[Bug]: Typescript parser crash on as-style assertion on generic instantiation expression

[ethanresnick]

How are you using Babel?

Other (Next.js, Gatsby, vue-cli, ...)

Input code

// produces a parser error, but is valid TS
const x = jsonParse<SomeType> as (str: string) => KeyType

jsonParse<SomeType> is an instantiation expression, which is followed by a cast. As also shown in the repl, the same code works when the cast is written with angle-bracket syntax.

See REPL: https://babel.dev/repl#?browsers=defaults%2C%20not%20ie%2011%2C%20not%20ie_mob%2011&build=&builtIns=false&corejs=3.21&spec=false&loose=false&code_lz=PTAEAcCcHsBMFcDGBTAzqAhhDlXMqPjJAFCLQB2qALqAB6gC8oAVqpQAo54A8AytAC2yACoBPcMgB8mdAAoakAFyhFASwoBzAJRMZAaWRjxkkiRCgA7tEgBrdADMNyMpRr0moHgurLVvjR09UENjCWk2Tm5kfiFRcKkgA&debug=false&forceAllTransforms=false&modules=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=typescript&prettier=false&targets=&version=7.22.20&externalPlugins=&assumptions={}

Configuration file name

No response

Configuration

See REPL.

Current and expected behavior

The code in the REPL (i.e. const x = jsonParse<SomeType> as (str: string) => KeyType) should parse successfully, as it's valid TS.

Environment

System:
OS: macOS 13.5.1
Binaries:
Node: 20.0.0 - ~/.nvm/versions/node/v20.0.0/bin/node
npm: 9.6.4 - ~/.nvm/versions/node/v20.0.0/bin/npm

Possible solution

No response

Additional context

No response

[babel-bot]

Hey @ethanresnick! 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.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite.

[nicolo-ribaudo]

Ugh very annoying that this code has two completely different meanings in JavaScript and in TypeScript:

let x = foo < 2 > as
F.getter;

[nicolo-ribaudo]

However, given that both Babel and SWC parse it according to the ECMAScript spec even when parsing TypeScript, we might try to get the TS team to change their parsing.

microsoft/TypeScript#55806

NOTE: We should still be able to parse the example in the OP, but let's wait for a decision on the TS side.

[yamafaktory]

We've just faced the same issue today at work with the following repro case (we use Vite):

Valid on TS side

https://www.typescriptlang.org/play?ts=4.8.4#code/JYWwDg9gTgLgBAJQKYEMDGMA0cDecBiArgHYbATEDCE4FSx8AvnAGZQ1wBEUqGnA3AChBaCgGd4AWQCe1WsXrwAvHAA8AFUwA+ABRh2YMQC446gJRwlW3ILh24PGISjE1AE2AA3LXgBSAZQB5ADkAOgkoYGIAc2AWaT0DMQtGVQB6D28hRiERcXgAI0JgABs3GTlIBQZLNU1dCys4CpoqxQ1rFDECEjIKSroGDv4gA

Parsing fails with Babel

https://babel.dev/repl#?browsers=defaults%2C%20not%20ie%2011%2C%20not%20ie_mob%2011&build=&builtIns=false&corejs=3.21&spec=false&loose=false&code_lz=JYWwDg9gTgLgBAJQKYEMDGMA0cDecBiArgHYbATEDCE4FSx8AvnAGZQ1wBEUqGnA3AChBaCgGd4AWQCe1WsXrwAvHAA8AFUwA-ABRh2YMQC446gJRwlW3ILh24PGISjE1AE2AA3LXgBSAZQB5ADkAOgkoYGIAc2AWaT0DMQtGVQB6D28hRiERcXgAI0JgABs3GTlIBQZLNU1dCys4CpoqxQ1rFDECEjIKSroGDv4gA&debug=false&forceAllTransforms=false&modules=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=react%2Ctypescript&prettier=false&targets=&version=7.22.20&externalPlugins=&assumptions=%7B%7D

For the record, SWC fails to parse it too (https://play.swc.rs/?version=1.3.86&code=H4sIAAAAAAAAA22OzQrCMBCE73mKoScLRe82zUXwIKigfYHaHwnYTdlshVLy7rYKKugcZz5mxradY8GpLkpJMGLbUynW0cZNAdUkCGjYtYh4RqJUqdKRF%2ByHD5JB54lZdOw6v0YeIzMYFSZxLT0TdGXvZsTufDwsvbClq22GFx8j6NUcpyq8yy%2B9vVV%2FFp7NX77ODQr%2Fe3ry0wcTfPp32gAAAA%3D%3D&config=H4sIAAAAAAAAA1WPSw7CMAxE9z1F5DUL1AUL7sAhouBWQfkpdiWqqncnf2AXv5nJ2MckBLxIwV0c6ZmGICNhHHMitDuW70SA94Ckog4Ml64yZYnjhoWcVQCWcUXOIaT5Os8tAMZ7woQXaQgbs9rpZf%2BtVN6GiET%2FxmyVbjUjXxun1grWP7citlPyunWDG3xNvWx8DJoePVnuOD9fu6hdFgEAAA%3D%3D).