checker: add is_mut check for disallowing taking address of map's key and array's element outside unsafe (#6573)

vlib/v/checker/checker.v

@@ -2754,13 +2754,20 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 				}
 				if node.right is ast.IndexExpr as index {
 					typ_sym := c.table.get_type_symbol(index.left_type)
-					if !c.inside_unsafe {
+					mut is_mut := false
+					if index.left is ast.Ident as ident {
+						if ident.obj is ast.Var {
+							v := ident.obj as ast.Var
+							is_mut = v.is_mut
+						}
+					}
+					if !c.inside_unsafe && is_mut {
 						if typ_sym.kind == .map {
-							c.error('cannot get address of map values outside unsafe blocks',
+							c.error('cannot take the address of mutable map values outside unsafe blocks',
 								index.pos)
 						}
 						if typ_sym.kind == .array {
-							c.error('cannot get address of array elements outside unsafe blocks',
+							c.error('cannot take the address of mutable array elements outside unsafe blocks',
 								index.pos)
 						}
 					}

vlib/v/checker/tests/array_get_element_address_err.out

@@ -1,7 +0,0 @@
-vlib/v/checker/tests/array_get_element_address_err.vv:3:20: error: cannot get address of array elements outside unsafe blocks
-    1 | fn main() {
-    2 |     arr_int := [int(23), 45, 7, 8]
-    3 |     ele := &arr_int[1]
-      |                    ~~~
-    4 |     println(ele)
-    5 | }

vlib/v/checker/tests/map_get_value_address_err.out

@@ -1,14 +0,0 @@
-vlib/v/checker/tests/map_get_value_address_err.vv:3:12: error: cannot get address of map values outside unsafe blocks
-    1 | fn main() {
-    2 |     m := {'key' : 3}
-    3 |     a := &m['key']
-      |            ~~~~~~~
-    4 |     b := &{'foo': 4}['foo']
-    5 |     println(a)
-vlib/v/checker/tests/map_get_value_address_err.vv:4:21: error: cannot get address of map values outside unsafe blocks
-    2 |     m := {'key' : 3}
-    3 |     a := &m['key']
-    4 |     b := &{'foo': 4}['foo']
-      |                     ~~~~~~~
-    5 |     println(a)
-    6 |     println(b)

vlib/v/checker/tests/map_get_value_address_err.vv

@@ -1,7 +0,0 @@
-fn main() {
-    m := {'key' : 3}
-    a := &m['key']
-    b := &{'foo': 4}['foo']
-    println(a)
-    println(b)
-}

vlib/v/checker/tests/mut_array_get_element_address_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/mut_array_get_element_address_err.vv:3:20: error: cannot take the address of mutable array elements outside unsafe blocks
+    1 | fn main() {
+    2 |     mut arr_int := [int(23), 45, 7, 8]
+    3 |     ele := &arr_int[1]
+      |                    ~~~
+    4 |     println(ele)
+    5 | }

vlib/v/checker/tests/mut_array_get_element_address_err.vv

@@ -1,5 +1,5 @@
 fn main() {
-    arr_int := [int(23), 45, 7, 8]
+    mut arr_int := [int(23), 45, 7, 8]
     ele := &arr_int[1]
     println(ele)
 }

vlib/v/checker/tests/mut_map_get_value_address_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/mut_map_get_value_address_err.vv:3:12: error: cannot take the address of mutable map values outside unsafe blocks
+    1 | fn main() {
+    2 |     mut m := {'key' : 3}
+    3 |     a := &m['key']
+      |            ~~~~~~~
+    4 |     println(a)
+    5 | }

vlib/v/checker/tests/mut_map_get_value_address_err.vv

@@ -0,0 +1,5 @@
+fn main() {
+    mut m := {'key' : 3}
+    a := &m['key']
+    println(a)
+}

vlib/v/tests/unsafe_test.v

@@ -51,12 +51,10 @@ fn test_unsafe_if_stmt() int {
 }
 
 fn test_map_address_index() {
-	m := {
+	mut m := {
 		'one': 1
 	}
-	unsafe {
-		mut one := &m['one']
-		one++
-		println(*one)
-	}
+	mut one := unsafe {&m['one']}
+	(*one)++
+	println(*one)
 }