From 26c7e700c3831f0455ff3987e6d5eb32d16d8729 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 26 Feb 2026 20:06:01 +0300
Subject: [PATCH] checker: fix aliased pointers not recognized (fixes #24621)

---
 vlib/v/checker/struct.v                       | 16 +++++++--
 ...as_pointer_struct_field_default_nil_test.v | 33 +++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/tests/aliases/alias_pointer_struct_field_default_nil_test.v

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 3e35c1151..c9ef1bb51 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -319,8 +319,20 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 					}
 				}
 				if field.default_expr.is_nil() {
-					if !field.typ.is_any_kind_of_pointer()
-						&& c.table.sym(field.typ).kind != .function {
+					mut nil_field_typ := field.typ
+					mut nil_field_sym := c.table.sym(nil_field_typ)
+					// Preserve pointer indirections while resolving alias chains.
+					for {
+						if mut nil_field_sym.info is ast.Alias {
+							parent_typ := nil_field_sym.info.parent_type
+							nil_field_typ = parent_typ.set_nr_muls(parent_typ.nr_muls() +
+								nil_field_typ.nr_muls())
+							nil_field_sym = c.table.sym(nil_field_typ)
+						} else {
+							break
+						}
+					}
+					if !nil_field_typ.is_any_kind_of_pointer() && nil_field_sym.kind != .function {
 						c.error('cannot assign `nil` to a non-pointer field', field.type_pos)
 					}
 				}
diff --git a/vlib/v/tests/aliases/alias_pointer_struct_field_default_nil_test.v b/vlib/v/tests/aliases/alias_pointer_struct_field_default_nil_test.v
new file mode 100644
index 000000000..b30b260bd
--- /dev/null
+++ b/vlib/v/tests/aliases/alias_pointer_struct_field_default_nil_test.v
@@ -0,0 +1,33 @@
+type NilAliasCol = int | string
+
+struct NilAliasMyType {
+	cols []NilAliasCol
+}
+
+type NilAliasPtr = &NilAliasMyType
+
+struct NilAliasStruct {
+mut:
+	alias_ptr     NilAliasPtr  = unsafe { nil }
+	alias_ptr_ptr &NilAliasPtr = unsafe { nil }
+}
+
+fn test_struct_field_default_nil_for_pointer_alias() {
+	value := NilAliasStruct{}
+	assert isnil(value.alias_ptr)
+	assert isnil(value.alias_ptr_ptr)
+}
+
+struct NilAliasInnerType {}
+
+type NilAliasInner = NilAliasInnerType
+
+struct NilAliasRefStruct {
+mut:
+	alias_ref &NilAliasInner = unsafe { nil }
+}
+
+fn test_struct_field_default_nil_for_reference_to_alias() {
+	value := NilAliasRefStruct{}
+	assert isnil(value.alias_ref)
+}
-- 
2.39.5