From cd042fdc384cf5591b3258ca80fdc002bb8c5e0d Mon Sep 17 00:00:00 2001
From: Max Neverov <neverov.max@gmail.com>
Date: Wed, 9 Oct 2024 01:59:04 +0200
Subject: [PATCH] Apply review suggestions.

---
 src/cmd/compile/internal/types2/decl.go      | 18 +++++++-----------
 src/cmd/compile/internal/types2/initorder.go | 10 ++++------
 src/go/types/decl.go                         | 19 ++++++++-----------
 src/go/types/initorder.go                    | 10 ++++------
 4 files changed, 23 insertions(+), 34 deletions(-)

diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 5cab086acc..53f471c4b9 100644
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -335,17 +335,13 @@ func (check *Checker) cycleError(cycle []Object, start int) {
 	} else {
 		err.addf(obj, "invalid cycle in declaration of %s", objName)
 	}
-	i := start
-	for range cycle {
-		currName := objName
-		currObj := obj
-		i++
-		if i >= len(cycle) {
-			i = 0
-		}
-		obj = cycle[i]
-		objName = name(obj)
-		err.addf(currObj, "%s refers to %s", currName, objName)
+	// "cycle[i] refers to cycle[j]" for (i,j) = (s, s+1), (s+1, s+2), ..., (n, 0), (0,1), ..., (s-1,s) for len(cycle) = n, s = start.
+	n := len(cycle)
+	rotate := func(i int) int { return (i + start) % n }
+	for i := range n {
+		obj := cycle[rotate(i)]
+		next := cycle[rotate(i+1)]
+		err.addf(obj, "%s refers to %s", name(obj), name(next))
 	}
 	err.report()
 }
diff --git a/src/cmd/compile/internal/types2/initorder.go b/src/cmd/compile/internal/types2/initorder.go
index 8be57f93eb..9efbf7f69f 100644
--- a/src/cmd/compile/internal/types2/initorder.go
+++ b/src/cmd/compile/internal/types2/initorder.go
@@ -163,12 +163,10 @@ func (check *Checker) reportCycle(cycle []Object) {
 
 	err := check.newError(InvalidInitCycle)
 	err.addf(obj, "initialization cycle for %s", obj.Name())
-	// subtle loop: print cycle[i] for i = 0, n-1, n-2, ... 1 for len(cycle) = n
-	for i := len(cycle) - 1; i >= 0; i-- {
-		currObj := obj
-		currName := obj.Name()
-		obj = cycle[i]
-		err.addf(currObj, "%s refers to %s", currName, obj.Name())
+	// "cycle[i] refers to cycle[j]" for (i,j) = (0, n-1), (n-1, n-2), ..., (1,0) for len(cycle) = n.
+	for j := len(cycle) - 1; j >= 0; j-- {
+		err.addf(obj, "%s refers to %s", obj.Name(), cycle[j].Name())
+		obj = cycle[j]
 	}
 	err.report()
 }
diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index e9f3f52eea..732214373d 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -336,17 +336,14 @@ func (check *Checker) cycleError(cycle []Object, start int) {
 	} else {
 		err.addf(obj, "invalid cycle in declaration of %s", objName)
 	}
-	i := start
-	for range cycle {
-		currName := objName
-		currObj := obj
-		i++
-		if i >= len(cycle) {
-			i = 0
-		}
-		obj = cycle[i]
-		objName = name(obj)
-		err.addf(currObj, "%s refers to %s", currName, objName)
+
+	// "cycle[i] refers to cycle[j]" for (i,j) = (s, s+1), (s+1, s+2), ..., (n, 0), (0,1), ..., (s-1,s) for len(cycle) = n, s = start.
+	n := len(cycle)
+	rotate := func(i int) int { return (i + start) % n }
+	for i := range n {
+		obj := cycle[rotate(i)]
+		next := cycle[rotate(i+1)]
+		err.addf(obj, "%s refers to %s", name(obj), name(next))
 	}
 	err.report()
 }
diff --git a/src/go/types/initorder.go b/src/go/types/initorder.go
index 411598f120..682a63e2d7 100644
--- a/src/go/types/initorder.go
+++ b/src/go/types/initorder.go
@@ -166,12 +166,10 @@ func (check *Checker) reportCycle(cycle []Object) {
 
 	err := check.newError(InvalidInitCycle)
 	err.addf(obj, "initialization cycle for %s", obj.Name())
-	// subtle loop: print cycle[i] for i = 0, n-1, n-2, ... 1 for len(cycle) = n
-	for i := len(cycle) - 1; i >= 0; i-- {
-		currObj := obj
-		currName := obj.Name()
-		obj = cycle[i]
-		err.addf(currObj, "%s refers to %s", currName, obj.Name())
+	// "cycle[i] refers to cycle[j]" for (i,j) = (0, n-1), (n-1, n-2), ..., (1,0) for len(cycle) = n.
+	for j := len(cycle) - 1; j >= 0; j-- {
+		err.addf(obj, "%s refers to %s", obj.Name(), cycle[j].Name())
+		obj = cycle[j]
 	}
 	err.report()
 }