go/types, types2: only use fileVersion if 1.21 or greater

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>

diff --git a/src/cmd/compile/internal/types2/api_test.go b/src/cmd/compile/internal/types2/api_test.go
index d9ba620888078ad3877cc4ac1ebcf2fc1838cc6e..37b26556892631a849d0d725f91bd4b5e2c5e2e3 100644 (file)
--- a/src/cmd/compile/internal/types2/api_test.go
+++ b/src/cmd/compile/internal/types2/api_test.go
@@ -3036,17 +3036,21 @@ func TestFileVersions(t *testing.T) {
                {"", "go1.20", ""},             // file upgrade ignored
                {"go1.19", "go1.20", "go1.20"}, // file upgrade permitted
                {"go1.20", "go1.19", "go1.20"}, // file downgrade not permitted
-               {"go1.21", "go1.19", "go1.19"}, // file downgrade permitted (module version is >= go1.21)
+               {"go1.21", "go1.20", "go1.21"}, // file downgrade not permitted
+               {"go1.22", "go1.21", "go1.21"}, // file downgrade permitted (file and module version are >= go1.21)
 
                // versions containing release numbers
                // (file versions containing release numbers are considered invalid)
                {"go1.19.0", "", "go1.19.0"},         // no file version specified
                {"go1.20", "go1.20.1", "go1.20"},     // file upgrade ignored
                {"go1.20.1", "go1.20", "go1.20.1"},   // file upgrade ignored
+               {"go1.21.0", "go1.21.1", "go1.21.0"}, // file upgrade ignored
+               {"go1.21", "go1.21.1", "go1.21"},     // file upgrade ignored
                {"go1.20.1", "go1.21", "go1.21"},     // file upgrade permitted
+               {"go1.21.1", "go1.21", "go1.21.1"},   // file downgrade ignored
                {"go1.20.1", "go1.19", "go1.20.1"},   // file downgrade not permitted
                {"go1.21.1", "go1.19.1", "go1.21.1"}, // file downgrade not permitted (invalid file version)
-               {"go1.21.1", "go1.19", "go1.19"},     // file downgrade permitted (module version is >= go1.21)
+               {"go1.22.1", "go1.21", "go1.21"},     // file downgrade permitted (file and module version is >= go1.21)
        } {
                var src string
                if test.fileVersion != "" {

diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index cd1b2d513c106c4106436b7e3e242a28386471be..5cee742063a795a299ed1560b9eb84e69d283de6 100644 (file)
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -353,12 +353,25 @@ func (check *Checker) initFiles(files []*syntax.File) {
                                // To work around this, downgrades are only allowed when the
                                // module's Go version is Go 1.21 or later.
                                //
+                               // Downgrades are also only allowed to Go versions Go 1.21 or later.
+                               // In GOPATH mode, there's no way to set a module version and the
+                               // -lang is set to the local toolchain version to allow the use of
+                               // new features in GOPATH mode. But //go:build lines added before go1.21
+                               // weren't intended to downgrade, so code with //go:build lines for
+                               // go versions earlier than 1.21 may use language features added
+                               // in later versions and compile.
+                               //
+                               // We should probably change the downgradeOk condition to capture this
+                               // instead of adding an extra condition, but to make the change simpler,
+                               // we've tried to limit it to one line.
+                               // TODO(gri): simplify this code after 1.23 has shipped
+                               //
                                // If there is no valid check.version, then we don't really know what
                                // Go version to apply.
                                // Legacy tools may do this, and they historically have accepted everything.
                                // Preserve that behavior by ignoring //go:build constraints entirely in that
                                // case (!pkgVersionOk).
-                               if cmp > 0 || cmp < 0 && downgradeOk {
+                               if cmp > 0 || cmp < 0 && downgradeOk && fileVersion.cmp(go1_21) >= 0 {
                                        v = file.GoVersion
                                }
                        }

