Esbuild throws errors on generic arrow functions in certain cases

[charliematters]

Bug description

We have upgraded esbuild-loader to avoid the node 18 bug in webpack, and suddenly we are getting syntax errors which are not being reported by tsc.

It seems that it can no longer parse this line:

const foo = async <T>(bar:T): Promise<T> => bar

The error thrown is Expected ")" but found ":"

I've added a repo which shows that when that file is consumed from stdin it fails, but passing the filename as an argument works as expected

Minimal reproduction link

https://github.com/charliematters/esbuild-issue

Environment

TODO

Can you contribute a fix?

• I’m interested in opening a pull request for this issue.

[charliematters]

This is the wrong repo - I'll move it

[privatenumber]

You didn't tell esbuild that the input is TypeScript.

Works fine when you do: https://hyrious.me/esbuild-repl/?version=0.17.16&mode=transform&input=const+foo+%3D+async+%3CT%3E%28bar%3AT%29%3A+Promise%3CT%3E+%3D%3E+bar&options=--loader%3Dts

Also, if you recently upgraded esbuild-loader to v3, see the migration guide:
https://github.com/esbuild-kit/esbuild-loader/releases/tag/v3.0.0