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

compiler-errors · compiler-errors · commit 2d633317f30d · 2024-03-21T11:42:49.000-04:00
Stop using `box PAT` syntax for deref patterns, as it's misleading and
also causes their semantics being tangled up.
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
@@ -621,7 +621,9 @@ impl Pat {
             | PatKind::Or(s) => s.iter().for_each(|p| p.walk(it)),
 
             // Trivial wrappers over inner patterns.
-            PatKind::Box(s) | PatKind::Ref(s, _) | PatKind::Paren(s) => s.walk(it),
+            PatKind::Box(s) | PatKind::Deref(s) | PatKind::Ref(s, _) | PatKind::Paren(s) => {
+                s.walk(it)
+            }
 
             // These patterns do not contain subpatterns, skip.
             PatKind::Wild
@@ -792,6 +794,9 @@ pub enum PatKind {
     /// A `box` pattern.
     Box(P<Pat>),
 
+    /// A `deref` pattern (currently `deref!()` macro-based syntax).
+    Deref(P<Pat>),
+
     /// A reference pattern (e.g., `&mut (a, b)`).
     Ref(P<Pat>, Mutability),
 
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
@@ -1295,6 +1295,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
             fields.flat_map_in_place(|field| vis.flat_map_pat_field(field));
         }
         PatKind::Box(inner) => vis.visit_pat(inner),
+        PatKind::Deref(inner) => vis.visit_pat(inner),
         PatKind::Ref(inner, _mutbl) => vis.visit_pat(inner),
         PatKind::Range(e1, e2, Spanned { span: _, node: _ }) => {
             visit_opt(e1, |e| vis.visit_expr(e));
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
@@ -576,7 +576,10 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Res
             try_visit!(visitor.visit_path(path, pattern.id));
             walk_list!(visitor, visit_pat_field, fields);
         }
-        PatKind::Box(subpattern) | PatKind::Ref(subpattern, _) | PatKind::Paren(subpattern) => {
+        PatKind::Box(subpattern)
+        | PatKind::Deref(subpattern)
+        | PatKind::Ref(subpattern, _)
+        | PatKind::Paren(subpattern) => {
             try_visit!(visitor.visit_pat(subpattern));
         }
         PatKind::Ident(_, ident, optional_subpattern) => {
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
@@ -91,6 +91,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     PatKind::Box(inner) => {
                         break hir::PatKind::Box(self.lower_pat(inner));
                     }
+                    PatKind::Deref(inner) => {
+                        break hir::PatKind::Deref(self.lower_pat(inner));
+                    }
                     PatKind::Ref(inner, mutbl) => {
                         break hir::PatKind::Ref(self.lower_pat(inner), *mutbl);
                     }
diff --git 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
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1626,6 +1626,12 @@ impl<'a> State<'a> {
                 self.word("box ");
                 self.print_pat(inner);
             }
+            PatKind::Deref(inner) => {
+                self.word("deref!");
+                self.popen();
+                self.print_pat(inner);
+                self.pclose();
+            }
             PatKind::Ref(inner, mutbl) => {
                 self.word("&");
                 if mutbl.is_mut() {
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
@@ -1015,7 +1015,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
-            Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
             Slice(before, slice, after) => {
@@ -1042,7 +1042,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
-            Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
             Slice(before, slice, after) => {
@@ -1185,6 +1185,9 @@ pub enum PatKind<'hir> {
     /// A `box` pattern.
     Box(&'hir Pat<'hir>),
 
+    /// A `deref` pattern (currently `deref!()` macro-based syntax).
+    Deref(&'hir Pat<'hir>),
+
     /// A reference pattern (e.g., `&mut (a, b)`).
     Ref(&'hir Pat<'hir>, Mutability),
 
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
@@ -660,7 +660,9 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
         PatKind::Tuple(tuple_elements, _) => {
             walk_list!(visitor, visit_pat, tuple_elements);
         }
-        PatKind::Box(ref subpattern) | PatKind::Ref(ref subpattern, _) => {
+        PatKind::Box(ref subpattern)
+        | PatKind::Deref(ref subpattern)
+        | PatKind::Ref(ref subpattern, _) => {
             try_visit!(visitor.visit_pat(subpattern));
         }
         PatKind::Binding(_, _hir_id, ident, ref optional_subpattern) => {
diff --git a/compiler/rustc_hir_analysis/src/check/region.rs b/compiler/rustc_hir_analysis/src/check/region.rs
@@ -668,7 +668,7 @@ fn resolve_local<'tcx>(
             | PatKind::TupleStruct(_, subpats, _)
             | PatKind::Tuple(subpats, _) => subpats.iter().any(|p| is_binding_pat(p)),
 
