Merge branch 'master' into is-symlink-stabilization

Cargo.toml

@@ -89,6 +89,15 @@ gimli.debug = 0
 miniz_oxide.debug = 0
 object.debug = 0
 
+# The only package that ever uses debug builds is bootstrap.
+# We care a lot about bootstrap's compile times, so don't include debug info for
+# dependencies, only bootstrap itself.
+[profile.dev]
+debug = 0
+[profile.dev.package]
+# Only use debuginfo=1 to further reduce compile times.
+bootstrap.debug = 1
+
 # We want the RLS to use the version of Cargo that we've got vendored in this
 # repository to ensure that the same exact version of Cargo is used by both the
 # RLS and the Cargo binary itself. The RLS depends on Cargo as a git repository

RELEASES.md

@@ -64,7 +64,6 @@ Stabilised APIs
 - [`VecDeque::shrink_to`]
 - [`HashMap::shrink_to`]
 - [`HashSet::shrink_to`]
-- [`task::ready!`]
 
 These APIs are now usable in const contexts:
 
@@ -128,7 +127,6 @@ and related tools.
 [`VecDeque::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.shrink_to
 [`HashMap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_map/struct.HashMap.html#method.shrink_to
 [`HashSet::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_set/struct.HashSet.html#method.shrink_to
-[`task::ready!`]: https://doc.rust-lang.org/stable/std/task/macro.ready.html
 [`std::mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
 [`slice::first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first
 [`slice::split_first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first

compiler/rustc_apfloat/src/ieee.rs

@@ -389,6 +389,7 @@ impl<S: Semantics> fmt::Display for IeeeFloat<S> {
         let _: Loss = sig::shift_right(&mut sig, &mut exp, trailing_zeros as usize);
 
         // Change the exponent from 2^e to 10^e.
+        #[allow(clippy::comparison_chain)]
         if exp == 0 {
             // Nothing to do.
         } else if exp > 0 {
@@ -2526,6 +2527,7 @@ mod sig {
         if *a_sign ^ b_sign {
             let (reverse, loss);
 
+            #[allow(clippy::comparison_chain)]
             if bits == 0 {
                 reverse = cmp(a_sig, b_sig) == Ordering::Less;
                 loss = Loss::ExactlyZero;

compiler/rustc_ast/src/lib.rs

@@ -20,16 +20,6 @@
 #[macro_use]
 extern crate rustc_macros;
 
-#[macro_export]
-macro_rules! unwrap_or {
-    ($opt:expr, $default:expr) => {
-        match $opt {
-            Some(x) => x,
-            None => $default,
-        }
-    };
-}
-
 pub mod util {
     pub mod classify;
     pub mod comments;

compiler/rustc_ast_lowering/src/asm.rs

@@ -202,39 +202,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let mut used_input_regs = FxHashMap::default();
         let mut used_output_regs = FxHashMap::default();
-        let mut required_features: Vec<&str> = vec![];
+
         for (idx, &(ref op, op_sp)) in operands.iter().enumerate() {
             if let Some(reg) = op.reg() {
-                // Make sure we don't accidentally carry features from the
-                // previous iteration.
-                required_features.clear();
-
                 let reg_class = reg.reg_class();
                 if reg_class == asm::InlineAsmRegClass::Err {
                     continue;
                 }
 
-                // We ignore target feature requirements for clobbers: if the
-                // feature is disabled then the compiler doesn't care what we
-                // do with the registers.
-                //
-                // Note that this is only possible for explicit register
-                // operands, which cannot be used in the asm string.
-                let is_clobber = matches!(
-                    op,
-                    hir::InlineAsmOperand::Out {
-                        reg: asm::InlineAsmRegOrRegClass::Reg(_),
-                        late: _,
-                        expr: None
-                    }
-                );
-
                 // Some register classes can only be used as clobbers. This
                 // means that we disallow passing a value in/out of the asm and
                 // require that the operand name an explicit register, not a
                 // register class.
                 if reg_class.is_clobber_only(asm_arch.unwrap())
-                    && !(is_clobber && matches!(reg, asm::InlineAsmRegOrRegClass::Reg(_)))
+                    && !(op.is_clobber() && matches!(reg, asm::InlineAsmRegOrRegClass::Reg(_)))
                 {
                     let msg = format!(
                         "register class `{}` can only be used as a clobber, \
@@ -245,47 +226,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     continue;
                 }
 
-                if !is_clobber {
-                    // Validate register classes against currently enabled target
-                    // features. We check that at least one type is available for
-                    // the current target.
-                    for &(_, feature) in reg_class.supported_types(asm_arch.unwrap()) {
-                        if let Some(feature) = feature {
-                            if self.sess.target_features.contains(&Symbol::intern(feature)) {
-                                required_features.clear();
-                                break;
-                            } else {
-                                required_features.push(feature);
-                            }
-                        } else {
-                            required_features.clear();
-                            break;
-                        }
-                    }
-                    // We are sorting primitive strs here and can use unstable sort here
-                    required_features.sort_unstable();
-                    required_features.dedup();
-                    match &required_features[..] {
-                        [] => {}
-                        [feature] => {
-                            let msg = format!(
-                                "register class `{}` requires the `{}` target feature",
-                                reg_class.name(),
-                                feature
-                            );
-                            sess.struct_span_err(op_sp, &msg).emit();
-                        }
-                        features => {
-                            let msg = format!(
-                                "register class `{}` requires at least one target feature: {}",
-                                reg_class.name(),
-                                features.join(", ")
-                            );
-                            sess.struct_span_err(op_sp, &msg).emit();
-                        }
-                    }
-                }
-
                 // Check for conflicts between explicit register operands.
                 if let asm::InlineAsmRegOrRegClass::Reg(reg) = reg {
                     let (input, output) = match op {

compiler/rustc_ast_lowering/src/item.rs

@@ -1345,8 +1345,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         generics
                             .params
                             .iter()
-                            .find(|p| def_id == self.resolver.local_def_id(p.id).to_def_id())
+                            .any(|p| def_id == self.resolver.local_def_id(p.id).to_def_id())
-                            .is_some()
                     }
                     // Either the `bounded_ty` is not a plain type parameter, or
                     // it's not found in the generic type parameters list.

compiler/rustc_borrowck/src/dataflow.rs

@@ -201,7 +201,7 @@ impl<'tcx> OutOfScopePrecomputer<'_, 'tcx> {
                 let bb_data = &self.body[bb];
                 debug_assert!(hi == bb_data.statements.len());
                 for &succ_bb in bb_data.terminator().successors() {
-                    if self.visited.insert(succ_bb) == false {
+                    if !self.visited.insert(succ_bb) {
                         if succ_bb == location.block && first_lo > 0 {
                             // `succ_bb` has been seen before. If it wasn't
                             // fully processed, add its first part to `stack`

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -972,8 +972,7 @@ fn suggest_ampmut<'tcx>(
     if let Some(assignment_rhs_span) = opt_assignment_rhs_span {
         if let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span) {
             let is_mutbl = |ty: &str| -> bool {
-                if ty.starts_with("mut") {
+                if let Some(rest) = ty.strip_prefix("mut") {
-                    let rest = &ty[3..];
                     match rest.chars().next() {
                         // e.g. `&mut x`
                         Some(c) if c.is_whitespace() => true,

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1153,28 +1153,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         .convert_all(data);
     }
 
-    /// Convenient wrapper around `relate_tys::relate_types` -- see
-    /// that fn for docs.
-    fn relate_types(
-        &mut self,
-        a: Ty<'tcx>,
-        v: ty::Variance,
-        b: Ty<'tcx>,
-        locations: Locations,
-        category: ConstraintCategory,
-    ) -> Fallible<()> {
-        relate_tys::relate_types(
-            self.infcx,
-            self.param_env,
-            a,
-            v,
-            b,
-            locations,
-            category,
-            self.borrowck_context,
-        )
-    }
-
     /// Try to relate `sub <: sup`
     fn sub_types(
         &mut self,

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -1,5 +1,5 @@
 use rustc_infer::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate};
-use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
+use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::{self, Const, Ty};
@@ -7,8 +7,9 @@ use rustc_trait_selection::traits::query::Fallible;
 
 use crate::constraints::OutlivesConstraint;
 use crate::diagnostics::UniverseInfo;
-use crate::type_check::{BorrowCheckContext, Locations};
+use crate::type_check::{Locations, TypeChecker};
 
+impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// Adds sufficient constraints to ensure that `a R b` where `R` depends on `v`:
     ///
     /// - "Covariant" `a <: b`
@@ -17,38 +18,27 @@ use crate::type_check::{BorrowCheckContext, Locations};
     ///
     /// N.B., the type `a` is permitted to have unresolved inference
     /// variables, but not the type `b`.
-#[instrument(skip(infcx, param_env, borrowck_context), level = "debug")]
+    #[instrument(skip(self), level = "debug")]
-pub(super) fn relate_types<'tcx>(
+    pub(super) fn relate_types(
-    infcx: &InferCtxt<'_, 'tcx>,
+        &mut self,
-    param_env: ty::ParamEnv<'tcx>,
         a: Ty<'tcx>,
         v: ty::Variance,
         b: Ty<'tcx>,
         locations: Locations,
         category: ConstraintCategory,
-    borrowck_context: &mut BorrowCheckContext<'_, 'tcx>,
     ) -> Fallible<()> {
         TypeRelating::new(
-        infcx,
+            self.infcx,
-        NllTypeRelatingDelegate::new(
+            NllTypeRelatingDelegate::new(self, locations, category, UniverseInfo::relate(a, b)),
-            infcx,
-            borrowck_context,
-            param_env,
-            locations,
-            category,
-            UniverseInfo::relate(a, b),
-        ),
             v,
         )
         .relate(a, b)?;
         Ok(())
     }
+}
 
 struct NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
-    infcx: &'me InferCtxt<'me, 'tcx>,
+    type_checker: &'me mut TypeChecker<'bccx, 'tcx>,
-    borrowck_context: &'me mut BorrowCheckContext<'bccx, 'tcx>,
-
-    param_env: ty::ParamEnv<'tcx>,
 
     /// Where (and why) is this relation taking place?
     locations: Locations,
@@ -63,25 +53,24 @@ struct NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
 
 impl NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
     fn new(
-        infcx: &'me InferCtxt<'me, 'tcx>,
+        type_checker: &'me mut TypeChecker<'bccx, 'tcx>,
-        borrowck_context: &'me mut BorrowCheckContext<'bccx, 'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         locations: Locations,
         category: ConstraintCategory,
         universe_info: UniverseInfo<'tcx>,
     ) -> Self {
-        Self { infcx, borrowck_context, param_env, locations, category, universe_info }
+        Self { type_checker, locations, category, universe_info }
     }
 }
 
 impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.param_env
+        self.type_checker.param_env
     }
 
     fn create_next_universe(&mut self) -> ty::UniverseIndex {
-        let universe = self.infcx.create_next_universe();
+        let universe = self.type_checker.infcx.create_next_universe();
-        self.borrowck_context
+        self.type_checker
+            .borrowck_context
             .constraints
             .universe_causes
             .insert(universe, self.universe_info.clone());
@@ -90,15 +79,18 @@ impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
 
     fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> {
         let origin = NllRegionVariableOrigin::Existential { from_forall };
-        self.infcx.next_nll_region_var(origin)
+        self.type_checker.infcx.next_nll_region_var(origin)
     }
 
     fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> {
-        self.borrowck_context.constraints.placeholder_region(self.infcx, placeholder)
+        self.type_checker
+            .borrowck_context
+            .constraints
+            .placeholder_region(self.type_checker.infcx, placeholder)
     }
 
     fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> {
-        self.infcx.next_nll_region_var_in_universe(
+        self.type_checker.infcx.next_nll_region_var_in_universe(
             NllRegionVariableOrigin::Existential { from_forall: false },
             universe,
         )
@@ -110,15 +102,17 @@ impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
         sub: ty::Region<'tcx>,
         info: ty::VarianceDiagInfo<'tcx>,
     ) {
-        let sub = self.borrowck_context.universal_regions.to_region_vid(sub);
+        let sub = self.type_checker.borrowck_context.universal_regions.to_region_vid(sub);
-        let sup = self.borrowck_context.universal_regions.to_region_vid(sup);
+        let sup = self.type_checker.borrowck_context.universal_regions.to_region_vid(sup);
-        self.borrowck_context.constraints.outlives_constraints.push(OutlivesConstraint {
+        self.type_checker.borrowck_context.constraints.outlives_constraints.push(
+            OutlivesConstraint {
                 sup,
                 sub,
                 locations: self.locations,
                 category: self.category,
                 variance_info: info,
-        });
+            },
+        );
     }
 
