Auto merge of #58098 - oli-obk:maybe_allow_internal_unstable, r=petrochenkov

Require a list of features in `#[allow_internal_unstable]`

The blanket-permission slip is not great and will likely give us trouble some point down the road.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 2c8a996cdb0..fff54814a38 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -136,11 +136,16 @@ fn call_intrinsic(cx: &ExtCtxt<'_>,
                   intrinsic: &str,
                   args: Vec<P<ast::Expr>>)
                   -> P<ast::Expr> {
-    if cx.current_expansion.mark.expn_info().unwrap().allow_internal_unstable {
+    let intrinsic_allowed_via_allow_internal_unstable = cx
+        .current_expansion.mark.expn_info().unwrap()
+        .allow_internal_unstable.map_or(false, |features| features.iter().any(|&s|
+            s == "core_intrinsics"
+        ));
+    if intrinsic_allowed_via_allow_internal_unstable {
         span = span.with_ctxt(cx.backtrace());
     } else { // Avoid instability errors with user defined curstom derives, cc #36316
         let mut info = cx.current_expansion.mark.expn_info().unwrap();
-        info.allow_internal_unstable = true;
+        info.allow_internal_unstable = Some(vec![Symbol::intern("core_intrinsics")].into());
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(info);
         span = span.with_ctxt(SyntaxContext::empty().apply_mark(mark));