Daniel Morsing (Gerrit)

unread,

Jan 16, 2026, 9:03:33 AM (yesterday) Jan 16

to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com

Daniel Morsing has uploaded the change for review

Commit message

go/analysis/passes/modernize: fix panic in stringscut

stringscut modernizer assumes that any CallExpr that occurs in the first
argument is a []byte(string) conversion, causing panics when given a function
call with no arguments at all.

Fixes golang/go#77208.

Change-Id: I17401c74c4681b24fb3a508cafafffee6a6a6964

Change diff

diff --git a/go/analysis/passes/modernize/stringscut.go b/go/analysis/passes/modernize/stringscut.go
index 08ce2a8..3835a10 100644
--- a/go/analysis/passes/modernize/stringscut.go
+++ b/go/analysis/passes/modernize/stringscut.go
@@ -345,6 +345,7 @@
 	switch expr := expr.(type) {
 	case *ast.CallExpr:
 		return types.Identical(tv.Type, byteSliceType) &&
+			types.Identical(info.Types[expr.Fun].Type, byteSliceType) && // make sure this isn't a function that returns a byte slice
 			indexArgValid(info, index, expr.Args[0], afterPos) // check s in []byte(s)
 	case *ast.Ident:
 		sObj := info.Uses[expr]
diff --git a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
index 0390eab..9500b08 100644
--- a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
+++ b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
@@ -289,6 +289,15 @@
 	return ""
 }
 
+func idx_call() {
+	i := bytes.Index(b(), []byte(""))
+	_ = i
+}
+
+func b() []byte {
+	return nil
+}
+
 func function(s string) {}
 
 func reference_str(s *string) {}
diff --git a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden
index a308fb2..2c3d81e 100644
--- a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden
+++ b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden
@@ -289,6 +289,15 @@
 	return ""
 }
 
+func idx_call() {
+	i := bytes.Index(b(), []byte(""))
+	_ = i
+}
+
+func b() []byte {
+	return nil
+}
+
 func function(s string) {}
 
 func reference_str(s *string) {}

Change information

Files:

M go/analysis/passes/modernize/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden

Change size: S

Delta: 3 files changed, 19 insertions(+), 0 deletions(-)

Open in Gerrit

Related details

Attention set is empty

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

satisfied_requirement

open

diffy

Daniel Morsing (Gerrit)

unread,

Jan 16, 2026, 9:06:44 AM (yesterday) Jan 16

to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com

Daniel Morsing uploaded new patchset

Daniel Morsing uploaded patch set #2 to this change.

Open in Gerrit

Related details

Attention set is empty

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

satisfied_requirement

open

diffy

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 12:35:50 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Alan Donovan added 3 comments

Patchset-level comments

File-level comment, Patchset 2 (Latest):

Alan Donovan . resolved

Thanks for the fix!

File go/analysis/passes/modernize/stringscut.go

Line 348, Patchset 2 (Latest):

			types.Identical(info.Types[expr.Fun].Type, byteSliceType) && // make sure this isn't a function that returns a byte slice

Alan Donovan . unresolved

A more direct check is `info.Types[expr.Fun].IsType()`, which reports whether this is a conversion without caring about the specific types involved.

File go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go

Line 292, Patchset 2 (Latest):func idx_call() {

Alan Donovan . unresolved

Explain the intent:

// Regression test for a crash (go.dev/issue/77208).

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review

No-Unresolved-Comments

Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

open

diffy

Daniel Morsing (Gerrit)

unread,

Jan 16, 2026, 12:51:32 PM (yesterday) Jan 16

to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Daniel Morsing uploaded new patchset

Daniel Morsing uploaded patch set #3 to this change.

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

open

diffy

Daniel Morsing (Gerrit)

unread,

Jan 16, 2026, 12:53:24 PM (yesterday) Jan 16

to goph...@pubsubhelper.golang.org, Madeline Kalil, Alan Donovan, golang-co...@googlegroups.com

Attention needed from Alan Donovan

Daniel Morsing voted and added 2 comments

Votes added by Daniel Morsing

Commit-Queue

+1

2 comments

File go/analysis/passes/modernize/stringscut.go

Line 348, Patchset 2:

			types.Identical(info.Types[expr.Fun].Type, byteSliceType) && // make sure this isn't a function that returns a byte slice

Alan Donovan . resolved

A more direct check is `info.Types[expr.Fun].IsType()`, which reports whether this is a conversion without caring about the specific types involved.

