Port another resource test to use classes

src/test/compile-fail/block-must-not-have-result-res.rs

@@ -1,7 +1,8 @@
 // error-pattern:mismatched types: expected `()` but found `bool`
 
-resource r(i: int) {
-    true
+class r {
+  new() {}
+  drop { true }
 }
 
 fn main() {