From 440d9372a2b8dfd01a98ba16a68f750792ab43fa Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 18 Sep 2021 18:04:40 -0400
Subject: [PATCH 1/8] Workaround ICE with if-let and RFC 2229

---
 compiler/rustc_errors/src/lib.rs         |  6 ++----
 compiler/rustc_typeck/src/astconv/mod.rs | 11 ++++++-----
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index b1526cf78d2..03e8534ef28 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -1028,15 +1028,13 @@ impl HandlerInner {
             let mut error_codes = self
                 .emitted_diagnostic_codes
                 .iter()
-                .filter_map(|x| {
-                    match &x {
+                .filter_map(|x| match &x {
                     DiagnosticId::Error(s)
-                        if let Ok(Some(_explanation)) = registry.try_find_description(s) =>
+                        if registry.try_find_description(s).map_or(false, |o| o.is_some()) =>
                     {
                         Some(s.clone())
                     }
                     _ => None,
-                }
                 })
                 .collect::<Vec<_>>();
             if !error_codes.is_empty() {
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index 2f2223ee822..33df541eb2b 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -2417,13 +2417,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
             if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
                 // Our own parameters are the resolved lifetimes.
-                match param.kind {
-                    GenericParamDefKind::Lifetime
-                        if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] =>
-                    {
+                if let GenericParamDefKind::Lifetime = param.kind {
+                    if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
                         self.ast_region_to_region(lifetime, None).into()
+                    } else {
+                        bug!()
                     }
-                    _ => bug!(),
+                } else {
+                    bug!()
                 }
             } else {
                 match param.kind {

From 5e1a614b5369c430a383beaf1aec04f09740edbb Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 19 Sep 2021 10:36:17 -0400
Subject: [PATCH 2/8] Adjust to SourceType::InTree in several places

These were left over in migrations to subtrees, which should generally be treated
as-if it was local.

Also fixes a warning caused by this change.
---
 .../rustc_codegen_cranelift/src/bin/cg_clif_build_sysroot.rs   | 1 -
 src/bootstrap/check.rs                                         | 2 +-
 src/bootstrap/compile.rs                                       | 3 +--
 src/bootstrap/test.rs                                          | 2 +-
 4 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_codegen_cranelift/src/bin/cg_clif_build_sysroot.rs b/compiler/rustc_codegen_cranelift/src/bin/cg_clif_build_sysroot.rs
index e7cd5edbbf6..89e0cb8d90e 100644
--- a/compiler/rustc_codegen_cranelift/src/bin/cg_clif_build_sysroot.rs
+++ b/compiler/rustc_codegen_cranelift/src/bin/cg_clif_build_sysroot.rs
@@ -8,7 +8,6 @@
 
 #![feature(rustc_private)]
 
-extern crate rustc_data_structures;
 extern crate rustc_driver;
 extern crate rustc_interface;
 extern crate rustc_session;
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index f5fad4b4136..f66f282bea9 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -262,7 +262,7 @@ impl Step for CodegenBackend {
         let mut cargo = builder.cargo(
             compiler,
             Mode::Codegen,
-            SourceType::Submodule,
+            SourceType::InTree,
             target,
             cargo_subcommand(builder.kind),
         );
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index df9e9bce415..ae234fb1dc7 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -817,8 +817,7 @@ impl Step for CodegenBackend {
 
         let out_dir = builder.cargo_out(compiler, Mode::Codegen, target);
 
-        let mut cargo =
-            builder.cargo(compiler, Mode::Codegen, SourceType::Submodule, target, "build");
+        let mut cargo = builder.cargo(compiler, Mode::Codegen, SourceType::InTree, target, "build");
         cargo
             .arg("--manifest-path")
             .arg(builder.src.join(format!("compiler/rustc_codegen_{}/Cargo.toml", backend)));
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 386ffb384a8..272b7153111 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -390,7 +390,7 @@ impl Step for Rustfmt {
             host,
             "test",
             "src/tools/rustfmt",
-            SourceType::Submodule,
+            SourceType::InTree,
             &[],
         );
 

From 45b989a03319c6a53bb726ec98dfe7d172035ac6 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 18 Sep 2021 17:37:24 -0400
Subject: [PATCH 3/8] Enable 2021 compatibility lints for all in-tree code

This just applies the suggested fixes from the compatibility warnings,
leaving any that are in practice spurious in. This is primarily intended to
provide a starting point to identify possible fixes to the migrations (e.g., by
avoiding spurious warnings).

A secondary commit cleans these up where they are false positives (as is true in
many of the cases).
---
 compiler/rustc_codegen_llvm/src/back/lto.rs   |  7 ++--
 .../src/interpret/validity.rs                 |  2 +-
 compiler/rustc_infer/src/infer/at.rs          | 32 +++++++++----------
 compiler/rustc_interface/src/util.rs          |  1 +
 compiler/rustc_mir_build/src/lints.rs         |  1 +
 .../src/traits/query/type_op/custom.rs        |  5 ++-
 .../src/traits/specialize/mod.rs              |  1 +
 .../traits/specialize/specialization_graph.rs | 29 +++++++++--------
 .../rustc_typeck/src/check/compare_method.rs  |  1 +
 .../rustc_typeck/src/check/method/probe.rs    |  1 +
 src/librustdoc/doctest.rs                     |  1 +
 src/tools/clippy/clippy_utils/src/lib.rs      |  5 ++-
 12 files changed, 52 insertions(+), 34 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index f612785e5a4..fcb79c8332c 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -906,8 +906,11 @@ impl ThinLTOKeysMap {
     ) -> Self {
         let keys = iter::zip(modules, names)
             .map(|(module, name)| {
-                let key = build_string(|rust_str| unsafe {
-                    llvm::LLVMRustComputeLTOCacheKey(rust_str, module.identifier, data.0);
+                let key = build_string(|rust_str| {
+                    let _ = &data;
+                    unsafe {
+                        llvm::LLVMRustComputeLTOCacheKey(rust_str, module.identifier, data.0);
+                    }
                 })
                 .expect("Invalid ThinLTO module key");
                 (name.clone().into_string().unwrap(), key)
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index a6375ad0e02..fc69770bf6a 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -77,7 +77,7 @@ macro_rules! throw_validation_failure {
 ///
 macro_rules! try_validation {
     ($e:expr, $where:expr,
-    $( $( $p:pat )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)?
+    $( $( $p:pat_param )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)?
     ) => {{
         match $e {
             Ok(x) => x,
diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs
index 11ee8fb17ad..33ce8f5f97f 100644
--- a/compiler/rustc_infer/src/infer/at.rs
+++ b/compiler/rustc_infer/src/infer/at.rs
@@ -195,10 +195,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields
-                .sub(a_is_expected)
-                .relate(a, b)
-                .map(move |_| InferOk { value: (), obligations: fields.obligations })
+            fields.sub(a_is_expected).relate(a, b).map(move |_| {
+                let _ = &fields;
+                InferOk { value: (), obligations: fields.obligations }
+            })
         })
     }
 
@@ -212,10 +212,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields
-                .equate(a_is_expected)
-                .relate(a, b)
-                .map(move |_| InferOk { value: (), obligations: fields.obligations })
+            fields.equate(a_is_expected).relate(a, b).map(move |_| {
+                let _ = &fields;
+                InferOk { value: (), obligations: fields.obligations }
+            })
         })
     }
 
@@ -227,10 +227,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields
-                .lub(a_is_expected)
-                .relate(a, b)
-                .map(move |t| InferOk { value: t, obligations: fields.obligations })
+            fields.lub(a_is_expected).relate(a, b).map(move |t| {
+                let _ = &fields;
+                InferOk { value: t, obligations: fields.obligations }
+            })
         })
     }
 
