checker: disallow none as match cond (#20688)

Author: Delta456

vlib/v/checker/match.v

@@ -59,6 +59,9 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 			c.error('`match` expression with Option type only checks against `none`, to match its value you must unwrap it first `var?`',
 				branch.pos)
 		}
+		if cond_type_sym.kind == .none_ {
+			c.error('`none` cannot be a match condition', node.pos)
+		}
 		// If the last statement is an expression, return its type
 		if branch.stmts.len > 0 {
 			mut stmt := branch.stmts.last()

vlib/v/checker/tests/none_match_cond_err.out

@@ -0,0 +1,5 @@
+vlib/v/checker/tests/none_match_cond_err.vv:1:1: error: `none` cannot be a match condition
+    1 | match none {
+      | ~~~~~~~~~~~~
+    2 |     none {}
+    3 |     else {}

vlib/v/checker/tests/none_match_cond_err.vv

@@ -0,0 +1,4 @@
+match none {
+	none {}
+	else {}
+}