If the source files include any type declaration files, like src/@types/my-modules/index.d.ts, the result is:
[15:08:25] Starting scripts
[15:08:25] scripts failed because Debug Failure. False expression: Output generation failed
[15:08:25] Task chain was aborted!
It took a while to figure this out. If I change the code to:
yield fly.source(['src/**/*.ts', '!src/@types/**/*']).typescript().target('dist');
then it will work.