From ea6d2d53db9cf0b2141bb626f3bd02dced4a562f Mon Sep 17 00:00:00 2001
From: Wertzui123 <46199283+Wertzui123@users.noreply.github.com>
Date: Wed, 27 Oct 2021 13:55:36 +0200
Subject: [PATCH] parser: disallow `for mut in range` (fix #12234) (#12277)

---
 vlib/builtin/js/array.js.v                            | 2 +-
 vlib/v/parser/for.v                                   | 3 +++
 vlib/v/parser/tests/for.out                           | 4 ----
 vlib/v/parser/tests/for_index_in_range.out            | 4 ++++
 vlib/v/parser/tests/{for.vv => for_index_in_range.vv} | 0
 vlib/v/parser/tests/for_mut_in_range.out              | 4 ++++
 vlib/v/parser/tests/for_mut_in_range.vv               | 2 ++
 7 files changed, 14 insertions(+), 5 deletions(-)
 delete mode 100644 vlib/v/parser/tests/for.out
 create mode 100644 vlib/v/parser/tests/for_index_in_range.out
 rename vlib/v/parser/tests/{for.vv => for_index_in_range.vv} (100%)
 create mode 100644 vlib/v/parser/tests/for_mut_in_range.out
 create mode 100644 vlib/v/parser/tests/for_mut_in_range.vv

diff --git a/vlib/builtin/js/array.js.v b/vlib/builtin/js/array.js.v
index 5e16df28f0..d20f4084ed 100644
--- a/vlib/builtin/js/array.js.v
+++ b/vlib/builtin/js/array.js.v
@@ -15,7 +15,7 @@ struct array_buffer {
 fn (mut a array_buffer) make_copy() {
 	if a.index_start != 0 || a.has_slice {
 		mut new_arr := JS.makeEmtpyJSArray()
-		for mut i in 0 .. a.len {
+		for i in 0 .. a.len {
 			#new_arr.push(a.val.get(i))
 
 			mut x := i
diff --git a/vlib/v/parser/for.v b/vlib/v/parser/for.v
index 36605c3ca0..ee00941bef 100644
--- a/vlib/v/parser/for.v
+++ b/vlib/v/parser/for.v
@@ -153,6 +153,9 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 				return p.error_with_pos('cannot declare index variable with range `for`',
 					key_var_pos)
 			}
+			if val_is_mut {
+				return p.error_with_pos('variable in range `for` cannot be mut', mut_pos)
+			}
 		} else {
 			// this type will be set in checker
 			p.scope.register(ast.Var{
diff --git a/vlib/v/parser/tests/for.out b/vlib/v/parser/tests/for.out
deleted file mode 100644
index acc089bb6a..0000000000
--- a/vlib/v/parser/tests/for.out
+++ /dev/null
@@ -1,4 +0,0 @@
-vlib/v/parser/tests/for.vv:1:5: error: cannot declare index variable with range `for`
-    1 | for i, k in 0..5 {
-      |     ^
-    2 | }
diff --git a/vlib/v/parser/tests/for_index_in_range.out b/vlib/v/parser/tests/for_index_in_range.out
new file mode 100644
index 0000000000..dab1a6e940
--- /dev/null
+++ b/vlib/v/parser/tests/for_index_in_range.out
@@ -0,0 +1,4 @@
+vlib/v/parser/tests/for_index_in_range.vv:1:5: error: cannot declare index variable with range `for`
+    1 | for i, k in 0..5 {
+      |     ^
+    2 | }
diff --git a/vlib/v/parser/tests/for.vv b/vlib/v/parser/tests/for_index_in_range.vv
similarity index 100%
rename from vlib/v/parser/tests/for.vv
rename to vlib/v/parser/tests/for_index_in_range.vv
diff --git a/vlib/v/parser/tests/for_mut_in_range.out b/vlib/v/parser/tests/for_mut_in_range.out
new file mode 100644
index 0000000000..6426bd4e86
--- /dev/null
+++ b/vlib/v/parser/tests/for_mut_in_range.out
@@ -0,0 +1,4 @@
+vlib/v/parser/tests/for_mut_in_range.vv:1:5: error: variable in range `for` cannot be mut
+    1 | for mut i in 0..5 {
+      |     ~~~
+    2 | }
diff --git a/vlib/v/parser/tests/for_mut_in_range.vv b/vlib/v/parser/tests/for_mut_in_range.vv
new file mode 100644
index 0000000000..7c0521e024
--- /dev/null
+++ b/vlib/v/parser/tests/for_mut_in_range.vv
@@ -0,0 +1,2 @@
+for mut i in 0..5 {
+}