[tools] go/analysis/passes/modernize: don't consider selects for min/max pass

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Daniel Morsing (Gerrit)

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Feb 18, 2026, 10:33:37 AM (9 days ago) Feb 18
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go/analysis/passes/modernize: don't consider selects for min/max pass

Fixes golang/go#77671.
Change-Id: I704fc5327218c5041fa56c29b92f23376a6a6964

Change diff

diff --git a/go/analysis/passes/modernize/minmax.go b/go/analysis/passes/modernize/minmax.go
index a77ed83..b4b8dba 100644
--- a/go/analysis/passes/modernize/minmax.go
+++ b/go/analysis/passes/modernize/minmax.go
@@ -147,6 +147,13 @@
 			lhs0 := fassign.Lhs[0]
 			rhs0 := fassign.Rhs[0]
 
+			// If the assignment occurs within a select
+			// comms clause (like "case lhs0 := <-rhs0:"),
+			// there's no way of rewriting it into a min/max call.
+			if prev.ParentEdgeKind() == edge.CommClause_Comm {
+				return
+			}
+
 			if astutil.EqualSyntax(lhs, lhs0) {
 				if astutil.EqualSyntax(rhs, a) && (astutil.EqualSyntax(rhs0, b) || astutil.EqualSyntax(lhs0, b)) {
 					sign = +sign
diff --git a/go/analysis/passes/modernize/testdata/src/minmax/minmax.go b/go/analysis/passes/modernize/testdata/src/minmax/minmax.go
index 74d84b2..4ef6723 100644
--- a/go/analysis/passes/modernize/testdata/src/minmax/minmax.go
+++ b/go/analysis/passes/modernize/testdata/src/minmax/minmax.go
@@ -169,3 +169,14 @@
 	}
 	return x
 }
+
+// Regression test for https://go.dev/issue/77671
+func selectComm(ch chan int) int {
+	select {
+	case n := <-ch:
+		if n > 100 {
+			n = 100
+		}
+		return n
+	}
+}
diff --git a/go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden b/go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
index f8dc94b..96b4965 100644
--- a/go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
+++ b/go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
@@ -168,3 +168,14 @@
 	}
 	return x
 }
+
+// Regression test for https://go.dev/issue/77671
+func selectComm(ch chan int) int {
+	select {
+	case n := <-ch:
+		if n > 100 {
+			n = 100
+		}
+		return n
+	}
+}

Change information

Files:
  • M go/analysis/passes/modernize/minmax.go
  • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go
  • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
Change size: S
Delta: 3 files changed, 29 insertions(+), 0 deletions(-)
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Alan Donovan (Gerrit)

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Feb 23, 2026, 11:44:03 AM (4 days ago) Feb 23
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Alan Donovan . resolved

Thanks for this fix. I feel like this is one of a whole category of grammar restrictions that we need to document in my (long awaiting) checklist for analyzer writers. Another example (of many) is that `if STMT; EXPR { ... }` can hold only certain kinds of STMT.

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Alan Donovan (Gerrit)

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Alan Donovan . resolved

Thanks for this fix. I feel like this is one of a whole category of grammar restrictions that we need to document in my (long awaiting) checklist for analyzer writers. Another example (of many) is that `if STMT; EXPR { ... }` can hold only certain kinds of STMT.

Alan Donovan

*long awaited

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David Chase (Gerrit)

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    Gopher Robot (Gerrit)

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    Feb 23, 2026, 4:01:46 PM (4 days ago) Feb 23
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    Change information

    Commit message:
    go/analysis/passes/modernize: don't consider selects for min/max pass

    Fixes golang/go#77671.
    Change-Id: I704fc5327218c5041fa56c29b92f23376a6a6964
    Auto-Submit: Alan Donovan <adon...@google.com>
    Reviewed-by: Alan Donovan <adon...@google.com>
    Reviewed-by: David Chase <drc...@google.com>
    Files:
    • M go/analysis/passes/modernize/minmax.go
    • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go
    • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
    Change size: S
    Delta: 3 files changed, 29 insertions(+), 0 deletions(-)
    Branch: refs/heads/master
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    David Chase (Gerrit)

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    Feb 26, 2026, 3:31:06 PM (24 hours ago) Feb 26
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    David Chase has uploaded the change for review

    Commit message

    [internal-branch.go1.26-vendor] go/analysis/passes/modernize: don't consider selects for min/max pass

    Updates golang/go#77804.


    Change-Id: I704fc5327218c5041fa56c29b92f23376a6a6964
    Reviewed-on: https://go-review.googlesource.com/c/tools/+/746541
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    Reviewed-by: David Chase <drc...@google.com>
    (cherry picked from commit 5c2a45909eac659b93659e0853eb43738b672c33)

    Change diff

    diff --git a/go/analysis/passes/modernize/minmax.go b/go/analysis/passes/modernize/minmax.go
    index 23a0977..812bad8 100644
    Change information
    Files:
    • M go/analysis/passes/modernize/minmax.go
    • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go
    • M go/analysis/passes/modernize/testdata/src/minmax/minmax.go.golden
    Change size: S
    Delta: 3 files changed, 29 insertions(+), 0 deletions(-)
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    Daniel Morsing (Gerrit)
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    File go/analysis/passes/modernize/minmax.go
    Line 153, Patchset 1 (Latest):			if prev.ParentEdgeKind() == edge.CommClause_Comm {
    Daniel Morsing . unresolved
    ```suggestion
    			if ek, _ := prev.ParentEdge(); ek == edge.CommClause_Comm {
    ```
    Since the vendor copy is from before we added `Cursor.ParentEdgeKind`
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      File go/analysis/passes/modernize/minmax.go
      Line 153, Patchset 1 (Latest):			if prev.ParentEdgeKind() == edge.CommClause_Comm {
      Daniel Morsing . resolved
      ```suggestion
      			if ek, _ := prev.ParentEdge(); ek == edge.CommClause_Comm {
      ```
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