Change the rules for how //go:build "file versions" are applied: instead
of considering whether a file version is an upgrade or downgrade from
the -lang version, always use max(fileVersion, go1.21). This prevents
file versions from downgrading the version below go1.21. Before Go 1.21
the //go:build version did not have the meaning of setting the file's
langage version.
This fixes an issue that was appearing in GOPATH builds: Go 1.23.0
started providing -lang versions to the compiler in GOPATH mode (among
other places) which it wasn't doing before, and it set -lang to the
toolchain version (1.23). Because the -lang version was greater than
go1.21, language version used to compile the file would be set to the
//go:build file version. //go:build file versions below 1.21 could cause
files that could previously build to stop building.
For example, take a Go file with a //go:build line specifying go1.10.
If that file used a 1.18 feature, that use would compile fine with a Go
1.22 toolchain. But it would produce an error when compiling with the
1.23.0 toolchain because it set the language version to 1.10 and
disallowed the 1.18 feature. This breaks backwards compatibility: when
the build tag was added, it did not have the meaning of restricting the
language version.
For #68658
Change-Id: I6cedda81a55bcccffaa3501eef9e2be6541b6ece
Reviewed-on: https://go-review.googlesource.com/c/go/+/607955
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
This reverts CL 603895
Reason for revert: We've decided to change the logic for how upgrades are done and want to submit the new logic in a self contained CL that can be cherry-picked onto release-branch.go1.23
Change-Id: I366af8e95ce1de7311b0385a23f9dd3df175745a
Reviewed-on: https://go-review.googlesource.com/c/go/+/605675
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Only honor //go:build language version downgrades if the version
specified is 1.21 or greater. Before 1.21 the version in //go:build
lines didn't have the meaning of setting the file's language version.
This fixes an issue that was appearing in GOPATH builds: Go 1.23 started
providing -lang versions to the compiler in GOPATH mode (among other
places) which it wasn't doing before.
For example, take a go file with a //go:build line specifying go1.10.
If that file used a 1.18 feature, that use would compile fine with a Go
1.22 toolchain. But, before this change, it would produce an error when
compiling with the 1.23 toolchain because it set the language version to
1.20 and disallowed the 1.18 feature. This breaks backwards
compatibility: when the build tag was added, it did not have the meaning
of restricting the language version.
Fixes#68658
Change-Id: I4ac2b45a981cd019183d52ba324ba8f0fed93a8e
Reviewed-on: https://go-review.googlesource.com/c/go/+/603895
Reviewed-by: Robert Griesemer <gri@google.com>
Commit-Queue: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Matloob <matloob@golang.org>
