Add ui test to ensure attributes generated from macros are kept as expected

src/test/ui/attr-from-macro.rs

@@ -0,0 +1,20 @@
+// aux-build:attr-from-macro.rs
+// run-pass
+
+extern crate attr_from_macro;
+
+attr_from_macro::creator! {
+    struct Foo;
+    enum Bar;
+    enum FooBar;
+}
+
+fn main() {
+    // Checking the `repr(u32)` on the enum.
+    assert_eq!(4, std::mem::size_of::<Bar>());
+    // Checking the `repr(u16)` on the enum.
+    assert_eq!(2, std::mem::size_of::<FooBar>());
+
+    // Checking the Debug impl on the types.
+    eprintln!("{:?} {:?} {:?}", Foo, Bar::A, FooBar::A);
+}

src/test/ui/auxiliary/attr-from-macro.rs

@@ -0,0 +1,15 @@
+#[macro_export]
+macro_rules! creator {
+    (struct $name1:ident; enum $name2:ident; enum $name3:ident;) => {
+        #[derive(Debug)]
+        pub struct $name1;
+
+        #[derive(Debug)]
+        #[repr(u32)]
+        pub enum $name2 { A }
+
+        #[derive(Debug)]
+        #[repr(u16)]
+        pub enum $name3 { A }
+    }
+}