Auto merge of #78889 - Dylan-DPC:rollup-6zjhahf, r=Dylan-DPC

Rollup of 12 pull requests

Successful merges:

 - #77640 (Refactor IntErrorKind to avoid "underflow" terminology)
 - #78026 (Define `fs::hard_link` to not follow symlinks.)
 - #78114 (Recognize `private_intra_doc_links` as a lint)
 - #78228 (Promote aarch64-unknown-linux-gnu to Tier 1)
 - #78345 (Fix handling of item names for HIR)
 - #78437 (BTreeMap: stop mistaking node for an orderly place)
 - #78476 (fix some incorrect aliasing in the BTree)
 - #78674 (inliner: Use substs_for_mir_body)
 - #78748 (Implement destructuring assignment for tuples)
 - #78868 (Fix tab focus on restyled switches)
 - #78878 (Avoid overlapping cfg attributes when both macOS and aarch64)
 - #78882 (Nicer hunk headers for rust files)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

Diff for: .gitattributes

@@ -3,7 +3,7 @@
 * text=auto eol=lf
 *.cpp rust
 *.h rust
-*.rs rust
+*.rs rust diff=rust
 *.fixed linguist-language=Rust
 src/etc/installer/gfx/* binary
 *.woff binary

Diff for: .github/workflows/ci.yml

@@ -154,6 +154,11 @@ jobs:
     strategy:
       matrix:
         include:
+          - name: aarch64-gnu
+            os:
+              - self-hosted
+              - ARM64
+              - linux
           - name: arm-android
             os: ubuntu-latest-xl
             env: {}
@@ -497,116 +502,6 @@ jobs:
           AWS_ACCESS_KEY_ID: "${{ env.ARTIFACTS_AWS_ACCESS_KEY_ID }}"
           AWS_SECRET_ACCESS_KEY: "${{ secrets[format('AWS_SECRET_ACCESS_KEY_{0}', env.ARTIFACTS_AWS_ACCESS_KEY_ID)] }}"
         if: "success() && !env.SKIP_JOB && (github.event_name == 'push' || env.DEPLOY == '1' || env.DEPLOY_ALT == '1')"
-  auto-fallible:
-    name: auto-fallible
-    env:
-      CI_JOB_NAME: "${{ matrix.name }}"
-      SCCACHE_BUCKET: rust-lang-gha-caches
-      DEPLOY_BUCKET: rust-lang-gha
-      TOOLSTATE_REPO: "https://github.com/pietroalbini/rust-toolstate"
-      TOOLSTATE_ISSUES_API_URL: "https://api.github.com/repos/pietroalbini/rust-toolstate/issues"
-      TOOLSTATE_PUBLISH: 1
-      CACHES_AWS_ACCESS_KEY_ID: AKIA46X5W6CZOMUQATD5
-      ARTIFACTS_AWS_ACCESS_KEY_ID: AKIA46X5W6CZH5AYXDVF
-      CACHE_DOMAIN: ci-caches-gha.rust-lang.org
-    if: "github.event_name == 'push' && github.ref == 'refs/heads/auto' && github.repository == 'rust-lang-ci/rust'"
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: aarch64-gnu
-            os:
-              - self-hosted
-              - ARM64
-              - linux
-    timeout-minutes: 600
-    runs-on: "${{ matrix.os }}"
-    steps:
-      - name: disable git crlf conversion
-        run: git config --global core.autocrlf false
-      - name: checkout the source code
-        uses: actions/checkout@v2
-        with:
-          fetch-depth: 2
-      - name: configure the PR in which the error message will be posted
-        run: "echo \"[CI_PR_NUMBER=$num]\""
-        env:
-          num: "${{ github.event.number }}"
-        if: "success() && !env.SKIP_JOBS && github.event_name == 'pull_request'"
-      - name: add extra environment variables
-        run: src/ci/scripts/setup-environment.sh
-        env:
-          EXTRA_VARIABLES: "${{ toJson(matrix.env) }}"
-        if: success() && !env.SKIP_JOB
-      - name: decide whether to skip this job
-        run: src/ci/scripts/should-skip-this.sh
-        if: success() && !env.SKIP_JOB
-      - name: configure GitHub Actions to kill the build when outdated
-        uses: rust-lang/simpleinfra/github-actions/cancel-outdated-builds@master
-        with:
-          github_token: "${{ secrets.github_token }}"
-        if: "success() && !env.SKIP_JOB && github.ref != 'refs/heads/try'"
-      - name: collect CPU statistics
