From 826f10c35ba31eb432445c071c578db7c617b2f9 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 11 Mar 2026 15:48:30 +0300
Subject: [PATCH] wasm: backend indexing issue (fixes #21997)

---
 vlib/v/gen/wasm/gen.v               |  3 +++
 vlib/v/gen/wasm/tests/arrays.vv     | 19 +++++++++++++++++++
 vlib/v/gen/wasm/tests/arrays.vv.out |  6 +++++-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/vlib/v/gen/wasm/gen.v b/vlib/v/gen/wasm/gen.v
index 9467190b5..f7338cbbc 100644
--- a/vlib/v/gen/wasm/gen.v
+++ b/vlib/v/gen/wasm/gen.v
@@ -966,7 +966,10 @@ pub fn (mut g Gen) expr(node ast.Expr, expected ast.Type) {
 
 			size, _ := g.pool.type_size(typ)
 
+			old_needs_address := g.needs_address
+			g.needs_address = false
 			g.expr(node.index, ast.int_type)
+			g.needs_address = old_needs_address
 
 			if !direct_array_access {
 				g.is_leaf_function = false // calls panic()
diff --git a/vlib/v/gen/wasm/tests/arrays.vv b/vlib/v/gen/wasm/tests/arrays.vv
index 35c9aa016..d43543c6f 100644
--- a/vlib/v/gen/wasm/tests/arrays.vv
+++ b/vlib/v/gen/wasm/tests/arrays.vv
@@ -37,6 +37,12 @@ struct AA {
 	a [10]&int
 }
 
+struct IndexedWrite {
+mut:
+	idx   u8
+	frame [4]u8
+}
+
 fn test_stuff() &int {
 	a := AA{}
 
@@ -46,6 +52,16 @@ fn test_stuff() &int {
 	return b
 }
 
+fn selector_index_assign() {
+	mut app := IndexedWrite{}
+	app.idx = 1
+	app.frame[app.idx] = 123
+
+	println(app.frame[0])
+	println(app.frame[1])
+	println(app.frame[app.idx])
+}
+
 fn main() {
 	println('--- static_arrays()')
 	a, b, c := static_arrays()
@@ -64,4 +80,7 @@ fn main() {
 	println('--- test_stuff()')
 	v := test_stuff()
 	println(v)
+
+	println('--- selector_index_assign()')
+	selector_index_assign()
 }
diff --git a/vlib/v/gen/wasm/tests/arrays.vv.out b/vlib/v/gen/wasm/tests/arrays.vv.out
index a710bbc41..f020c11b5 100644
--- a/vlib/v/gen/wasm/tests/arrays.vv.out
+++ b/vlib/v/gen/wasm/tests/arrays.vv.out
@@ -11,4 +11,8 @@
 10
 10
 --- test_stuff()
-0
\ No newline at end of file
+0
+--- selector_index_assign()
+0
+123
+123
-- 
2.39.5