Rollup merge of rust-lang#90521 - jhpratt:stabilize-destructuring_ass…

…ignment, r=jackh726,pnkfelix

Stabilize `destructuring_assignment`

Closes rust-lang#71126

- [Stabilization report](rust-lang#71126 (comment))
- [Completed FCP](rust-lang#71126 (comment))

`@rustbot` label +F-destructuring-assignment +T-lang
Also needs +relnotes but I don't have permission to add that tag.

compiler/rustc_ast_lowering/src/expr.rs

@@ -9,7 +9,6 @@ use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::definitions::DefPathData;
-use rustc_session::parse::feature_err;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
 use rustc_span::symbol::{sym, Ident, Symbol};
@@ -930,24 +929,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 self.lower_span(eq_sign_span),
             );
         }
-        if !self.sess.features_untracked().destructuring_assignment {
-            let mut err = feature_err(
-                &self.sess.parse_sess,
-                sym::destructuring_assignment,
-                eq_sign_span,
-                "destructuring assignments are unstable",
-            );
-            err.span_label(lhs.span, "cannot assign to this expression");
-            if self.is_in_loop_condition {
-                err.span_suggestion_verbose(
-                    lhs.span.shrink_to_lo(),
-                    "you might have meant to use pattern destructuring",
-                    "let ".to_string(),
-                    rustc_errors::Applicability::MachineApplicable,
-                );
-            }
-            err.emit();
-        }
 
         let mut assignments = vec![];
 

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -724,11 +724,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
     gate_all!(inline_const, "inline-const is experimental");
     gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
-    if sess.parse_sess.span_diagnostic.err_count() == 0 {
-        // Errors for `destructuring_assignment` can get quite noisy, especially where `_` is
-        // involved, so we only emit errors where there are no other parsing errors.
-        gate_all!(destructuring_assignment, "destructuring assignments are unstable");
-    }
 
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).

compiler/rustc_expand/src/lib.rs

@@ -1,6 +1,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
-#![feature(destructuring_assignment)]
+#![cfg_attr(bootstrap, feature(destructuring_assignment))]
 #![feature(if_let_guard)]
 #![feature(iter_zip)]
 #![feature(let_else)]

compiler/rustc_feature/src/accepted.rs

@@ -114,6 +114,8 @@ declare_features! (
     (accepted, default_type_params, "1.0.0", None, None),
     /// Allows `#[deprecated]` attribute.
     (accepted, deprecated, "1.9.0", Some(29935), None),
+    /// Allows the use of destructuring assignments.
+    (accepted, destructuring_assignment, "1.59.0", Some(71126), None),
     /// Allows `#[doc(alias = "...")]`.
     (accepted, doc_alias, "1.48.0", Some(50146), None),
     /// Allows `..` in tuple (struct) patterns.

compiler/rustc_feature/src/active.rs

@@ -356,8 +356,6 @@ declare_features! (
     (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
     /// Allows `#[derive(Default)]` and `#[default]` on enums.
     (active, derive_default_enum, "1.56.0", Some(86985), None),
-    /// Allows the use of destructuring assignments.
-    (active, destructuring_assignment, "1.49.0", Some(71126), None),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
     (active, doc_auto_cfg, "1.58.0", Some(43781), None),
     /// Allows `#[doc(cfg(...))]`.

compiler/rustc_parse/src/parser/expr.rs

@@ -1265,7 +1265,6 @@ impl<'a> Parser<'a> {
         } else if self.eat_keyword(kw::Let) {
             self.parse_let_expr(attrs)
         } else if self.eat_keyword(kw::Underscore) {
-            self.sess.gated_spans.gate(sym::destructuring_assignment, self.prev_token.span);
             Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore, attrs))
         } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
             // Don't complain about bare semicolons after unclosed braces
@@ -2588,7 +2587,6 @@ impl<'a> Parser<'a> {
                 let exp_span = self.prev_token.span;
                 // We permit `.. }` on the left-hand side of a destructuring assignment.
                 if self.check(&token::CloseDelim(close_delim)) {
-                    self.sess.gated_spans.gate(sym::destructuring_assignment, self.prev_token.span);
                     base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
                     break;
                 }

compiler/rustc_typeck/src/check/expr.rs

@@ -877,11 +877,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         "let ".to_string(),
                         Applicability::MachineApplicable,
                     );
-                    if !self.sess().features_untracked().destructuring_assignment {
-                        // We already emit an E0658 with a suggestion for `while let`, this is
-                        // redundant output.
-                        err.delay_as_bug();
-                    }
                     break;
                 }
                 hir::Node::Item(_)

