From 79b7420ee105b3b5478db35240151af33749e45d Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Thu, 21 Sep 2023 23:00:06 +0200
Subject: [PATCH] interp: fix issue where a var is reused instead of redefined

Avoid a spurious optimisation which forces a variable to be reused instead of redefined for assignment operation. This ensures that a variable defined in a loop is re-allocated, preserving the previous instance when used by a closure for example.

Fix #1594
---
 _test/issue-1594.go | 17 +++++++++++++++++
 interp/cfg.go       |  2 +-
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 _test/issue-1594.go

diff --git a/_test/issue-1594.go b/_test/issue-1594.go
new file mode 100644
index 000000000..3bfa5f181
--- /dev/null
+++ b/_test/issue-1594.go
@@ -0,0 +1,17 @@
+package main
+
+func main() {
+	var fns []func()
+	for _, v := range []int{1, 2, 3} {
+		x := v*100 + v
+		fns = append(fns, func() { println(x) })
+	}
+	for _, fn := range fns {
+		fn()
+	}
+}
+
+// Output:
+// 101
+// 202
+// 303
diff --git a/interp/cfg.go b/interp/cfg.go
index 8bc45910e..39133a4c8 100644
--- a/interp/cfg.go
+++ b/interp/cfg.go
@@ -755,7 +755,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					n.gen = nop
 					src.findex = dest.findex
 					src.level = level
-				case len(n.child) < 4 && isArithmeticAction(src) && !isInterface(dest.typ):
+				case len(n.child) < 4 && n.kind != defineStmt && isArithmeticAction(src) && !isInterface(dest.typ):
 					// Optimize single assignments from some arithmetic operations.
 					src.typ = dest.typ
 					src.findex = dest.findex