     // We don't have to worry about the equality of consts during borrow checking

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -594,7 +594,7 @@ impl<'a> TraitDef<'a> {
             GenericParamKind::Const { ty, kw_span, .. } => {
                 let const_nodefault_kind = GenericParamKind::Const {
                     ty: ty.clone(),
-                    kw_span: kw_span.clone(),
+                    kw_span: *kw_span,
 
                     // We can't have default values inside impl block
                     default: None,

compiler/rustc_codegen_gcc/src/debuginfo.rs

@@ -2,7 +2,7 @@ use gccjit::RValue;
 use rustc_codegen_ssa::mir::debuginfo::{FunctionDebugContext, VariableKind};
 use rustc_codegen_ssa::traits::{DebugInfoBuilderMethods, DebugInfoMethods};
 use rustc_middle::mir;
-use rustc_middle::ty::{Instance, Ty};
+use rustc_middle::ty::{Instance, PolyExistentialTraitRef, Ty};
 use rustc_span::{SourceFile, Span, Symbol};
 use rustc_target::abi::Size;
 use rustc_target::abi::call::FnAbi;
@@ -31,7 +31,7 @@ impl<'a, 'gcc, 'tcx> DebugInfoBuilderMethods for Builder<'a, 'gcc, 'tcx> {
 }
 
 impl<'gcc, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
-    fn create_vtable_metadata(&self, _ty: Ty<'tcx>, _vtable: Self::Value) {
+    fn create_vtable_metadata(&self, _ty: Ty<'tcx>, _trait_ref: Option<PolyExistentialTraitRef<'tcx>>, _vtable: Self::Value) {
         // TODO(antoyo)
     }
 

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -596,7 +596,7 @@ pub(crate) fn run_pass_manager(
     //      tools/lto/LTOCodeGenerator.cpp
     debug!("running the pass manager");
     unsafe {
-        if write::should_use_new_llvm_pass_manager(config) {
+        if write::should_use_new_llvm_pass_manager(cgcx, config) {
             let opt_stage = if thin { llvm::OptStage::ThinLTO } else { llvm::OptStage::FatLTO };
             let opt_level = config.opt_level.unwrap_or(config::OptLevel::No);
             write::optimize_with_new_llvm_pass_manager(

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -377,10 +377,19 @@ fn get_pgo_sample_use_path(config: &ModuleConfig) -> Option<CString> {
         .map(|path_buf| CString::new(path_buf.to_string_lossy().as_bytes()).unwrap())
 }
 
-pub(crate) fn should_use_new_llvm_pass_manager(config: &ModuleConfig) -> bool {
+pub(crate) fn should_use_new_llvm_pass_manager(
+    cgcx: &CodegenContext<LlvmCodegenBackend>,
+    config: &ModuleConfig,
+) -> bool {
     // The new pass manager is enabled by default for LLVM >= 13.
     // This matches Clang, which also enables it since Clang 13.
-    config.new_llvm_pass_manager.unwrap_or_else(|| llvm_util::get_version() >= (13, 0, 0))
+
+    // FIXME: There are some perf issues with the new pass manager
+    // when targeting s390x, so it is temporarily disabled for that
+    // arch, see https://github.com/rust-lang/rust/issues/89609
+    config
+        .new_llvm_pass_manager
+        .unwrap_or_else(|| cgcx.target_arch != "s390x" && llvm_util::get_version() >= (13, 0, 0))
 }
 
 pub(crate) unsafe fn optimize_with_new_llvm_pass_manager(
@@ -482,7 +491,7 @@ pub(crate) unsafe fn optimize(
     }
 
     if let Some(opt_level) = config.opt_level {
-        if should_use_new_llvm_pass_manager(config) {
+        if should_use_new_llvm_pass_manager(cgcx, config) {
             let opt_stage = match cgcx.lto {
                 Lto::Fat => llvm::OptStage::PreLinkFatLTO,
                 Lto::Thin | Lto::ThinLocal => llvm::OptStage::PreLinkThinLTO,

compiler/rustc_codegen_llvm/src/builder.rs

@@ -828,6 +828,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn fcmp(&mut self, op: RealPredicate, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
+        let op = llvm::RealPredicate::from_generic(op);
         unsafe { llvm::LLVMBuildFCmp(self.llbuilder, op as c_uint, lhs, rhs, UNNAMED) }
     }
 

compiler/rustc_codegen_llvm/src/callee.rs

@@ -175,7 +175,7 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
             // should use dllimport for functions.
             if cx.use_dll_storage_attrs
                 && tcx.is_dllimport_foreign_item(instance_def_id)
-                && tcx.sess.target.env != "gnu"
+                && !matches!(tcx.sess.target.env.as_ref(), "gnu" | "uclibc")
             {
                 llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
             }

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -2,7 +2,7 @@ use self::MemberDescriptionFactory::*;
 use self::RecursiveTypeDescription::*;
 
 use super::namespace::mangled_name_of_instance;
-use super::type_names::compute_debuginfo_type_name;
+use super::type_names::{compute_debuginfo_type_name, compute_debuginfo_vtable_name};
 use super::utils::{
     create_DIArray, debug_context, get_namespace_for_item, is_node_local_to_unit, DIB,
 };
@@ -29,8 +29,9 @@ use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::mir::{self, GeneratorLayout};
 use rustc_middle::ty::layout::{self, IntegerExt, LayoutOf, PrimitiveExt, TyAndLayout};
 use rustc_middle::ty::subst::GenericArgKind;
-use rustc_middle::ty::Instance;
+use rustc_middle::ty::{
-use rustc_middle::ty::{self, AdtKind, GeneratorSubsts, ParamEnv, Ty, TyCtxt};
+    self, AdtKind, GeneratorSubsts, Instance, ParamEnv, Ty, TyCtxt, COMMON_VTABLE_ENTRIES,
+};
 use rustc_middle::{bug, span_bug};
 use rustc_query_system::ich::NodeIdHashingMode;
 use rustc_session::config::{self, DebugInfo};
@@ -2591,11 +2592,45 @@ pub fn create_global_var_metadata(cx: &CodegenCx<'ll, '_>, def_id: DefId, global
     }
 }
 
+/// Generates LLVM debuginfo for a vtable.
+fn vtable_type_metadata(
+    cx: &CodegenCx<'ll, 'tcx>,
+    ty: Ty<'tcx>,
+    poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+) -> &'ll DIType {
+    let tcx = cx.tcx;
+
+    let vtable_entries = if let Some(poly_trait_ref) = poly_trait_ref {
+        let trait_ref = poly_trait_ref.with_self_ty(tcx, ty);
+        let trait_ref = tcx.erase_regions(trait_ref);
+
+        tcx.vtable_entries(trait_ref)
+    } else {
+        COMMON_VTABLE_ENTRIES
+    };
+
+    // FIXME: We describe the vtable as an array of *const () pointers. The length of the array is
+    //        correct - but we could create a more accurate description, e.g. by describing it
+    //        as a struct where each field has a name that corresponds to the name of the method
+    //        it points to.
+    //        However, this is not entirely straightforward because there might be multiple
+    //        methods with the same name if the vtable is for multiple traits. So for now we keep
+    //        things simple instead of adding some ad-hoc disambiguation scheme.
+    let vtable_type = tcx.mk_array(tcx.mk_imm_ptr(tcx.types.unit), vtable_entries.len() as u64);
+
+    type_metadata(cx, vtable_type, rustc_span::DUMMY_SP)
+}
+
 /// Creates debug information for the given vtable, which is for the
 /// given type.
 ///
 /// Adds the created metadata nodes directly to the crate's IR.
-pub fn create_vtable_metadata(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>, vtable: &'ll Value) {
+pub fn create_vtable_metadata(
+    cx: &CodegenCx<'ll, 'tcx>,
+    ty: Ty<'tcx>,
+    poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    vtable: &'ll Value,
+) {
     if cx.dbg_cx.is_none() {
         return;
     }
@@ -2605,42 +2640,16 @@ pub fn create_vtable_metadata(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>, vtable: &
         return;
     }
 
-    let type_metadata = type_metadata(cx, ty, rustc_span::DUMMY_SP);
+    let vtable_name = compute_debuginfo_vtable_name(cx.tcx, ty, poly_trait_ref);
+    let vtable_type = vtable_type_metadata(cx, ty, poly_trait_ref);
 
     unsafe {
-        // `LLVMRustDIBuilderCreateStructType()` wants an empty array. A null
-        // pointer will lead to hard to trace and debug LLVM assertions
-        // later on in `llvm/lib/IR/Value.cpp`.
-        let empty_array = create_DIArray(DIB(cx), &[]);
-        let name = "vtable";
-
-        // Create a new one each time. We don't want metadata caching
-        // here, because each vtable will refer to a unique containing
-        // type.
-        let vtable_type = llvm::LLVMRustDIBuilderCreateStructType(
-            DIB(cx),
-            NO_SCOPE_METADATA,
-            name.as_ptr().cast(),
-            name.len(),
-            unknown_file_metadata(cx),
-            UNKNOWN_LINE_NUMBER,
-            Size::ZERO.bits(),
-            cx.tcx.data_layout.pointer_align.abi.bits() as u32,
-            DIFlags::FlagArtificial,
-            None,
-            empty_array,
-            0,
-            Some(type_metadata),
-            name.as_ptr().cast(),
-            name.len(),
-        );
-
         let linkage_name = "";
         llvm::LLVMRustDIBuilderCreateStaticVariable(
             DIB(cx),
             NO_SCOPE_METADATA,
-            name.as_ptr().cast(),
+            vtable_name.as_ptr().cast(),
-            name.len(),
+            vtable_name.len(),
             linkage_name.as_ptr().cast(),
             linkage_name.len(),
             unknown_file_metadata(cx),

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -550,8 +550,13 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe { llvm::LLVMRustDIBuilderCreateDebugLocation(line, col, scope, inlined_at) }
     }
 
-    fn create_vtable_metadata(&self, ty: Ty<'tcx>, vtable: Self::Value) {
+    fn create_vtable_metadata(
-        metadata::create_vtable_metadata(self, ty, vtable)
+        &self,
+        ty: Ty<'tcx>,
+        trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+        vtable: Self::Value,
+    ) {
+        metadata::create_vtable_metadata(self, ty, trait_ref, vtable)
     }
 
     fn extend_scope_to_file(

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -223,6 +223,33 @@ pub enum RealPredicate {
     RealPredicateTrue = 15,
 }
 
