Adjust generator element type, cf. dart-lang/language#3148 #3218
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Friendly ping. Note that the current specification is unsound (cf. #3148 (comment)). |
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We will need a plan for making sure whatever specification we end up gets tested and implemented. |
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Also, how does this interact with https://github.com/dart-lang/language/pull/3151/files ? |
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[Edit: Corrected link]
There is a co19 task in the pipeline, cf. |
It's a dart-lang/co19#2139 |
If we do not introduce new compile-time errors (for declarations like |
…c change Calculation of element type for the value returned from async/async*/sync* functions was recently adjusted in the spec to address soundness issue (dart-lang/language#3218). This change adjusts Dart VM to conform to the new spec. TEST=language/async/regression_54311_test TEST=co19/Language/Functions/element_type_* Fixes #54316 Issue #54311 Issue #54159 Change-Id: I4c51e7cba704d034350519375210bdb2086c5432 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/342082 Reviewed-by: Alexander Aprelev <aam@google.com> Reviewed-by: Erik Ernst <eernst@google.com> Commit-Queue: Alexander Markov <alexmarkov@google.com>
In issue #3148, it is reported that there is a soundness issue with the computation of the element type of a generator function whose declared return type is
FutureOr<Iterable<int>?>, and similar issues with other union types.This PR changes the definition of this element type such that return types are simplified to
Iterable<...>orStream<...>before the element type is computed, if possible.Objectand top types still yield the element typedynamic.Moreover, this PR also adjusts the specification of the dynamic type of the returned iterable/stream accordingly.
NB: This PR introduces null-safety related material into the existing language specification. We have done this in other cases as well. In general, we're aiming to integrate all the null-safety related material into the language specification, piece by piece, so there is no violation of current practice in doing that with this PR as well.