-        run: src/ci/scripts/collect-cpu-stats.sh
-        if: success() && !env.SKIP_JOB
-      - name: show the current environment
-        run: src/ci/scripts/dump-environment.sh
-        if: success() && !env.SKIP_JOB
-      - name: install awscli
-        run: src/ci/scripts/install-awscli.sh
-        if: success() && !env.SKIP_JOB
-      - name: install sccache
-        run: src/ci/scripts/install-sccache.sh
-        if: success() && !env.SKIP_JOB
-      - name: select Xcode
-        run: src/ci/scripts/select-xcode.sh
-        if: success() && !env.SKIP_JOB
-      - name: install clang
-        run: src/ci/scripts/install-clang.sh
-        if: success() && !env.SKIP_JOB
-      - name: install WIX
-        run: src/ci/scripts/install-wix.sh
-        if: success() && !env.SKIP_JOB
-      - name: ensure the build happens on a partition with enough space
-        run: src/ci/scripts/symlink-build-dir.sh
-        if: success() && !env.SKIP_JOB
-      - name: disable git crlf conversion
-        run: src/ci/scripts/disable-git-crlf-conversion.sh
-        if: success() && !env.SKIP_JOB
-      - name: install MSYS2
-        run: src/ci/scripts/install-msys2.sh
-        if: success() && !env.SKIP_JOB
-      - name: install MinGW
-        run: src/ci/scripts/install-mingw.sh
-        if: success() && !env.SKIP_JOB
-      - name: install ninja
-        run: src/ci/scripts/install-ninja.sh
-        if: success() && !env.SKIP_JOB
-      - name: enable ipv6 on Docker
-        run: src/ci/scripts/enable-docker-ipv6.sh
-        if: success() && !env.SKIP_JOB
-      - name: disable git crlf conversion
-        run: src/ci/scripts/disable-git-crlf-conversion.sh
-        if: success() && !env.SKIP_JOB
-      - name: checkout submodules
-        run: src/ci/scripts/checkout-submodules.sh
-        if: success() && !env.SKIP_JOB
-      - name: ensure line endings are correct
-        run: src/ci/scripts/verify-line-endings.sh
-        if: success() && !env.SKIP_JOB
-      - name: run the build
-        run: src/ci/scripts/run-build-from-ci.sh
-        env:
-          AWS_ACCESS_KEY_ID: "${{ env.CACHES_AWS_ACCESS_KEY_ID }}"
-          AWS_SECRET_ACCESS_KEY: "${{ secrets[format('AWS_SECRET_ACCESS_KEY_{0}', env.CACHES_AWS_ACCESS_KEY_ID)] }}"
-          TOOLSTATE_REPO_ACCESS_TOKEN: "${{ secrets.TOOLSTATE_REPO_ACCESS_TOKEN }}"
-        if: success() && !env.SKIP_JOB
-      - name: upload artifacts to S3
-        run: src/ci/scripts/upload-artifacts.sh
-        env:
-          AWS_ACCESS_KEY_ID: "${{ env.ARTIFACTS_AWS_ACCESS_KEY_ID }}"
-          AWS_SECRET_ACCESS_KEY: "${{ secrets[format('AWS_SECRET_ACCESS_KEY_{0}', env.ARTIFACTS_AWS_ACCESS_KEY_ID)] }}"
-        if: "success() && !env.SKIP_JOB && (github.event_name == 'push' || env.DEPLOY == '1' || env.DEPLOY_ALT == '1')"
   try:
     name: try
     env:

Diff for: compiler/rustc_ast_lowering/src/expr.rs

@@ -9,6 +9,7 @@ use rustc_data_structures::thin_vec::ThinVec;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
+use rustc_session::parse::feature_err;
 use rustc_span::hygiene::ForLoopLoc;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
 use rustc_span::symbol::{sym, Ident, Symbol};
@@ -146,7 +147,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
                 }
                 ExprKind::Assign(ref el, ref er, span) => {
-                    hir::ExprKind::Assign(self.lower_expr(el), self.lower_expr(er), span)
+                    self.lower_expr_assign(el, er, span, e.span)
                 }
                 ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
                     self.lower_binop(op),
@@ -840,6 +841,134 @@ impl<'hir> LoweringContext<'_, 'hir> {
         })
     }
 