@@ -242,10 +242,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields
-                .glb(a_is_expected)
-                .relate(a, b)
-                .map(move |t| InferOk { value: t, obligations: fields.obligations })
+            fields.glb(a_is_expected).relate(a, b).map(move |t| {
+                let _ = &fields;
+                InferOk { value: t, obligations: fields.obligations }
+            })
         })
     }
 }
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index a5f0c014778..3d90a6c9345 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -125,6 +125,7 @@ pub fn scoped_thread<F: FnOnce() -> R + Send, R: Send>(cfg: thread::Builder, f:
     let result_ptr = Ptr(&mut result as *mut _ as *mut ());
 
     let thread = cfg.spawn(move || {
+        let _ = (&run, &result_ptr);
         let run = unsafe { (*(run.0 as *mut Option<F>)).take().unwrap() };
         let result = unsafe { &mut *(result_ptr.0 as *mut Option<R>) };
         *result = Some(run());
diff --git a/compiler/rustc_mir_build/src/lints.rs b/compiler/rustc_mir_build/src/lints.rs
index ef8bd20d510..2d408e577d1 100644
--- a/compiler/rustc_mir_build/src/lints.rs
+++ b/compiler/rustc_mir_build/src/lints.rs
@@ -41,6 +41,7 @@ crate fn check<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         let sp = tcx.sess.source_map().guess_head_span(tcx.hir().span_with_body(hir_id));
         tcx.struct_span_lint_hir(UNCONDITIONAL_RECURSION, hir_id, sp, |lint| {
+            let _ = &vis;
             let mut db = lint.build("function cannot return without recursing");
             db.span_label(sp, "cannot return without recursing");
             // offer some help to the programmer.
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
index b5398f8a435..8ee217655d9 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
@@ -40,7 +40,10 @@ where
             info!("fully_perform({:?})", self);
         }
 
-        scrape_region_constraints(infcx, || (self.closure)(infcx))
+        scrape_region_constraints(infcx, || {
+            let _ = &self;
+            (self.closure)(infcx)
+        })
     }
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 88aca794a6b..36fe0594983 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -394,6 +394,7 @@ fn report_conflicting_impls(
     // now because the struct_lint methods don't return back the DiagnosticBuilder
     // that's passed in.
     let decorate = |err: LintDiagnosticBuilder<'_>| {
+        let _ = &overlap;
         let msg = format!(
             "conflicting implementations of trait `{}`{}{}",
             overlap.trait_desc,
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
index c8bcab6efd7..c3e5b79c8f4 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
@@ -104,19 +104,22 @@ impl ChildrenExt for Children {
                 let self_ty = trait_ref.self_ty();
 
                 // FIXME: should postpone string formatting until we decide to actually emit.
-                with_no_trimmed_paths(|| OverlapError {
-                    with_impl: possible_sibling,
-                    trait_desc: trait_ref.print_only_trait_path().to_string(),
-                    // Only report the `Self` type if it has at least
-                    // some outer concrete shell; otherwise, it's
-                    // not adding much information.
-                    self_desc: if self_ty.has_concrete_skeleton() {
-                        Some(self_ty.to_string())
-                    } else {
-                        None
-                    },
-                    intercrate_ambiguity_causes: overlap.intercrate_ambiguity_causes,
-                    involves_placeholder: overlap.involves_placeholder,
+                with_no_trimmed_paths(|| {
+                    let _ = &overlap;
+                    OverlapError {
+                        with_impl: possible_sibling,
+                        trait_desc: trait_ref.print_only_trait_path().to_string(),
+                        // Only report the `Self` type if it has at least
+                        // some outer concrete shell; otherwise, it's
+                        // not adding much information.
+                        self_desc: if self_ty.has_concrete_skeleton() {
+                            Some(self_ty.to_string())
+                        } else {
+                            None
+                        },
+                        intercrate_ambiguity_causes: overlap.intercrate_ambiguity_causes,
+                        involves_placeholder: overlap.involves_placeholder,
+                    }
                 })
             };
 
diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
index d5b631df058..b359e8b2ebe 100644
--- a/compiler/rustc_typeck/src/check/compare_method.rs
+++ b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -1192,6 +1192,7 @@ fn compare_type_predicate_entailment<'tcx>(
         normalize_cause.clone(),
     );
     tcx.infer_ctxt().enter(|infcx| {
+        let _ = &impl_ty_own_bounds;
         let inh = Inherited::new(infcx, impl_ty.def_id.expect_local());
         let infcx = &inh.infcx;
 
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index cbfdce96bc5..56b15883013 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -441,6 +441,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // this creates one big transaction so that all type variables etc
         // that we create during the probe process are removed later
         self.probe(|_| {
+            let _ = &steps;
             let mut probe_cx = ProbeContext::new(
                 self,
                 span,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index dbeea9cddf3..71bdfdd4ade 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -964,6 +964,7 @@ impl Tester for Collector {
                 test_type: test::TestType::DocTest,
             },
             testfn: test::DynTestFn(Box::new(move || {
+                let _ = &config;
                 let report_unused_externs = |uext| {
                     unused_externs.lock().unwrap().push(uext);
                 };
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 3a94f472983..5c505f6851a 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -990,7 +990,10 @@ pub fn can_move_expr_to_closure(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) ->
         captures: HirIdMap::default(),
     };
     v.visit_expr(expr);
-    v.allow_closure.then(|| v.captures)
+    v.allow_closure.then(|| {
+        let _ = &v;
+        v.captures
+    })
 }
 
 /// Returns the method names and argument list of nested method call expressions that make up

From c746be2219fac78e5adad715082dedeb2d737f0d Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 19 Sep 2021 12:49:55 -0400
Subject: [PATCH 4/8] Migrate to 2021

