[6.0] Concurrency: Fix default type witness for AsyncSequence.Failure #74520
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Setting this to Self.AsyncIterator.Failure doesn't work because we replace it with its reduced type Self.Failure, and then if you run a binary compiled against an older version of the stdlib that does not declare the Failure associated type, we hit infinite recursion while instantiating the witness table and trying to populate the default type witness. Instead, let's set the default to `any Error`. Associated type inference is already smart enough to infer the type witness from the AsyncIterator's Failure type; we don't need to rely on the default mechanism for that. Fixes rdar://129605725.
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@swift-ci Please test |
hborla
approved these changes
Jun 18, 2024
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6.0 cherry-pick of #74445
Description: Fix an infinite loop when running older binaries that were built against a standard library that doesn't have the AsyncSequence.Failure associated type.
Origination: New bug introduced with typed throws.
Reviewed by: @hborla
Radar: rdar://129605725
Tested: No test case because we don't have a way to automate testing binaries built against an old compiler/stdlib yet.