+    /// Destructure the LHS of complex assignments.
+    /// For instance, lower `(a, b) = t` to `{ let (lhs1, lhs2) = t; a = lhs1; b = lhs2; }`.
+    fn lower_expr_assign(
+        &mut self,
+        lhs: &Expr,
+        rhs: &Expr,
+        eq_sign_span: Span,
+        whole_span: Span,
+    ) -> hir::ExprKind<'hir> {
+        // Return early in case of an ordinary assignment.
+        fn is_ordinary(lhs: &Expr) -> bool {
+            match &lhs.kind {
+                ExprKind::Tup(..) => false,
+                ExprKind::Paren(e) => {
+                    match e.kind {
+                        // We special-case `(..)` for consistency with patterns.
+                        ExprKind::Range(None, None, RangeLimits::HalfOpen) => false,
+                        _ => is_ordinary(e),
+                    }
+                }
+                _ => true,
+            }
+        }
+        if is_ordinary(lhs) {
+            return hir::ExprKind::Assign(self.lower_expr(lhs), self.lower_expr(rhs), eq_sign_span);
+        }
+        if !self.sess.features_untracked().destructuring_assignment {
+            feature_err(
+                &self.sess.parse_sess,
+                sym::destructuring_assignment,
+                eq_sign_span,
+                "destructuring assignments are unstable",
+            )
+            .span_label(lhs.span, "cannot assign to this expression")
+            .emit();
+        }
+
+        let mut assignments = vec![];
+
+        // The LHS becomes a pattern: `(lhs1, lhs2)`.
+        let pat = self.destructure_assign(lhs, eq_sign_span, &mut assignments);
+        let rhs = self.lower_expr(rhs);
+
+        // Introduce a `let` for destructuring: `let (lhs1, lhs2) = t`.
+        let destructure_let = self.stmt_let_pat(
+            ThinVec::new(),
+            whole_span,
+            Some(rhs),
+            pat,
+            hir::LocalSource::AssignDesugar(eq_sign_span),
+        );
+
+        // `a = lhs1; b = lhs2;`.
+        let stmts = self
+            .arena
+            .alloc_from_iter(std::iter::once(destructure_let).chain(assignments.into_iter()));
+
+        // Wrap everything in a block.
+        hir::ExprKind::Block(&self.block_all(whole_span, stmts, None), None)
+    }
+
+    /// Convert the LHS of a destructuring assignment to a pattern.
+    /// Each sub-assignment is recorded in `assignments`.
+    fn destructure_assign(
+        &mut self,
+        lhs: &Expr,
+        eq_sign_span: Span,
+        assignments: &mut Vec<hir::Stmt<'hir>>,
+    ) -> &'hir hir::Pat<'hir> {
+        match &lhs.kind {
+            // Tuples.
+            ExprKind::Tup(elements) => {
+                let (pats, rest) =
+                    self.destructure_sequence(elements, "tuple", eq_sign_span, assignments);
+                let tuple_pat = hir::PatKind::Tuple(pats, rest.map(|r| r.0));
+                return self.pat_without_dbm(lhs.span, tuple_pat);
+            }
+            ExprKind::Paren(e) => {
+                // We special-case `(..)` for consistency with patterns.
+                if let ExprKind::Range(None, None, RangeLimits::HalfOpen) = e.kind {
+                    let tuple_pat = hir::PatKind::Tuple(&[], Some(0));
+                    return self.pat_without_dbm(lhs.span, tuple_pat);
+                } else {
+                    return self.destructure_assign(e, eq_sign_span, assignments);
+                }
+            }
+            _ => {}
+        }
+        // Treat all other cases as normal lvalue.
+        let ident = Ident::new(sym::lhs, lhs.span);
+        let (pat, binding) = self.pat_ident(lhs.span, ident);
+        let ident = self.expr_ident(lhs.span, ident, binding);
+        let assign = hir::ExprKind::Assign(self.lower_expr(lhs), ident, eq_sign_span);
+        let expr = self.expr(lhs.span, assign, ThinVec::new());
+        assignments.push(self.stmt_expr(lhs.span, expr));
+        pat
+    }
+
+    /// Destructure a sequence of expressions occurring on the LHS of an assignment.
+    /// Such a sequence occurs in a tuple (struct)/slice.
+    /// Return a sequence of corresponding patterns, and the index and the span of `..` if it
+    /// exists.
+    /// Each sub-assignment is recorded in `assignments`.
+    fn destructure_sequence(
+        &mut self,
+        elements: &[AstP<Expr>],
+        ctx: &str,
+        eq_sign_span: Span,
+        assignments: &mut Vec<hir::Stmt<'hir>>,
+    ) -> (&'hir [&'hir hir::Pat<'hir>], Option<(usize, Span)>) {
+        let mut rest = None;
+        let elements =
+            self.arena.alloc_from_iter(elements.iter().enumerate().filter_map(|(i, e)| {
+                // Check for `..` pattern.
+                if let ExprKind::Range(None, None, RangeLimits::HalfOpen) = e.kind {
+                    if let Some((_, prev_span)) = rest {
+                        self.ban_extra_rest_pat(e.span, prev_span, ctx);
+                    } else {
+                        rest = Some((i, e.span));
+                    }
+                    None
+                } else {
+                    Some(self.destructure_assign(e, eq_sign_span, assignments))
+                }
+            }));
+        (elements, rest)
+    }
+
     /// Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
     fn lower_expr_range_closed(&mut self, span: Span, e1: &Expr, e2: &Expr) -> hir::ExprKind<'hir> {
         let e1 = self.lower_expr_mut(e1);

