Rollup merge of #90521 - jhpratt:stabilize-destructuring_assignment, r=jackh726,pnkfelix

Stabilize `destructuring_assignment`

Closes #71126

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

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

Author: matthiaskrgr

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};
@@ -962,24 +961,6 @@ 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(let_else)]
 #![feature(proc_macro_diagnostic)]

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

@@ -1297,7 +1297,6 @@ 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
@@ -2620,7 +2619,6 @@ 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

@@ -878,11 +878,6 @@ 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

@@ -136,7 +136,7 @@
 #![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
 }