+impl RealPredicate {
+    pub fn from_generic(realp: rustc_codegen_ssa::common::RealPredicate) -> Self {
+        match realp {
+            rustc_codegen_ssa::common::RealPredicate::RealPredicateFalse => {
+                RealPredicate::RealPredicateFalse
+            }
+            rustc_codegen_ssa::common::RealPredicate::RealOEQ => RealPredicate::RealOEQ,
+            rustc_codegen_ssa::common::RealPredicate::RealOGT => RealPredicate::RealOGT,
+            rustc_codegen_ssa::common::RealPredicate::RealOGE => RealPredicate::RealOGE,
+            rustc_codegen_ssa::common::RealPredicate::RealOLT => RealPredicate::RealOLT,
+            rustc_codegen_ssa::common::RealPredicate::RealOLE => RealPredicate::RealOLE,
+            rustc_codegen_ssa::common::RealPredicate::RealONE => RealPredicate::RealONE,
+            rustc_codegen_ssa::common::RealPredicate::RealORD => RealPredicate::RealORD,
+            rustc_codegen_ssa::common::RealPredicate::RealUNO => RealPredicate::RealUNO,
+            rustc_codegen_ssa::common::RealPredicate::RealUEQ => RealPredicate::RealUEQ,
+            rustc_codegen_ssa::common::RealPredicate::RealUGT => RealPredicate::RealUGT,
+            rustc_codegen_ssa::common::RealPredicate::RealUGE => RealPredicate::RealUGE,
+            rustc_codegen_ssa::common::RealPredicate::RealULT => RealPredicate::RealULT,
+            rustc_codegen_ssa::common::RealPredicate::RealULE => RealPredicate::RealULE,
+            rustc_codegen_ssa::common::RealPredicate::RealUNE => RealPredicate::RealUNE,
+            rustc_codegen_ssa::common::RealPredicate::RealPredicateTrue => {
+                RealPredicate::RealPredicateTrue
+            }
+        }
+    }
+}
+
 /// LLVMTypeKind
 #[derive(Copy, Clone, PartialEq, Debug)]
 #[repr(C)]

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -843,19 +843,18 @@ fn link_natively<'a, B: ArchiveBuilder<'a>>(
         let msg_bus = "clang: error: unable to execute command: Bus error: 10";
         if out.contains(msg_segv) || out.contains(msg_bus) {
             warn!(
+                ?cmd, %out,
                 "looks like the linker segfaulted when we tried to call it, \
-                 automatically retrying again. cmd = {:?}, out = {}.",
+                 automatically retrying again",
-                cmd, out,
             );
             continue;
         }
 
         if is_illegal_instruction(&output.status) {
             warn!(
+                ?cmd, %out, status = %output.status,
                 "looks like the linker hit an illegal instruction when we \
-                 tried to call it, automatically retrying again. cmd = {:?}, ]\
+                 tried to call it, automatically retrying again.",
-                 out = {}, status = {}.",
-                cmd, out, output.status,
             );
             continue;
         }

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -446,6 +446,62 @@ fn push_debuginfo_type_name<'tcx>(
     }
 }
 
+/// Computes a name for the global variable storing a vtable.
+///
+/// The name is of the form:
+///
+/// `<path::to::SomeType as path::to::SomeTrait>::{vtable}`
+///
+/// or, when generating C++-like names:
+///
+/// `impl$<path::to::SomeType, path::to::SomeTrait>::vtable$`
+pub fn compute_debuginfo_vtable_name<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    t: Ty<'tcx>,
+    trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+) -> String {
+    let cpp_like_names = cpp_like_names(tcx);
+
+    let mut vtable_name = String::with_capacity(64);
+
+    if cpp_like_names {
+        vtable_name.push_str("impl$<");
+    } else {
+        vtable_name.push('<');
+    }
+
+    let mut visited = FxHashSet::default();
+    push_debuginfo_type_name(tcx, t, true, &mut vtable_name, &mut visited);
+
+    if cpp_like_names {
+        vtable_name.push_str(", ");
+    } else {
+        vtable_name.push_str(" as ");
+    }
+
+    if let Some(trait_ref) = trait_ref {
+        push_item_name(tcx, trait_ref.skip_binder().def_id, true, &mut vtable_name);
+        visited.clear();
+        push_generic_params_internal(
+            tcx,
+            trait_ref.skip_binder().substs,
+            &mut vtable_name,
+            &mut visited,
+        );
+    } else {
+        vtable_name.push_str("_");
+    }
+
+    push_close_angle_bracket(cpp_like_names, &mut vtable_name);
+
+    let suffix = if cpp_like_names { "::vtable$" } else { "::{vtable}" };
+
+    vtable_name.reserve_exact(suffix.len());
+    vtable_name.push_str(suffix);
+
+    vtable_name
+}
+
 pub fn push_item_name(tcx: TyCtxt<'tcx>, def_id: DefId, qualified: bool, output: &mut String) {
     let def_key = tcx.def_key(def_id);
     if qualified {

compiler/rustc_codegen_ssa/src/meth.rs

@@ -78,7 +78,7 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
     let align = cx.data_layout().pointer_align.abi;
     let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
 
-    cx.create_vtable_metadata(ty, vtable);
+    cx.create_vtable_metadata(ty, trait_ref, vtable);
     cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
     vtable
 }

compiler/rustc_codegen_ssa/src/traits/debuginfo.rs

@@ -1,13 +1,18 @@
 use super::BackendTypes;
 use crate::mir::debuginfo::{FunctionDebugContext, VariableKind};
 use rustc_middle::mir;
-use rustc_middle::ty::{Instance, Ty};
+use rustc_middle::ty::{Instance, PolyExistentialTraitRef, Ty};
 use rustc_span::{SourceFile, Span, Symbol};
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::Size;
 
 pub trait DebugInfoMethods<'tcx>: BackendTypes {
-    fn create_vtable_metadata(&self, ty: Ty<'tcx>, vtable: Self::Value);
+    fn create_vtable_metadata(
+        &self,
+        ty: Ty<'tcx>,
+        trait_ref: Option<PolyExistentialTraitRef<'tcx>>,
+        vtable: Self::Value,
+    );
 
     /// Creates the function-specific debug context.
     ///

compiler/rustc_data_structures/src/base_n.rs

@@ -14,7 +14,7 @@ const BASE_64: &[u8; MAX_BASE as usize] =
 
 #[inline]
 pub fn push_str(mut n: u128, base: usize, output: &mut String) {
-    debug_assert!(base >= 2 && base <= MAX_BASE);
+    debug_assert!((2..=MAX_BASE).contains(&base));
     let mut s = [0u8; 128];
     let mut index = 0;
 

compiler/rustc_data_structures/src/graph/implementation/mod.rs

@@ -206,17 +206,11 @@ impl<N: Debug, E: Debug> Graph<N, E> {
         AdjacentEdges { graph: self, direction, next: first_edge }
     }
 
-    pub fn successor_nodes<'a>(
+    pub fn successor_nodes(&self, source: NodeIndex) -> impl Iterator<Item = NodeIndex> + '_ {
-        &'a self,
-        source: NodeIndex,
-    ) -> impl Iterator<Item = NodeIndex> + 'a {
         self.outgoing_edges(source).targets()
     }
 
-    pub fn predecessor_nodes<'a>(
+    pub fn predecessor_nodes(&self, target: NodeIndex) -> impl Iterator<Item = NodeIndex> + '_ {
-        &'a self,
-        target: NodeIndex,
-    ) -> impl Iterator<Item = NodeIndex> + 'a {
         self.incoming_edges(target).sources()
     }
 

compiler/rustc_data_structures/src/graph/iterate/mod.rs

@@ -48,7 +48,7 @@ fn post_order_walk<G: DirectedGraph + WithSuccessors + WithNumNodes>(
         let node = frame.node;
         visited[node] = true;
 
-        while let Some(successor) = frame.iter.next() {
+        for successor in frame.iter.by_ref() {
             if !visited[successor] {
                 stack.push(PostOrderFrame { node: successor, iter: graph.successors(successor) });
                 continue 'recurse;
@@ -112,7 +112,7 @@ where
     /// This is equivalent to just invoke `next` repeatedly until
     /// you get a `None` result.
     pub fn complete_search(&mut self) {
-        while let Some(_) = self.next() {}
+        for _ in self {}
     }
 
     /// Returns true if node has been visited thus far.

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -390,7 +390,7 @@ impl<O: ForestObligation> ObligationForest<O> {
             .map(|(index, _node)| Error { error: error.clone(), backtrace: self.error_at(index) })
             .collect();
 
-        self.compress(|_| assert!(false));
+        self.compress(|_| unreachable!());
         errors
     }
 
@@ -612,7 +612,7 @@ impl<O: ForestObligation> ObligationForest<O> {
     fn compress(&mut self, mut outcome_cb: impl FnMut(&O)) {
         let orig_nodes_len = self.nodes.len();
         let mut node_rewrites: Vec<_> = std::mem::take(&mut self.reused_node_vec);
-        debug_assert!(node_rewrites.is_empty());
+        assert!(node_rewrites.is_empty());
         node_rewrites.extend(0..orig_nodes_len);
         let mut dead_nodes = 0;
 
@@ -623,13 +623,13 @@ impl<O: ForestObligation> ObligationForest<O> {
         //     self.nodes[0..index - dead_nodes] are the first remaining nodes
         //     self.nodes[index - dead_nodes..index] are all dead
         //     self.nodes[index..] are unchanged
-        for index in 0..orig_nodes_len {
+        for (index, node_rewrite) in node_rewrites.iter_mut().enumerate() {
             let node = &self.nodes[index];
             match node.state.get() {
                 NodeState::Pending | NodeState::Waiting => {
                     if dead_nodes > 0 {
                         self.nodes.swap(index, index - dead_nodes);
-                        node_rewrites[index] -= dead_nodes;
+                        *node_rewrite -= dead_nodes;
                     }
                 }
                 NodeState::Done => {
@@ -646,7 +646,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                     }
                     // Extract the success stories.
                     outcome_cb(&node.obligation);
-                    node_rewrites[index] = orig_nodes_len;
+                    *node_rewrite = orig_nodes_len;
                     dead_nodes += 1;
                 }
                 NodeState::Error => {
@@ -655,7 +655,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                     // check against.
                     self.active_cache.remove(&node.obligation.as_cache_key());
                     self.insert_into_error_cache(index);
-                    node_rewrites[index] = orig_nodes_len;
+                    *node_rewrite = orig_nodes_len;
                     dead_nodes += 1;
                 }
                 NodeState::Success => unreachable!(),

compiler/rustc_data_structures/src/sorted_map.rs

@@ -205,10 +205,10 @@ impl<K: Ord, V> SortedMap<K, V> {
         R: RangeBounds<K>,
     {
         let start = match range.start_bound() {
-            Bound::Included(ref k) => match self.lookup_index_for(k) {
+            Bound::Included(k) => match self.lookup_index_for(k) {
                 Ok(index) | Err(index) => index,
             },
-            Bound::Excluded(ref k) => match self.lookup_index_for(k) {
+            Bound::Excluded(k) => match self.lookup_index_for(k) {
                 Ok(index) => index + 1,
                 Err(index) => index,
             },
@@ -216,11 +216,11 @@ impl<K: Ord, V> SortedMap<K, V> {
         };
 
         let end = match range.end_bound() {
-            Bound::Included(ref k) => match self.lookup_index_for(k) {
+            Bound::Included(k) => match self.lookup_index_for(k) {
                 Ok(index) => index + 1,
                 Err(index) => index,
             },
-            Bound::Excluded(ref k) => match self.lookup_index_for(k) {
+            Bound::Excluded(k) => match self.lookup_index_for(k) {
                 Ok(index) | Err(index) => index,
             },
             Bound::Unbounded => self.data.len(),

compiler/rustc_data_structures/src/sorted_map/index_map.rs

@@ -75,7 +75,7 @@ impl<I: Idx, K: Ord, V> SortedIndexMultiMap<I, K, V> {
     ///
     /// If there are multiple items that are equivalent to `key`, they will be yielded in
     /// insertion order.
-    pub fn get_by_key(&'a self, key: K) -> impl 'a + Iterator<Item = &'a V> {
+    pub fn get_by_key(&self, key: K) -> impl Iterator<Item = &V> {
         self.get_by_key_enumerated(key).map(|(_, v)| v)
     }
 
