Stabilize bindings_after_at

compiler/rustc_ast_passes/src/lib.rs

@@ -4,7 +4,7 @@
 //!
 //! The crate also contains other misc AST visitors, e.g. `node_count` and `show_span`.
 
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(iter_is_partitioned)]
 #![feature(box_patterns)]
 #![recursion_limit = "256"]

compiler/rustc_feature/src/accepted.rs

@@ -287,6 +287,9 @@ declare_features! (
     (accepted, const_fn_unsize, "1.54.0", Some(64992), None),
     /// Allows `impl Trait` with multiple unrelated lifetimes.
     (accepted, member_constraints, "1.54.0", Some(61997), None),
+    /// Allows bindings in the subpattern of a binding pattern.
+    /// For example, you can write `x @ Some(y)`.
+    (accepted, bindings_after_at, "1.54.0", Some(65490), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

compiler/rustc_feature/src/active.rs

@@ -513,10 +513,6 @@ declare_features! (
     /// Allows using `&mut` in constant functions.
     (active, const_mut_refs, "1.41.0", Some(57349), None),
 
-    /// Allows bindings in the subpattern of a binding pattern.
-    /// For example, you can write `x @ Some(y)`.
-    (active, bindings_after_at, "1.41.0", Some(65490), None),
-
     /// Allows `impl const Trait for T` syntax.
     (active, const_trait_impl, "1.42.0", Some(67792), None),
 

compiler/rustc_mir/src/lib.rs

@@ -8,7 +8,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(in_band_lifetimes)]
 #![feature(array_windows)]
 #![feature(assert_matches)]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -16,9 +16,8 @@ use rustc_middle::thir::PatKind;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::lint::builtin::BINDINGS_WITH_VARIANT_NAME;
 use rustc_session::lint::builtin::{IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS};
-use rustc_session::parse::feature_err;
 use rustc_session::Session;
-use rustc_span::{sym, Span};
+use rustc_span::Span;
 use std::slice;
 
 crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) {
@@ -123,9 +122,6 @@ impl PatCtxt<'_, '_> {
 impl<'tcx> MatchVisitor<'_, 'tcx> {
     fn check_patterns(&mut self, pat: &Pat<'_>) {
         pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
-        if !self.tcx.features().bindings_after_at {
-            check_legality_of_bindings_in_at_patterns(self, pat);
-        }
         check_for_bindings_named_same_as_variants(self, pat);
     }
 
@@ -740,46 +736,3 @@ fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_
         err.emit();
     }
 }
-
-/// Forbids bindings in `@` patterns. This used to be is necessary for memory safety,
-/// because of the way rvalues were handled in the borrow check. (See issue #14587.)
-fn check_legality_of_bindings_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_>) {
-    AtBindingPatternVisitor { cx, bindings_allowed: true }.visit_pat(pat);
-
-    struct AtBindingPatternVisitor<'a, 'b, 'tcx> {
-        cx: &'a MatchVisitor<'b, 'tcx>,
-        bindings_allowed: bool,
-    }
-
-    impl<'v> Visitor<'v> for AtBindingPatternVisitor<'_, '_, '_> {
-        type Map = intravisit::ErasedMap<'v>;
-
-        fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
-            NestedVisitorMap::None
-        }
-
-        fn visit_pat(&mut self, pat: &Pat<'_>) {
-            match pat.kind {
-                hir::PatKind::Binding(.., ref subpat) => {
-                    if !self.bindings_allowed {
-                        feature_err(
-                            &self.cx.tcx.sess.parse_sess,
-                            sym::bindings_after_at,
-                            pat.span,
-                            "pattern bindings after an `@` are unstable",
-                        )
-                        .emit();
-                    }
-
-                    if subpat.is_some() {
-                        let bindings_were_allowed = self.bindings_allowed;
-                        self.bindings_allowed = false;
-                        intravisit::walk_pat(self, pat);
-                        self.bindings_allowed = bindings_were_allowed;
-                    }
-                }
-                _ => intravisit::walk_pat(self, pat),
-            }
-        }
-    }
-}

compiler/rustc_parse/src/lib.rs

@@ -2,7 +2,7 @@
 
 #![feature(array_windows)]
 #![feature(crate_visibility_modifier)]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(box_syntax)]
 #![feature(box_patterns)]
 #![recursion_limit = "256"]

compiler/rustc_typeck/src/lib.rs

@@ -56,7 +56,7 @@ This API is completely unstable and subject to change.
 */
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(bindings_after_at)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]

library/alloc/src/lib.rs

@@ -82,6 +82,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]
 #![feature(async_stream)]
+#![cfg_attr(bootstrap, feature(bindings_after_at))]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(cfg_sanitize)]
@@ -144,7 +145,6 @@
 #![feature(associated_type_bounds)]
 #![feature(slice_group_by)]
 #![feature(decl_macro)]
-#![feature(bindings_after_at)]
 // Allow testing this library
 
