[lang2/macro] add test for multiple #[ink(storage)] structs

lang2/macro/tests/compile_tests.rs

@@ -38,4 +38,5 @@ fn compile_tests() {
     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");
+    t.compile_fail("tests/ui/fail/15-multiple-storage-structs.rs");
 }

lang2/macro/tests/ui/fail/15-multiple-storage-structs.rs

+#![feature(proc_macro_hygiene)]
+
+use ink_lang2 as ink;
+
+#[ink::contract(version = "0.1.0")]
+mod noop {
+    #[ink(storage)]
+    struct FirstStorage {}
+
+    // ink! currently doesn't allow for multiple #[ink(storage)] structs
+    #[ink(storage)]
+    struct SecondStorage {}
+
+    impl FirstStorage {
+        #[ink(constructor)]
+        fn new(&mut self) {}
+
+        #[ink(message)]
+        fn do_something(&self) {}
+    }
+
+    impl SecondStorage {
+        #[ink(constructor)]
+        fn new(&mut self) {}
+
+        #[ink(message)]
+        fn do_something(&self) {}
+    }
+}
+
+fn main() {}

lang2/macro/tests/ui/fail/15-multiple-storage-structs.stderr

+error: 2 conflicting storage struct found
+ --> $DIR/15-multiple-storage-structs.rs:8:12
+  |
+8 |     struct FirstStorage {}
+  |            ^^^^^^^^^^^^
+
+error: 2 conflicting storage struct found
+  --> $DIR/15-multiple-storage-structs.rs:12:12
+   |
+12 |     struct SecondStorage {}
+   |            ^^^^^^^^^^^^^