@@ -84,7 +84,7 @@ impl<I: Idx, K: Ord, V> SortedIndexMultiMap<I, K, V> {
     ///
     /// If there are multiple items that are equivalent to `key`, they will be yielded in
     /// insertion order.
-    pub fn get_by_key_enumerated(&'a self, key: K) -> impl '_ + Iterator<Item = (I, &V)> {
+    pub fn get_by_key_enumerated(&self, key: K) -> impl Iterator<Item = (I, &V)> {
         let lower_bound = self.idx_sorted_by_item_key.partition_point(|&i| self.items[i].0 < key);
         self.idx_sorted_by_item_key[lower_bound..].iter().map_while(move |&i| {
             let (k, v) = &self.items[i];

compiler/rustc_data_structures/src/sso/map.rs

@@ -257,11 +257,7 @@ impl<K: Eq + Hash, V> SsoHashMap<K, V> {
     pub fn remove(&mut self, key: &K) -> Option<V> {
         match self {
             SsoHashMap::Array(array) => {
-                if let Some(index) = array.iter().position(|(k, _v)| k == key) {
+                array.iter().position(|(k, _v)| k == key).map(|index| array.swap_remove(index).1)
-                    Some(array.swap_remove(index).1)
-                } else {
-                    None
-                }
             }
             SsoHashMap::Map(map) => map.remove(key),
         }
@@ -272,11 +268,7 @@ impl<K: Eq + Hash, V> SsoHashMap<K, V> {
     pub fn remove_entry(&mut self, key: &K) -> Option<(K, V)> {
         match self {
             SsoHashMap::Array(array) => {
-                if let Some(index) = array.iter().position(|(k, _v)| k == key) {
+                array.iter().position(|(k, _v)| k == key).map(|index| array.swap_remove(index))
-                    Some(array.swap_remove(index))
-                } else {
-                    None
-                }
             }
             SsoHashMap::Map(map) => map.remove_entry(key),
         }
@@ -423,14 +415,14 @@ impl<K, V> IntoIterator for SsoHashMap<K, V> {
 
 /// adapts Item of array reference iterator to Item of hashmap reference iterator.
 #[inline(always)]
-fn adapt_array_ref_it<K, V>(pair: &'a (K, V)) -> (&'a K, &'a V) {
+fn adapt_array_ref_it<K, V>(pair: &(K, V)) -> (&K, &V) {
     let (a, b) = pair;
     (a, b)
 }
 
 /// adapts Item of array mut reference iterator to Item of hashmap mut reference iterator.
 #[inline(always)]
-fn adapt_array_mut_it<K, V>(pair: &'a mut (K, V)) -> (&'a K, &'a mut V) {
+fn adapt_array_mut_it<K, V>(pair: &mut (K, V)) -> (&K, &mut V) {
     let (a, b) = pair;
     (a, b)
 }

compiler/rustc_data_structures/src/sso/set.rs

@@ -75,7 +75,7 @@ impl<T> SsoHashSet<T> {
     /// An iterator visiting all elements in arbitrary order.
     /// The iterator element type is `&'a T`.
     #[inline]
-    pub fn iter(&'a self) -> impl Iterator<Item = &'a T> {
+    pub fn iter(&self) -> impl Iterator<Item = &T> {
         self.into_iter()
     }
 

compiler/rustc_data_structures/src/stable_hasher.rs

@@ -229,14 +229,14 @@ impl<CTX> HashStable<CTX> for ::std::num::NonZeroUsize {
 
 impl<CTX> HashStable<CTX> for f32 {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        let val: u32 = unsafe { ::std::mem::transmute(*self) };
+        let val: u32 = self.to_bits();
         val.hash_stable(ctx, hasher);
     }
 }
 
 impl<CTX> HashStable<CTX> for f64 {
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        let val: u64 = unsafe { ::std::mem::transmute(*self) };
+        let val: u64 = self.to_bits();
         val.hash_stable(ctx, hasher);
     }
 }

compiler/rustc_data_structures/src/stack.rs

@@ -5,6 +5,7 @@ const RED_ZONE: usize = 100 * 1024; // 100k
 
 // Only the first stack that is pushed, grows exponentially (2^n * STACK_PER_RECURSION) from then
 // on. This flag has performance relevant characteristics. Don't set it too high.
+#[allow(clippy::identity_op)]
 const STACK_PER_RECURSION: usize = 1 * 1024 * 1024; // 1MB
 
 /// Grows the stack on demand to prevent stack overflow. Call this in strategic locations

compiler/rustc_data_structures/src/steal.rs

@@ -34,7 +34,7 @@ impl<T> Steal<T> {
     #[track_caller]
     pub fn borrow(&self) -> MappedReadGuard<'_, T> {
         let borrow = self.value.borrow();
-        if let None = &*borrow {
+        if borrow.is_none() {
             panic!("attempted to read from stolen value: {}", std::any::type_name::<T>());
         }
         ReadGuard::map(borrow, |opt| opt.as_ref().unwrap())

compiler/rustc_data_structures/src/tiny_list.rs

@@ -48,7 +48,7 @@ impl<T: PartialEq> TinyList<T> {
     #[inline]
     pub fn contains(&self, data: &T) -> bool {
         let mut elem = self.head.as_ref();
-        while let Some(ref e) = elem {
+        while let Some(e) = elem {
             if &e.data == data {
                 return true;
             }

compiler/rustc_data_structures/src/vec_linked_list.rs

@@ -2,8 +2,8 @@ use rustc_index::vec::{Idx, IndexVec};
 
 pub fn iter<Ls>(
     first: Option<Ls::LinkIndex>,
-    links: &'a Ls,
+    links: &Ls,
-) -> impl Iterator<Item = Ls::LinkIndex> + 'a
+) -> impl Iterator<Item = Ls::LinkIndex> + '_
 where
     Ls: Links,
 {

compiler/rustc_driver/src/lib.rs

@@ -1253,12 +1253,16 @@ pub fn init_rustc_env_logger() {
 /// tracing crate version. In contrast to `init_rustc_env_logger` it allows you to choose an env var
 /// other than `RUSTC_LOG`.
 pub fn init_env_logger(env: &str) {
-    // Don't register a dispatcher if there's no filter to print anything
+    use tracing_subscriber::{
-    match std::env::var(env) {
+        filter::{self, EnvFilter, LevelFilter},
-        Err(_) => return,
+        layer::SubscriberExt,
-        Ok(s) if s.is_empty() => return,
+    };
-        Ok(_) => {}
+
-    }
+    let filter = match std::env::var(env) {
+        Ok(env) => EnvFilter::new(env),
+        _ => EnvFilter::default().add_directive(filter::Directive::from(LevelFilter::WARN)),
+    };
+
     let color_logs = match std::env::var(String::from(env) + "_COLOR") {
         Ok(value) => match value.as_ref() {
             "always" => true,
@@ -1278,7 +1282,7 @@ pub fn init_env_logger(env: &str) {
             "non-Unicode log color value: expected one of always, never, or auto",
         ),
     };
-    let filter = tracing_subscriber::EnvFilter::from_env(env);
+
     let layer = tracing_tree::HierarchicalLayer::default()
         .with_writer(io::stderr)
         .with_indent_lines(true)
@@ -1288,7 +1292,6 @@ pub fn init_env_logger(env: &str) {
     #[cfg(parallel_compiler)]
     let layer = layer.with_thread_ids(true).with_thread_names(true);
 
-    use tracing_subscriber::layer::SubscriberExt;
     let subscriber = tracing_subscriber::Registry::default().with(filter).with(layer);
     tracing::subscriber::set_global_default(subscriber).unwrap();
 }

compiler/rustc_error_codes/src/error_codes.rs

@@ -242,6 +242,7 @@ E0468: include_str!("./error_codes/E0468.md"),
 E0469: include_str!("./error_codes/E0469.md"),
 E0477: include_str!("./error_codes/E0477.md"),
 E0478: include_str!("./error_codes/E0478.md"),
+E0482: include_str!("./error_codes/E0482.md"),
 E0491: include_str!("./error_codes/E0491.md"),
 E0492: include_str!("./error_codes/E0492.md"),
 E0493: include_str!("./error_codes/E0493.md"),
@@ -599,7 +600,6 @@ E0785: include_str!("./error_codes/E0785.md"),
 //  E0479, // the type `..` (provided as the value of a type parameter) is...
 //  E0480, // lifetime of method receiver does not outlive the method call
 //  E0481, // lifetime of function argument does not outlive the function call
-    E0482, // lifetime of return value does not outlive the function call
 //  E0483, // lifetime of operand does not outlive the operation
 //  E0484, // reference is not valid at the time of borrow
 //  E0485, // automatically reference is not valid at the time of borrow

compiler/rustc_error_codes/src/error_codes/E0482.md

@@ -0,0 +1,73 @@
+A lifetime of a returned value does not outlive the function call.
+
+Erroneous code example:
+
+```compile_fail,E0482
+fn prefix<'a>(
+    words: impl Iterator<Item = &'a str>
+) -> impl Iterator<Item = String> { // error!
+    words.map(|v| format!("foo-{}", v))
+}
+```
+
+To fix this error, make the lifetime of the returned value explicit:
+
+```
+fn prefix<'a>(
+    words: impl Iterator<Item = &'a str> + 'a
+) -> impl Iterator<Item = String> + 'a { // ok!
+    words.map(|v| format!("foo-{}", v))
+}
+```
+
+The [`impl Trait`] feature in this example uses an implicit `'static` lifetime
+restriction in the returned type. However the type implementing the `Iterator`
+passed to the function lives just as long as `'a`, which is not long enough.
+
+The solution involves adding lifetime bound to both function argument and
+the return value to make sure that the values inside the iterator
+are not dropped when the function goes out of the scope.
+
+An alternative solution would be to guarantee that the `Item` references
+in the iterator are alive for the whole lifetime of the program.
+
+```
+fn prefix(
+    words: impl Iterator<Item = &'static str>
+) -> impl Iterator<Item = String> {  // ok!
+    words.map(|v| format!("foo-{}", v))
+}
+```
+
+A similar lifetime problem might arise when returning closures:
+
+```compile_fail,E0482
+fn foo(
+    x: &mut Vec<i32>
+) -> impl FnMut(&mut Vec<i32>) -> &[i32] { // error!
+    |y| {
+        y.append(x);
+        y
+    }
+}
+```
+
+Analogically, a solution here is to use explicit return lifetime
+and move the ownership of the variable to the closure.
+
+```
+fn foo<'a>(
+    x: &'a mut Vec<i32>
+) -> impl FnMut(&mut Vec<i32>) -> &[i32] + 'a { // ok!
+    move |y| {
+        y.append(x);
+        y
+    }
+}
+```
+
+To better understand the lifetime treatment in the [`impl Trait`],
+please see the [RFC 1951].
+
+[`impl Trait`]: https://doc.rust-lang.org/reference/types/impl-trait.html
+[RFC 1951]: https://rust-lang.github.io/rfcs/1951-expand-impl-trait.html

compiler/rustc_errors/src/emitter.rs

@@ -2308,7 +2308,7 @@ pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
     let found = match sm.span_to_snippet(sp) {
         Ok(snippet) => snippet,
         Err(e) => {
-            warn!("Invalid span {:?}. Err={:?}", sp, e);
+            warn!(error = ?e, "Invalid span {:?}", sp);
             return false;
         }
     };

compiler/rustc_feature/src/accepted.rs

@@ -288,7 +288,7 @@ declare_features! (
     (accepted, member_constraints, "1.54.0", Some(61997), None),
     /// Allows bindings in the subpattern of a binding pattern.
     /// For example, you can write `x @ Some(y)`.
-    (accepted, bindings_after_at, "1.54.0", Some(65490), None),
+    (accepted, bindings_after_at, "1.56.0", Some(65490), None),
     /// Allows calling `transmute` in const fn
     (accepted, const_fn_transmute, "1.56.0", Some(53605), None),
     /// Allows accessing fields of unions inside `const` functions.

