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
• tsconfig.json
• src/a/tsconfig.json
• 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

从链接的 repro 的 tsconfig.base.json、tsconfig.json、src/a/tsconfig.json 和 src/a/Wat.tsx 开始，将其重复编译行为与 #38406 中的讨论进行比较。跟踪处理重复源代码包含的 composite 项目引用编译和诊断入口点。完成的标准是：错误配置会产生明确的指示，而不是静默地重复编译并导致不一致的 narrowing。