From 549654aece7c549138180b110f1f0506231592a3 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Sat, 16 Mar 2024 22:27:30 +0530
Subject: [PATCH]  checker: disallow `Optional` and `Result` high val in a `for
 x in low..high {` loop  (#21043)

---
 vlib/v/checker/for.v                             |  3 +++
 .../tests/for_in_range_result_optional_err.out   | 14 ++++++++++++++
 .../tests/for_in_range_result_optional_err.vv    | 16 ++++++++++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 vlib/v/checker/tests/for_in_range_result_optional_err.out
 create mode 100644 vlib/v/checker/tests/for_in_range_result_optional_err.vv

diff --git a/vlib/v/checker/for.v b/vlib/v/checker/for.v
index 9f19d6d49..9184e784b 100644
--- a/vlib/v/checker/for.v
+++ b/vlib/v/checker/for.v
@@ -57,6 +57,9 @@ fn (mut c Checker) for_in_stmt(mut node ast.ForInStmt) {
 				node.cond.pos().extend(node.high.pos()))
 		} else if typ_idx !in ast.integer_type_idxs {
 			c.error('range type can only be an integer type', node.cond.pos().extend(node.high.pos()))
+		} else if high_type.has_option_or_result() {
+			c.error('the `high` value in a `for x in low..high {` loop, cannot be Result or Option',
+				node.high.pos())
 		}
 		if high_type in [ast.int_type, ast.int_literal_type] {
 			node.val_type = typ
diff --git a/vlib/v/checker/tests/for_in_range_result_optional_err.out b/vlib/v/checker/tests/for_in_range_result_optional_err.out
new file mode 100644
index 000000000..7c2bebeb4
--- /dev/null
+++ b/vlib/v/checker/tests/for_in_range_result_optional_err.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/for_in_range_result_optional_err.vv:11:23: error: the `high` value in a `for x in low..high {` loop, cannot be Result or Option
+    9 | fn main() {
+   10 |     arr := [1, 2, 3, 4, 5, 6, 7, 8, 9]
+   11 |     for _ in 0 .. arrays.idx_min(arr) {
+      |                          ~~~~~~~~~~~~
+   12 |     }
+   13 |
+vlib/v/checker/tests/for_in_range_result_optional_err.vv:14:16: error: the `high` value in a `for x in low..high {` loop, cannot be Result or Option
+   12 |     }
+   13 | 
+   14 |     for _ in 0 .. foo() {
+      |                   ~~~~~
+   15 |     }
+   16 | }
diff --git a/vlib/v/checker/tests/for_in_range_result_optional_err.vv b/vlib/v/checker/tests/for_in_range_result_optional_err.vv
new file mode 100644
index 000000000..73082b70f
--- /dev/null
+++ b/vlib/v/checker/tests/for_in_range_result_optional_err.vv
@@ -0,0 +1,16 @@
+module main
+
+import arrays
+
+fn foo() ?int {
+	return 12
+}
+
+fn main() {
+	arr := [1, 2, 3, 4, 5, 6, 7, 8, 9]
+	for _ in 0 .. arrays.idx_min(arr) {
+	}
+
+	for _ in 0 .. foo() {
+	}
+}
-- 
2.39.5