compiler/rustc_feature/src/active.rs

@@ -678,6 +678,9 @@ declare_features! (
     /// Allows `#[doc(cfg_hide(...))]`.
     (active, doc_cfg_hide, "1.57.0", Some(43781), None),
 
+    /// Allows using the `non_exhaustive_omitted_patterns` lint.
+    (active, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

compiler/rustc_graphviz/src/lib.rs

@@ -512,7 +512,7 @@ impl<'a> LabelText<'a> {
     pub fn to_dot_string(&self) -> String {
         match *self {
             LabelStr(ref s) => format!("\"{}\"", s.escape_default()),
-            EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(&s)),
+            EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(s)),
             HtmlStr(ref s) => format!("<{}>", s),
         }
     }

compiler/rustc_hir/src/hir.rs

@@ -2293,6 +2293,13 @@ impl<'hir> InlineAsmOperand<'hir> {
             Self::Const { .. } | Self::Sym { .. } => None,
         }
     }
+
+    pub fn is_clobber(&self) -> bool {
+        matches!(
+            self,
+            InlineAsmOperand::Out { reg: InlineAsmRegOrRegClass::Reg(_), late: _, expr: None }
+        )
+    }
 }
 
 #[derive(Debug, HashStable_Generic)]

compiler/rustc_index/src/bit_set.rs

@@ -990,9 +990,8 @@ impl<R: Idx, C: Idx> BitMatrix<R, C> {
     pub fn insert_all_into_row(&mut self, row: R) {
         assert!(row.index() < self.num_rows);
         let (start, end) = self.range(row);
-        let words = &mut self.words[..];
+        for word in self.words[start..end].iter_mut() {
-        for index in start..end {
+            *word = !0;
-            words[index] = !0;
         }
         self.clear_excess_bits(row);
     }
@@ -1144,7 +1143,7 @@ impl<R: Idx, C: Idx> SparseBitMatrix<R, C> {
 
     /// Iterates through all the columns set to true in a given row of
     /// the matrix.
-    pub fn iter<'a>(&'a self, row: R) -> impl Iterator<Item = C> + 'a {
+    pub fn iter(&self, row: R) -> impl Iterator<Item = C> + '_ {
         self.row(row).into_iter().flat_map(|r| r.iter())
     }
 

compiler/rustc_index/src/vec.rs

@@ -634,18 +634,15 @@ impl<I: Idx, T> IndexVec<I, T> {
     }
 
     #[inline]
-    pub fn drain<'a, R: RangeBounds<usize>>(
+    pub fn drain<R: RangeBounds<usize>>(&mut self, range: R) -> impl Iterator<Item = T> + '_ {
-        &'a mut self,
-        range: R,
-    ) -> impl Iterator<Item = T> + 'a {
         self.raw.drain(range)
     }
 
     #[inline]
-    pub fn drain_enumerated<'a, R: RangeBounds<usize>>(
+    pub fn drain_enumerated<R: RangeBounds<usize>>(
-        &'a mut self,
+        &mut self,
         range: R,
-    ) -> impl Iterator<Item = (I, T)> + 'a {
+    ) -> impl Iterator<Item = (I, T)> + '_ {
         self.raw.drain(range).enumerate().map(|(n, t)| (I::new(n), t))
     }
 
@@ -741,6 +738,12 @@ impl<I: Idx, T> IndexVec<I, Option<T>> {
         self.ensure_contains_elem(index, || None);
         self[index].get_or_insert_with(value)
     }
+
+    #[inline]
+    pub fn remove(&mut self, index: I) -> Option<T> {
+        self.ensure_contains_elem(index, || None);
+        self[index].take()
+    }
 }
 
 impl<I: Idx, T: Clone> IndexVec<I, T> {

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2060,14 +2060,24 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     expected: exp_found.expected.print_only_trait_path(),
                     found: exp_found.found.print_only_trait_path(),
                 };
-                self.expected_found_str(pretty_exp_found)
+                match self.expected_found_str(pretty_exp_found) {
+                    Some((expected, found)) if expected == found => {
+                        self.expected_found_str(exp_found)
+                    }
+                    ret => ret,
+                }
             }
             infer::PolyTraitRefs(exp_found) => {
                 let pretty_exp_found = ty::error::ExpectedFound {
                     expected: exp_found.expected.print_only_trait_path(),
                     found: exp_found.found.print_only_trait_path(),
                 };
-                self.expected_found_str(pretty_exp_found)
+                match self.expected_found_str(pretty_exp_found) {
+                    Some((expected, found)) if expected == found => {
+                        self.expected_found_str(exp_found)
+                    }
+                    ret => ret,
+                }
             }
         }
     }

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -130,8 +130,8 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             .tcx()
             .sess
             .struct_span_err(span, &format!("`impl` associated type signature for `{}` doesn't match `trait` associated type signature", item_name));
-        err.span_label(impl_sp, &format!("found"));
+        err.span_label(impl_sp, "found");
-        err.span_label(trait_sp, &format!("expected"));
+        err.span_label(trait_sp, "expected");
 
         err.emit();
     }

compiler/rustc_lexer/src/unescape.rs

@@ -68,11 +68,10 @@ pub enum EscapeError {
 impl EscapeError {
     /// Returns true for actual errors, as opposed to warnings.
     pub fn is_fatal(&self) -> bool {
-        match self {
+        !matches!(
-            EscapeError::UnskippedWhitespaceWarning => false,
+            self,
-            EscapeError::MultipleSkippedLinesWarning => false,
+            EscapeError::UnskippedWhitespaceWarning | EscapeError::MultipleSkippedLinesWarning
-            _ => true,
+        )
-        }
     }
 }
 
@@ -330,7 +329,7 @@ where
             callback(start..end, Err(EscapeError::MultipleSkippedLinesWarning));
         }
         let tail = &tail[first_non_space..];
-        if let Some(c) = tail.chars().nth(0) {
+        if let Some(c) = tail.chars().next() {
             // For error reporting, we would like the span to contain the character that was not
             // skipped.  The +1 is necessary to account for the leading \ that started the escape.
             let end = start + first_non_space + c.len_utf8() + 1;

compiler/rustc_lint/src/enum_intrinsics_non_enums.rs

@@ -0,0 +1,106 @@
+use crate::{context::LintContext, LateContext, LateLintPass};
+use rustc_hir as hir;
+use rustc_middle::ty::{fold::TypeFoldable, Ty};
+use rustc_span::{symbol::sym, Span};
+
+declare_lint! {
+    /// The `enum_intrinsics_non_enums` lint detects calls to
+    /// intrinsic functions that require an enum ([`core::mem::discriminant`],
+    /// [`core::mem::variant_count`]), but are called with a non-enum type.
+    ///
+    /// [`core::mem::discriminant`]: https://doc.rust-lang.org/core/mem/fn.discriminant.html
+    /// [`core::mem::variant_count`]: https://doc.rust-lang.org/core/mem/fn.variant_count.html
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(enum_intrinsics_non_enums)]
+    /// core::mem::discriminant::<i32>(&123);
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In order to accept any enum, the `mem::discriminant` and
+    /// `mem::variant_count` functions are generic over a type `T`.
+    /// This makes it technically possible for `T` to be a non-enum,
+    /// in which case the return value is unspecified.
+    ///
+    /// This lint prevents such incorrect usage of these functions.
+    ENUM_INTRINSICS_NON_ENUMS,
+    Deny,
+    "detects calls to `core::mem::discriminant` and `core::mem::variant_count` with non-enum types"
+}
+
+declare_lint_pass!(EnumIntrinsicsNonEnums => [ENUM_INTRINSICS_NON_ENUMS]);
+
+/// Returns `true` if we know for sure that the given type is not an enum. Note that for cases where
+/// the type is generic, we can't be certain if it will be an enum so we have to assume that it is.
+fn is_non_enum(t: Ty<'_>) -> bool {
+    !t.is_enum() && !t.potentially_needs_subst()
+}
+
+fn enforce_mem_discriminant(
+    cx: &LateContext<'_>,
+    func_expr: &hir::Expr<'_>,
+    expr_span: Span,
+    args_span: Span,
+) {
+    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    if is_non_enum(ty_param) {
+        cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, expr_span, |builder| {
+            builder
+                .build(
+                    "the return value of `mem::discriminant` is \
+                        unspecified when called with a non-enum type",
+                )
+                .span_note(
+                    args_span,
+                    &format!(
+                        "the argument to `discriminant` should be a \
+                            reference to an enum, but it was passed \
+                            a reference to a `{}`, which is not an enum.",
+                        ty_param,
+                    ),
+                )
+                .emit();
+        });
+    }
+}
+
+fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
+    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    if is_non_enum(ty_param) {
+        cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, span, |builder| {
+            builder
+                .build(
+                    "the return value of `mem::variant_count` is \
+                        unspecified when called with a non-enum type",
+                )
+                .note(&format!(
+                    "the type parameter of `variant_count` should \
+                            be an enum, but it was instantiated with \
+                            the type `{}`, which is not an enum.",
+                    ty_param,
+                ))
+                .emit();
+        });
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        if let hir::ExprKind::Call(ref func, ref args) = expr.kind {
+            if let hir::ExprKind::Path(ref qpath) = func.kind {
+                if let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() {
+                    if cx.tcx.is_diagnostic_item(sym::mem_discriminant, def_id) {
+                        enforce_mem_discriminant(cx, func, expr.span, args[0].span);
+                    } else if cx.tcx.is_diagnostic_item(sym::mem_variant_count, def_id) {
+                        enforce_mem_variant_count(cx, func, expr.span);
+                    }
+                }
+            }
+        }
+    }
+}

compiler/rustc_lint/src/levels.rs

@@ -1,7 +1,6 @@
 use crate::context::{CheckLintNameResult, LintStore};
 use crate::late::unerased_lint_store;
 use rustc_ast as ast;
-use rustc_ast::unwrap_or;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
@@ -233,7 +232,10 @@ impl<'s> LintLevelsBuilder<'s> {
                 Some(lvl) => lvl,
             };
 
