Currently it's possible for next and yield to be called out of sequence,
which will result in surprising behavior due to the implementation.
Because we blindly coroswitch between goroutines, calling next from the
iterator, or yield from the calling goroutine, will actually switch back
to the other goroutine. In the case of next, we'll switch back with a
stale (or zero) value: the results are basically garbage. In the case of
yield, we're switching back to the *same* goroutine, which will crash in
the runtime.
This change adds a single bool to ensure that next and yield are always
called in sequence. That is, every next must always be paired with a
yield before continuing. This restricts what can be done with Pull, but
prevents observing some truly strange behaviors that the user of Pull
likely did not intend, or can't easily predict.
Change-Id: I6f72461f49c5635d6914bc5b968ad6970cd3c734
Reviewed-on: https://go-review.googlesource.com/c/go/+/583676
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
These were previously only available with GOEXPERIMENT=rangefunc.
For #61897.
Change-Id: I86aea5ae8be1f7a2975b623325811221ed40d384
Reviewed-on: https://go-review.googlesource.com/c/go/+/557836
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Pull2 tests are failing with -race, giving false-positive race conditions
due to bad race instrumentation.
No tests for this as it should be caught by the race builders. The only
reason it was not caught is because it is behind GOEXPERIMENT=rangefunc.
Fixes#64651
Change-Id: I20554da930b0e19594e0e267f01a1e7a9cbc577a
GitHub-Last-Rev: 7c1f19238d
GitHub-Pull-Request: golang/go#64653
Reviewed-on: https://go-review.googlesource.com/c/go/+/548895
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
The exported API is only available with GOEXPERIMENT=rangefunc.
This will let Go 1.22 users who want to experiment with rangefuncs
access an efficient implementation of iter.Pull and iter.Pull2.
For #61897.
Change-Id: I6ef5fa8f117567efe4029b7b8b0f4d9b85697fb7
Reviewed-on: https://go-review.googlesource.com/c/go/+/543319
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Michael Anthony Knyszek
Russ Cox
Mauri de Souza Meneguzzo