From 13efcad6cbb4d0befb3c464e0edef18d6623aa8f Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Mon, 27 Oct 2025 12:55:47 +0530
Subject: [PATCH] parser,checker: smart detect `or {}` inside loop when using
 `c <-val` (fix #24550) (#25435)

---
 vlib/v/checker/checker.v                      |  8 +++++
 vlib/v/parser/expr.v                          | 11 +++++++
 .../inout/for_channel_or_expr_block.out       |  1 +
 .../inout/for_channel_or_expr_block.vv        | 31 +++++++++++++++++++
 4 files changed, 51 insertions(+)
 create mode 100644 vlib/v/slow_tests/inout/for_channel_or_expr_block.out
 create mode 100644 vlib/v/slow_tests/inout/for_channel_or_expr_block.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 38f632320..a6b446460 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2339,6 +2339,14 @@ fn (mut c Checker) stmt(mut node ast.Stmt) {
 							c.error('unused expression', node.pos)
 						}
 					}
+					if node.expr.op == .arrow {
+						if mut node.expr.right is ast.CallExpr {
+							if node.expr.right.return_type.has_flag(.result) {
+								node.expr.or_block.err_used = node.expr.or_block.scope.known_var('err')
+								node.expr.right.or_block = node.expr.or_block
+							}
+						}
+					}
 				}
 			}
 			if !c.inside_return {
diff --git a/vlib/v/parser/expr.v b/vlib/v/parser/expr.v
index d6bb02c01..a82aacdd3 100644
--- a/vlib/v/parser/expr.v
+++ b/vlib/v/parser/expr.v
@@ -827,6 +827,17 @@ fn (mut p Parser) infix_expr(left ast.Expr) ast.Expr {
 	mut or_scope := &ast.Scope(unsafe { nil })
 	// allow `x := <-ch or {...}` to handle closed channel
 	if op == .arrow {
+		if mut right is ast.SelectorExpr {
+			or_kind = right.or_block.kind
+			or_stmts = right.or_block.stmts.clone()
+			right.or_block = ast.OrExpr{}
+		}
+		if mut right is ast.CallExpr {
+			or_kind = right.or_block.kind
+			or_stmts = right.or_block.stmts.clone()
+			or_scope = right.or_block.scope
+			right.or_block = ast.OrExpr{}
+		}
 		if p.tok.kind == .key_orelse {
 			or_kind = .block
 			or_stmts, or_pos, or_scope = p.or_block(.with_err_var)
diff --git a/vlib/v/slow_tests/inout/for_channel_or_expr_block.out b/vlib/v/slow_tests/inout/for_channel_or_expr_block.out
new file mode 100644
index 000000000..5feb36d0a
--- /dev/null
+++ b/vlib/v/slow_tests/inout/for_channel_or_expr_block.out
@@ -0,0 +1 @@
+[vlib/v/slow_tests/inout/for_channel_or_expr_block.vv:22] a.any(it in [i64(1), 2, 3, 4, 5, 6, 7]): true
diff --git a/vlib/v/slow_tests/inout/for_channel_or_expr_block.vv b/vlib/v/slow_tests/inout/for_channel_or_expr_block.vv
new file mode 100644
index 000000000..0b48302ee
--- /dev/null
+++ b/vlib/v/slow_tests/inout/for_channel_or_expr_block.vv
@@ -0,0 +1,31 @@
+import time
+
+fn writer(c chan i64, delay i64) {
+	for {
+		time.sleep(delay)
+
+		c <- time.now().day_of_week() or {
+			break
+		}
+	}
+}
+
+fn reader(c chan i64, max int) {
+	mut a := []i64{}
+	for {
+		a << <-c
+		if a.len > max {
+			c.close()
+			break
+		}
+	}
+	dump(a.any(it in [i64(1), 2, 3, 4, 5, 6, 7]))
+}
+
+fn main() {
+	c := chan i64{}
+	mut t := []thread{}
+	t << spawn reader(c, 0)
+	t << spawn writer(c, 10 * time.millisecond)
+	t.wait()
+}
-- 
2.39.5