-            let mut metas = unwrap_or!(attr.meta_item_list(), continue);
+            let mut metas = match attr.meta_item_list() {
+                Some(x) => x,
+                None => continue,
+            };
 
             if metas.is_empty() {
                 // FIXME (#55112): issue unused-attributes lint for `#[level()]`

compiler/rustc_lint/src/lib.rs

@@ -47,6 +47,7 @@ mod array_into_iter;
 pub mod builtin;
 mod context;
 mod early;
+mod enum_intrinsics_non_enums;
 mod internal;
 mod late;
 mod levels;
@@ -76,6 +77,7 @@ use rustc_span::Span;
 
 use array_into_iter::ArrayIntoIter;
 use builtin::*;
+use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
 use internal::*;
 use methods::*;
 use non_ascii_idents::*;
@@ -168,6 +170,7 @@ macro_rules! late_lint_passes {
                 TemporaryCStringAsPtr: TemporaryCStringAsPtr,
                 NonPanicFmt: NonPanicFmt,
                 NoopMethodCall: NoopMethodCall,
+                EnumIntrinsicsNonEnums: EnumIntrinsicsNonEnums,
                 InvalidAtomicOrdering: InvalidAtomicOrdering,
                 NamedAsmLabels: NamedAsmLabels,
             ]

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -230,8 +230,7 @@ fn check_panic_str<'tcx>(
         Err(_) => (None, None),
     };
 
-    let mut fmt_parser =
+    let mut fmt_parser = Parser::new(fmt, style, snippet.clone(), false, ParseMode::Format);
-        Parser::new(fmt.as_ref(), style, snippet.clone(), false, ParseMode::Format);
     let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
 
     if n_arguments > 0 && fmt_parser.errors.is_empty() {

compiler/rustc_lint_defs/src/builtin.rs

@@ -6,6 +6,7 @@
 
 use crate::{declare_lint, declare_lint_pass, FutureIncompatibilityReason};
 use rustc_span::edition::Edition;
+use rustc_span::symbol::sym;
 
 declare_lint! {
     /// The `forbidden_lint_groups` lint detects violations of
@@ -3476,6 +3477,8 @@ declare_lint! {
     /// }
     ///
     /// // in crate B
+    /// #![feature(non_exhaustive_omitted_patterns_lint)]
+    ///
     /// match Bar::A {
     ///     Bar::A => {},
     ///     #[warn(non_exhaustive_omitted_patterns)]
@@ -3512,6 +3515,7 @@ declare_lint! {
     pub NON_EXHAUSTIVE_OMITTED_PATTERNS,
     Allow,
     "detect when patterns of types marked `non_exhaustive` are missed",
+    @feature_gate = sym::non_exhaustive_omitted_patterns_lint;
 }
 
 declare_lint! {

compiler/rustc_macros/src/hash_stable.rs

@@ -24,8 +24,7 @@ fn parse_attributes(field: &syn::Field) -> Attributes {
                         }
                         if meta.path().is_ident("project") {
                             if let Meta::List(list) = meta {
-                                if let Some(nested) = list.nested.iter().next() {
+                                if let Some(NestedMeta::Meta(meta)) = list.nested.iter().next() {
-                                    if let NestedMeta::Meta(meta) = nested {
                                     attrs.project = meta.path().get_ident().cloned();
                                     any_attr = true;
                                 }
@@ -34,7 +33,6 @@ fn parse_attributes(field: &syn::Field) -> Attributes {
                     }
                 }
             }
-            }
             if !any_attr {
                 panic!("error parsing stable_hasher");
             }

compiler/rustc_macros/src/session_diagnostic.rs

@@ -349,14 +349,14 @@ impl<'a> SessionDiagnosticDeriveBuilder<'a> {
     ) -> Result<proc_macro2::TokenStream, SessionDiagnosticDeriveError> {
         let field_binding = &info.binding.binding;
 
-        let option_ty = option_inner_ty(&info.ty);
+        let option_ty = option_inner_ty(info.ty);
 
         let generated_code = self.generate_non_option_field_code(
             attr,
             FieldInfo {
                 vis: info.vis,
                 binding: info.binding,
-                ty: option_ty.unwrap_or(&info.ty),
+                ty: option_ty.unwrap_or(info.ty),
                 span: info.span,
             },
         )?;
@@ -388,7 +388,7 @@ impl<'a> SessionDiagnosticDeriveBuilder<'a> {
                 let formatted_str = self.build_format(&s.value(), attr.span());
                 match name {
                     "message" => {
-                        if type_matches_path(&info.ty, &["rustc_span", "Span"]) {
+                        if type_matches_path(info.ty, &["rustc_span", "Span"]) {
                             quote! {
                                 #diag.set_span(*#field_binding);
                                 #diag.set_primary_message(#formatted_str);
@@ -401,7 +401,7 @@ impl<'a> SessionDiagnosticDeriveBuilder<'a> {
                         }
                     }
                     "label" => {
-                        if type_matches_path(&info.ty, &["rustc_span", "Span"]) {
+                        if type_matches_path(info.ty, &["rustc_span", "Span"]) {
                             quote! {
                                 #diag.span_label(*#field_binding, #formatted_str);
                             }

compiler/rustc_metadata/src/native_libs.rs

@@ -363,7 +363,7 @@ impl Collector<'tcx> {
                 .collect::<Vec<_>>();
             if existing.is_empty() {
                 // Add if not found
-                let new_name = passed_lib.new_name.as_ref().map(|s| &**s); // &Option<String> -> Option<&str>
+                let new_name: Option<&str> = passed_lib.new_name.as_deref();
                 let lib = NativeLib {
                     name: Some(Symbol::intern(new_name.unwrap_or(&passed_lib.name))),
                     kind: passed_lib.kind,

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -63,6 +63,7 @@ use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
 use rustc_hir::definitions::DefPathHash;
 use rustc_hir::HirId;
+use rustc_query_system::dep_graph::FingerprintStyle;
 use rustc_span::symbol::Symbol;
 use std::hash::Hash;
 
@@ -89,9 +90,9 @@ pub struct DepKindStruct {
 
     /// Whether the query key can be recovered from the hashed fingerprint.
     /// See [DepNodeParams] trait for the behaviour of each key type.
-    // FIXME: Make this a simple boolean once DepNodeParams::can_reconstruct_query_key
+    // FIXME: Make this a simple boolean once DepNodeParams::fingerprint_style
     // can be made a specialized associated const.
-    can_reconstruct_query_key: fn() -> bool,
+    fingerprint_style: fn() -> FingerprintStyle,
 }
 
 impl std::ops::Deref for DepKind {
@@ -103,14 +104,14 @@ impl std::ops::Deref for DepKind {
 
 impl DepKind {
     #[inline(always)]
-    pub fn can_reconstruct_query_key(&self) -> bool {
+    pub fn fingerprint_style(&self) -> FingerprintStyle {
         // Only fetch the DepKindStruct once.
         let data: &DepKindStruct = &**self;
         if data.is_anon {
-            return false;
+            return FingerprintStyle::Opaque;
         }
 
-        (data.can_reconstruct_query_key)()
+        (data.fingerprint_style)()
     }
 }
 
@@ -151,6 +152,7 @@ macro_rules! contains_eval_always_attr {
 pub mod dep_kind {
     use super::*;
     use crate::ty::query::query_keys;
+    use rustc_query_system::dep_graph::FingerprintStyle;
 
     // We use this for most things when incr. comp. is turned off.
     pub const Null: DepKindStruct = DepKindStruct {
@@ -158,7 +160,7 @@ pub mod dep_kind {
         is_anon: false,
         is_eval_always: false,
 
-        can_reconstruct_query_key: || true,
+        fingerprint_style: || FingerprintStyle::Unit,
     };
 
     pub const TraitSelect: DepKindStruct = DepKindStruct {
@@ -166,7 +168,7 @@ pub mod dep_kind {
         is_anon: true,
         is_eval_always: false,
 
-        can_reconstruct_query_key: || true,
+        fingerprint_style: || FingerprintStyle::Unit,
     };
 
     pub const CompileCodegenUnit: DepKindStruct = DepKindStruct {
@@ -174,7 +176,7 @@ pub mod dep_kind {
         is_anon: false,
         is_eval_always: false,
 
-        can_reconstruct_query_key: || false,
+        fingerprint_style: || FingerprintStyle::Opaque,
     };
 
     pub const CompileMonoItem: DepKindStruct = DepKindStruct {
@@ -182,7 +184,7 @@ pub mod dep_kind {
         is_anon: false,
         is_eval_always: false,
 
-        can_reconstruct_query_key: || false,
+        fingerprint_style: || FingerprintStyle::Opaque,
     };
 
     macro_rules! define_query_dep_kinds {
@@ -196,16 +198,16 @@ pub mod dep_kind {
                 const is_eval_always: bool = contains_eval_always_attr!($($attrs)*);
 
                 #[inline(always)]
-                fn can_reconstruct_query_key() -> bool {
+                fn fingerprint_style() -> rustc_query_system::dep_graph::FingerprintStyle {
                     <query_keys::$variant<'_> as DepNodeParams<TyCtxt<'_>>>
-                        ::can_reconstruct_query_key()
+                        ::fingerprint_style()
                 }
 
                 DepKindStruct {
                     has_params,
                     is_anon,
                     is_eval_always,
-                    can_reconstruct_query_key,
+                    fingerprint_style,
                 }
             };)*
         );
@@ -320,7 +322,7 @@ impl DepNodeExt for DepNode {
     /// method will assert that the given DepKind actually requires a
     /// single DefId/DefPathHash parameter.
     fn from_def_path_hash(def_path_hash: DefPathHash, kind: DepKind) -> DepNode {
-        debug_assert!(kind.can_reconstruct_query_key() && kind.has_params);
+        debug_assert!(kind.fingerprint_style() == FingerprintStyle::DefPathHash);
         DepNode { kind, hash: def_path_hash.0.into() }
     }
 
@@ -335,7 +337,7 @@ impl DepNodeExt for DepNode {
     /// refers to something from the previous compilation session that
     /// has been removed.
     fn extract_def_id(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
-        if self.kind.can_reconstruct_query_key() {
+        if self.kind.fingerprint_style() == FingerprintStyle::DefPathHash {
             Some(
                 tcx.on_disk_cache
                     .as_ref()?
@@ -350,14 +352,16 @@ impl DepNodeExt for DepNode {
     fn from_label_string(label: &str, def_path_hash: DefPathHash) -> Result<DepNode, ()> {
         let kind = dep_kind_from_label_string(label)?;
 
-        if !kind.can_reconstruct_query_key() {
+        match kind.fingerprint_style() {
-            return Err(());
+            FingerprintStyle::Opaque => Err(()),
-        }
+            FingerprintStyle::Unit => {
-
+                if !kind.has_params {
-        if kind.has_params {
-            Ok(DepNode::from_def_path_hash(def_path_hash, kind))
-        } else {
                     Ok(DepNode::new_no_params(kind))
+                } else {
+                    Err(())
+                }
+            }
+            FingerprintStyle::DefPathHash => Ok(DepNode::from_def_path_hash(def_path_hash, kind)),
         }
     }
 
@@ -369,8 +373,8 @@ impl DepNodeExt for DepNode {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for () {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        true
+        FingerprintStyle::Unit
     }
 
     fn to_fingerprint(&self, _: TyCtxt<'tcx>) -> Fingerprint {
@@ -384,8 +388,8 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for () {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for DefId {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        true
+        FingerprintStyle::DefPathHash
     }
 
     fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
@@ -403,8 +407,8 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for DefId {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for LocalDefId {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        true
+        FingerprintStyle::DefPathHash
     }
 
     fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
@@ -422,8 +426,8 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for LocalDefId {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for CrateNum {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        true
+        FingerprintStyle::DefPathHash
     }
 
     fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
@@ -442,8 +446,8 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for CrateNum {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for (DefId, DefId) {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        false
+        FingerprintStyle::Opaque
     }
 