Diff for: compiler/rustc_ast_lowering/src/lib.rs

@@ -2531,6 +2531,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 hir_id,
                 kind: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
                 span,
+                default_binding_modes: true,
             }),
             hir_id,
         )
@@ -2541,7 +2542,21 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn pat(&mut self, span: Span, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
-        self.arena.alloc(hir::Pat { hir_id: self.next_id(), kind, span })
+        self.arena.alloc(hir::Pat {
+            hir_id: self.next_id(),
+            kind,
+            span,
+            default_binding_modes: true,
+        })
+    }
+
+    fn pat_without_dbm(&mut self, span: Span, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
+        self.arena.alloc(hir::Pat {
+            hir_id: self.next_id(),
+            kind,
+            span,
+            default_binding_modes: false,
+        })
     }
 
     fn ty_path(

Diff for: compiler/rustc_ast_lowering/src/pat.rs

@@ -273,11 +273,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
     /// Construct a `Pat` with the `HirId` of `p.id` lowered.
     fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
-        self.arena.alloc(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span })
+        self.arena.alloc(hir::Pat {
+            hir_id: self.lower_node_id(p.id),
+            kind,
+            span: p.span,
+            default_binding_modes: true,
+        })
     }
 
     /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
-    fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
+    crate fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
         self.diagnostic()
             .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
             .span_label(sp, &format!("can only be used once per {} pattern", ctx))

Diff for: compiler/rustc_codegen_cranelift/src/common.rs

@@ -361,13 +361,11 @@ impl<'tcx, M: Module> FunctionCx<'_, 'tcx, M> {
     where
         T: TypeFoldable<'tcx> + Copy,
     {
-        if let Some(substs) = self.instance.substs_for_mir_body() {
-            self.tcx
-                .subst_and_normalize_erasing_regions(substs, ty::ParamEnv::reveal_all(), value)
-        } else {
-            self.tcx
-                .normalize_erasing_regions(ty::ParamEnv::reveal_all(), *value)
-        }
+        self.instance.subst_mir_and_normalize_erasing_regions(
+            self.tcx,
+            ty::ParamEnv::reveal_all(),
+            value
+        )
     }
 
     pub(crate) fn clif_type(&self, ty: Ty<'tcx>) -> Option<Type> {

Diff for: compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -92,15 +92,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         T: Copy + TypeFoldable<'tcx>,
     {
         debug!("monomorphize: self.instance={:?}", self.instance);
-        if let Some(substs) = self.instance.substs_for_mir_body() {
-            self.cx.tcx().subst_and_normalize_erasing_regions(
-                substs,
-                ty::ParamEnv::reveal_all(),
-                &value,
-            )
-        } else {
-            self.cx.tcx().normalize_erasing_regions(ty::ParamEnv::reveal_all(), *value)
-        }
+        self.instance.subst_mir_and_normalize_erasing_regions(
+            self.cx.tcx(),
+            ty::ParamEnv::reveal_all(),
+            value,
+        )
     }
 }
 

Diff for: compiler/rustc_feature/src/active.rs

@@ -610,6 +610,9 @@ declare_features! (
     /// Allows unsized fn parameters.
     (active, unsized_fn_params, "1.49.0", Some(48055), None),
 
+    /// Allows the use of destructuring assignments.
+    (active, destructuring_assignment, "1.49.0", Some(71126), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------