[lang2/macro] add UI test for missing #[ink(storage)] struct

lang2/macro/tests/compile_tests.rs

@@ -37,4 +37,5 @@ fn compile_tests() {
     t.compile_fail("tests/ui/fail/11-unsafe-constructor.rs");
     t.compile_fail("tests/ui/fail/12-const-constructor.rs");
     t.compile_fail("tests/ui/fail/13-abi-constructor.rs");
+    t.compile_fail("tests/ui/fail/14-missing-storage-struct.rs");
 }

lang2/macro/tests/ui/fail/14-missing-storage-struct.rs

+#![feature(proc_macro_hygiene)]
+
+use ink_lang2 as ink;
+
+#[ink::contract(version = "0.1.0")]
+mod noop {
+    // We are missing the #[ink(storage)] attribute here
+    struct Noop {}
+
+    impl Noop {
+        #[ink(constructor)]
+        fn new(&mut self) {}
+
+        #[ink(message)]
+        fn noop(&self) {}
+    }
+}
+
+fn main() {}

lang2/macro/tests/ui/fail/14-missing-storage-struct.stderr

+error: no #[ink(storage)] struct found but expected exactly 1
+ --> $DIR/14-missing-storage-struct.rs:5:1
+  |
+5 | #[ink::contract(version = "0.1.0")]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^