-            PatKind::Box(subpat) => is_binding_pat(subpat),
+            PatKind::Box(subpat) | PatKind::Deref(subpat) => is_binding_pat(subpat),
 
             PatKind::Ref(_, _)
             | PatKind::Binding(hir::BindingAnnotation(hir::ByRef::No, _), ..)
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
@@ -1808,6 +1808,12 @@ impl<'a> State<'a> {
                     self.pclose();
                 }
             }
+            PatKind::Deref(inner) => {
+                self.word("deref!");
+                self.popen();
+                self.print_pat(inner);
+                self.pclose();
+            }
             PatKind::Ref(inner, mutbl) => {
                 let is_range_inner = matches!(inner.kind, PatKind::Range(..));
                 self.word("&");
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -463,6 +463,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                     }
                     PatKind::Or(_)
                     | PatKind::Box(_)
+                    | PatKind::Deref(_)
                     | PatKind::Ref(..)
                     | PatKind::Wild
                     | PatKind::Err(_) => {
diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -719,7 +719,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 self.cat_pattern_(place_with_id, subpat, op)?;
             }
 
-            PatKind::Box(subpat) | PatKind::Ref(subpat, _) => {
+            PatKind::Box(subpat) | PatKind::Ref(subpat, _) | PatKind::Deref(subpat) => {
                 // box p1, &p1, &mut p1. we can ignore the mutability of
                 // PatKind::Ref since that information is already contained
                 // in the type.
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
@@ -210,10 +210,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatKind::Tuple(elements, ddpos) => {
                 self.check_pat_tuple(pat.span, elements, ddpos, expected, pat_info)
             }
-            PatKind::Box(inner) if self.tcx.features().deref_patterns => {
-                self.check_pat_deref(pat.span, inner, expected, pat_info)
-            }
             PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, pat_info),
+            PatKind::Deref(inner) => self.check_pat_deref(pat.span, inner, expected, pat_info),
             PatKind::Ref(inner, mutbl) => self.check_pat_ref(pat, inner, mutbl, expected, pat_info),
             PatKind::Slice(before, slice, after) => {
                 self.check_pat_slice(pat.span, before, slice, after, expected, pat_info)
@@ -297,6 +295,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | PatKind::TupleStruct(..)
             | PatKind::Tuple(..)
             | PatKind::Box(_)
+            | PatKind::Deref(_)
             | PatKind::Range(..)
             | PatKind::Slice(..) => AdjustMode::Peel,
             // A never pattern behaves somewhat like a literal or unit variant.
@@ -762,6 +761,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         | PatKind::Binding(..)
                         | PatKind::Path(..)
                         | PatKind::Box(..)
+                        | PatKind::Deref(_)
                         | PatKind::Ref(..)
                         | PatKind::Lit(..)
                         | PatKind::Range(..)
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
@@ -1183,7 +1183,7 @@ impl EarlyLintPass for UnusedParens {
                 self.check_unused_parens_pat(cx, &f.pat, false, false, keep_space);
             },
             // Avoid linting on `i @ (p0 | .. | pn)` and `box (p0 | .. | pn)`, #64106.
-            Ident(.., Some(p)) | Box(p) => self.check_unused_parens_pat(cx, p, true, false, keep_space),
+            Ident(.., Some(p)) | Box(p) | Deref(p) => self.check_unused_parens_pat(cx, p, true, false, keep_space),
             // Avoid linting on `&(mut x)` as `&mut x` has a different meaning, #55342.
             // Also avoid linting on `& mut? (p0 | .. | pn)`, #64106.
             Ref(p, m) => self.check_unused_parens_pat(cx, p, true, *m == Mutability::Not, keep_space),
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
@@ -1179,7 +1179,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
                 write!(f, "{subpattern}")
             }
             PatKind::DerefPattern { ref subpattern } => {
-                write!(f, "k#deref {subpattern}")
+                write!(f, "deref!({subpattern})")
             }
             PatKind::Constant { value } => write!(f, "{value}"),
             PatKind::InlineConstant { def: _, ref subpattern } => {
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -257,7 +257,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                 return self.lower_path(qpath, pat.hir_id, pat.span);
             }
 