---
 compiler/rustc/Cargo.toml                                       | 2 +-
 compiler/rustc_apfloat/Cargo.toml                               | 2 +-
 compiler/rustc_arena/Cargo.toml                                 | 2 +-
 compiler/rustc_ast/Cargo.toml                                   | 2 +-
 compiler/rustc_ast_lowering/Cargo.toml                          | 2 +-
 compiler/rustc_ast_passes/Cargo.toml                            | 2 +-
 compiler/rustc_ast_pretty/Cargo.toml                            | 2 +-
 compiler/rustc_attr/Cargo.toml                                  | 2 +-
 compiler/rustc_borrowck/Cargo.toml                              | 2 +-
 compiler/rustc_builtin_macros/Cargo.toml                        | 2 +-
 compiler/rustc_codegen_cranelift/Cargo.toml                     | 2 +-
 compiler/rustc_codegen_llvm/Cargo.toml                          | 2 +-
 compiler/rustc_codegen_ssa/Cargo.toml                           | 2 +-
 compiler/rustc_const_eval/Cargo.toml                            | 2 +-
 compiler/rustc_data_structures/Cargo.toml                       | 2 +-
 compiler/rustc_driver/Cargo.toml                                | 2 +-
 compiler/rustc_error_codes/Cargo.toml                           | 2 +-
 compiler/rustc_errors/Cargo.toml                                | 2 +-
 compiler/rustc_expand/Cargo.toml                                | 2 +-
 compiler/rustc_feature/Cargo.toml                               | 2 +-
 compiler/rustc_fs_util/Cargo.toml                               | 2 +-
 compiler/rustc_graphviz/Cargo.toml                              | 2 +-
 compiler/rustc_hir/Cargo.toml                                   | 2 +-
 compiler/rustc_hir_pretty/Cargo.toml                            | 2 +-
 compiler/rustc_incremental/Cargo.toml                           | 2 +-
 compiler/rustc_index/Cargo.toml                                 | 2 +-
 compiler/rustc_infer/Cargo.toml                                 | 2 +-
 compiler/rustc_interface/Cargo.toml                             | 2 +-
 compiler/rustc_lexer/Cargo.toml                                 | 2 +-
 compiler/rustc_lint/Cargo.toml                                  | 2 +-
 compiler/rustc_lint_defs/Cargo.toml                             | 2 +-
 compiler/rustc_llvm/Cargo.toml                                  | 2 +-
 compiler/rustc_macros/Cargo.toml                                | 2 +-
 compiler/rustc_metadata/Cargo.toml                              | 2 +-
 compiler/rustc_middle/Cargo.toml                                | 2 +-
 compiler/rustc_mir_build/Cargo.toml                             | 2 +-
 compiler/rustc_mir_dataflow/Cargo.toml                          | 2 +-
 compiler/rustc_mir_transform/Cargo.toml                         | 2 +-
 .../rustc_mir_transform/src/coverage/test_macros/Cargo.toml     | 2 +-
 compiler/rustc_monomorphize/Cargo.toml                          | 2 +-
 compiler/rustc_parse/Cargo.toml                                 | 2 +-
 compiler/rustc_parse_format/Cargo.toml                          | 2 +-
 compiler/rustc_passes/Cargo.toml                                | 2 +-
 compiler/rustc_plugin_impl/Cargo.toml                           | 2 +-
 compiler/rustc_privacy/Cargo.toml                               | 2 +-
 compiler/rustc_query_impl/Cargo.toml                            | 2 +-
 compiler/rustc_query_system/Cargo.toml                          | 2 +-
 compiler/rustc_resolve/Cargo.toml                               | 2 +-
 compiler/rustc_save_analysis/Cargo.toml                         | 2 +-
 compiler/rustc_serialize/Cargo.toml                             | 2 +-
 compiler/rustc_session/Cargo.toml                               | 2 +-
 compiler/rustc_span/Cargo.toml                                  | 2 +-
 compiler/rustc_symbol_mangling/Cargo.toml                       | 2 +-
 compiler/rustc_target/Cargo.toml                                | 2 +-
 compiler/rustc_trait_selection/Cargo.toml                       | 2 +-
 compiler/rustc_traits/Cargo.toml                                | 2 +-
 compiler/rustc_ty_utils/Cargo.toml                              | 2 +-
 compiler/rustc_type_ir/Cargo.toml                               | 2 +-
 compiler/rustc_typeck/Cargo.toml                                | 2 +-
 src/bootstrap/Cargo.toml                                        | 2 +-
 src/build_helper/Cargo.toml                                     | 2 +-
 src/etc/test-float-parse/Cargo.toml                             | 2 +-
 src/librustdoc/Cargo.toml                                       | 2 +-
 src/rustdoc-json-types/Cargo.toml                               | 2 +-
 src/tools/build-manifest/Cargo.toml                             | 2 +-
 src/tools/bump-stage0/Cargo.toml                                | 2 +-
 src/tools/cargotest/Cargo.toml                                  | 2 +-
 src/tools/compiletest/Cargo.toml                                | 2 +-
 src/tools/error_index_generator/Cargo.toml                      | 2 +-
 src/tools/expand-yaml-anchors/Cargo.toml                        | 2 +-
 src/tools/html-checker/Cargo.toml                               | 2 +-
 src/tools/jsondocck/Cargo.toml                                  | 2 +-
 src/tools/linkchecker/Cargo.toml                                | 2 +-
 src/tools/lint-docs/Cargo.toml                                  | 2 +-
 src/tools/remote-test-client/Cargo.toml                         | 2 +-
 src/tools/remote-test-server/Cargo.toml                         | 2 +-
 src/tools/rust-demangler/Cargo.toml                             | 2 +-
 src/tools/rustbook/Cargo.toml                                   | 2 +-
 src/tools/rustc-workspace-hack/Cargo.toml                       | 2 +-
 src/tools/rustdoc-themes/Cargo.toml                             | 2 +-
 src/tools/rustdoc/Cargo.toml                                    | 2 +-
 src/tools/rustfmt/Cargo.toml                                    | 2 +-
 src/tools/tidy/Cargo.toml                                       | 2 +-
 src/tools/tier-check/Cargo.toml                                 | 2 +-
 src/tools/unicode-table-generator/Cargo.toml                    | 2 +-
 src/tools/unstable-book-gen/Cargo.toml                          | 2 +-
 src/tools/x/Cargo.toml                                          | 2 +-
 87 files changed, 87 insertions(+), 87 deletions(-)

diff --git a/compiler/rustc/Cargo.toml b/compiler/rustc/Cargo.toml
index 37f90bf3c10..277cf0f51d3 100644
--- a/compiler/rustc/Cargo.toml
+++ b/compiler/rustc/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc-main"
 version = "0.0.0"
-edition = '2018'
+edition = "2021"
 
 [dependencies]
 rustc_driver = { path = "../rustc_driver" }
diff --git a/compiler/rustc_apfloat/Cargo.toml b/compiler/rustc_apfloat/Cargo.toml
index 9f266b1fb97..bb01d4f51b8 100644
--- a/compiler/rustc_apfloat/Cargo.toml
+++ b/compiler/rustc_apfloat/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_apfloat"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 bitflags = "1.2.1"
diff --git a/compiler/rustc_arena/Cargo.toml b/compiler/rustc_arena/Cargo.toml
index eba8a2a082f..33ccd044503 100644
--- a/compiler/rustc_arena/Cargo.toml
+++ b/compiler/rustc_arena/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_arena"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_ast/Cargo.toml b/compiler/rustc_ast/Cargo.toml
index 67cf5d92b00..58b967a3704 100644
--- a/compiler/rustc_ast/Cargo.toml
+++ b/compiler/rustc_ast/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_ast"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_ast_lowering/Cargo.toml b/compiler/rustc_ast_lowering/Cargo.toml
index 4e848a6a2b8..f4859ee4ae9 100644
--- a/compiler/rustc_ast_lowering/Cargo.toml
+++ b/compiler/rustc_ast_lowering/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_ast_lowering"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_ast_passes/Cargo.toml b/compiler/rustc_ast_passes/Cargo.toml
index 4a6eb80fb30..9312a68bc60 100644
--- a/compiler/rustc_ast_passes/Cargo.toml
+++ b/compiler/rustc_ast_passes/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_ast_passes"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 itertools = "0.9"
diff --git a/compiler/rustc_ast_pretty/Cargo.toml b/compiler/rustc_ast_pretty/Cargo.toml
index fa88740103b..29f2be4cf46 100644
--- a/compiler/rustc_ast_pretty/Cargo.toml
+++ b/compiler/rustc_ast_pretty/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_ast_pretty"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_attr/Cargo.toml b/compiler/rustc_attr/Cargo.toml
index 0566379e1f5..ba310a6860e 100644
--- a/compiler/rustc_attr/Cargo.toml
+++ b/compiler/rustc_attr/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_attr"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_borrowck/Cargo.toml b/compiler/rustc_borrowck/Cargo.toml
index c683c388ba9..75e9c69af4e 100644
--- a/compiler/rustc_borrowck/Cargo.toml
+++ b/compiler/rustc_borrowck/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_borrowck"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index 2370ac201b0..fd34f947f72 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_builtin_macros"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_codegen_cranelift/Cargo.toml b/compiler/rustc_codegen_cranelift/Cargo.toml
index 6f40fc0fcb8..61d40702a32 100644
--- a/compiler/rustc_codegen_cranelift/Cargo.toml
+++ b/compiler/rustc_codegen_cranelift/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_codegen_cranelift"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 crate-type = ["dylib"]
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index 3c99febbd57..3f024434581 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_codegen_llvm"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 1446624b881..0713e167c53 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_codegen_ssa"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/compiler/rustc_const_eval/Cargo.toml b/compiler/rustc_const_eval/Cargo.toml
index 1653d5cf6c5..a51273732ae 100644
--- a/compiler/rustc_const_eval/Cargo.toml
+++ b/compiler/rustc_const_eval/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_const_eval"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
index bc13ca26e2e..49962570129 100644
--- a/compiler/rustc_data_structures/Cargo.toml
+++ b/compiler/rustc_data_structures/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_data_structures"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_driver/Cargo.toml b/compiler/rustc_driver/Cargo.toml
index ba8616cc6ef..6721e00027d 100644
--- a/compiler/rustc_driver/Cargo.toml
+++ b/compiler/rustc_driver/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_driver"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 crate-type = ["dylib"]
diff --git a/compiler/rustc_error_codes/Cargo.toml b/compiler/rustc_error_codes/Cargo.toml
index 270e5301895..7d5f3e4672a 100644
--- a/compiler/rustc_error_codes/Cargo.toml
+++ b/compiler/rustc_error_codes/Cargo.toml
@@ -1,4 +1,4 @@
 [package]
 name = "rustc_error_codes"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index c74fd60e530..4846dc43605 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_errors"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_expand/Cargo.toml b/compiler/rustc_expand/Cargo.toml
index 1be9321e4fe..45237ab2e9f 100644
--- a/compiler/rustc_expand/Cargo.toml
+++ b/compiler/rustc_expand/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_expand"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 build = false
 
