Check and emit fixes for async iteration #15277
Merged
+249
−233
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This changes the emit for the
__asyncGenerator
and__asyncDelegator
helpers to fix issues withyield*
delegation in an async generator. The main change involves modifying__asyncDelegator
to use a two-phase approach to iteration:next
/throw
/return
to__asyncGenerator
as if it were anawait
and switch phase. After awaiting the result,__asyncGenerator
sends it back to the delegator via a call to itsnext
method.__asyncGenerator
either as ayield
or areturn
and switch phase.This also addresses a bug in the checker and correctly emits
__asyncValues
in some cases where it was missing.This also addresses an issue where a Promise rejection during delegation of an async iterator was not properly handled.
Fixes: #15143, #14725, and #14442
Related: microsoft/tslib#29