-            hir::PatKind::Box(subpattern) if self.tcx.features().deref_patterns => {
+            hir::PatKind::Deref(subpattern) => {
                 PatKind::DerefPattern { subpattern: self.lower_pattern(subpattern) }
             }
             hir::PatKind::Ref(subpattern, _) | hir::PatKind::Box(subpattern) => {
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
@@ -498,11 +498,14 @@ impl<'a> Parser<'a> {
             } else {
                 PatKind::Lit(const_expr)
             }
+        } else if self.is_builtin() {
+            self.parse_pat_builtin()?
+        }
         // Don't eagerly error on semantically invalid tokens when matching
         // declarative macros, as the input to those doesn't have to be
         // semantically valid. For attribute/derive proc macros this is not the
         // case, so doing the recovery for them is fine.
-        } else if self.can_be_ident_pat()
+        else if self.can_be_ident_pat()
             || (self.is_lit_bad_ident().is_some() && self.may_recover())
         {
             // Parse `ident @ pat`
@@ -1119,6 +1122,21 @@ impl<'a> Parser<'a> {
         .contains(&self.token.kind)
     }
 
+    fn parse_pat_builtin(&mut self) -> PResult<'a, PatKind> {
+        self.parse_builtin(|self_, _lo, ident| {
+            Ok(match ident.name {
+                // builtin#deref(PAT)
+                sym::deref => Some(ast::PatKind::Deref(self_.parse_pat_allow_top_alt(
+                    None,
+                    RecoverComma::Yes,
+                    RecoverColon::Yes,
+                    CommaRecoveryMode::LikelyTuple,
+                )?)),
+                _ => None,
+            })
+        })
+    }
+
     /// Parses `box pat`
     fn parse_pat_box(&mut self) -> PResult<'a, PatKind> {
         let box_span = self.prev_token.span;
diff --git a/compiler/rustc_passes/src/hir_stats.rs b/compiler/rustc_passes/src/hir_stats.rs
@@ -300,6 +300,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
                 Path,
                 Tuple,
                 Box,
+                Deref,
                 Ref,
                 Lit,
                 Range,
@@ -566,6 +567,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
                 Path,
                 Tuple,
                 Box,
+                Deref,
                 Ref,
                 Lit,
                 Range,
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
@@ -1714,6 +1714,18 @@ pub(crate) mod builtin {
         builtin # type_ascribe($expr, $ty)
     }
 
+    #[cfg(not(bootstrap))]
+    /// Unstable placeholder for deref patterns.
+    #[allow_internal_unstable(builtin_syntax)]
+    #[unstable(
+        feature = "deref_patterns",
+        issue = "87121",
+        reason = "placeholder syntax for deref patterns"
+    )]
+    pub macro deref($pat:pat) {
+        builtin # deref($pat)
+    }
+
     /// Unstable implementation detail of the `rustc` compiler, do not use.
     #[rustc_builtin_macro]
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/core/src/prelude/v1.rs b/library/core/src/prelude/v1.rs
@@ -103,3 +103,11 @@ pub use crate::macros::builtin::cfg_eval;
     reason = "placeholder syntax for type ascription"
 )]
 pub use crate::macros::builtin::type_ascribe;
+
+#[cfg(not(bootstrap))]
+#[unstable(
+    feature = "deref_patterns",
+    issue = "87121",
+    reason = "placeholder syntax for deref patterns"
+)]
+pub use crate::macros::builtin::deref;
diff --git a/library/std/src/prelude/v1.rs b/library/std/src/prelude/v1.rs
@@ -91,6 +91,15 @@ pub use core::prelude::v1::cfg_eval;
 )]
 pub use core::prelude::v1::type_ascribe;
 