library/alloc/src/lib.rs

@@ -137,7 +137,7 @@
 #![feature(cfg_target_has_atomic)]
 #![feature(const_fn_trait_bound)]
 #![feature(const_trait_impl)]
-#![feature(destructuring_assignment)]
+#![cfg_attr(bootstrap, feature(destructuring_assignment))]
 #![feature(dropck_eyepatch)]
 #![feature(exclusive_range_pattern)]
 #![feature(fundamental)]

src/test/ui/associated-types/associated-type-destructuring-assignment.rs

@@ -1,6 +1,5 @@
 // check-pass
 
-#![feature(destructuring_assignment)]
 #![feature(more_qualified_paths)]
 
 enum E { V() }

src/test/ui/cross/cross-file-errors/main.rs

@@ -4,5 +4,4 @@ mod underscore;
 fn main() {
     underscore!();
     //~^ ERROR `_` can only be used on the left-hand side of an assignment
-    //~| ERROR destructuring assignments are unstable
 }

src/test/ui/cross/cross-file-errors/main.stderr

@@ -1,18 +1,3 @@
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/underscore.rs:8:9
-   |
-LL |         _
-   |         ^
-   |
-  ::: $DIR/main.rs:5:5
-   |
-LL |     underscore!();
-   |     ------------- in this macro invocation
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-   = note: this error originates in the macro `underscore` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error: in expressions, `_` can only be used on the left-hand side of an assignment
   --> $DIR/underscore.rs:8:9
    |
@@ -26,6 +11,5 @@ LL |     underscore!();
    |
    = note: this error originates in the macro `underscore` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/destructuring-assignment/bad-expr-lhs.rs

@@ -1,12 +1,9 @@
 fn main() {
     1 = 2; //~ ERROR invalid left-hand side of assignment
     1 += 2; //~ ERROR invalid left-hand side of assignment
-    (1, 2) = (3, 4); //~ ERROR destructuring assignments are unstable
+    (1, 2) = (3, 4);
+    //~^ ERROR invalid left-hand side of assignment
     //~| ERROR invalid left-hand side of assignment
-    //~| ERROR invalid left-hand side of assignment
-
-    let (a, b) = (1, 2);
-    (a, b) = (3, 4); //~ ERROR destructuring assignments are unstable
 
     None = Some(3); //~ ERROR invalid left-hand side of assignment
 }

src/test/ui/destructuring-assignment/bad-expr-lhs.stderr

@@ -1,25 +1,3 @@
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/bad-expr-lhs.rs:4:12
-   |
-LL |     (1, 2) = (3, 4);
-   |     ------ ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/bad-expr-lhs.rs:9:12
-   |
-LL |     (a, b) = (3, 4);
-   |     ------ ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
 error[E0070]: invalid left-hand side of assignment
   --> $DIR/bad-expr-lhs.rs:2:7
    |
@@ -53,14 +31,14 @@ LL |     (1, 2) = (3, 4);
    |         cannot assign to this expression
 
 error[E0070]: invalid left-hand side of assignment
-  --> $DIR/bad-expr-lhs.rs:11:10
+  --> $DIR/bad-expr-lhs.rs:8:10
    |
 LL |     None = Some(3);
    |     ---- ^
    |     |
    |     cannot assign to this expression
 
-error: aborting due to 7 previous errors
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0067, E0070, E0658.
+Some errors have detailed explanations: E0067, E0070.
 For more information about an error, try `rustc --explain E0067`.

src/test/ui/destructuring-assignment/default-match-bindings-forbidden.rs

@@ -1,5 +1,3 @@
-#![feature(destructuring_assignment)]
-
 fn main() {
     let mut x = &0;
     let mut y = &0;

src/test/ui/destructuring-assignment/default-match-bindings-forbidden.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/default-match-bindings-forbidden.rs:6:5
+  --> $DIR/default-match-bindings-forbidden.rs:4:5
    |
 LL |     (x, y) = &(1, 2);
    |     ^^^^^^   ------- this expression has type `&({integer}, {integer})`

src/test/ui/destructuring-assignment/drop-order.rs

@@ -2,7 +2,6 @@
 
 //! Test that let bindings and destructuring assignments have consistent drop orders
 
-#![feature(destructuring_assignment)]
 #![allow(unused_variables, unused_assignments)]
 
 use std::cell::RefCell;

src/test/ui/destructuring-assignment/nested_destructure.rs

@@ -1,7 +1,5 @@
 // run-pass
 
-#![feature(destructuring_assignment)]
-
 struct Struct<S, T> {
     a: S,
     b: T,

src/test/ui/destructuring-assignment/note-unsupported.rs

@@ -3,25 +3,20 @@ struct S { x: u8, y: u8 }
 fn main() {
     let (a, b) = (1, 2);
 
-    (a, b) = (3, 4); //~ ERROR destructuring assignments are unstable
+    (a, b) = (3, 4);
     (a, b) += (3, 4); //~ ERROR invalid left-hand side of assignment
     //~| ERROR binary assignment operation `+=` cannot be applied
 