 [lib]
diff --git a/compiler/rustc_feature/Cargo.toml b/compiler/rustc_feature/Cargo.toml
index ee381e34251..3d8d0db20d1 100644
--- a/compiler/rustc_feature/Cargo.toml
+++ b/compiler/rustc_feature/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_feature"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_fs_util/Cargo.toml b/compiler/rustc_fs_util/Cargo.toml
index c417e978b31..34c3fe2a005 100644
--- a/compiler/rustc_fs_util/Cargo.toml
+++ b/compiler/rustc_fs_util/Cargo.toml
@@ -1,4 +1,4 @@
 [package]
 name = "rustc_fs_util"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
diff --git a/compiler/rustc_graphviz/Cargo.toml b/compiler/rustc_graphviz/Cargo.toml
index 87c41ae171e..d657fdb1a77 100644
--- a/compiler/rustc_graphviz/Cargo.toml
+++ b/compiler/rustc_graphviz/Cargo.toml
@@ -1,4 +1,4 @@
 [package]
 name = "rustc_graphviz"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index ff6758e66df..47bd4b7245b 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_hir"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_hir_pretty/Cargo.toml b/compiler/rustc_hir_pretty/Cargo.toml
index c7510b7ec14..46a8e7deeed 100644
--- a/compiler/rustc_hir_pretty/Cargo.toml
+++ b/compiler/rustc_hir_pretty/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_hir_pretty"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_incremental/Cargo.toml b/compiler/rustc_incremental/Cargo.toml
index 9156243a10c..dece752c194 100644
--- a/compiler/rustc_incremental/Cargo.toml
+++ b/compiler/rustc_incremental/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_incremental"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_index/Cargo.toml b/compiler/rustc_index/Cargo.toml
index e1a2b619763..b984a1321e0 100644
--- a/compiler/rustc_index/Cargo.toml
+++ b/compiler/rustc_index/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_index"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_infer/Cargo.toml b/compiler/rustc_infer/Cargo.toml
index 15649bb678e..f87ea43b1a7 100644
--- a/compiler/rustc_infer/Cargo.toml
+++ b/compiler/rustc_infer/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_infer"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
index e76fa6d8a1b..07af2201f5f 100644
--- a/compiler/rustc_interface/Cargo.toml
+++ b/compiler/rustc_interface/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_interface"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_lexer/Cargo.toml b/compiler/rustc_lexer/Cargo.toml
index 7e05fe545ca..60c146f457b 100644
--- a/compiler/rustc_lexer/Cargo.toml
+++ b/compiler/rustc_lexer/Cargo.toml
@@ -2,7 +2,7 @@
 name = "rustc_lexer"
 version = "0.1.0"
 license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
 
