Add tests for more than one level of reference

Author: HMPerson1

tests/ui/mem_discriminant.rs

@@ -40,10 +40,16 @@ fn main() {
 
     mem_discriminant_but_in_a_macro!(&rro);
 
+    let rrrrro = &&&rro;
+    mem::discriminant(&rrrrro);
+    mem::discriminant(*rrrrro);
+
     // ok
     mem::discriminant(&Some(2));
     mem::discriminant(&None::<u8>);
     mem::discriminant(&Foo::One(5));
     mem::discriminant(&Foo::Two(5));
     mem::discriminant(ro);
+    mem::discriminant(*rro);
+    mem::discriminant(****rrrrro);
 }

tests/ui/mem_discriminant.stderr

@@ -84,5 +84,21 @@ error: calling `mem::discriminant` on non-enum type `&&std::option::Option<i32>`
    |     |                                help: try dereferencing: `*rro`
    |     in this macro invocation
 
-error: aborting due to 10 previous errors
+error: calling `mem::discriminant` on non-enum type `&&&&&std::option::Option<i32>`
+  --> $DIR/mem_discriminant.rs:44:5
+   |
+44 |     mem::discriminant(&rrrrro);
+   |     ^^^^^^^^^^^^^^^^^^-------^
+   |                       |
+   |                       help: try dereferencing: `****rrrrro`
+
+error: calling `mem::discriminant` on non-enum type `&&&std::option::Option<i32>`
+  --> $DIR/mem_discriminant.rs:45:5
+   |
+45 |     mem::discriminant(*rrrrro);
+   |     ^^^^^^^^^^^^^^^^^^-------^
+   |                       |
+   |                       help: try dereferencing: `****rrrrro`
+
+error: aborting due to 12 previous errors