From 0ade4ff77b2ced2f450f86102c5b9fd4f01531ec Mon Sep 17 00:00:00 2001
From: Luc Talatinian <lucix@amazon.com>
Date: Fri, 31 Jul 2026 15:19:05 -0400
Subject: [PATCH] fix schema-serde sparse collection deser to not point to the
 same value

---
 .../amazon/smithy/go/codegen/serde2/ListDeserializer.java     | 4 +++-
 .../amazon/smithy/go/codegen/serde2/MapDeserializer.java      | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/ListDeserializer.java b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/ListDeserializer.java
index 20a4f849..6df9bf0d 100644
--- a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/ListDeserializer.java
+++ b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/ListDeserializer.java
@@ -69,7 +69,6 @@ private void renderDense(GoWriter writer) {
     private void renderSparse(GoWriter writer) {
         writer.writeGoTemplate("""
                 func deserialize$shapeName:L(d smithy.ShapeDeserializer, s *smithy.Schema, v *$symbol:T) error {
-                    var vv $memberSymbol:T
                     return smithy.ReadList(d, s, func() error {
                         if isNil, err := d.ReadNil(s.ListMember()); err != nil {
                             return err
@@ -78,6 +77,9 @@ private void renderSparse(GoWriter writer) {
                             return nil
                         }
 
+                        // vv must be declared per-element for sparse since we
+                        // are taking its pointer
+                        var vv $memberSymbol:T
                         $zeroValue:W
                         if err := $deserializeMember:W; err != nil {
                             return err
diff --git a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/MapDeserializer.java b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/MapDeserializer.java
index 5b89bc13..e4e8f095 100644
--- a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/MapDeserializer.java
+++ b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/serde2/MapDeserializer.java
@@ -71,7 +71,6 @@ private void renderSparse(GoWriter writer) {
         writer.writeGoTemplate("""
                 func deserialize$shapeName:L(d smithy.ShapeDeserializer, s *smithy.Schema, v *$symbol:T) error {
                     *v = make($symbol:T)
-                    var vv $valueSymbol:T
                     return smithy.ReadMap(d, s, func(k string) error {
                         if isNil, err := d.ReadNil(s.MapValue()); err != nil {
                             return err
@@ -80,6 +79,9 @@ private void renderSparse(GoWriter writer) {
                             return nil
                         }
 
+                        // vv must be declared per-element for sparse since we
+                        // are taking its pointer
+                        var vv $valueSymbol:T
                         $zeroValue:W
                         if err := $deserializeValue:W; err != nil {
                             return err