Concurrency: Fix default type witness for AsyncSequence.Failure #74445
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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.
ktoso
approved these changes
Jun 15, 2024
| @@ -1786,12 +1788,26 @@ bool ExtensionDecl::isConstrainedExtension() const { | |||
| return !typeSig->isEqual(extSig); | |||
| } | |||
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| /// Is the extension written as an unconstrained extension? This is not the same | |||
| /// as isConstrainedExtension() in the case where the extended nominal type has | |||
| /// inverse requirements, because an extension of such a type introduces default | |||
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What's an example of an inverse requirement?
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Slava wrote a code example a few lines below this using ~Copyable
hborla
approved these changes
Jun 16, 2024
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@swift-ci Please smoke test |
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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 typeinference 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.