From 591af866ba49fc1d61d62419373509f4e1ce1352 Mon Sep 17 00:00:00 2001
From: shadow <49539636+shadowninja55@users.noreply.github.com>
Date: Wed, 21 Jul 2021 04:39:22 -0400
Subject: [PATCH] checker: prohibit returning a fixed array (#10882)

---
 vlib/v/checker/checker.v                    |  8 ++++++--
 vlib/v/checker/tests/return_fixed_array.out | 12 ++++++++++++
 vlib/v/checker/tests/return_fixed_array.vv  |  7 +++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/return_fixed_array.out
 create mode 100644 vlib/v/checker/tests/return_fixed_array.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index b8edca6bb1..33cc111eb3 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -7790,17 +7790,21 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 		return_sym := c.table.get_type_symbol(node.return_type)
 		if return_sym.info is ast.MultiReturn {
 			for multi_type in return_sym.info.types {
+				multi_sym := c.table.get_type_symbol(multi_type)
 				if multi_type == ast.error_type {
 					c.error('type `IError` cannot be used in multi-return, return an option instead',
 						node.return_type_pos)
 				} else if multi_type.has_flag(.optional) {
 					c.error('option cannot be used in multi-return, return an option instead',
 						node.return_type_pos)
+				} else if multi_sym.kind == .array_fixed {
+					c.error('fixed array cannot be used in multi-return', node.return_type_pos)
 				}
 			}
+		} else if return_sym.kind == .array_fixed {
+			c.error('fixed array cannot be returned by function', node.return_type_pos)
 		}
-	}
-	if node.return_type == ast.void_type {
+	} else {
 		for mut a in node.attrs {
 			if a.kind == .comptime_define {
 				c.evaluate_once_comptime_if_attribute(mut a)
diff --git a/vlib/v/checker/tests/return_fixed_array.out b/vlib/v/checker/tests/return_fixed_array.out
new file mode 100644
index 0000000000..3ac7df0fe6
--- /dev/null
+++ b/vlib/v/checker/tests/return_fixed_array.out
@@ -0,0 +1,12 @@
+vlib/v/checker/tests/return_fixed_array.vv:1:25: error: fixed array cannot be returned by function
+    1 | fn return_fixed_array() [3]int {
+      |                         ~~~~~~
+    2 |     return [1, 2, 3]!
+    3 | }
+vlib/v/checker/tests/return_fixed_array.vv:5:41: error: fixed array cannot be used in multi-return
+    3 | }
+    4 | 
+    5 | fn return_fixed_array_in_multi_return() ([3]int, [3]int) {
+      |                                         ~~~~~~~~~~~~~~~~
+    6 |     return [1, 2, 3]!, [4, 5, 6]!
+    7 | }
diff --git a/vlib/v/checker/tests/return_fixed_array.vv b/vlib/v/checker/tests/return_fixed_array.vv
new file mode 100644
index 0000000000..dc24da155c
--- /dev/null
+++ b/vlib/v/checker/tests/return_fixed_array.vv
@@ -0,0 +1,7 @@
+fn return_fixed_array() [3]int {
+	return [1, 2, 3]!
+}
+
+fn return_fixed_array_in_multi_return() ([3]int, [3]int) {
+	return [1, 2, 3]!, [4, 5, 6]!
+}