Hi there,

Not sure if this will truly be helpful or not, but wanted to try.

I've run into an issue in building out a new library with tsup where the pinned version of rollup-plugin-dts doesn't support types with negative numbers as keys, such as:

type Foo = {
 [-1]: string
}

I ran into this trying to setup a design system library with https://vanilla-extract.style.

I've setup a minimal reproduction of the issue here: https://github.com/oscarnewman/tsup-repro

In my testing, updating rollup-plugin-dts (and rollup as is required by it's new peer-dep version) fixes this issue, and the test suite passes locally for me.

We've currently just switched to running a fork with these updates at @oscarnewman/tsup but would love to help out anyone else who's also faced this issue.