+#[cfg(not(bootstrap))]
+// Do not `doc(no_inline)` either.
+#[unstable(
+    feature = "deref_patterns",
+    issue = "87121",
+    reason = "placeholder syntax for deref patterns"
+)]
+pub use core::prelude::v1::deref;
+
 // The file so far is equivalent to core/src/prelude/v1.rs. It is duplicated
 // rather than glob imported because we want docs to show these re-exports as
 // pointing to within `std`.
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
@@ -329,6 +329,7 @@ pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
             elts.iter().map(|p| name_from_pat(p).to_string()).collect::<Vec<String>>().join(", ")
         ),
         PatKind::Box(p) => return name_from_pat(&*p),
+        PatKind::Deref(p) => format!("deref!({})", name_from_pat(&*p)),
         PatKind::Ref(p, _) => return name_from_pat(&*p),
         PatKind::Lit(..) => {
             warn!(
diff --git a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
@@ -55,7 +55,7 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
         | PatKind::Err(_) => false,
         PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),
         PatKind::Tuple(a, etc) | PatKind::TupleStruct(_, a, etc) => etc.as_opt_usize().is_none() && array_rec(a),
-        PatKind::Ref(x, _) | PatKind::Box(x) => unary_pattern(x),
+        PatKind::Ref(x, _) | PatKind::Box(x) | PatKind::Deref(x) => unary_pattern(x),
         PatKind::Path(_) | PatKind::Lit(_) => true,
     }
 }
diff --git a/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs b/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs
@@ -243,7 +243,7 @@ impl<'a> NormalizedPat<'a> {
     fn from_pat(cx: &LateContext<'_>, arena: &'a DroplessArena, pat: &'a Pat<'_>) -> Self {
         match pat.kind {
             PatKind::Wild | PatKind::Binding(.., None) => Self::Wild,
-            PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Ref(pat, _) => {
+            PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Deref(pat) | PatKind::Ref(pat, _) => {
                 Self::from_pat(cx, arena, pat)
             },
             PatKind::Never => Self::Never,
diff --git a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
@@ -242,6 +242,8 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec<P<Pat>>, focus_idx: us
             |k| matches!(k, Box(_)),
             |k| always_pat!(k, Box(p) => p),
         ),
+        // FIXME(deref_patterns): Should we merge patterns here?
+        Deref(_) => false,
         // Transform `&mut x | ... | &mut y` into `&mut (x | y)`.
         Ref(target, Mutability::Mut) => extend_with_matching(
             target, start, alternatives,
diff --git a/src/tools/clippy/clippy_lints/src/utils/author.rs b/src/tools/clippy/clippy_lints/src/utils/author.rs
@@ -689,6 +689,11 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 kind!("Box({pat})");
                 self.pat(pat);
             },
+            PatKind::Deref(pat) => {
+                bind!(self, pat);
+                kind!("Deref({pat})");
+                self.pat(pat);
+            },
             PatKind::Ref(pat, muta) => {
                 bind!(self, pat);
                 kind!("Ref({pat}, Mutability::{muta:?})");
diff --git a/src/tools/clippy/clippy_utils/src/hir_utils.rs b/src/tools/clippy/clippy_utils/src/hir_utils.rs
@@ -955,6 +955,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 }
             },
             PatKind::Box(pat) => self.hash_pat(pat),
+            PatKind::Deref(pat) => self.hash_pat(pat),
             PatKind::Lit(expr) => self.hash_expr(expr),
             PatKind::Or(pats) => {
                 for pat in pats {
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -1678,7 +1678,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
     match pat.kind {
         PatKind::Wild | PatKind::Never => false, // If `!` typechecked then the type is empty, so not refutable.
         PatKind::Binding(_, _, _, pat) => pat.map_or(false, |pat| is_refutable(cx, pat)),
-        PatKind::Box(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat),
+        PatKind::Box(pat) | PatKind::Deref(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat),
         PatKind::Path(ref qpath) => is_enum_variant(cx, qpath, pat.hir_id),
         PatKind::Or(pats) => {
             // TODO: should be the honest check, that pats is exhaustive set
diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs
diff --git a/tests/ui/pattern/deref-patterns/typeck.rs b/tests/ui/pattern/deref-patterns/typeck.rs
diff --git a/tests/ui/unboxed-closures/unboxed-closures-type-mismatch-closure-from-another-scope.stderr b/tests/ui/unboxed-closures/unboxed-closures-type-mismatch-closure-from-another-scope.stderr