 repository = "https://github.com/rust-lang/rust/"
 description = """
diff --git a/compiler/rustc_lint/Cargo.toml b/compiler/rustc_lint/Cargo.toml
index 8294d5878fa..414fcbeb9e4 100644
--- a/compiler/rustc_lint/Cargo.toml
+++ b/compiler/rustc_lint/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_lint"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 if_chain = "1.0"
diff --git a/compiler/rustc_lint_defs/Cargo.toml b/compiler/rustc_lint_defs/Cargo.toml
index f9ada5cc95f..798d50819e2 100644
--- a/compiler/rustc_lint_defs/Cargo.toml
+++ b/compiler/rustc_lint_defs/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_lint_defs"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 rustc_ast = { path = "../rustc_ast" }
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index 2f0f3dd9ecb..d8dfcc84e68 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_llvm"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [features]
 static-libstdcpp = []
diff --git a/compiler/rustc_macros/Cargo.toml b/compiler/rustc_macros/Cargo.toml
index e4dddbab067..a9192be4d6e 100644
--- a/compiler/rustc_macros/Cargo.toml
+++ b/compiler/rustc_macros/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_macros"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 proc-macro = true
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index 42596f3318d..cc46a2fb9d3 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_metadata"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index 68b83fccc85..b1fcc34bee1 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_middle"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_mir_build/Cargo.toml b/compiler/rustc_mir_build/Cargo.toml
index e9fbc1b186d..998b80a36c2 100644
--- a/compiler/rustc_mir_build/Cargo.toml
+++ b/compiler/rustc_mir_build/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_mir_build"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_mir_dataflow/Cargo.toml b/compiler/rustc_mir_dataflow/Cargo.toml
index 3cd4892402e..ffd7e3cd06b 100644
--- a/compiler/rustc_mir_dataflow/Cargo.toml
+++ b/compiler/rustc_mir_dataflow/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_mir_dataflow"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_mir_transform/Cargo.toml b/compiler/rustc_mir_transform/Cargo.toml
index 5e1a587b0ec..bde4e215a2a 100644
--- a/compiler/rustc_mir_transform/Cargo.toml
+++ b/compiler/rustc_mir_transform/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_mir_transform"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_mir_transform/src/coverage/test_macros/Cargo.toml b/compiler/rustc_mir_transform/src/coverage/test_macros/Cargo.toml
index cc93fd482b5..f5e8b65656a 100644
--- a/compiler/rustc_mir_transform/src/coverage/test_macros/Cargo.toml
+++ b/compiler/rustc_mir_transform/src/coverage/test_macros/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "coverage_test_macros"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 proc-macro = true
diff --git a/compiler/rustc_monomorphize/Cargo.toml b/compiler/rustc_monomorphize/Cargo.toml
index 350ae088777..f812afe6b62 100644
--- a/compiler/rustc_monomorphize/Cargo.toml
+++ b/compiler/rustc_monomorphize/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_monomorphize"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_parse/Cargo.toml b/compiler/rustc_parse/Cargo.toml
index 1ca1a92252e..1decaaa955f 100644
--- a/compiler/rustc_parse/Cargo.toml
+++ b/compiler/rustc_parse/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_parse"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_parse_format/Cargo.toml b/compiler/rustc_parse_format/Cargo.toml
index 7b77560717e..aa1714e820f 100644
--- a/compiler/rustc_parse_format/Cargo.toml
+++ b/compiler/rustc_parse_format/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_parse_format"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index bf1e52cd9a8..39e578bce7e 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_passes"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tracing = "0.1"
diff --git a/compiler/rustc_plugin_impl/Cargo.toml b/compiler/rustc_plugin_impl/Cargo.toml
index c8eaca0703c..4e666e7e93d 100644
--- a/compiler/rustc_plugin_impl/Cargo.toml
+++ b/compiler/rustc_plugin_impl/Cargo.toml
@@ -2,7 +2,7 @@
 name = "rustc_plugin_impl"
 version = "0.0.0"
 build = false
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_privacy/Cargo.toml b/compiler/rustc_privacy/Cargo.toml
index 6ac2915c345..d952e288a64 100644
--- a/compiler/rustc_privacy/Cargo.toml
+++ b/compiler/rustc_privacy/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_privacy"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_query_impl/Cargo.toml b/compiler/rustc_query_impl/Cargo.toml
index 7c8dbe34240..89df3d4674b 100644
--- a/compiler/rustc_query_impl/Cargo.toml
+++ b/compiler/rustc_query_impl/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_query_impl"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_query_system/Cargo.toml b/compiler/rustc_query_system/Cargo.toml
index 47fb78be640..11c18a497e5 100644
--- a/compiler/rustc_query_system/Cargo.toml
+++ b/compiler/rustc_query_system/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_query_system"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 1581b056275..f1d3315d6e6 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_resolve"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/compiler/rustc_save_analysis/Cargo.toml b/compiler/rustc_save_analysis/Cargo.toml
index 535a48bcda1..15a89d82fa6 100644
--- a/compiler/rustc_save_analysis/Cargo.toml
+++ b/compiler/rustc_save_analysis/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_save_analysis"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tracing = "0.1"
diff --git a/compiler/rustc_serialize/Cargo.toml b/compiler/rustc_serialize/Cargo.toml
index 593a7563e36..49778f82253 100644
--- a/compiler/rustc_serialize/Cargo.toml
+++ b/compiler/rustc_serialize/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_serialize"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 indexmap = "1"
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index 5b617a2997c..4cff21bee3d 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_session"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 getopts = "0.2"
diff --git a/compiler/rustc_span/Cargo.toml b/compiler/rustc_span/Cargo.toml
index e475e89d87e..781fb8c1e5d 100644
--- a/compiler/rustc_span/Cargo.toml
+++ b/compiler/rustc_span/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_span"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_symbol_mangling/Cargo.toml b/compiler/rustc_symbol_mangling/Cargo.toml
index aebf77a1fd8..d5befa10e23 100644
--- a/compiler/rustc_symbol_mangling/Cargo.toml
+++ b/compiler/rustc_symbol_mangling/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_symbol_mangling"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_target/Cargo.toml b/compiler/rustc_target/Cargo.toml
index e47a84dbc11..925813e6bb4 100644
--- a/compiler/rustc_target/Cargo.toml
+++ b/compiler/rustc_target/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_target"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 bitflags = "1.2.1"
diff --git a/compiler/rustc_trait_selection/Cargo.toml b/compiler/rustc_trait_selection/Cargo.toml
index e2c626d1b22..9a9737362c6 100644
--- a/compiler/rustc_trait_selection/Cargo.toml
+++ b/compiler/rustc_trait_selection/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_trait_selection"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_traits/Cargo.toml b/compiler/rustc_traits/Cargo.toml
index 219165ff550..2e56a1bf683 100644
--- a/compiler/rustc_traits/Cargo.toml
+++ b/compiler/rustc_traits/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_traits"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tracing = "0.1"
diff --git a/compiler/rustc_ty_utils/Cargo.toml b/compiler/rustc_ty_utils/Cargo.toml
index 2eb27fb1ad6..78df95e680e 100644
--- a/compiler/rustc_ty_utils/Cargo.toml
+++ b/compiler/rustc_ty_utils/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_ty_utils"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tracing = "0.1"
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index 1f6acbe0d81..439e6cdf706 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_type_ir"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 doctest = false
diff --git a/compiler/rustc_typeck/Cargo.toml b/compiler/rustc_typeck/Cargo.toml
index dd76a5e4b99..7e570e151c5 100644
--- a/compiler/rustc_typeck/Cargo.toml
+++ b/compiler/rustc_typeck/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustc_typeck"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 0b76a13e02b..1ce1f0b26db 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "bootstrap"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 build = "build.rs"
 
 [lib]
diff --git a/src/build_helper/Cargo.toml b/src/build_helper/Cargo.toml
index 17a9e55b323..d88df0e08fa 100644
--- a/src/build_helper/Cargo.toml
+++ b/src/build_helper/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "build_helper"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/etc/test-float-parse/Cargo.toml b/src/etc/test-float-parse/Cargo.toml
index 8226e815c2c..7ee19a0b6d9 100644
--- a/src/etc/test-float-parse/Cargo.toml
+++ b/src/etc/test-float-parse/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "test-float-parse"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 publish = false
 