     // We actually would not need to specialize the implementation of this
@@ -467,8 +471,8 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for (DefId, DefId) {
 
 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for HirId {
     #[inline(always)]
-    fn can_reconstruct_query_key() -> bool {
+    fn fingerprint_style() -> FingerprintStyle {
-        false
+        FingerprintStyle::Opaque
     }
 
     // We actually would not need to specialize the implementation of this

compiler/rustc_middle/src/dep_graph/mod.rs

@@ -25,8 +25,8 @@ impl rustc_query_system::dep_graph::DepKind for DepKind {
     const NULL: Self = DepKind::Null;
 
     #[inline(always)]
-    fn can_reconstruct_query_key(&self) -> bool {
+    fn fingerprint_style(&self) -> rustc_query_system::dep_graph::FingerprintStyle {
-        DepKind::can_reconstruct_query_key(self)
+        DepKind::fingerprint_style(self)
     }
 
     #[inline(always)]

compiler/rustc_middle/src/traits/select.rs

@@ -264,14 +264,14 @@ impl EvaluationResult {
 /// Indicates that trait evaluation caused overflow and in which pass.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable)]
 pub enum OverflowError {
-    Cannonical,
+    Canonical,
     ErrorReporting,
 }
 
 impl<'tcx> From<OverflowError> for SelectionError<'tcx> {
     fn from(overflow_error: OverflowError) -> SelectionError<'tcx> {
         match overflow_error {
-            OverflowError::Cannonical => SelectionError::Overflow,
+            OverflowError::Canonical => SelectionError::Overflow,
             OverflowError::ErrorReporting => SelectionError::ErrorReporting,
         }
     }

compiler/rustc_middle/src/ty/layout.rs

@@ -986,7 +986,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                             let niche = if def.repr.hide_niche() {
                                 None
                             } else {
-                                Niche::from_scalar(dl, Size::ZERO, scalar.clone())
+                                Niche::from_scalar(dl, Size::ZERO, *scalar)
                             };
                             if let Some(niche) = niche {
                                 match st.largest_niche {
@@ -2273,7 +2273,7 @@ where
         ) -> TyMaybeWithLayout<'tcx> {
             let tcx = cx.tcx();
             let tag_layout = |tag: Scalar| -> TyAndLayout<'tcx> {
-                let layout = Layout::scalar(cx, tag.clone());
+                let layout = Layout::scalar(cx, tag);
                 TyAndLayout { layout: tcx.intern_layout(layout), ty: tag.value.to_ty(tcx) }
             };
 
@@ -3012,7 +3012,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         };
 
         let target = &self.tcx.sess.target;
-        let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl");
+        let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
         let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
         let linux_s390x_gnu_like =
             target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
@@ -3110,7 +3110,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
             if arg.layout.is_zst() {
                 // For some forsaken reason, x86_64-pc-windows-gnu
                 // doesn't ignore zero-sized struct arguments.
-                // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl}.
+                // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
                 if is_return
                     || rust_abi
                     || (!win_x64_gnu

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -130,7 +130,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     TerminatorKind::Call {
                         func: exchange_malloc,
                         args: vec![Operand::Move(size), Operand::Move(align)],
-                        destination: Some((Place::from(storage), success)),
+                        destination: Some((storage, success)),
                         cleanup: None,
                         from_hir_call: false,
                         fn_span: expr_span,
@@ -153,7 +153,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
 
                 // Transmute `*mut u8` to the box (thus far, uninitialized):
-                let box_ = Rvalue::ShallowInitBox(Operand::Move(Place::from(storage)), value.ty);
+                let box_ = Rvalue::ShallowInitBox(Operand::Move(storage), value.ty);
                 this.cfg.push_assign(block, source_info, Place::from(result), box_);
 
                 // initialize the box contents:

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

@@ -1068,9 +1068,7 @@ impl<'tcx> SplitWildcard<'tcx> {
                     Missing {
                         nonexhaustive_enum_missing_real_variants: self
                             .iter_missing(pcx)
-                            .filter(|c| !c.is_non_exhaustive())
+                            .any(|c| !c.is_non_exhaustive()),
-                            .next()
-                            .is_some(),
                     }
                 } else {
                     Missing { nonexhaustive_enum_missing_real_variants: false }

compiler/rustc_mir_dataflow/src/rustc_peek.rs

@@ -289,7 +289,7 @@ impl<'tcx> RustcPeekAt<'tcx> for MaybeMutBorrowedLocals<'_, 'tcx> {
         flow_state: &BitSet<Local>,
         call: PeekCall,
     ) {
-        warn!("peek_at: place={:?}", place);
+        info!(?place, "peek_at");
         let local = if let Some(l) = place.as_local() {
             l
         } else {
@@ -311,7 +311,7 @@ impl<'tcx> RustcPeekAt<'tcx> for MaybeLiveLocals {
         flow_state: &BitSet<Local>,
         call: PeekCall,
     ) {
-        warn!("peek_at: place={:?}", place);
+        info!(?place, "peek_at");
         let local = if let Some(l) = place.as_local() {
             l
         } else {

compiler/rustc_mir_transform/src/early_otherwise_branch.rs

@@ -263,7 +263,7 @@ impl<'a, 'tcx> Helper<'a, 'tcx> {
             }
 
             // check that the value being matched on is the same. The
-            if this_bb_discr_info.targets_with_values.iter().find(|x| x.0 == value).is_none() {
+            if !this_bb_discr_info.targets_with_values.iter().any(|x| x.0 == value) {
                 trace!("NO: values being matched on are not the same");
                 return None;
             }

compiler/rustc_mir_transform/src/normalize_array_len.rs

@@ -111,8 +111,7 @@ impl<'a, 'tcx> Patcher<'a, 'tcx> {
                         Operand::Copy(place) | Operand::Move(place) => {
                             // create new local
                             let ty = operand.ty(self.local_decls, self.tcx);
-                            let local_decl =
+                            let local_decl = LocalDecl::with_source_info(ty, statement.source_info);
-                                LocalDecl::with_source_info(ty, statement.source_info.clone());
                             let local = self.local_decls.push(local_decl);
                             // make it live
                             let mut make_live_statement = statement.clone();

compiler/rustc_parse/src/parser/expr.rs

@@ -1096,7 +1096,7 @@ impl<'a> Parser<'a> {
             (Err(ref mut err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
                 let name = pprust::path_to_string(&path);
                 snapshot.bump(); // `(`
-                match snapshot.parse_struct_fields(path.clone(), false, token::Paren) {
+                match snapshot.parse_struct_fields(path, false, token::Paren) {
                     Ok((fields, ..)) if snapshot.eat(&token::CloseDelim(token::Paren)) => {
                         // We have are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
                         // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.

compiler/rustc_passes/src/check_attr.rs

@@ -1767,8 +1767,7 @@ impl CheckAttrVisitor<'tcx> {
     fn check_macro_export(&self, hir_id: HirId, attr: &Attribute, target: Target) {
         if target != Target::MacroDef {
             self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                lint.build(&format!("`#[macro_export]` only has an effect on macro definitions"))
+                lint.build("`#[macro_export]` only has an effect on macro definitions").emit();
-                    .emit();
             });
         }
     }

compiler/rustc_passes/src/check_const.rs

@@ -8,7 +8,6 @@
 //! through, but errors for structured control flow in a `const` should be emitted here.
 
 use rustc_attr as attr;
-use rustc_data_structures::stable_set::FxHashSet;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
@@ -83,30 +82,39 @@ impl<'tcx> hir::itemlikevisit::ItemLikeVisitor<'tcx> for CheckConstTraitVisitor<
         let _: Option<_> = try {
             if let hir::ItemKind::Impl(ref imp) = item.kind {
                 if let hir::Constness::Const = imp.constness {
-                    let did = imp.of_trait.as_ref()?.trait_def_id()?;
+                    let trait_def_id = imp.of_trait.as_ref()?.trait_def_id()?;
-                    let mut to_implement = FxHashSet::default();
+                    let ancestors = self
+                        .tcx
+                        .trait_def(trait_def_id)
+                        .ancestors(self.tcx, item.def_id.to_def_id())
+                        .ok()?;
+                    let mut to_implement = Vec::new();
 
-                    for did in self.tcx.associated_item_def_ids(did) {
+                    for trait_item in self.tcx.associated_items(trait_def_id).in_definition_order()
+                    {
                         if let ty::AssocItem {
                             kind: ty::AssocKind::Fn, ident, defaultness, ..
-                        } = self.tcx.associated_item(*did)
+                        } = trait_item
                         {
                             // we can ignore functions that do not have default bodies:
                             // if those are unimplemented it will be catched by typeck.
-                            if defaultness.has_value()
+                            if !defaultness.has_value()
-                                && !self.tcx.has_attr(*did, sym::default_method_body_is_const)
+                                || self
+                                    .tcx
+                                    .has_attr(trait_item.def_id, sym::default_method_body_is_const)
                             {
-                                to_implement.insert(ident);
+                                continue;
-                            }
-                        }
                             }
 
-                    for it in imp
+                            let is_implemented = ancestors
-                        .items
+                                .leaf_def(self.tcx, trait_item.ident, trait_item.kind)
-                        .iter()
+                                .map(|node_item| !node_item.defining_node.is_from_trait())
-                        .filter(|it| matches!(it.kind, hir::AssocItemKind::Fn { .. }))
+                                .unwrap_or(false);
-                    {
+
-                        to_implement.remove(&it.ident);
+                            if !is_implemented {
+                                to_implement.push(ident.to_string());
+                            }
+                        }
                     }
 
                     // all nonconst trait functions (not marked with #[default_method_body_is_const])
@@ -118,7 +126,7 @@ impl<'tcx> hir::itemlikevisit::ItemLikeVisitor<'tcx> for CheckConstTraitVisitor<
                                 item.span,
                                 "const trait implementations may not use non-const default functions",
                             )
-                            .note(&format!("`{}` not implemented", to_implement.into_iter().map(|id| id.to_string()).collect::<Vec<_>>().join("`, `")))
+                            .note(&format!("`{}` not implemented", to_implement.join("`, `")))
                             .emit();
                     }
                 }

compiler/rustc_passes/src/intrinsicck.rs

@@ -141,6 +141,7 @@ impl ExprVisitor<'tcx> {
         template: &[InlineAsmTemplatePiece],
         is_input: bool,
         tied_input: Option<(&hir::Expr<'tcx>, Option<InlineAsmType>)>,
+        target_features: &[Symbol],
     ) -> Option<InlineAsmType> {
         // Check the type against the allowed types for inline asm.
         let ty = self.typeck_results.expr_ty_adjusted(expr);
@@ -283,17 +284,20 @@ impl ExprVisitor<'tcx> {
         };
 
         // Check whether the selected type requires a target feature. Note that
-        // this is different from the feature check we did earlier in AST
+        // this is different from the feature check we did earlier. While the
-        // lowering. While AST lowering checked that this register class is
+        // previous check checked that this register class is usable at all
-        // usable at all with the currently enabled features, some types may
+        // with the currently enabled features, some types may only be usable
-        // only be usable with a register class when a certain feature is
+        // with a register class when a certain feature is enabled. We check
-        // enabled. We check this here since it depends on the results of typeck.
+        // this here since it depends on the results of typeck.
         //
         // Also note that this check isn't run when the operand type is never
-        // (!). In that case we still need the earlier check in AST lowering to
+        // (!). In that case we still need the earlier check to verify that the
-        // verify that the register class is usable at all.
+        // register class is usable at all.
         if let Some(feature) = feature {
-            if !self.tcx.sess.target_features.contains(&Symbol::intern(feature)) {
+            let feat_sym = Symbol::intern(feature);
+            if !self.tcx.sess.target_features.contains(&feat_sym)
+                && !target_features.contains(&feat_sym)
+            {
                 let msg = &format!("`{}` target feature is not enabled", feature);
                 let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
                 err.note(&format!(
@@ -349,23 +353,122 @@ impl ExprVisitor<'tcx> {
         Some(asm_ty)
     }
 
