From 3dfd06be79feb3a7c5908f255cad2fd654998593 Mon Sep 17 00:00:00 2001
From: JMD <56417208+StunxFS@users.noreply.github.com>
Date: Wed, 22 Oct 2025 07:28:32 -0400
Subject: [PATCH] checker: fix type inference, when pushing an empty array to a
 2D array (fix #23854) (#25508)

---
 vlib/v/checker/infix.v                                     | 7 +++++++
 .../builtin_arrays/array_2d_append_empty_array_test.v      | 7 +++++++
 2 files changed, 14 insertions(+)
 create mode 100644 vlib/v/tests/builtin_arrays/array_2d_append_empty_array_test.v

diff --git a/vlib/v/checker/infix.v b/vlib/v/checker/infix.v
index 6f354c2f5..3173441ff 100644
--- a/vlib/v/checker/infix.v
+++ b/vlib/v/checker/infix.v
@@ -71,6 +71,13 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 					}
 				}
 			}
+		} else if mut node.right is ast.ArrayInit {
+			if node.right.exprs.len == 0 && node.right.elem_type == ast.void_type {
+				// handle arr << [] where [] is empty
+				info := c.table.sym(left_type).array_info()
+				node.right.elem_type = info.elem_type
+				c.expected_type = info.elem_type
+			}
 		}
 	}
 	mut right_type := c.expr(mut node.right)
diff --git a/vlib/v/tests/builtin_arrays/array_2d_append_empty_array_test.v b/vlib/v/tests/builtin_arrays/array_2d_append_empty_array_test.v
new file mode 100644
index 000000000..4fd2e52d9
--- /dev/null
+++ b/vlib/v/tests/builtin_arrays/array_2d_append_empty_array_test.v
@@ -0,0 +1,7 @@
+fn test_array_2d_append_empty_array() {
+	mut b := [][]int{}
+	b << [1, 2, 3]
+	b << []
+	assert b[0][0] == 1
+	assert b[1] == []
+}
-- 
2.39.5