Original file line number	Diff line number	Diff line change
`@@ -1295,6 +1295,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {`
`1295`	`1295`	`fields.flat_map_in_place(\|field\| vis.flat_map_pat_field(field));`
`1296`	`1296`	`}`
`1297`	`1297`	`PatKind::Box(inner) => vis.visit_pat(inner),`
	`1298`	`+ PatKind::Deref(inner) => vis.visit_pat(inner),`
`1298`	`1299`	`PatKind::Ref(inner, _mutbl) => vis.visit_pat(inner),`
`1299`	`1300`	`PatKind::Range(e1, e2, Spanned { span: _, node: _ }) => {`
`1300`	`1301`	`visit_opt(e1, \|e\| vis.visit_expr(e));`
Original file line number	Diff line number	Diff line change
`@@ -576,7 +576,10 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Res`
`576`	`576`	`try_visit!(visitor.visit_path(path, pattern.id));`
`577`	`577`	`walk_list!(visitor, visit_pat_field, fields);`
`578`	`578`	`}`
`579`		`- PatKind::Box(subpattern) \| PatKind::Ref(subpattern, _) \| PatKind::Paren(subpattern) => {`
	`579`	`+ PatKind::Box(subpattern)`
	`580`	`+ \| PatKind::Deref(subpattern)`
	`581`	`+ \| PatKind::Ref(subpattern, _)`
	`582`	`+ \| PatKind::Paren(subpattern) => {`
`580`	`583`	`try_visit!(visitor.visit_pat(subpattern));`
`581`	`584`	`}`
`582`	`585`	`PatKind::Ident(_, ident, optional_subpattern) => {`
Original file line number	Diff line number	Diff line change
`@@ -91,6 +91,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {`
`91`	`91`	`PatKind::Box(inner) => {`
`92`	`92`	`break hir::PatKind::Box(self.lower_pat(inner));`
`93`	`93`	`}`
	`94`	`+ PatKind::Deref(inner) => {`
	`95`	`+ break hir::PatKind::Deref(self.lower_pat(inner));`
	`96`	`+ }`
`94`	`97`	`PatKind::Ref(inner, mutbl) => {`
`95`	`98`	`break hir::PatKind::Ref(self.lower_pat(inner), *mutbl);`
`96`	`99`	`}`
Original file line number	Diff line number	Diff line change
`@@ -413,10 +413,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {`
`413`	`413`	`}`
`414`	`414`	`}`
`415`	`415`	`PatKind::Box(..) => {`
`416`		`- if !self.features.deref_patterns {`
`417`		- // Allow box patterns under `deref_patterns`.
`418`		`- gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");`
`419`		`- }`
	`416`	`+ gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");`
`420`	`417`	`}`
`421`	`418`	`PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {`
`422`	`419`	`gate!(`
`@@ -610,10 +607,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {`
`610`	`607`	`};`
`611`	`608`	`}`
`612`	`609`
`613`		`- if !visitor.features.deref_patterns {`
`614`		- // Allow box patterns under `deref_patterns`.
`615`		`- gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");`
`616`		`- }`
	`610`	`+ gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");`
`617`	`611`	`gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");`
`618`	`612`	// Despite being a new feature, `where T: Trait<Assoc(): Sized>`, which is RTN syntax now,
`619`	`613`	`// used to be gated under associated_type_bounds, which are right above, so RTN needs to`
Original file line number	Diff line number	Diff line change
`@@ -660,7 +660,9 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:`
`660`	`660`	`PatKind::Tuple(tuple_elements, _) => {`
`661`	`661`	`walk_list!(visitor, visit_pat, tuple_elements);`
`662`	`662`	`}`
`663`		`- PatKind::Box(ref subpattern) \| PatKind::Ref(ref subpattern, _) => {`
	`663`	`+ PatKind::Box(ref subpattern)`
	`664`	`+ \| PatKind::Deref(ref subpattern)`
	`665`	`+ \| PatKind::Ref(ref subpattern, _) => {`
`664`	`666`	`try_visit!(visitor.visit_pat(subpattern));`
`665`	`667`	`}`
`666`	`668`	`PatKind::Binding(_, _hir_id, ident, ref optional_subpattern) => {`
Original file line number	Diff line number	Diff line change
`@@ -1808,6 +1808,12 @@ impl<'a> State<'a> {`
`1808`	`1808`	`self.pclose();`
`1809`	`1809`	`}`
`1810`	`1810`	`}`
	`1811`	`+ PatKind::Deref(inner) => {`
	`1812`	`+ self.word("deref!");`
	`1813`	`+ self.popen();`
	`1814`	`+ self.print_pat(inner);`
	`1815`	`+ self.pclose();`
	`1816`	`+ }`
`1811`	`1817`	`PatKind::Ref(inner, mutbl) => {`
`1812`	`1818`	`let is_range_inner = matches!(inner.kind, PatKind::Range(..));`
`1813`	`1819`	`self.word("&");`