Composite (-b) projects don't report duplicate compilations

**TypeScript Version:** 4.0.0-dev.20200615 **Search Terms:** type narrowing composite build project references duplicate compilations **Code** * [`tsconfig.base.json`](https://github.com/JoshuaKGoldberg/ts-repro-project-narrowing/blob/5b71a26b336e6b5267d919832e076923dbb38296/tsconfig.base.json) * [`tsconfig.json`](https://github.com/JoshuaKGoldberg/ts-repro-project-narrowing/blob/5b71a26b336e6b5267d919832e076923dbb38296/tsconfig.json) * [`src/a/tsconfig.json`](https://github.com/JoshuaKGoldberg/ts-repro-project-narrowing/blob/5b71a26b336e6b5267d919832e076923dbb38296/src/a/tsconfig.json) * [`src/a/Wat.tsx`](https://github.com/JoshuaKGoldberg/ts-repro-project-narrowing/blob/5b71a26b336e6b5267d919832e076923dbb38296/src/a/Wat.tsx) **Expected behavior:** As determined in #38406, the above projects are misconfigured so that `Wat.tsx` is included twice in compilation (https://github.com/microsoft/TypeScript/issues/38406#issuecomment-625546420). There should be some indication that the projects are misconfigured. **Actual behavior:** Mysterious, difficult-to-debug inconsistencies in type narrowing during compile checking coupled with unusually slow builds. **Repository Link:** https://github.com/JoshuaKGoldberg/ts-repro-project-narrowing/tree/5b71a26b336e6b5267d919832e076923dbb38296 **Related Issues:** #38406