 [workspace]
diff --git a/src/librustdoc/Cargo.toml b/src/librustdoc/Cargo.toml
index e02cef235ae..945b2a8e9a8 100644
--- a/src/librustdoc/Cargo.toml
+++ b/src/librustdoc/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/rustdoc-json-types/Cargo.toml b/src/rustdoc-json-types/Cargo.toml
index a692f6f896d..d60699efd36 100644
--- a/src/rustdoc-json-types/Cargo.toml
+++ b/src/rustdoc-json-types/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-json-types"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/tools/build-manifest/Cargo.toml b/src/tools/build-manifest/Cargo.toml
index 334407c2b2e..340acff34f2 100644
--- a/src/tools/build-manifest/Cargo.toml
+++ b/src/tools/build-manifest/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "build-manifest"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 toml = "0.5"
diff --git a/src/tools/bump-stage0/Cargo.toml b/src/tools/bump-stage0/Cargo.toml
index 7d64e20a3d3..cf8840ff6ee 100644
--- a/src/tools/bump-stage0/Cargo.toml
+++ b/src/tools/bump-stage0/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "bump-stage0"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
diff --git a/src/tools/cargotest/Cargo.toml b/src/tools/cargotest/Cargo.toml
index a88272d2344..bfd894e2bd2 100644
--- a/src/tools/cargotest/Cargo.toml
+++ b/src/tools/cargotest/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "cargotest2"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "cargotest"
diff --git a/src/tools/compiletest/Cargo.toml b/src/tools/compiletest/Cargo.toml
index d6aa3fd2631..e9426a2d9f5 100644
--- a/src/tools/compiletest/Cargo.toml
+++ b/src/tools/compiletest/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "compiletest"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 colored = "2"
diff --git a/src/tools/error_index_generator/Cargo.toml b/src/tools/error_index_generator/Cargo.toml
index 2e4b7beb376..c84b79e11e9 100644
--- a/src/tools/error_index_generator/Cargo.toml
+++ b/src/tools/error_index_generator/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "error_index_generator"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 rustdoc = { path = "../../librustdoc" }
diff --git a/src/tools/expand-yaml-anchors/Cargo.toml b/src/tools/expand-yaml-anchors/Cargo.toml
index 358dff06532..9a25b6c1f1c 100644
--- a/src/tools/expand-yaml-anchors/Cargo.toml
+++ b/src/tools/expand-yaml-anchors/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "expand-yaml-anchors"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 yaml-rust = "0.4.3"
diff --git a/src/tools/html-checker/Cargo.toml b/src/tools/html-checker/Cargo.toml
index e88d2f0d928..34d3954db28 100644
--- a/src/tools/html-checker/Cargo.toml
+++ b/src/tools/html-checker/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "html-checker"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "html-checker"
diff --git a/src/tools/jsondocck/Cargo.toml b/src/tools/jsondocck/Cargo.toml
index a65deb12541..ccabe6483d7 100644
--- a/src/tools/jsondocck/Cargo.toml
+++ b/src/tools/jsondocck/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "jsondocck"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 jsonpath_lib = "0.2"
diff --git a/src/tools/linkchecker/Cargo.toml b/src/tools/linkchecker/Cargo.toml
index 21ba2269556..1d8f2f91882 100644
--- a/src/tools/linkchecker/Cargo.toml
+++ b/src/tools/linkchecker/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "linkchecker"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "linkchecker"
diff --git a/src/tools/lint-docs/Cargo.toml b/src/tools/lint-docs/Cargo.toml
index 6792887fa5d..3578bda8276 100644
--- a/src/tools/lint-docs/Cargo.toml
+++ b/src/tools/lint-docs/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "lint-docs"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 description = "A script to extract the lint documentation for the rustc book."
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
diff --git a/src/tools/remote-test-client/Cargo.toml b/src/tools/remote-test-client/Cargo.toml
index 7b20ba83546..d59cd6b3d8e 100644
--- a/src/tools/remote-test-client/Cargo.toml
+++ b/src/tools/remote-test-client/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "remote-test-client"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
diff --git a/src/tools/remote-test-server/Cargo.toml b/src/tools/remote-test-server/Cargo.toml
index 01309aec9a3..e6be8530cf6 100644
--- a/src/tools/remote-test-server/Cargo.toml
+++ b/src/tools/remote-test-server/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "remote-test-server"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
diff --git a/src/tools/rust-demangler/Cargo.toml b/src/tools/rust-demangler/Cargo.toml
index 157409bc847..2bb73b3262d 100644
--- a/src/tools/rust-demangler/Cargo.toml
+++ b/src/tools/rust-demangler/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rust-demangler"
 version = "0.0.1"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 regex = "1.0"
diff --git a/src/tools/rustbook/Cargo.toml b/src/tools/rustbook/Cargo.toml
index da36ce0e690..de1327d74ff 100644
--- a/src/tools/rustbook/Cargo.toml
+++ b/src/tools/rustbook/Cargo.toml
@@ -2,7 +2,7 @@
 name = "rustbook"
 version = "0.1.0"
 license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 clap = "2.25.0"
diff --git a/src/tools/rustc-workspace-hack/Cargo.toml b/src/tools/rustc-workspace-hack/Cargo.toml
index 38b9fefbaf5..a28cf28841e 100644
--- a/src/tools/rustc-workspace-hack/Cargo.toml
+++ b/src/tools/rustc-workspace-hack/Cargo.toml
@@ -5,7 +5,7 @@ license = 'MIT OR Apache-2.0'
 description = """
 Hack for the compiler's own build system
 """
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/tools/rustdoc-themes/Cargo.toml b/src/tools/rustdoc-themes/Cargo.toml
index 4b2ad982a84..3d8c77d36d7 100644
--- a/src/tools/rustdoc-themes/Cargo.toml
+++ b/src/tools/rustdoc-themes/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-themes"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "rustdoc-themes"
diff --git a/src/tools/rustdoc/Cargo.toml b/src/tools/rustdoc/Cargo.toml
index 5625707b25a..c4101f72cc2 100644
--- a/src/tools/rustdoc/Cargo.toml
+++ b/src/tools/rustdoc/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-tool"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 # Cargo adds a number of paths to the dylib search path on windows, which results in
 # the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
diff --git a/src/tools/rustfmt/Cargo.toml b/src/tools/rustfmt/Cargo.toml
index 81e3e26e8b0..7b4667c17c8 100644
--- a/src/tools/rustfmt/Cargo.toml
+++ b/src/tools/rustfmt/Cargo.toml
@@ -8,7 +8,7 @@ readme = "README.md"
 license = "Apache-2.0/MIT"
 build = "build.rs"
 categories = ["development-tools"]
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "rustfmt"
diff --git a/src/tools/tidy/Cargo.toml b/src/tools/tidy/Cargo.toml
index 57fe5a62e9a..69c8063f42e 100644
--- a/src/tools/tidy/Cargo.toml
+++ b/src/tools/tidy/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "tidy"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 autobins = false
 
 [dependencies]
diff --git a/src/tools/tier-check/Cargo.toml b/src/tools/tier-check/Cargo.toml
index d6119cac5f3..3f08165a3fc 100644
--- a/src/tools/tier-check/Cargo.toml
+++ b/src/tools/tier-check/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "tier-check"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 
 [dependencies]
diff --git a/src/tools/unicode-table-generator/Cargo.toml b/src/tools/unicode-table-generator/Cargo.toml
index 948773f7810..ef01877c0b9 100644
--- a/src/tools/unicode-table-generator/Cargo.toml
+++ b/src/tools/unicode-table-generator/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "unicode-bdd"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
diff --git a/src/tools/unstable-book-gen/Cargo.toml b/src/tools/unstable-book-gen/Cargo.toml
index febeaa446b3..73e5a91bec7 100644
--- a/src/tools/unstable-book-gen/Cargo.toml
+++ b/src/tools/unstable-book-gen/Cargo.toml
@@ -2,7 +2,7 @@
 name = "unstable-book-gen"
 version = "0.1.0"
 license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tidy = { path = "../tidy" }
diff --git a/src/tools/x/Cargo.toml b/src/tools/x/Cargo.toml
index 264a741159a..31502727962 100644
--- a/src/tools/x/Cargo.toml
+++ b/src/tools/x/Cargo.toml
@@ -2,5 +2,5 @@
 name = "x"
 version = "0.1.0"
 description = "Run x.py slightly more conveniently"
-edition = "2018"
+edition = "2021"
 publish = false

From 662daee6582c84cdb7fc9b053bba4fb211a73299 Mon Sep 17 00:00:00 2001
From: Noah Lev <camelidcamel@gmail.com>
Date: Sat, 18 Sep 2021 17:31:54 -0700
Subject: [PATCH 5/8] Adjust tidy edition lint to force 2021

This has a few exceptions today (library crates, a few submodules), but is
mostly accurate.
---
 src/tools/tidy/src/edition.rs | 44 ++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/src/tools/tidy/src/edition.rs b/src/tools/tidy/src/edition.rs
index 283c43e325c..b5e9ceddbaf 100644
--- a/src/tools/tidy/src/edition.rs
+++ b/src/tools/tidy/src/edition.rs
@@ -1,10 +1,15 @@
-//! Tidy check to ensure that crate `edition` is '2018'
+//! Tidy check to ensure that crate `edition` is '2018' or '2021'.
 
 use std::path::Path;
 
 fn is_edition_2018(mut line: &str) -> bool {
     line = line.trim();
-    line == "edition = \"2018\"" || line == "edition = \'2018\'"
+    line == "edition = \"2018\""
+}
+
+fn is_edition_2021(mut line: &str) -> bool {
+    line = line.trim();
+    line == "edition = \"2021\""
 }
 
 pub fn check(path: &Path, bad: &mut bool) {
@@ -13,17 +18,38 @@ pub fn check(path: &Path, bad: &mut bool) {
         &mut |path| super::filter_dirs(path) || path.ends_with("src/test"),
         &mut |entry, contents| {
             let file = entry.path();
+            let filestr = file.to_string_lossy().replace("\\", "/");
             let filename = file.file_name().unwrap();
             if filename != "Cargo.toml" {
                 return;
             }
-            let has_edition = contents.lines().any(is_edition_2018);
-            if !has_edition {
-                tidy_error!(
-                    bad,
-                    "{} doesn't have `edition = \"2018\"` on a separate line",
-                    file.display()
-                );
+
+            // Library crates are not yet ready to migrate to 2021.
+            //
+            // The reference and rustc-dev-guide are submodules, so are left at
+            // 2018 for now. They should be removed from this exception list
+            // when bumped.
+            if path.components().any(|c| c.as_os_str() == "library")
+                || filestr.contains("src/doc/reference/style-check/Cargo.toml")
+                || filestr.contains("src/doc/rustc-dev-guide/ci/date-check/Cargo.toml")
+            {
+                let has = contents.lines().any(is_edition_2018);
+                if !has {
+                    tidy_error!(
+                        bad,
+                        "{} doesn't have `edition = \"2018\"` on a separate line",
+                        file.display()
+                    );
+                }
+            } else {
+                let is_2021 = contents.lines().any(is_edition_2021);
+                if !is_2021 {
+                    tidy_error!(
+                        bad,
+                        "{} doesn't have `edition = \"2021\"` on a separate line",
+                        file.display()
+                    );
+                }
             }
         },
     );