diff --git a/src/go/types/api_test.go b/src/go/types/api_test.go
index f5bf49b4f8fe5cc3ee6c54627e1c1bfa242fb0f6..d2096c114afc3a58a5e1df8378cebce14d9fca58 100644 (file)
--- a/src/go/types/api_test.go
+++ b/src/go/types/api_test.go
@@ -3040,17 +3040,21 @@ func TestFileVersions(t *testing.T) {
                {"", "go1.20", ""},             // file upgrade ignored
                {"go1.19", "go1.20", "go1.20"}, // file upgrade permitted
                {"go1.20", "go1.19", "go1.20"}, // file downgrade not permitted
-               {"go1.21", "go1.19", "go1.19"}, // file downgrade permitted (module version is >= go1.21)
+               {"go1.21", "go1.20", "go1.21"}, // file downgrade not permitted
+               {"go1.22", "go1.21", "go1.21"}, // file downgrade permitted (file and module version are >= go1.21)
 
                // versions containing release numbers
                // (file versions containing release numbers are considered invalid)
                {"go1.19.0", "", "go1.19.0"},         // no file version specified
                {"go1.20", "go1.20.1", "go1.20"},     // file upgrade ignored
                {"go1.20.1", "go1.20", "go1.20.1"},   // file upgrade ignored
+               {"go1.21.0", "go1.21.1", "go1.21.0"}, // file upgrade ignored
+               {"go1.21", "go1.21.1", "go1.21"},     // file upgrade ignored
                {"go1.20.1", "go1.21", "go1.21"},     // file upgrade permitted
+               {"go1.21.1", "go1.21", "go1.21.1"},   // file downgrade ignored
                {"go1.20.1", "go1.19", "go1.20.1"},   // file downgrade not permitted
                {"go1.21.1", "go1.19.1", "go1.21.1"}, // file downgrade not permitted (invalid file version)
-               {"go1.21.1", "go1.19", "go1.19"},     // file downgrade permitted (module version is >= go1.21)
+               {"go1.22.1", "go1.21", "go1.21"},     // file downgrade permitted (file and module version is >= go1.21)
        } {
                var src string
                if test.fileVersion != "" {

diff --git a/src/go/types/check.go b/src/go/types/check.go
index 2d56b0f75c584600982aac46650a79473395ae2a..7472c9c5cd440685056ce339b162805b3db0668c 100644 (file)
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -374,12 +374,25 @@ func (check *Checker) initFiles(files []*ast.File) {
                                // To work around this, downgrades are only allowed when the
                                // module's Go version is Go 1.21 or later.
                                //
+                               // Downgrades are also only allowed to Go versions Go 1.21 or later.
+                               // In GOPATH mode, there's no way to set a module version and the
+                               // -lang is set to the local toolchain version to allow the use of
+                               // new features in GOPATH mode. But //go:build lines added before go1.21
+                               // weren't intended to downgrade, so code with //go:build lines for
+                               // go versions earlier than 1.21 may use language features added
+                               // in later versions and compile.
+                               //
+                               // We should probably change the downgradeOk condition to capture this
+                               // instead of adding an extra condition, but to make the change simpler,
+                               // we've tried to limit it to one line.
+                               // TODO(gri): simplify this code after 1.23 has shipped
+                               //
                                // If there is no valid check.version, then we don't really know what
                                // Go version to apply.
                                // Legacy tools may do this, and they historically have accepted everything.
                                // Preserve that behavior by ignoring //go:build constraints entirely in that
                                // case (!pkgVersionOk).
-                               if cmp > 0 || cmp < 0 && downgradeOk {
+                               if cmp > 0 || cmp < 0 && downgradeOk && fileVersion.cmp(go1_21) >= 0 {
                                        v = file.GoVersion
                                }
                        }

