Throw better error message when await is not used in async functions in errorRecovery mode

[fisker]

Bug Report

• I would like to work on a fix!

Current behavior

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
}

Should throw an error with better message.

Input Code

function foo () {await bar();}

Expected behavior

Mabe like this, when errorRecovery: false

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
}

The error message is much better.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

Through API, without config

Environment

- Babel version(s): v7.12.7
- Node/npm version: Node 14/npm 6
- OS: Windows 10
- Monorepo: no
- How you are using Babel: api

Possible Solution

I have no idea

Additional context

Issue on Prettier prettier/prettier#9799 and prettier/prettier#9084

[babel-bot]

Hey @fisker! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

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[nicolo-ribaudo]

When improving this error, we should be careful since

function foo () {
  await
  bar();
}

is valid code.

The reason for this "expected ;" is that await is a normal identifier: we finish parsing the expression statement (await) and then we expect either a newline or a semicolon before the following satement (bar();).

[sosukesuzuki]

This happens for yield too.

require('@babel/parser').parse('function foo () { yield bar();}', {sourceType: 'module', errorRecovery: true })

SyntaxError: Unexpected token, expected ";" (1:24)