From 073feb5e69c762bffc53e615d2fde844e0d08a92 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 24 Sep 2023 10:44:31 +0200
Subject: [PATCH 1/2] Rename the legacy feature gating macro

It had a really confusing name by shadowing the previous name, which has
caused issues in the past where people added their new syntax in the
legacy location.

This makes it clear.
---
 compiler/rustc_ast_passes/src/feature_gate.rs | 21 +++++++++++--------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 8405ae6ff8e8b..3b80751698bcf 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -578,11 +578,11 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         }
     }
 
-    // All uses of `gate_all!` below this point were added in #65742,
+    // All uses of `gate_all_legacy_dont_use!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).
     // We emit an early future-incompatible warning for these.
     // New syntax gates should go above here to get a hard error gate.
-    macro_rules! gate_all {
+    macro_rules! gate_all_legacy_dont_use {
         ($gate:ident, $msg:literal) => {
             for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
                 gate_feature_post!(future_incompatible; &visitor, $gate, *span, $msg);
@@ -590,13 +590,16 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         };
     }
 
-    gate_all!(trait_alias, "trait aliases are experimental");
-    gate_all!(associated_type_bounds, "associated type bounds are unstable");
-    gate_all!(return_type_notation, "return type notation is experimental");
-    gate_all!(decl_macro, "`macro` is experimental");
-    gate_all!(box_patterns, "box pattern syntax is experimental");
-    gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
-    gate_all!(try_blocks, "`try` blocks are unstable");
+    gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");
+    gate_all_legacy_dont_use!(associated_type_bounds, "associated type bounds are unstable");
+    gate_all_legacy_dont_use!(return_type_notation, "return type notation is experimental");
+    gate_all_legacy_dont_use!(decl_macro, "`macro` is experimental");
+    gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
+    gate_all_legacy_dont_use!(
+        exclusive_range_pattern,
+        "exclusive range pattern syntax is experimental"
+    );
+    gate_all_legacy_dont_use!(try_blocks, "`try` blocks are unstable");
 
     visit::walk_crate(&mut visitor, krate);
 }

From 845a027ddb3750bb841d0676b7eb460b7c1a2f9d Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 24 Sep 2023 10:47:31 +0200
Subject: [PATCH 2/2] Add comment about RTN feature gating

---
 compiler/rustc_ast_passes/src/feature_gate.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 3b80751698bcf..62dc7ae58a2f0 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -592,6 +592,9 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
 
     gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");
     gate_all_legacy_dont_use!(associated_type_bounds, "associated type bounds are unstable");
+    // Despite being a new feature, `where T: Trait<Assoc(): Sized>`, which is RTN syntax now,
+    // used to be gated under associated_type_bounds, which are right above, so RTN needs to
+    // be too.
     gate_all_legacy_dont_use!(return_type_notation, "return type notation is experimental");
     gate_all_legacy_dont_use!(decl_macro, "`macro` is experimental");
     gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");