checker: check for receiver name clashing with global var (fix #22698) (#22708)

vlib/v/checker/fn.v

@@ -192,6 +192,10 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 		}
 	}
 	if node.is_method {
+		if node.receiver.name in c.global_names {
+			c.error('cannot use global variable name `${node.receiver.name}` as receiver',
+				node.receiver_pos)
+		}
 		if node.receiver.typ.has_flag(.option) {
 			c.error('option types cannot have methods', node.receiver_pos)
 		}

vlib/v/checker/tests/globals/global_receiver_var_name_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/globals/global_receiver_var_name_err.vv:17:9: error: cannot use global variable name `game` as receiver
+   15 | }
+   16 | 
+   17 | fn (mut game Game) init() {
+      |         ~~~~~~~~~
+   18 |     game.world = GameObject{}
+   19 | }

vlib/v/checker/tests/globals/global_receiver_var_name_err.vv

@@ -0,0 +1,21 @@
+module main
+
+struct Game {
+mut:
+	world     GameObject
+	object_id u32
+}
+
+__global (
+	game Game
+)
+
+struct GameObject {
+	id int = game.object_id++
+}
+
+fn (mut game Game) init() {
+	game.world = GameObject{}
+}
+
+fn main() {}