 #[cfg(test)]

src/test/ui/borrowck/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs

@@ -1,5 +1,4 @@
 // Tests using a combination of pattern features has the expected borrow checking behavior
-#![feature(bindings_after_at)]
 #![feature(box_patterns)]
 
 enum Test {

src/test/ui/borrowck/bindings-after-at-or-patterns-slice-patterns-box-patterns.stderr

@@ -1,5 +1,5 @@
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:37:9
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:36:9
    |
 LL |         ref foo @ [.., ref mut bar] => (),
    |         -------^^^^^^^^-----------^
@@ -8,7 +8,7 @@ LL |         ref foo @ [.., ref mut bar] => (),
    |         immutable borrow, by `foo`, occurs here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:121:9
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:120:9
    |
 LL |         ref foo @ Some(box ref mut s) => (),
    |         -------^^^^^^^^^^^^---------^
@@ -17,7 +17,7 @@ LL |         ref foo @ Some(box ref mut s) => (),
    |         immutable borrow, by `foo`, occurs here
 
 error[E0382]: borrow of moved value: `x`
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:19:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:18:5
    |
 LL | fn bindings_after_at_slice_patterns_move_binding(x: [String; 4]) {
    |                                                  - move occurs because `x` has type `[String; 4]`, which does not implement the `Copy` trait
@@ -29,7 +29,7 @@ LL |     &x;
    |     ^^ value borrowed here after move
 
 error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:29:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:28:5
    |
 LL |         ref mut foo @ [.., _] => Some(foo),
    |         --------------------- mutable borrow occurs here
@@ -41,7 +41,7 @@ LL |     drop(r);
    |          - mutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:51:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:50:5
    |
 LL |         [ref foo @ .., ref bar] => Some(foo),
    |          ------------ immutable borrow occurs here
@@ -53,7 +53,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:63:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:62:5
    |
 LL |         ref foo @ [.., ref bar] => Some(foo),
    |         ----------------------- immutable borrow occurs here
@@ -65,7 +65,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0382]: borrow of moved value: `x`
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:77:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:76:5
    |
 LL | fn bindings_after_at_or_patterns_move(x: Option<Test>) {
    |                                       - move occurs because `x` has type `Option<Test>`, which does not implement the `Copy` trait
@@ -80,7 +80,7 @@ LL |     &x;
    |     ^^ value borrowed here after move
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:87:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:86:5
    |
 LL |         ref foo @ Some(Test::Foo | Test::Bar) => Some(foo),
    |         ------------------------------------- immutable borrow occurs here
@@ -92,7 +92,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:99:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:98:5
    |
 LL |         ref mut foo @ Some(Test::Foo | Test::Bar) => Some(foo),
    |         ----------------------------------------- mutable borrow occurs here
@@ -104,7 +104,7 @@ LL |     drop(r);
    |          - mutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:113:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:112:5
    |
 LL |         ref foo @ Some(box ref s) => Some(foo),
    |         ------------------------- immutable borrow occurs here
@@ -116,7 +116,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0382]: borrow of moved value: `x`
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:135:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:134:5
    |
 LL | fn bindings_after_at_slice_patterns_or_patterns_moves(x: [Option<Test>; 4]) {
    |                                                       - move occurs because `x` has type `[Option<Test>; 4]`, which does not implement the `Copy` trait
@@ -131,7 +131,7 @@ LL |     &x;
    |     ^^ value borrowed here after move
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:145:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:144:5
    |
 LL |         ref a @ [ref b @ .., Some(Test::Foo | Test::Bar)] => Some(a),
    |         ------------------------------------------------- immutable borrow occurs here
@@ -143,7 +143,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:157:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:156:5
    |
 LL |         ref a @ [ref b @ .., Some(Test::Foo | Test::Bar)] => Some(b),
    |                  ---------- immutable borrow occurs here
@@ -155,7 +155,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:171:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:170:5
    |
 LL |         [_, ref a @ Some(box ref b), ..] => Some(a),
    |             ----------------------- immutable borrow occurs here
@@ -167,7 +167,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:187:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:186:5
    |
 LL |         [_, ref a @ Some(box Test::Foo | box Test::Bar), ..] => Some(a),
    |             ------------------------------------------- immutable borrow occurs here
@@ -179,7 +179,7 @@ LL |     drop(r);
    |          - immutable borrow later used here
 
