: 23
}

[fisker]

Filed an issue on babel babel/babel#12436

[sosukesuzuki]

Fixed by #10345