[SOLVED] How do I find out what causes a "Debug Error" in TypeScript's compiler?

How do I find out what causes a "Debug Error" in TypeScript's compiler?

When running nx serve (using NRWL NX) on my TypeScript project, the build now fails with this error:

<my-file>.ts - Error: Module build failed (from ./node_modules/@ngtools/webpack/src/ivy/index.js):
Error: Debug Failure. False expression: Lexical environment is suspended.

<my-file>.ts¹ has not been changed in a couple of days and I think it had already been properly compiling after my last changes to it a few days ago.

I suspect the above might be a bug in the TS compiler or similar, but to properly reproduce this issue in a minimal example, is there anything I can do to find out what particular part of <my-file>.ts causes the issue, or what constructs I should watch out for that might cause this error?

Some notes about the environment:

The nx serve command launches the @angular-devkit/build-angular:dev-server executor.
That in turn uses the @angular-devkit/build-angular:browser executor to build the project.

¹: This is a placeholder for the real file name.

Solution

I was able to reproduce the same error in the context of a Jest test.

The difference was between a method declaration in an Angular service like this:

public async doSomething<T extends object>(): Promise<{
  get value(): number
}> {
// ....

(does not work, produces the "Error: Debug Failure. False expression: Lexical environment is suspended." message)

versus this

public async doSomething<T extends object>(): Promise<{
  readonly value: number
}> {
// ....

(works, produces no compiler errors)

Unfortunately, I was unable to reproduce this on the TS Playground, so I still do not have an isolated example that I can report, but maybe this still helps some future visitors.