From 584597aa3d678d814f73428f87db0485559c4c33 Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Fri, 12 Aug 2022 22:23:14 +0800
Subject: [PATCH] checker: check mismatch of return result type (#15413)

---
 vlib/v/checker/return.v                            |  6 ++++++
 .../checker/tests/return_result_type_mismatch.out  |  7 +++++++
 .../v/checker/tests/return_result_type_mismatch.vv | 14 ++++++++++++++
 3 files changed, 27 insertions(+)
 create mode 100644 vlib/v/checker/tests/return_result_type_mismatch.out
 create mode 100644 vlib/v/checker/tests/return_result_type_mismatch.vv

diff --git a/vlib/v/checker/return.v b/vlib/v/checker/return.v
index 1ca9a846f..f263ff5d1 100644
--- a/vlib/v/checker/return.v
+++ b/vlib/v/checker/return.v
@@ -104,6 +104,12 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 			c.error('cannot use `${c.table.type_to_str(got_typ)}` as type `${c.table.type_to_str(exp_type)}` in return argument',
 				pos)
 		}
+		if got_typ.has_flag(.result) && (!exp_type.has_flag(.result)
+			|| c.table.type_to_str(got_typ) != c.table.type_to_str(exp_type)) {
+			pos := node.exprs[expr_idxs[i]].pos()
+			c.error('cannot use `${c.table.type_to_str(got_typ)}` as type `${c.table.type_to_str(exp_type)}` in return argument',
+				pos)
+		}
 		if node.exprs[expr_idxs[i]] !is ast.ComptimeCall && !c.check_types(got_typ, exp_type) {
 			got_typ_sym := c.table.sym(got_typ)
 			mut exp_typ_sym := c.table.sym(exp_type)
diff --git a/vlib/v/checker/tests/return_result_type_mismatch.out b/vlib/v/checker/tests/return_result_type_mismatch.out
new file mode 100644
index 000000000..a65943164
--- /dev/null
+++ b/vlib/v/checker/tests/return_result_type_mismatch.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/return_result_type_mismatch.vv:8:9: error: cannot use `!int` as type `?int` in return argument
+    6 | // Option
+    7 | fn bar(a int) ?int {
+    8 |     return foo(a)
+      |            ~~~~~~
+    9 | }
+   10 |
diff --git a/vlib/v/checker/tests/return_result_type_mismatch.vv b/vlib/v/checker/tests/return_result_type_mismatch.vv
new file mode 100644
index 000000000..4d06d2cef
--- /dev/null
+++ b/vlib/v/checker/tests/return_result_type_mismatch.vv
@@ -0,0 +1,14 @@
+// Result
+fn foo(a int) !int {
+	return a + 1
+}
+
+// Option
+fn bar(a int) ?int {
+	return foo(a)
+}
+
+fn main() {
+	x := bar(1)?
+	println('$x')
+}
-- 
2.39.5