From 083eb3450be533516f8d33af1eca8574ee0b200c Mon Sep 17 00:00:00 2001
From: shove <shove@163.com>
Date: Mon, 11 Dec 2023 06:59:50 +0800
Subject: [PATCH] checker: fix struct init update with generics (fix #20136)
 (#20139)

---
 vlib/v/checker/struct.v                       |  3 ++-
 .../struct_init_update_with_generics_test.v   | 20 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/struct_init_update_with_generics_test.v

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 33bf4a60dc..f5a156ed95 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -874,9 +874,10 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 	if node.has_update_expr {
 		update_type := c.expr(mut node.update_expr)
 		node.update_expr_type = update_type
+		expr_sym := c.table.final_sym(c.unwrap_generic(update_type))
 		if node.update_expr is ast.ComptimeSelector {
 			c.error('cannot use struct update syntax in compile time expressions', node.update_expr_pos)
-		} else if c.table.final_sym(update_type).kind != .struct_ {
+		} else if expr_sym.kind != .struct_ {
 			s := c.table.type_to_str(update_type)
 			c.error('expected struct, found `${s}`', node.update_expr.pos())
 		} else if update_type != node.typ {
diff --git a/vlib/v/tests/struct_init_update_with_generics_test.v b/vlib/v/tests/struct_init_update_with_generics_test.v
new file mode 100644
index 0000000000..c1f30a80f5
--- /dev/null
+++ b/vlib/v/tests/struct_init_update_with_generics_test.v
@@ -0,0 +1,20 @@
+struct Foo {
+	a      int
+	b      string
+	isbool bool
+}
+
+fn do[T](f T) T {
+	return T{
+		...f
+		isbool: true
+	}
+}
+
+fn test_main() {
+	foo := do(Foo{
+		a: 1
+		b: '2'
+	})
+	assert foo.a == 1 && foo.b == '2' && foo.isbool
+}