[tools] go/analysis/passes/modernize: treat 'i += 1' as 'i++'
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Matthew “strager” Glazar (Gerrit)
Dec 23, 2025, 6:36:21 PM (2 days ago) Dec 23
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Matthew “strager” Glazar has uploaded the change for review![]( "Open in Gerrit")
Commit message
go/analysis/passes/modernize: treat 'i += 1' as 'i++'
The rangeint modernize pass converts the first loop but not the second, despite
them being equivalent:
for i := 0; i < 10; i++ {}
for i := 0; i < 10; i += 1 {}
Teach the pass to permit i += 1, increasing the pass's usefulness.
Fixes golang/go#76977
Change-Id: I3e993b7d73c59cef8a3e672ca413bb16be897b1e
Change diff
diff --git a/go/analysis/passes/modernize/rangeint.go b/go/analysis/passes/modernize/rangeint.go
index edffcee..fccd6e5 100644
--- a/go/analysis/passes/modernize/rangeint.go
+++ b/go/analysis/passes/modernize/rangeint.go
@@ -123,9 +123,21 @@
continue nextLoop
}
+ validIncrement := false
if inc, ok := loop.Post.(*ast.IncDecStmt); ok &&
inc.Tok == token.INC &&
astutil.EqualSyntax(compare.X, inc.X) {
+ // Have: i++
+ validIncrement = true
+ } else if assign, ok := loop.Post.(*ast.AssignStmt); ok &&
+ assign.Tok == token.ADD_ASSIGN &&
+ len(assign.Rhs) == 1 && isIntLiteral(info, assign.Rhs[0], 1) &&
+ len(assign.Lhs) == 1 && astutil.EqualSyntax(compare.X, assign.Lhs[0]) {
+ // Have: i += 1
+ validIncrement = true
+ }
+
+ if validIncrement {
// Have: for i = 0; i < limit; i++ {}
// Find references to i within the loop body.
@@ -246,7 +258,7 @@
pass.Report(analysis.Diagnostic{
Pos: init.Pos(),
- End: inc.End(),
+ End: loop.Post.End(),
Message: "for loop can be modernized using range over int",
SuggestedFixes: []analysis.SuggestedFix{{
Message: fmt.Sprintf("Replace for loop with range %s",
@@ -272,7 +284,7 @@
// Delete inc.
{
Pos: limit.End(),
- End: inc.End(),
+ End: loop.Post.End(),
},
// Add ")" after limit, if needed.
{
diff --git a/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go b/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go
index 11ddc69..a14dc38 100644
--- a/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go
+++ b/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go
@@ -92,6 +92,19 @@
i = 8
}
+ for i := 0; i < 10; i += 1 { // want "for loop can be modernized using range over int"
+ println(i)
+ }
+ for i := 0; i < 10; s.i += 1 { // nope: modifies another variable
+ println(i)
+ }
+ for i := 0; i < 10; i -= 1 { // nope: decrements i
+ println(i)
+ }
+ for i := 0; i < 10; i += 2 { // nope: range only increments by 1
+ println(i)
+ }
+
// The limit expression must be loop invariant;
// see https://github.com/golang/go/issues/72917
for i := 0; i < f(); i++ { // nope
diff --git a/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go.golden b/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go.golden
index 2b52145..0e92147 100644
--- a/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go.golden
+++ b/go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go.golden
@@ -90,7 +90,20 @@
for i := 0; i < 10; i++ { // nope: assigns i
i = 8
}
-
+
+ for i := range 10 { // want "for loop can be modernized using range over int"
+ println(i)
+ }
+ for i := 0; i < 10; s.i += 1 { // nope: modifies another variable
+ println(i)
+ }
+ for i := 0; i < 10; i -= 1 { // nope: decrements i
+ println(i)
+ }
+ for i := 0; i < 10; i += 2 { // nope: range only increments by 1
+ println(i)
+ }
+
// The limit expression must be loop invariant;
// see https://github.com/golang/go/issues/72917
for i := 0; i < f(); i++ { // nope
Change information
Files:
- M go/analysis/passes/modernize/rangeint.go
- M go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go
- M go/analysis/passes/modernize/testdata/src/rangeint/rangeint.go.golden
Change size: S
Delta: 3 files changed, 41 insertions(+), 3 deletions(-)
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Gopher Robot (Gerrit)
Dec 23, 2025, 6:38:16 PM (2 days ago) Dec 23
to Matthew “strager” Glazar, goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
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Alan Donovan (Gerrit)
Dec 23, 2025, 9:42:09 PM (2 days ago) Dec 23
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1 comment
Patchset-level comments
File-level comment, Patchset 1 (Latest):
Alan Donovan . resolved
Very nice; many thanks for contributing this fix.
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Hongxiang Jiang (Gerrit)
Dec 24, 2025, 12:59:35 AM (yesterday) Dec 24
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