From a3774a8b8c7cdb1f3fa298b8c976e22024802b07 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 15 Apr 2026 05:50:59 +0300
Subject: [PATCH] cgen: fix appending reference to array of sumtype references
 generating new memory address (fixes #14832)

---
 vlib/v/gen/c/fn.v                             | 18 +++++++++------
 .../array_of_reference_sumtype_test.v         | 23 +++++++++++++++++++
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index 88a353432..8c8a1e883 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -6288,13 +6288,17 @@ fn (mut g Gen) ref_or_deref_arg_ex(arg ast.CallArg, expected_type_ ast.Type, lan
 				|| (arg.expr is ast.UnsafeExpr && arg.expr.expr is ast.Nil) {
 				g.write('((void*)0)')
 			} else {
-				// sumtype conversions call memdup internally, so ADDR is sufficient.
-				// interface conversions don't, so HEAP is needed to ensure the pointer
-				// remains valid after the current scope ends.
-				wrap := if expected_ref_inner_sym.kind == .interface { 'HEAP' } else { 'ADDR' }
-				g.write('${wrap}(${expected_ref_inner_sym.cname}, ')
-				g.expr_with_cast(arg.expr, arg_typ, expected_ref_inner_type)
-				g.write(')')
+				if expected_ref_inner_sym.kind == .sum_type {
+					// `&Variant` -> `&SumType` needs a stable heap-allocated wrapper and
+					// must preserve aliasing with the original variant payload.
+					g.expr_with_cast(arg.expr, arg_typ, expected_type)
+				} else {
+					// interface conversions don't box by reference, so HEAP is needed to
+					// ensure the pointer remains valid after the current scope ends.
+					g.write('HEAP(${expected_ref_inner_sym.cname}, ')
+					g.expr_with_cast(arg.expr, arg_typ, expected_ref_inner_type)
+					g.write(')')
+				}
 			}
 			return
 		}
diff --git a/vlib/v/tests/builtin_arrays/array_of_reference_sumtype_test.v b/vlib/v/tests/builtin_arrays/array_of_reference_sumtype_test.v
index 88962e12a..09db62488 100644
--- a/vlib/v/tests/builtin_arrays/array_of_reference_sumtype_test.v
+++ b/vlib/v/tests/builtin_arrays/array_of_reference_sumtype_test.v
@@ -43,3 +43,26 @@ fn test_array_of_reference_sumtype() {
 	assert parent.child_nodes[0].name == 'child'
 	assert ret == 0
 }
+
+fn test_array_of_reference_sumtype_attribute_variant_aliases_original_payload() {
+	mut parent := &Element{
+		name: 'parent'
+	}
+	attr := &Attribute{
+		name:  'foo'
+		value: 'bar'
+	}
+	parent.append_child(attr)
+
+	attr_node := &Node(attr)
+	assert parent.has_child(attr_node) == 0
+
+	if parent.child_nodes[0] is Attribute {
+		parent.child_nodes[0].value = 'baz'
+	} else {
+		assert false
+	}
+
+	assert attr.value == 'baz'
+	assert parent.child_nodes[0].name == 'foo'
+}
-- 
2.39.5