The `NgccReflectionHost`s have logic for detecting certain known
declarations (such as `Object.assign()` and TypeScript helpers), which
allows the `PartialEvaluator` to evaluate expressions it would not be
able to statically evaluate otherwise.
In #36089, `DelegatingReflectionHost` was introduced, which delegates to
a TypeScript `ReflectionHost` when reflecting on TypeScript files, which
for ngcc's case means `.d.ts` files of dependencies. As a result, ngcc
lost the ability to detect TypeScript helpers imported from `tslib`,
because `DelegatingReflectionHost` was not able to apply the known
declaration detection logic while reflecting on `tslib`'s `.d.ts` files.
This commit fixes this by ensuring `DelegatingReflectionHost` calls the
`NgccReflectionHost`'s `detectKnownDeclaration()` method as necessary,
even when using the TypeScript `ReflectionHost`.
NOTE:
The previous commit exposed a bug in ngcc that was hidden due to the
tests' being inconsistent with how the `ReflectionHost`s are used in the
actual program. The changes in this commit are verified by ensuring the
failing tests are now passing (hence no new tests are added).
PR Close#36284
ca25c957bf