From 10b9ea32583a8eaa7ecff248a299a1cd53e2e22f Mon Sep 17 00:00:00 2001
From: shadowninja55 <49539636+shadowninja55@users.noreply.github.com>
Date: Thu, 10 Jun 2021 12:18:14 -0400
Subject: [PATCH] checker: add an error for assigning to array slices `a[..2] =
 [0, 0]` (#10412)

---
 vlib/v/checker/checker.v                    | 5 +++++
 vlib/v/checker/tests/slice_reassignment.out | 7 +++++++
 vlib/v/checker/tests/slice_reassignment.vv  | 5 +++++
 3 files changed, 17 insertions(+)
 create mode 100644 vlib/v/checker/tests/slice_reassignment.out
 create mode 100644 vlib/v/checker/tests/slice_reassignment.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 54beed80e0..a6456c2322 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3268,6 +3268,11 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 		if left is ast.CallExpr {
 			c.error('cannot call function `${left.name}()` on the left side of an assignment',
 				left.pos)
+		} else if left is ast.IndexExpr {
+			if left.index is ast.RangeExpr {
+				c.error('cannot reassign using range expression on the left side of an assignment',
+					left.pos)
+			}
 		}
 		is_blank_ident := left.is_blank_ident()
 		mut left_type := ast.void_type
diff --git a/vlib/v/checker/tests/slice_reassignment.out b/vlib/v/checker/tests/slice_reassignment.out
new file mode 100644
index 0000000000..7ab478fa4c
--- /dev/null
+++ b/vlib/v/checker/tests/slice_reassignment.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/slice_reassignment.vv:3:5: error: cannot reassign using range expression on the left side of an assignment
+    1 | fn main() {
+    2 |     mut arr := [1, 2, 3, 4, 5]
+    3 |     arr[..2] = [0, 0]
+      |        ~~~~~
+    4 |     println(arr)
+    5 | }
diff --git a/vlib/v/checker/tests/slice_reassignment.vv b/vlib/v/checker/tests/slice_reassignment.vv
new file mode 100644
index 0000000000..602bd647b7
--- /dev/null
+++ b/vlib/v/checker/tests/slice_reassignment.vv
@@ -0,0 +1,5 @@
+fn main() {
+	mut arr := [1, 2, 3, 4, 5]
+	arr[..2] = [0, 0]
+	println(arr)
+}