From 7fc601f690a72f43285a796b41ec4ec76c1a3ee4 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sun, 24 May 2026 15:58:02 +0300
Subject: [PATCH] cgen: fix `IError` assignment to `?IError` field (fix #26973)
 (#27227)

---
 vlib/v/gen/c/cgen.v                           |  3 ++-
 .../tests/options/option_ierror_field_test.v  | 23 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/options/option_ierror_field_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 46aa951de..5ad38bc56 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -3367,7 +3367,8 @@ fn (mut g Gen) expr_with_tmp_var(expr ast.Expr, expr_typ ast.Type, ret_typ ast.T
 		g.write('${tmp_styp} ${tmp_var} = ')
 		g.gen_option_error(error_target_type, expr)
 		g.writeln(';')
-	} else if expr is ast.Ident && expr_typ == ast.error_type {
+	} else if expr is ast.Ident && expr_typ == ast.error_type
+		&& !(unwrapped_ret_typ.has_flag(.option) && unwrapped_ret_typ.idx() == ast.error_type_idx) {
 		g.writeln('${g.styp(unwrapped_ret_typ)} ${tmp_var} = {.state=2, .err=${expr.name}};')
 	} else {
 		mut simple_assign := false
diff --git a/vlib/v/tests/options/option_ierror_field_test.v b/vlib/v/tests/options/option_ierror_field_test.v
new file mode 100644
index 000000000..6de029a9e
--- /dev/null
+++ b/vlib/v/tests/options/option_ierror_field_test.v
@@ -0,0 +1,23 @@
+struct Holder {
+mut:
+	err ?IError
+}
+
+fn (mut h Holder) set_err(e IError) {
+	h.err = e
+}
+
+fn test_direct_assignment() {
+	mut h := Holder{}
+	assert h.err == none
+	h.err = error('boom')
+	got := h.err or { panic('expected Some, got none') }
+	assert got.msg() == 'boom'
+}
+
+fn test_method_assignment() {
+	mut h := Holder{}
+	h.set_err(error('method boom'))
+	got := h.err or { panic('expected Some, got none') }
+	assert got.msg() == 'method boom'
+}
-- 
2.39.5