add feature gates for eii(-internals)

Author: jdonszelmann

tests/ui/feature-gates/feature-gate-eii-internals.rs

@@ -0,0 +1,13 @@
+#![crate_type = "rlib"]
+#![feature(decl_macro)]
+#![feature(rustc_attrs)]
+
+#[eii_macro_for(bar)] //~ ERROR use of unstable library feature `eii_internals`
+#[rustc_builtin_macro(eii_macro)]
+macro foo() {
+
+}
+
+unsafe extern "Rust" {
+    safe fn bar(x: u64) -> u64;
+}

tests/ui/feature-gates/feature-gate-eii-internals.stderr

@@ -0,0 +1,12 @@
+error[E0658]: use of unstable library feature `eii_internals`
+  --> $DIR/feature-gate-eii-internals.rs:5:3
+   |
+LL | #[eii_macro_for(bar)]
+   |   ^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(eii_internals)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.

tests/ui/feature-gates/feature-gate-eii.rs

@@ -0,0 +1,9 @@
+#![crate_type = "rlib"]
+
+#[eii] //~ ERROR use of unstable library feature `eii`
+fn hello(x: u64);
+
+#[hello]
+fn hello_impl(x: u64) {
+    println!("{x:?}")
+}

tests/ui/feature-gates/feature-gate-eii.stderr

@@ -0,0 +1,13 @@
+error[E0658]: use of unstable library feature `eii`
+  --> $DIR/feature-gate-eii.rs:3:3
+   |
+LL | #[eii]
+   |   ^^^
+   |
+   = note: see issue #125418 <https://github.com/rust-lang/rust/issues/125418> for more information
+   = help: add `#![feature(eii)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.