-    [a, b] = [3, 4]; //~ ERROR destructuring assignments are unstable
+    [a, b] = [3, 4];
     [a, b] += [3, 4]; //~ ERROR invalid left-hand side of assignment
     //~| ERROR binary assignment operation `+=` cannot be applied
 
     let s = S { x: 3, y: 4 };
 
-    S { x: a, y: b } = s; //~ ERROR destructuring assignments are unstable
+    S { x: a, y: b } = s;
     S { x: a, y: b } += s; //~ ERROR invalid left-hand side of assignment
     //~| ERROR binary assignment operation `+=` cannot be applied
 
     S { x: a, ..s } = S { x: 3, y: 4 };
     //~^ ERROR functional record updates are not allowed in destructuring assignments
-    //~| ERROR destructuring assignments are unstable
-
-    let c = 3;
-
-    ((a, b), c) = ((3, 4), 5); //~ ERROR destructuring assignments are unstable
 }

src/test/ui/destructuring-assignment/note-unsupported.stderr

@@ -1,64 +1,9 @@
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/note-unsupported.rs:6:12
-   |
-LL |     (a, b) = (3, 4);
-   |     ------ ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/note-unsupported.rs:10:12
-   |
-LL |     [a, b] = [3, 4];
-   |     ------ ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/note-unsupported.rs:16:22
-   |
-LL |     S { x: a, y: b } = s;
-   |     ---------------- ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/note-unsupported.rs:20:21
-   |
-LL |     S { x: a, ..s } = S { x: 3, y: 4 };
-   |     --------------- ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
 error: functional record updates are not allowed in destructuring assignments
   --> $DIR/note-unsupported.rs:20:17
    |
 LL |     S { x: a, ..s } = S { x: 3, y: 4 };
    |                 ^ help: consider removing the trailing pattern
 
-error[E0658]: destructuring assignments are unstable
-  --> $DIR/note-unsupported.rs:26:17
-   |
-LL |     ((a, b), c) = ((3, 4), 5);
-   |     ----------- ^
-   |     |
-   |     cannot assign to this expression
-   |
-   = note: see issue #71126 <https://github.com/rust-lang/rust/issues/71126> for more information
-   = help: add `#![feature(destructuring_assignment)]` to the crate attributes to enable
-
 error[E0368]: binary assignment operation `+=` cannot be applied to type `({integer}, {integer})`
   --> $DIR/note-unsupported.rs:7:5
    |
@@ -124,7 +69,7 @@ LL |     S { x: a, y: b } += s;
    |     |
    |     cannot assign to this expression
 
-error: aborting due to 12 previous errors
+error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0067, E0368, E0658.
+Some errors have detailed explanations: E0067, E0368.
 For more information about an error, try `rustc --explain E0067`.

src/test/ui/destructuring-assignment/slice_destructure.rs

@@ -1,7 +1,5 @@
 // run-pass
 
-#![feature(destructuring_assignment)]
-
 fn main() {
   let (mut a, mut b);
   [a, b] = [0, 1];

src/test/ui/destructuring-assignment/slice_destructure_fail.rs

@@ -1,5 +1,3 @@
-#![feature(destructuring_assignment)]
-
 fn main() {
   let (mut a, mut b);
   [a, .., b, ..] = [0, 1]; //~ ERROR `..` can only be used once per slice pattern

src/test/ui/destructuring-assignment/slice_destructure_fail.stderr

@@ -1,19 +1,19 @@
 error: `..` can only be used once per slice pattern
-  --> $DIR/slice_destructure_fail.rs:5:14
+  --> $DIR/slice_destructure_fail.rs:3:14
    |
 LL |   [a, .., b, ..] = [0, 1];
    |       --     ^^ can only be used once per slice pattern
    |       |
    |       previously used here
 
 error[E0527]: pattern requires 3 elements but array has 2
-  --> $DIR/slice_destructure_fail.rs:6:3
+  --> $DIR/slice_destructure_fail.rs:4:3
    |
 LL |   [a, a, b] = [1, 2];
    |   ^^^^^^^^^ expected 2 elements
 
 error[E0527]: pattern requires 1 element but array has 2
-  --> $DIR/slice_destructure_fail.rs:7:3
+  --> $DIR/slice_destructure_fail.rs:5:3
    |
 LL |   [_] = [1, 2];
    |   ^^^ expected 2 elements

src/test/ui/destructuring-assignment/struct_destructure.rs

@@ -1,6 +1,5 @@
 // run-pass
 
-#![feature(destructuring_assignment)]
 struct Struct<S, T> {
     a: S,
     b: T,

src/test/ui/destructuring-assignment/struct_destructure_fail.rs

@@ -1,4 +1,3 @@
-#![feature(destructuring_assignment)]
 struct Struct<S, T> {
     a: S,
     b: T,