Daniel Morsing

Done

File go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go

Line 292, Patchset 2:func idx_call() {

Alan Donovan . resolved

Explain the intent:
// Regression test for a crash (go.dev/issue/77208).

Daniel Morsing

Done

Open in Gerrit

Related details

Attention is currently required from:

Alan Donovan

Submit Requirements:

Code-Review

No-Unresolved-Comments

Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

satisfied_requirement

open

diffy

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 12:58:59 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, Go LUCI, Madeline Kalil, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Alan Donovan voted and added 1 comment

Votes added by Alan Donovan

Auto-Submit	+1
Code-Review	+2
Commit-Queue	+1

1 comment

Patchset-level comments

File-level comment, Patchset 3 (Latest):

Alan Donovan . resolved

Thanks!

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review

No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 1:08:53 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, Go LUCI, Madeline Kalil, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Alan Donovan added 1 comment

Patchset-level comments

File-level comment, Patchset 3 (Latest):

Alan Donovan . resolved

The test failure is spurious; I've filed https://github.com/golang/go/issues/77211.

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Madeline Kalil (Gerrit)

unread,

Jan 16, 2026, 2:15:11 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, Go LUCI, Alan Donovan, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Madeline Kalil voted and added 1 comment

Votes added by Madeline Kalil

Code-Review	+2
Commit-Queue	+1

1 comment

Patchset-level comments

File-level comment, Patchset 3 (Latest):

Madeline Kalil . resolved

Thank you!

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review
No-Unresolved-Comments

Review-Enforcement

TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 2:32:28 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, Madeline Kalil, Go LUCI, golang-co...@googlegroups.com

Attention needed from Daniel Morsing

Alan Donovan voted Commit-Queue+1

Commit-Queue

+1

Open in Gerrit

Related details

Attention is currently required from:

Daniel Morsing

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Gopher Robot (Gerrit)

unread,

Jan 16, 2026, 2:38:19 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Madeline Kalil, Go LUCI, Alan Donovan, golang-co...@googlegroups.com

Gopher Robot submitted the change

Change information

Commit message:

go/analysis/passes/modernize: fix panic in stringscut

stringscut modernizer assumes that any CallExpr that occurs in the first
argument is a []byte(string) conversion, causing panics when given a
function call with no arguments at all.

Fixes golang/go#77208.

Change-Id: I17401c74c4681b24fb3a508cafafffee6a6a6964

Reviewed-on: https://go-review.googlesource.com/c/tools/+/737000

Reviewed-by: Alan Donovan <adon...@google.com>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Reviewed-by: Madeline Kalil <mka...@google.com>

Auto-Submit: Alan Donovan <adon...@google.com>

Files:

M go/analysis/passes/modernize/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden

Change size: S

Delta: 3 files changed, 21 insertions(+), 0 deletions(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +2 by Alan Donovan, +2 by Madeline Kalil
TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

Open in Gerrit

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

open

diffy

satisfied_requirement

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 2:55:31 PM (yesterday) Jan 16

to goph...@pubsubhelper.golang.org, Daniel Morsing, golang-co...@googlegroups.com

Alan Donovan has uploaded the change for review

Commit message

[internal-branch.go1.26-vendor] go/analysis/passes/modernize: fix panic in stringscut



stringscut modernizer assumes that any CallExpr that occurs in the first
argument is a []byte(string) conversion, causing panics when given a
function call with no arguments at all.

Fixes golang/go#77208.