From 5e344da2170da48f6fe7ba28770b11b00796fa5f Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 19 Sep 2021 13:13:16 -0400
Subject: [PATCH 6/8] Drop migration lint for Send/Sync bound in LTO backend

The closure in question does not require Send/Sync impls, so it's OK to lose
them when we just capture data.0.
---
 compiler/rustc_codegen_llvm/src/back/lto.rs | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index fcb79c8332c..f612785e5a4 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -906,11 +906,8 @@ impl ThinLTOKeysMap {
     ) -> Self {
         let keys = iter::zip(modules, names)
             .map(|(module, name)| {
-                let key = build_string(|rust_str| {
-                    let _ = &data;
-                    unsafe {
-                        llvm::LLVMRustComputeLTOCacheKey(rust_str, module.identifier, data.0);
-                    }
+                let key = build_string(|rust_str| unsafe {
+                    llvm::LLVMRustComputeLTOCacheKey(rust_str, module.identifier, data.0);
                 })
                 .expect("Invalid ThinLTO module key");
                 (name.clone().into_string().unwrap(), key)

From f33890082603434eb640dfd256819b0d722e911d Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 19 Sep 2021 13:46:05 -0400
Subject: [PATCH 7/8] Remove Drop-caused migration-added captures

All of these were added due to insignificant Drop types being present.
---
 compiler/rustc_infer/src/infer/at.rs          | 32 +++++++++----------
 compiler/rustc_mir_build/src/lints.rs         |  1 -
 .../src/traits/query/type_op/custom.rs        |  5 +--
 .../src/traits/specialize/mod.rs              |  1 -
 .../traits/specialize/specialization_graph.rs |  1 -
 .../rustc_typeck/src/check/compare_method.rs  |  1 -
 .../rustc_typeck/src/check/method/probe.rs    |  1 -
 src/librustdoc/doctest.rs                     |  1 -
 src/tools/clippy/clippy_utils/src/lib.rs      |  5 +--
 9 files changed, 18 insertions(+), 30 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs
index 33ce8f5f97f..11ee8fb17ad 100644
--- a/compiler/rustc_infer/src/infer/at.rs
+++ b/compiler/rustc_infer/src/infer/at.rs
@@ -195,10 +195,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields.sub(a_is_expected).relate(a, b).map(move |_| {
-                let _ = &fields;
-                InferOk { value: (), obligations: fields.obligations }
-            })
+            fields
+                .sub(a_is_expected)
+                .relate(a, b)
+                .map(move |_| InferOk { value: (), obligations: fields.obligations })
         })
     }
 
@@ -212,10 +212,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields.equate(a_is_expected).relate(a, b).map(move |_| {
-                let _ = &fields;
-                InferOk { value: (), obligations: fields.obligations }
-            })
+            fields
+                .equate(a_is_expected)
+                .relate(a, b)
+                .map(move |_| InferOk { value: (), obligations: fields.obligations })
         })
     }
 
@@ -227,10 +227,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields.lub(a_is_expected).relate(a, b).map(move |t| {
-                let _ = &fields;
-                InferOk { value: t, obligations: fields.obligations }
-            })
+            fields
+                .lub(a_is_expected)
+                .relate(a, b)
+                .map(move |t| InferOk { value: t, obligations: fields.obligations })
         })
     }
 
@@ -242,10 +242,10 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
         let Trace { at, trace, a_is_expected } = self;
         at.infcx.commit_if_ok(|_| {
             let mut fields = at.infcx.combine_fields(trace, at.param_env);
-            fields.glb(a_is_expected).relate(a, b).map(move |t| {
-                let _ = &fields;
-                InferOk { value: t, obligations: fields.obligations }
-            })
+            fields
+                .glb(a_is_expected)
+                .relate(a, b)
+                .map(move |t| InferOk { value: t, obligations: fields.obligations })
         })
     }
 }
diff --git a/compiler/rustc_mir_build/src/lints.rs b/compiler/rustc_mir_build/src/lints.rs
index 2d408e577d1..ef8bd20d510 100644
--- a/compiler/rustc_mir_build/src/lints.rs
+++ b/compiler/rustc_mir_build/src/lints.rs
@@ -41,7 +41,6 @@ crate fn check<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         let sp = tcx.sess.source_map().guess_head_span(tcx.hir().span_with_body(hir_id));
         tcx.struct_span_lint_hir(UNCONDITIONAL_RECURSION, hir_id, sp, |lint| {
-            let _ = &vis;
             let mut db = lint.build("function cannot return without recursing");
             db.span_label(sp, "cannot return without recursing");
             // offer some help to the programmer.
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
index 8ee217655d9..b5398f8a435 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
@@ -40,10 +40,7 @@ where
             info!("fully_perform({:?})", self);
         }
 
-        scrape_region_constraints(infcx, || {
-            let _ = &self;
-            (self.closure)(infcx)
-        })
+        scrape_region_constraints(infcx, || (self.closure)(infcx))
     }
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 36fe0594983..88aca794a6b 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -394,7 +394,6 @@ fn report_conflicting_impls(
     // now because the struct_lint methods don't return back the DiagnosticBuilder
     // that's passed in.
     let decorate = |err: LintDiagnosticBuilder<'_>| {
-        let _ = &overlap;
         let msg = format!(
             "conflicting implementations of trait `{}`{}{}",
             overlap.trait_desc,
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
index c3e5b79c8f4..2ecc169e1cf 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
@@ -105,7 +105,6 @@ impl ChildrenExt for Children {
 
                 // FIXME: should postpone string formatting until we decide to actually emit.
                 with_no_trimmed_paths(|| {
-                    let _ = &overlap;
                     OverlapError {
                         with_impl: possible_sibling,
                         trait_desc: trait_ref.print_only_trait_path().to_string(),
diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
index b359e8b2ebe..d5b631df058 100644
--- a/compiler/rustc_typeck/src/check/compare_method.rs
+++ b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -1192,7 +1192,6 @@ fn compare_type_predicate_entailment<'tcx>(
         normalize_cause.clone(),
     );
     tcx.infer_ctxt().enter(|infcx| {
-        let _ = &impl_ty_own_bounds;
         let inh = Inherited::new(infcx, impl_ty.def_id.expect_local());
         let infcx = &inh.infcx;
 
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index 56b15883013..cbfdce96bc5 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -441,7 +441,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // this creates one big transaction so that all type variables etc
         // that we create during the probe process are removed later
         self.probe(|_| {
-            let _ = &steps;
             let mut probe_cx = ProbeContext::new(
                 self,
                 span,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 71bdfdd4ade..dbeea9cddf3 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -964,7 +964,6 @@ impl Tester for Collector {
                 test_type: test::TestType::DocTest,
             },
             testfn: test::DynTestFn(Box::new(move || {
-                let _ = &config;
                 let report_unused_externs = |uext| {
                     unused_externs.lock().unwrap().push(uext);
                 };
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 5c505f6851a..3a94f472983 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -990,10 +990,7 @@ pub fn can_move_expr_to_closure(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) ->
         captures: HirIdMap::default(),
     };
     v.visit_expr(expr);
-    v.allow_closure.then(|| {
-        let _ = &v;
-        v.captures
-    })
+    v.allow_closure.then(|| v.captures)
 }
 
