From d32dfa5ad1afb1bfde5b71f2626873d835e76e94 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 23 Apr 2026 21:21:47 +0300
Subject: [PATCH] cgen: fix cast between pointer and integer of different size
 with a sum type (fixes #14492)

---
 vlib/v/gen/c/struct.v                         |  2 +-
 .../sumtype_generic_ptr_field_default.out     |  1 +
 .../sumtype_generic_ptr_field_default.vv      | 26 +++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.out
 create mode 100644 vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.vv

diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index c3fcd0cbe..47a11a65c 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -743,7 +743,7 @@ fn (mut g Gen) zero_struct_field(field ast.StructField) bool {
 	} else if field.typ.has_flag(.option) {
 		g.gen_option_error(field.typ, ast.None{})
 		return true
-	} else if sym.info is ast.SumType {
+	} else if sym.info is ast.SumType && !field.typ.is_any_kind_of_pointer() {
 		g.write(g.type_default_sumtype(field.typ, sym))
 		return true
 	} else if sym.info is ast.ArrayFixed {
diff --git a/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.out b/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.out
new file mode 100644
index 000000000..f599e28b8
--- /dev/null
+++ b/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.out
@@ -0,0 +1 @@
+10
diff --git a/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.vv b/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.vv
new file mode 100644
index 000000000..67ef985ae
--- /dev/null
+++ b/vlib/v/gen/c/testdata/sumtype_generic_ptr_field_default.vv
@@ -0,0 +1,26 @@
+module main
+
+@[heap]
+struct JoshTree[T] {
+	primary_key int
+	value       T
+mut:
+	leaf &Node[T]
+}
+
+struct Empty {}
+
+type Node[T] = Empty | JoshTree[T]
+
+fn get_leaf[T](node &Node[T]) &JoshTree[T] {
+	return unsafe { &JoshTree[T](node) }
+}
+
+fn main() {
+	root := Node[int](JoshTree[int]{
+		primary_key: 1
+		value:       10
+	})
+	leaf := get_leaf[int](&root)
+	println(leaf.value)
+}
-- 
2.39.5