 error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:201:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:200:5
    |
 LL |         [_, ref mut a @ Some(box Test::Foo | box Test::Bar), ..] => Some(a),
    |             ----------------------------------------------- mutable borrow occurs here
@@ -191,7 +191,7 @@ LL |     drop(r);
    |          - mutable borrow later used here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:215:5
+  --> $DIR/bindings-after-at-or-patterns-slice-patterns-box-patterns.rs:214:5
    |
 LL |         ref a @ [_, ref b @ Some(box Test::Foo | box Test::Bar), ..] => Some(a),
    |         ------------------------------------------------------------ immutable borrow occurs here

src/test/ui/drop/dynamic-drop.rs

@@ -2,7 +2,6 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait)]
-#![feature(bindings_after_at)]
 
 #![allow(unused_assignments)]
 #![allow(unused_variables)]

src/test/ui/pattern/bindings-after-at/bind-by-copy.rs

@@ -2,8 +2,6 @@
 
 // Test copy
 
-#![feature(bindings_after_at)]
-
 struct A { a: i32, b: i32 }
 struct B { a: i32, b: C }
 struct D { a: i32, d: C }

src/test/ui/pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.rs

@@ -2,8 +2,6 @@
 // It checks that you cannot use an AND-pattern (`binding @ pat`)
 // where one side is by-ref and the other is by-move.
 
-#![feature(bindings_after_at)]
-
 struct X {
     x: (),
 }

src/test/ui/pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.stderr

@@ -1,5 +1,5 @@
 error: cannot move out of value because it is borrowed
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:14:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:12:14
    |
 LL |         Some(ref _y @ _z) => {}
    |              ------^^^--
@@ -8,7 +8,7 @@ LL |         Some(ref _y @ _z) => {}
    |              value borrowed, by `_y`, here
 
 error: borrow of moved value
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:21:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:19:14
    |
 LL |         Some(_z @ ref _y) => {}
    |              --^^^------
@@ -18,7 +18,7 @@ LL |         Some(_z @ ref _y) => {}
    |              move occurs because `_z` has type `X` which does not implement the `Copy` trait
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:28:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:26:14
    |
 LL |         Some(ref mut _y @ _z) => {}
    |              ----------^^^--
@@ -27,7 +27,7 @@ LL |         Some(ref mut _y @ _z) => {}
    |              value borrowed, by `_y`, here
 
 error: borrow of moved value
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:35:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:33:14
    |
 LL |         Some(_z @ ref mut _y) => {}
    |              --^^^----------
@@ -37,7 +37,7 @@ LL |         Some(_z @ ref mut _y) => {}
    |              move occurs because `_z` has type `X` which does not implement the `Copy` trait
 
 error[E0382]: borrow of moved value
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:14:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:12:14
    |
 LL |         Some(ref _y @ _z) => {}
    |              ^^^^^^^^^--
@@ -52,7 +52,7 @@ LL |         Some(ref _y @ ref _z) => {}
    |                       ^^^
 
 error[E0382]: borrow of moved value
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:28:14
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:26:14
    |
 LL |         Some(ref mut _y @ _z) => {}
    |              ^^^^^^^^^^^^^--

src/test/ui/pattern/bindings-after-at/bind-by-move-no-subbindings-fun-param.rs

@@ -1,7 +1,5 @@
 // See issue #12534.
 
-#![feature(bindings_after_at)]
-
 fn main() {}
 
 struct A(Box<u8>);

src/test/ui/pattern/bindings-after-at/bind-by-move-no-subbindings-fun-param.stderr

@@ -1,5 +1,5 @@
 error[E0382]: use of partially moved value
-  --> $DIR/bind-by-move-no-subbindings-fun-param.rs:9:6
+  --> $DIR/bind-by-move-no-subbindings-fun-param.rs:7:6
    |
 LL | fn f(a @ A(u): A) -> Box<u8> {
    |      ^^^^^^-^

src/test/ui/pattern/bindings-after-at/borrowck-move-and-move.rs

@@ -1,7 +1,5 @@
 // Test that moving on both sides of an `@` pattern is not allowed.
 
-#![feature(bindings_after_at)]
-
 fn main() {
     struct U; // Not copy!