Implement macro-based deref!() syntax for deref patterns

Stop using `box PAT` syntax for deref patterns, as it's misleading and
also causes their semantics being tangled up.

1 files changed, 2 insertions, 8 deletions

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 277e82b4e53..81065fa3dce 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -413,10 +413,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
             PatKind::Box(..) => {
-                if !self.features.deref_patterns {
-                    // Allow box patterns under `deref_patterns`.
-                    gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");
-                }
+                gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");
             }
             PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {
                 gate!(
@@ -610,10 +607,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         };
     }
 
-    if !visitor.features.deref_patterns {
-        // Allow box patterns under `deref_patterns`.
-        gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
-    }
+    gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
     gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");
     // 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