From 30a877ee36595ae38625480e246aa2dbf977442e Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 24 Apr 2026 22:21:24 +0300
Subject: [PATCH] checker: err fix (fixes #26975)

---
 vlib/v/checker/fn.v                           |  5 +++++
 vlib/v/tests/return_result_in_or_block_test.v | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 1ecd47b32..295631f40 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -1439,6 +1439,11 @@ fn (mut c Checker) call_expr(mut node ast.CallExpr) ast.Type {
 	old_expected_or_type := c.expected_or_type
 	c.expected_or_type = node.return_type.clear_flag(.result)
 	c.stmts_ending_with_expression(mut node.or_block.stmts, c.expected_or_type)
+	if node.or_block.kind == .block && !node.or_block.err_used {
+		if err_var := node.or_block.scope.find_var('err') {
+			node.or_block.err_used = err_var.is_used
+		}
+	}
 
 	if node.or_block.kind == .block {
 		mut return_context_type := ast.no_type
diff --git a/vlib/v/tests/return_result_in_or_block_test.v b/vlib/v/tests/return_result_in_or_block_test.v
index 0cf2d81a2..1a0dc1329 100644
--- a/vlib/v/tests/return_result_in_or_block_test.v
+++ b/vlib/v/tests/return_result_in_or_block_test.v
@@ -10,6 +10,14 @@ fn unwrap_function2() ?int {
 	return unwrap_int() or { none }
 }
 
+fn unwrap_error() !int {
+	return error('original error')
+}
+
+fn wrap_error_in_return_or_block() !int {
+	return unwrap_error() or { error('wrapped error: ${err}') }
+}
+
 fn test_return_result_in_or_block() {
 	x1 := unwrap_function1() or { panic(err) }
 	println(x1)
@@ -19,3 +27,11 @@ fn test_return_result_in_or_block() {
 	println(x2)
 	assert x2 == 1
 }
+
+fn test_err_interpolation_in_return_or_block() {
+	wrap_error_in_return_or_block() or {
+		assert err.msg() == 'wrapped error: original error'
+		return
+	}
+	assert false
+}
-- 
2.39.5