From 0d53705776fa473fa8711d1c2bdacbd52b7183d1 Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Thu, 7 Oct 2021 02:04:33 +0800
Subject: [PATCH] v.checker: check fn returning void type (fix #12076) (#12078)

---
 vlib/v/checker/checker.v                      | 3 +++
 vlib/v/checker/tests/return_void_type_err.out | 6 ++++++
 vlib/v/checker/tests/return_void_type_err.vv  | 7 +++++++
 3 files changed, 16 insertions(+)
 create mode 100644 vlib/v/checker/tests/return_void_type_err.out
 create mode 100644 vlib/v/checker/tests/return_void_type_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 44bfbeb692..67326f7a73 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3706,6 +3706,9 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 	mut got_types := []ast.Type{}
 	for expr in node.exprs {
 		typ := c.expr(expr)
+		if typ == ast.void_type {
+			c.error('`$expr` used as value', node.pos)
+		}
 		// Unpack multi return types
 		sym := c.table.get_type_symbol(typ)
 		if sym.kind == .multi_return {
diff --git a/vlib/v/checker/tests/return_void_type_err.out b/vlib/v/checker/tests/return_void_type_err.out
new file mode 100644
index 0000000000..19393f164e
--- /dev/null
+++ b/vlib/v/checker/tests/return_void_type_err.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/return_void_type_err.vv:2:2: error: `println(msg)` used as value
+    1 | fn hello(msg string) ? {
+    2 |     return println(msg)
+      |     ~~~~~~~~~~~~~~~~~~~
+    3 | }
+    4 |
diff --git a/vlib/v/checker/tests/return_void_type_err.vv b/vlib/v/checker/tests/return_void_type_err.vv
new file mode 100644
index 0000000000..177da908ca
--- /dev/null
+++ b/vlib/v/checker/tests/return_void_type_err.vv
@@ -0,0 +1,7 @@
+fn hello(msg string) ? {
+	return println(msg)
+}
+
+fn main() {
+	hello('test') ?
+}