diff --git a/src/internal/types/testdata/check/go1_20_19.go b/src/internal/types/testdata/check/go1_20_19.go
index 08365a7cfb564d09e7cc5180d38f814bfec40456..ba1c454332322c88b20c05212c37e1219b388cb6 100644 (file)
--- a/src/internal/types/testdata/check/go1_20_19.go
+++ b/src/internal/types/testdata/check/go1_20_19.go
@@ -14,4 +14,4 @@ type Slice []byte
 type Array [8]byte
 
 var s Slice
-var p = (Array)(s /* ok because Go 1.20 ignored the //go:build go1.19 */)
+var p = (Array)(s /* ok because downgrades below 1.21 are ignored */)

diff --git a/src/internal/types/testdata/check/go1_21_19.go b/src/internal/types/testdata/check/go1_21_19.go
index 2acd25865d4b69a7b88e3ada60b3f62dced43537..6c0900d02727626ed84185bfd9cc95c43fc2eee7 100644 (file)
--- a/src/internal/types/testdata/check/go1_21_19.go
+++ b/src/internal/types/testdata/check/go1_21_19.go
@@ -14,4 +14,4 @@ type Slice []byte
 type Array [8]byte
 
 var s Slice
-var p = (Array)(s /* ERROR "requires go1.20 or later" */)
+var p = (Array)(s /* ok because downgrades below 1.21 are ignored */)

diff --git a/src/internal/types/testdata/check/go1_21_22.go b/src/internal/types/testdata/check/go1_21_22.go
new file mode 100644 (file)
index 0000000..695503a
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_21_22.go
@@ -0,0 +1,16 @@
+// -lang=go1.21
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+//go:build go1.22
+
+package p
+
+func f() {
+       for _ = range /* ok because of upgrade to 1.22 */ 10 {
+       }
+}
\ No newline at end of file

diff --git a/src/internal/types/testdata/check/go1_22_21.go b/src/internal/types/testdata/check/go1_22_21.go
new file mode 100644 (file)
index 0000000..79e21a7
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_22_21.go
@@ -0,0 +1,16 @@
+// -lang=go1.22
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+//go:build go1.21
+
+package p
+
+func f() {
+       for _ = range 10 /* ERROR "requires go1.22 or later" */ {
+       }
+}
\ No newline at end of file

diff --git a/src/internal/types/testdata/fixedbugs/issue66285.go b/src/internal/types/testdata/fixedbugs/issue66285.go
index 9811fec3f35549aaeb0ce670de453b0d1b1ad8fc..4af76f05da8e41a53fed50217f4af57eb83c447f 100644 (file)
--- a/src/internal/types/testdata/fixedbugs/issue66285.go
+++ b/src/internal/types/testdata/fixedbugs/issue66285.go
@@ -1,14 +1,9 @@
-// -lang=go1.21
+// -lang=go1.13
 
 // Copyright 2024 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Note: Downgrading to go1.13 requires at least go1.21,
-//       hence the need for -lang=go1.21 at the top.
-
-//go:build go1.13
-
 package p
 
 import "io"

diff --git a/test/fixedbugs/issue63489a.go b/test/fixedbugs/issue63489a.go
index b88120f2c045ef326a647a18c2dd0191d86025c1..9b06d949bfa96248d608698a43f0b5c8f496cf6e 100644 (file)
--- a/test/fixedbugs/issue63489a.go
+++ b/test/fixedbugs/issue63489a.go
@@ -1,16 +1,20 @@
-// errorcheck -lang=go1.21
+// errorcheck -lang=go1.22
 
 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.4
+// This file has been changed from its original version as
+// //go:build language downgrades below go1.21 are no longer
+// supported. The original tested a downgrade from go1.21 to
+// go1.4 while this new version tests a downgrade from go1.22
+// to go1.21
 
-package p
-
-const c = 0o123 // ERROR "file declares //go:build go1.4"
+//go:build go1.21
 
-// ERROR "file declares //go:build go1.4"
+package p
 
-//line issue63489a.go:13:1
-const d = 0o124
+func f() {
+       for _ = range 10 { // ERROR "file declares //go:build go1.21"
+       }
+}