add test for rejecting EIIs in statement position

tests/ui/eii/error_statement_position.rs

@@ -1,11 +1,6 @@
 #![feature(extern_item_impls)]
-// EIIs can, despite not being super useful, be declared in statement position
-// nested inside items. Items in statement position, when expanded as part of a macro,
-// need to be wrapped slightly differently (in an `ast::Statement`).
-// We did this on the happy path (no errors), but when there was an error, we'd
-// replace it with *just* an `ast::Item` not wrapped in an `ast::Statement`.
-// This caused an ICE (https://github.com/rust-lang/rust/issues/149980).
-// this test fails to build, but demonstrates that no ICE is produced.
+// EIIs cannot be used in statement position.
+// This is also a regression test for an ICE (https://github.com/rust-lang/rust/issues/149980).
 
 fn main() {
     struct Bar;
@@ -13,4 +8,10 @@ fn main() {
     #[eii]
     //~^ ERROR `#[eii]` is only valid on functions
     impl Bar {}
+
+
+    // Even on functions, eiis in statement position are rejected
+    #[eii]
+    //~^ ERROR `#[eii]` can only be used on functions inside a module
+    fn foo() {}
 }

tests/ui/eii/error_statement_position.stderr

@@ -1,8 +1,17 @@
 error: `#[eii]` is only valid on functions
-  --> $DIR/error_statement_position.rs:13:5
+  --> $DIR/error_statement_position.rs:8:5
    |
 LL |     #[eii]
    |     ^^^^^^
 
-error: aborting due to 1 previous error
+error: `#[eii]` can only be used on functions inside a module
+  --> $DIR/error_statement_position.rs:14:5
+   |
+LL |     #[eii]
+   |     ^^^^^^
+LL |
+LL |     fn foo() {}
+   |        --- `#[eii]` is used on this item, which is part of another item's local scope
+
+error: aborting due to 2 previous errors