From 86a5e72c742b3ad41dd70a3b6bde4cd99768f8fa Mon Sep 17 00:00:00 2001
From: 05st <60903484+05st@users.noreply.github.com>
Date: Sat, 2 Oct 2021 15:26:46 -0500
Subject: [PATCH] v.checker: fix return type checking being skipped for mutable
 method receivers (#12043)

---
 vlib/v/checker/checker.v                            |  5 +----
 .../tests/mut_receiver_wrong_return_type.out        | 13 +++++++++++++
 .../checker/tests/mut_receiver_wrong_return_type.vv |  9 +++++++++
 3 files changed, 23 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/checker/tests/mut_receiver_wrong_return_type.out
 create mode 100644 vlib/v/checker/tests/mut_receiver_wrong_return_type.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index ce84dbf390..a61d662bad 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3758,10 +3758,6 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 		if !c.check_types(got_typ, exp_type) {
 			got_typ_sym := c.table.get_type_symbol(got_typ)
 			mut exp_typ_sym := c.table.get_type_symbol(exp_type)
-			pos := node.exprs[i].position()
-			if node.exprs[i].is_auto_deref_var() {
-				continue
-			}
 			if exp_typ_sym.kind == .interface_ {
 				if c.type_implements(got_typ, exp_type, node.pos) {
 					if !got_typ.is_ptr() && !got_typ.is_pointer() && got_typ_sym.kind != .interface_
@@ -3771,6 +3767,7 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 				}
 				continue
 			}
+			pos := node.exprs[i].position()
 			c.error('cannot use `$got_typ_sym.name` as type `${c.table.type_to_str(exp_type)}` in return argument',
 				pos)
 		}
diff --git a/vlib/v/checker/tests/mut_receiver_wrong_return_type.out b/vlib/v/checker/tests/mut_receiver_wrong_return_type.out
new file mode 100644
index 0000000000..3524822d3c
--- /dev/null
+++ b/vlib/v/checker/tests/mut_receiver_wrong_return_type.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/mut_receiver_wrong_return_type.vv:4:9: error: cannot use `Test` as type `?int` in return argument
+    2 |
+    3 | fn (mut test Test) test() ?int {
+    4 |     return test
+      |            ~~~~
+    5 | }
+    6 |
+vlib/v/checker/tests/mut_receiver_wrong_return_type.vv:8:9: error: cannot use `Test` as type `int` in return argument
+    6 |
+    7 | fn (mut test Test) test2() int {
+    8 |     return test
+      |            ~~~~
+    9 | }
diff --git a/vlib/v/checker/tests/mut_receiver_wrong_return_type.vv b/vlib/v/checker/tests/mut_receiver_wrong_return_type.vv
new file mode 100644
index 0000000000..e223907ecb
--- /dev/null
+++ b/vlib/v/checker/tests/mut_receiver_wrong_return_type.vv
@@ -0,0 +1,9 @@
+struct Test {}
+
+fn (mut test Test) test() ?int {
+	return test
+}
+
+fn (mut test Test) test2() int {
+	return test
+}