From 554f21a29c236a1c863f846f8f120122ec352d2d Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Fri, 12 Jan 2024 00:01:44 +0530
Subject: [PATCH] checker: disallow `option` or `result` return type, for infix
 operator overloading (#20494)

---
 vlib/v/checker/fn.v                           |  2 ++
 ...erloading_return_type_option_or_result.out | 14 ++++++++++++
 ...verloading_return_type_option_or_result.vv | 22 +++++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 vlib/v/checker/tests/operator_overloading_return_type_option_or_result.out
 create mode 100644 vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv

diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index d58adb7931d4d7..1bbcd5c94072d9 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -346,6 +346,8 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 						sptype := c.table.type_to_str(param_type)
 						c.error('the receiver type `${srtype}` should be the same type as the operand `${sptype}`',
 							node.pos)
+					} else if node.return_type.has_option_or_result() {
+						c.error('return type cannot be Option or Result', node.return_type_pos)
 					}
 				}
 			}
diff --git a/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.out b/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.out
new file mode 100644
index 00000000000000..4034dde74f9811
--- /dev/null
+++ b/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv:3:22: error: return type cannot be Option or Result
+    1 | type Vec = []int
+    2 | 
+    3 | fn (v Vec) + (u Vec) !Vec {
+      |                      ~~~~
+    4 |     if v.len != u.len {
+    5 |         return error("Operations require dim(v) == dim(u)")
+vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv:10:22: error: return type cannot be Option or Result
+    8 | }
+    9 | 
+   10 | fn (v Vec) - (u Vec) ?Vec {
+      |                      ~~~~
+   11 |     if v.len != u.len {
+   12 |         return none
diff --git a/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv b/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv
new file mode 100644
index 00000000000000..06db596e35d1c5
--- /dev/null
+++ b/vlib/v/checker/tests/operator_overloading_return_type_option_or_result.vv
@@ -0,0 +1,22 @@
+type Vec = []int
+
+fn (v Vec) + (u Vec) !Vec {
+	if v.len != u.len {
+		return error("Operations require dim(v) == dim(u)")
+	}
+	return Vec([v[0] + u[0], v[1] + u[1], v[2] + u[2]])
+}
+
+fn (v Vec) - (u Vec) ?Vec {
+	if v.len != u.len {
+		return none
+	}
+	return Vec([v[0] + u[0], v[1] + u[1], v[2] + u[2]])
+}
+
+
+
+fn main() {
+	vec := Vec([1, 2, 3])
+	dump(vec + vec)
+}