Change-Id: I17401c74c4681b24fb3a508cafafffee6a6a6964
Reviewed-on: https://go-review.googlesource.com/c/tools/+/737000
Reviewed-by: Alan Donovan <adon...@google.com>
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Madeline Kalil <mka...@google.com>
Auto-Submit: Alan Donovan <adon...@google.com>

(cherry picked from commit 3d35eff1a742037163a41b9e4b2ec9977618d1f8)

Change diff

diff --git a/go/analysis/passes/modernize/stringscut.go b/go/analysis/passes/modernize/stringscut.go
index 08ce2a8..62088f0 100644


--- a/go/analysis/passes/modernize/stringscut.go
+++ b/go/analysis/passes/modernize/stringscut.go
@@ -345,6 +345,7 @@
 	switch expr := expr.(type) {
 	case *ast.CallExpr:
 		return types.Identical(tv.Type, byteSliceType) &&

+			info.Types[expr.Fun].IsType() && // make sure this isn't a function that returns a byte slice


 			indexArgValid(info, index, expr.Args[0], afterPos) // check s in []byte(s)
 	case *ast.Ident:
 		sObj := info.Uses[expr]
diff --git a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go

index 0390eab..5990771 100644
--- a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
+++ b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
@@ -289,6 +289,16 @@
 	return ""
 }
 
+// Regression test for a crash (https://go.dev/issue/77208)


+func idx_call() {
+	i := bytes.Index(b(), []byte(""))
+	_ = i
+}
+
+func b() []byte {
+	return nil
+}
+
 func function(s string) {}
 
 func reference_str(s *string) {}
diff --git a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden

index a308fb2..e274382 100644
--- a/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden
+++ b/go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden
@@ -289,6 +289,16 @@
 	return ""
 }
 
+// Regression test for a crash (https://go.dev/issue/77208)


+func idx_call() {
+	i := bytes.Index(b(), []byte(""))
+	_ = i
+}
+
+func b() []byte {
+	return nil
+}
+
 func function(s string) {}
 
 func reference_str(s *string) {}

Change information

Files:

M go/analysis/passes/modernize/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go
M go/analysis/passes/modernize/testdata/src/stringscut/stringscut.go.golden

Change size: S

Delta: 3 files changed, 21 insertions(+), 0 deletions(-)

Open in Gerrit

Related details

Attention set is empty

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement

TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

unsatisfied_requirement

satisfied_requirement

open

diffy

Madeline Kalil (Gerrit)

unread,

Jan 16, 2026, 3:04:28 PM (yesterday) Jan 16

to Alan Donovan, Daniel Morsing, goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com

Attention needed from Alan Donovan

Madeline Kalil voted Code-Review+2

Code-Review

+2

Open in Gerrit

Related details

Attention is currently required from:

Alan Donovan

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement

TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Alan Donovan (Gerrit)

unread,

Jan 16, 2026, 3:10:02 PM (yesterday) Jan 16

to Daniel Morsing, goph...@pubsubhelper.golang.org, Madeline Kalil, golang-co...@googlegroups.com

Alan Donovan voted

Code-Review	+2
Commit-Queue	+1

Open in Gerrit

Related details

Attention set is empty

Submit Requirements:

Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass

Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings.

Gerrit

satisfied_requirement

unsatisfied_requirement

open

diffy

Reply all

Reply to author

Forward

[tools] go/analysis/passes/modernize: fix panic in stringscut

Daniel Morsing (Gerrit)

Daniel Morsing has uploaded the change for review

Commit message

Change diff

Change information

Related details

Daniel Morsing (Gerrit)

Daniel Morsing uploaded new patchset

Related details

Alan Donovan (Gerrit)

Alan Donovan added 3 comments

Related details

Daniel Morsing (Gerrit)

Daniel Morsing uploaded new patchset

Related details

Daniel Morsing (Gerrit)

Daniel Morsing voted and added 2 comments

Votes added by Daniel Morsing

2 comments

Related details

Alan Donovan (Gerrit)

Alan Donovan voted and added 1 comment

Votes added by Alan Donovan

1 comment

Related details

Alan Donovan (Gerrit)

Alan Donovan added 1 comment

Related details

Madeline Kalil (Gerrit)

Madeline Kalil voted and added 1 comment

Votes added by Madeline Kalil

1 comment

Related details

Alan Donovan (Gerrit)

Alan Donovan voted Commit-Queue+1

Related details

Gopher Robot (Gerrit)

Gopher Robot submitted the change

Change information

Alan Donovan (Gerrit)

Alan Donovan has uploaded the change for review

Commit message

Change diff

Change information

Related details

Madeline Kalil (Gerrit)

Madeline Kalil voted Code-Review+2

Related details

Alan Donovan (Gerrit)

Alan Donovan voted

Related details