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Track recursive callback-covariance calls to compareSignaturesRelated #19078

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Track recursive callback-covariance calls to compareSignaturesRelated #19078

wants to merge 2 commits into from

Commits on Oct 10, 2017

  1. Track recursive calls to compareSignaturesRelated 

    Previously, `compareSignaturesRelated` would try to relate (parameters
of) callback parameters covariantly without checking whether the two
signatures were already being checked. This led to an infinite recursion
when checking recursive types with callbacks:

```ts
interface Foo<T> { (bar: Bar<T>): void }
type Bar<T> = (foo: Foo<T>) => Foo<T>
declare function foo<T>(bar: Bar<T>): void
declare var bar: Bar<{}>
bar = foo
```

The fix is to track which callbacks are already being compared. The
mechanism is per-call to compareSignaturesRelated, so it only stops
recursions on the callback-covariance code path. However, the maybe
cache check in recursiveTypeRelatedTo will catch infinite recursions on
the usual code path through isRelatedTo.

Fixes #18277
    @sandersn
    sandersn committed Oct 10, 2017
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  2. Test fix #18277:mutually recursive callbacks

    @sandersn
    sandersn committed Oct 10, 2017
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