From 7d5d00328e4e9b97d911d6540d4715825e778869 Mon Sep 17 00:00:00 2001
From: ckaznocha <ckaznocha@gmail.com>
Date: Sat, 9 Nov 2024 15:24:29 -0800
Subject: [PATCH] Add note about scopes on assignment

---
 intrange.go             | 13 ++++++++++++-
 testdata/main.go        |  6 ++++++
 testdata/main.go.golden |  6 ++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/intrange.go b/intrange.go
index 4d3430e..6ebd668 100644
--- a/intrange.go
+++ b/intrange.go
@@ -79,6 +79,8 @@ func checkForStmt(pass *analysis.Pass, forStmt *ast.ForStmt) {
 		return
 	}
 
+	initAssign := init.Tok == token.ASSIGN
+
 	if len(init.Lhs) != 1 || len(init.Rhs) != 1 {
 		return
 	}
@@ -229,6 +231,15 @@ func checkForStmt(pass *analysis.Pass, forStmt *ast.ForStmt) {
 		return
 	}
 
+	if initAssign {
+		pass.Report(analysis.Diagnostic{
+			Pos:     forStmt.Pos(),
+			Message: msg + "\nBecause the key is not part of the loop's scope, take care to consider side effects.",
+		})
+
+		return
+	}
+
 	rangeX := operandToString(pass, initIdent, operand)
 
 	pass.Report(analysis.Diagnostic{
@@ -523,7 +534,7 @@ func operandToString(pass *analysis.Pass, i *ast.Ident, operand ast.Expr) string
 		return s
 	}
 
-	if len(s) > 2 && s[len(s)-1:] == ")" {
+	if len(s) > 2 && s[len(s)-1] == ')' {
 		return s
 	}
 
diff --git a/testdata/main.go b/testdata/main.go
index f017619..06b2316 100644
--- a/testdata/main.go
+++ b/testdata/main.go
@@ -335,3 +335,9 @@ func issue27() {
 func notLen(any) int {
 	return 0
 }
+
+func issue33() {
+	var i int
+	for i = 0; i < 10; i++ { // want `for loop can be changed to use an integer range \(Go 1\.22\+\)\nBecause the key is not part of the loop's scope, take care to consider side effects.`
+	}
+}
diff --git a/testdata/main.go.golden b/testdata/main.go.golden
index 48501eb..da98ccf 100644
--- a/testdata/main.go.golden
+++ b/testdata/main.go.golden
@@ -335,3 +335,9 @@ func issue27() {
 func notLen(any) int {
 	return 0
 }
+
+func issue33() {
+	var i int
+	for i = 0; i < 10; i++ { // want `for loop can be changed to use an integer range \(Go 1\.22\+\)\nBecause the key is not part of the loop's scope, take care to consider side effects.`
+	}
+}