 /// Returns the method names and argument list of nested method call expressions that make up

From 3b896796719ed1e151d507b4bf2ea635a89cda9e Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Mon, 20 Sep 2021 08:46:26 -0400
Subject: [PATCH 8/8] Adjust documentation for compatibility with 2021

This also adjusts the lint docs generation to accept (and ignore) an allow
attribute, rather than expecting the documentation to be immediately followed by
the lint name.
---
 compiler/rustc_lint/src/array_into_iter.rs    |  2 +-
 compiler/rustc_lint/src/builtin.rs            |  2 +-
 compiler/rustc_lint/src/non_fmt_panic.rs      |  2 +-
 compiler/rustc_lint_defs/src/builtin.rs       |  6 ++-
 .../rustc_metadata/src/dependency_format.rs   | 44 +++++++++----------
 compiler/rustc_middle/src/middle/region.rs    |  3 +-
 src/tools/lint-docs/src/lib.rs                |  4 ++
 7 files changed, 35 insertions(+), 28 deletions(-)

diff --git a/compiler/rustc_lint/src/array_into_iter.rs b/compiler/rustc_lint/src/array_into_iter.rs
index 5ac42c50c72..1facd973754 100644
--- a/compiler/rustc_lint/src/array_into_iter.rs
+++ b/compiler/rustc_lint/src/array_into_iter.rs
@@ -13,7 +13,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust
+    /// ```rust,edition2018
     /// # #![allow(unused)]
     /// [1, 2, 3].into_iter().for_each(|n| { *n; });
     /// ```
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 2850e7a6b44..e1bcc3aa52b 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1686,7 +1686,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust
+    /// ```rust,edition2018
     /// let x = 123;
     /// match x {
     ///     0...100 => {}
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index 33a6edafa26..ae9c5ce5c3c 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -18,7 +18,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,no_run
+    /// ```rust,no_run,edition2018
     /// panic!("{}");
     /// panic!(123);
     /// ```
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index a00561e5213..b14abb9e5db 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -1584,7 +1584,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust
+    /// ```rust,edition2018
     /// trait Trait { }
     ///
     /// fn takes_trait_object(_: Box<Trait>) {
@@ -3313,7 +3313,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ```rust,edition2018,compile_fail
     /// #![deny(rust_2021_prefixes_incompatible_syntax)]
     ///
     /// macro_rules! m {
@@ -3333,6 +3333,8 @@ declare_lint! {
     ///
     /// This lint suggests to add whitespace between the `z` and `"hey"` tokens
     /// to keep them separated in Rust 2021.
+    // Allow this lint -- rustdoc doesn't yet support threading edition into this lint's parser.
+    #[allow(rustdoc::invalid_rust_codeblocks)]
     pub RUST_2021_PREFIXES_INCOMPATIBLE_SYNTAX,
     Allow,
     "identifiers that will be parsed as a prefix in Rust 2021",
diff --git a/compiler/rustc_metadata/src/dependency_format.rs b/compiler/rustc_metadata/src/dependency_format.rs
index b8d22560618..8c41fd9c4a2 100644
--- a/compiler/rustc_metadata/src/dependency_format.rs
+++ b/compiler/rustc_metadata/src/dependency_format.rs
@@ -11,10 +11,10 @@
 //! should be used when linking each output type requested in this session. This
 //! generally follows this set of rules:
 //!
-//!     1. Each library must appear exactly once in the output.
-//!     2. Each rlib contains only one library (it's just an object file)
-//!     3. Each dylib can contain more than one library (due to static linking),
-//!        and can also bring in many dynamic dependencies.
+//! 1. Each library must appear exactly once in the output.
+//! 2. Each rlib contains only one library (it's just an object file)
+//! 3. Each dylib can contain more than one library (due to static linking),
+//!    and can also bring in many dynamic dependencies.
 //!
 //! With these constraints in mind, it's generally a very difficult problem to
 //! find a solution that's not "all rlibs" or "all dylibs". I have suspicions
@@ -22,24 +22,24 @@
 //!
 //! The current selection algorithm below looks mostly similar to:
 //!
-//!     1. If static linking is required, then require all upstream dependencies
-//!        to be available as rlibs. If not, generate an error.
-//!     2. If static linking is requested (generating an executable), then
-//!        attempt to use all upstream dependencies as rlibs. If any are not
-//!        found, bail out and continue to step 3.
-//!     3. Static linking has failed, at least one library must be dynamically
-//!        linked. Apply a heuristic by greedily maximizing the number of
-//!        dynamically linked libraries.
-//!     4. Each upstream dependency available as a dynamic library is
-//!        registered. The dependencies all propagate, adding to a map. It is
-//!        possible for a dylib to add a static library as a dependency, but it
-//!        is illegal for two dylibs to add the same static library as a
-//!        dependency. The same dylib can be added twice. Additionally, it is
-//!        illegal to add a static dependency when it was previously found as a
-//!        dylib (and vice versa)
-//!     5. After all dynamic dependencies have been traversed, re-traverse the
-//!        remaining dependencies and add them statically (if they haven't been
-//!        added already).
+//! 1. If static linking is required, then require all upstream dependencies
+//!    to be available as rlibs. If not, generate an error.
+//! 2. If static linking is requested (generating an executable), then
+//!    attempt to use all upstream dependencies as rlibs. If any are not
+//!    found, bail out and continue to step 3.
+//! 3. Static linking has failed, at least one library must be dynamically
+//!    linked. Apply a heuristic by greedily maximizing the number of
+//!    dynamically linked libraries.
+//! 4. Each upstream dependency available as a dynamic library is
+//!    registered. The dependencies all propagate, adding to a map. It is
+//!    possible for a dylib to add a static library as a dependency, but it
+//!    is illegal for two dylibs to add the same static library as a
+//!    dependency. The same dylib can be added twice. Additionally, it is
+//!    illegal to add a static dependency when it was previously found as a
+//!    dylib (and vice versa)
+//! 5. After all dynamic dependencies have been traversed, re-traverse the
+//!    remaining dependencies and add them statically (if they haven't been
+//!    added already).
 //!
 //! While not perfect, this algorithm should help support use-cases such as leaf
 //! dependencies being static while the larger tree of inner dependencies are
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index bd4e83a42ef..e271f59da87 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -257,7 +257,8 @@ pub struct ScopeTree {
     /// ```
     ///
     /// With the HIR tree (calls numbered for expository purposes)
-    /// ```
+    ///
+    /// ```text
     ///     Call#0(foo, [Call#1(f), Yield(y), Call#2(bar, Call#3(g))])
     /// ```
     ///
diff --git a/src/tools/lint-docs/src/lib.rs b/src/tools/lint-docs/src/lib.rs
index e5c7f125712..fdc89a184da 100644
--- a/src/tools/lint-docs/src/lib.rs
+++ b/src/tools/lint-docs/src/lib.rs
@@ -149,6 +149,10 @@ impl<'a> LintExtractor<'a> {
                         } else if line.starts_with("// ") {
                             // Ignore comments.
                             continue;
+                        } else if line.starts_with("#[allow") {
+                            // Ignore allow of lints (useful for
+                            // invalid_rust_codeblocks).
+                            continue;
                         } else {
                             let name = lint_name(line).map_err(|e| {
                                 format!(