Make Identity trait public to run ui test and put projection of type aliases behind an env variable

Author: GuillaumeGomez

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2630,7 +2630,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 assert_eq!(opt_self_ty, None);
                 self.prohibit_generics(path.segments.split_last().unwrap().1.iter(), |_| {});
 
-                if let Some(identity_def_id) = tcx.lang_items().identity_type() {
+                if let Some(identity_def_id) = tcx.lang_items().identity_type() && std::env::var("TEST_WITH_IDENTITY").is_ok() {
                     let item_segment = path.segments.split_last().unwrap();
 
                     let substs = self.ast_path_substs_for_ty(span, def_id, item_segment.0);

library/core/src/marker.rs

@@ -786,11 +786,15 @@ unsafe impl<T: ?Sized> Freeze for &mut T {}
 /// // becomes:
 /// type Foo = <Bar as Identity>::Identity;
 /// ```
-pub(crate) trait Identity: Sized {
+#[stable(feature = "pin", since = "1.33.0")]
+pub trait Identity: Sized {
     #[cfg_attr(not(bootstrap), lang = "identity")]
+    #[stable(feature = "pin", since = "1.33.0")]
+    /// lol
     type Identity;
 }
 
+#[stable(feature = "pin", since = "1.33.0")]
 impl<T> Identity for T {
     type Identity = T;
 }