checker: disallow using unsafe { none } (#16431)

vlib/v/checker/assign.v

@@ -54,7 +54,13 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 			}
 		}
 		if mut right is ast.None {
-			c.error('you can not assign a `none` value to a variable', right.pos)
+			c.error('cannot assign a `none` value to a variable', right.pos)
+		}
+		// Handle `left_name := unsafe { none }`
+		if mut right is ast.UnsafeExpr {
+			if mut right.expr is ast.None {
+				c.error('cannot use `none` in `unsafe` blocks', right.expr.pos)
+			}
 		}
 	}
 	if node.left.len != right_len {

vlib/v/checker/return.v

@@ -42,6 +42,12 @@ pub fn (mut c Checker) return_stmt(mut node ast.Return) {
 		if typ == 0 {
 			return
 		}
+		// Handle `return unsafe { none }`
+		if expr is ast.UnsafeExpr {
+			if expr.expr is ast.None {
+				c.error('cannot return `none` in unsafe block', expr.expr.pos)
+			}
+		}
 		if typ == ast.void_type {
 			c.error('`${expr}` used as value', node.pos)
 			return

vlib/v/checker/tests/assing_none.out

@@ -1,4 +1,4 @@
-vlib/v/checker/tests/assing_none.vv:2:9: error: you can not assign a `none` value to a variable
+vlib/v/checker/tests/assing_none.vv:2:9: error: cannot assign a `none` value to a variable
     1 | fn main() {
     2 |     val := none
       |            ~~~~

vlib/v/checker/tests/unsafe_assign_none_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/unsafe_assign_none_err.vv:2:20: error: cannot use `none` in `unsafe` blocks
+    1 | fn f() {
+    2 |     mut s := unsafe { none }
+      |                       ~~~~
+    3 |     println(s)
+    4 | }

vlib/v/checker/tests/unsafe_assign_none_err.vv

@@ -0,0 +1,6 @@
+fn f() {
+	mut s := unsafe { none }
+	println(s)
+}
+
+f()

vlib/v/checker/tests/unsafe_none_return_err.out

@@ -0,0 +1,5 @@
+vlib/v/checker/tests/unsafe_none_return_err.vv:2:18: error: cannot return `none` in unsafe block
+    1 | fn f() ?int {
+    2 |     return unsafe { none }
+      |                     ~~~~
+    3 | }

vlib/v/checker/tests/unsafe_none_return_err.vv

@@ -0,0 +1,3 @@
+fn f() ?int {
+	return unsafe { none }
+}