-    fn check_asm(&self, asm: &hir::InlineAsm<'tcx>) {
+    fn check_asm(&self, asm: &hir::InlineAsm<'tcx>, hir_id: hir::HirId) {
-        for (idx, (op, _)) in asm.operands.iter().enumerate() {
+        let hir = self.tcx.hir();
+        let enclosing_id = hir.enclosing_body_owner(hir_id);
+        let enclosing_def_id = hir.local_def_id(enclosing_id).to_def_id();
+        let attrs = self.tcx.codegen_fn_attrs(enclosing_def_id);
+        for (idx, (op, op_sp)) in asm.operands.iter().enumerate() {
+            // Validate register classes against currently enabled target
+            // features. We check that at least one type is available for
+            // the enabled features.
+            //
+            // We ignore target feature requirements for clobbers: if the
+            // feature is disabled then the compiler doesn't care what we
+            // do with the registers.
+            //
+            // Note that this is only possible for explicit register
+            // operands, which cannot be used in the asm string.
+            if let Some(reg) = op.reg() {
+                if !op.is_clobber() {
+                    let mut missing_required_features = vec![];
+                    let reg_class = reg.reg_class();
+                    for &(_, feature) in reg_class.supported_types(self.tcx.sess.asm_arch.unwrap())
+                    {
+                        match feature {
+                            Some(feature) => {
+                                let feat_sym = Symbol::intern(feature);
+                                if self.tcx.sess.target_features.contains(&feat_sym)
+                                    || attrs.target_features.contains(&feat_sym)
+                                {
+                                    missing_required_features.clear();
+                                    break;
+                                } else {
+                                    missing_required_features.push(feature);
+                                }
+                            }
+                            None => {
+                                missing_required_features.clear();
+                                break;
+                            }
+                        }
+                    }
+
+                    // We are sorting primitive strs here and can use unstable sort here
+                    missing_required_features.sort_unstable();
+                    missing_required_features.dedup();
+                    match &missing_required_features[..] {
+                        [] => {}
+                        [feature] => {
+                            let msg = format!(
+                                "register class `{}` requires the `{}` target feature",
+                                reg_class.name(),
+                                feature
+                            );
+                            self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
+                            // register isn't enabled, don't do more checks
+                            continue;
+                        }
+                        features => {
+                            let msg = format!(
+                                "register class `{}` requires at least one of the following target features: {}",
+                                reg_class.name(),
+                                features.join(", ")
+                            );
+                            self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
+                            // register isn't enabled, don't do more checks
+                            continue;
+                        }
+                    }
+                }
+            }
+
             match *op {
                 hir::InlineAsmOperand::In { reg, ref expr } => {
-                    self.check_asm_operand_type(idx, reg, expr, asm.template, true, None);
+                    self.check_asm_operand_type(
+                        idx,
+                        reg,
+                        expr,
+                        asm.template,
+                        true,
+                        None,
+                        &attrs.target_features,
+                    );
                 }
                 hir::InlineAsmOperand::Out { reg, late: _, ref expr } => {
                     if let Some(expr) = expr {
-                        self.check_asm_operand_type(idx, reg, expr, asm.template, false, None);
+                        self.check_asm_operand_type(
+                            idx,
+                            reg,
+                            expr,
+                            asm.template,
+                            false,
+                            None,
+                            &attrs.target_features,
+                        );
                     }
                 }
                 hir::InlineAsmOperand::InOut { reg, late: _, ref expr } => {
-                    self.check_asm_operand_type(idx, reg, expr, asm.template, false, None);
+                    self.check_asm_operand_type(
+                        idx,
+                        reg,
+                        expr,
+                        asm.template,
+                        false,
+                        None,
+                        &attrs.target_features,
+                    );
                 }
                 hir::InlineAsmOperand::SplitInOut { reg, late: _, ref in_expr, ref out_expr } => {
-                    let in_ty =
+                    let in_ty = self.check_asm_operand_type(
-                        self.check_asm_operand_type(idx, reg, in_expr, asm.template, true, None);
+                        idx,
+                        reg,
+                        in_expr,
+                        asm.template,
+                        true,
+                        None,
+                        &attrs.target_features,
+                    );
                     if let Some(out_expr) = out_expr {
                         self.check_asm_operand_type(
                             idx,
@@ -374,6 +477,7 @@ impl ExprVisitor<'tcx> {
                             asm.template,
                             false,
                             Some((in_expr, in_ty)),
+                            &attrs.target_features,
                         );
                     }
                 }
@@ -422,7 +526,7 @@ impl Visitor<'tcx> for ExprVisitor<'tcx> {
                 }
             }
 
-            hir::ExprKind::InlineAsm(asm) => self.check_asm(asm),
+            hir::ExprKind::InlineAsm(asm) => self.check_asm(asm, expr.hir_id),
 
             _ => {}
         }

compiler/rustc_query_impl/src/plumbing.rs

@@ -428,6 +428,7 @@ macro_rules! define_queries {
             use rustc_middle::ty::query::query_keys;
             use rustc_query_system::dep_graph::DepNodeParams;
             use rustc_query_system::query::{force_query, QueryDescription};
+            use rustc_query_system::dep_graph::FingerprintStyle;
 
             // We use this for most things when incr. comp. is turned off.
             pub const Null: QueryStruct = QueryStruct {
@@ -454,9 +455,9 @@ macro_rules! define_queries {
                 const is_anon: bool = is_anon!([$($modifiers)*]);
 
                 #[inline(always)]
-                fn can_reconstruct_query_key() -> bool {
+                fn fingerprint_style() -> FingerprintStyle {
                     <query_keys::$name<'_> as DepNodeParams<TyCtxt<'_>>>
-                        ::can_reconstruct_query_key()
+                        ::fingerprint_style()
                 }
 
                 fn recover<'tcx>(tcx: TyCtxt<'tcx>, dep_node: &DepNode) -> Option<query_keys::$name<'tcx>> {
@@ -472,7 +473,7 @@ macro_rules! define_queries {
                         return
                     }
 
-                    if !can_reconstruct_query_key() {
+                    if !fingerprint_style().reconstructible() {
                         return
                     }
 

compiler/rustc_query_impl/src/stats.rs

@@ -5,8 +5,6 @@ use rustc_query_system::query::{QueryCache, QueryCacheStore};
 
 use std::any::type_name;
 use std::mem;
-#[cfg(debug_assertions)]
-use std::sync::atomic::Ordering;
 
 trait KeyStats {
     fn key_stats(&self, stats: &mut QueryStats);
@@ -27,7 +25,6 @@ impl KeyStats for DefId {
 #[derive(Clone)]
 struct QueryStats {
     name: &'static str,
-    cache_hits: usize,
     key_size: usize,
     key_type: &'static str,
     value_size: usize,
@@ -42,10 +39,6 @@ where
 {
     let mut stats = QueryStats {
         name,
-        #[cfg(debug_assertions)]
-        cache_hits: map.cache_hits.load(Ordering::Relaxed),
-        #[cfg(not(debug_assertions))]
-        cache_hits: 0,
         key_size: mem::size_of::<C::Key>(),
         key_type: type_name::<C::Key>(),
         value_size: mem::size_of::<C::Value>(),
@@ -63,12 +56,6 @@ where
 pub fn print_stats(tcx: TyCtxt<'_>) {
     let queries = query_stats(tcx);
 
-    if cfg!(debug_assertions) {
-        let hits: usize = queries.iter().map(|s| s.cache_hits).sum();
-        let results: usize = queries.iter().map(|s| s.entry_count).sum();
-        eprintln!("\nQuery cache hit rate: {}", hits as f64 / (hits + results) as f64);
-    }
-
     let mut query_key_sizes = queries.clone();
     query_key_sizes.sort_by_key(|q| q.key_size);
     eprintln!("\nLarge query keys:");
@@ -83,20 +70,6 @@ pub fn print_stats(tcx: TyCtxt<'_>) {
         eprintln!("   {} - {} x {} - {}", q.name, q.value_size, q.entry_count, q.value_type);
     }
 
-    if cfg!(debug_assertions) {
-        let mut query_cache_hits = queries.clone();
-        query_cache_hits.sort_by_key(|q| q.cache_hits);
-        eprintln!("\nQuery cache hits:");
-        for q in query_cache_hits.iter().rev() {
-            eprintln!(
-                "   {} - {} ({}%)",
-                q.name,
-                q.cache_hits,
-                q.cache_hits as f64 / (q.cache_hits + q.entry_count) as f64
-            );
-        }
-    }
-
     let mut query_value_count = queries.clone();
     query_value_count.sort_by_key(|q| q.entry_count);
     eprintln!("\nQuery value count:");

compiler/rustc_query_system/src/dep_graph/dep_node.rs

@@ -42,7 +42,7 @@
 //!   `DefId` it was computed from. In other cases, too much information gets
 //!   lost during fingerprint computation.
 
-use super::{DepContext, DepKind};
+use super::{DepContext, DepKind, FingerprintStyle};
 use crate::ich::StableHashingContext;
 
 use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint};
@@ -75,7 +75,7 @@ impl<K: DepKind> DepNode<K> {
 
         #[cfg(debug_assertions)]
         {
-            if !kind.can_reconstruct_query_key()
+            if !kind.fingerprint_style().reconstructible()
                 && (tcx.sess().opts.debugging_opts.incremental_info
                     || tcx.sess().opts.debugging_opts.query_dep_graph)
             {
@@ -94,7 +94,7 @@ impl<K: DepKind> fmt::Debug for DepNode<K> {
 }
 
 pub trait DepNodeParams<Ctxt: DepContext>: fmt::Debug + Sized {
-    fn can_reconstruct_query_key() -> bool;
+    fn fingerprint_style() -> FingerprintStyle;
 
     /// This method turns the parameters of a DepNodeConstructor into an opaque
     /// Fingerprint to be used in DepNode.
@@ -111,7 +111,7 @@ pub trait DepNodeParams<Ctxt: DepContext>: fmt::Debug + Sized {
     /// This method tries to recover the query key from the given `DepNode`,
     /// something which is needed when forcing `DepNode`s during red-green
     /// evaluation. The query system will only call this method if
-    /// `can_reconstruct_query_key()` is `true`.
+    /// `fingerprint_style()` is not `FingerprintStyle::Opaque`.
     /// It is always valid to return `None` here, in which case incremental
     /// compilation will treat the query as having changed instead of forcing it.
     fn recover(tcx: Ctxt, dep_node: &DepNode<Ctxt::DepKind>) -> Option<Self>;
@@ -122,8 +122,8 @@ where
     T: for<'a> HashStable<StableHashingContext<'a>> + fmt::Debug,
 {
     #[inline]
-    default fn can_reconstruct_query_key() -> bool {
+    default fn fingerprint_style() -> FingerprintStyle {
-        false
+        FingerprintStyle::Opaque
     }
 
     default fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint {

compiler/rustc_query_system/src/dep_graph/mod.rs

@@ -50,6 +50,27 @@ impl<T: DepContext> HasDepContext for T {
     }
 }
 
+/// Describes the contents of the fingerprint generated by a given query.
+#[derive(PartialEq, Eq, Copy, Clone)]
+pub enum FingerprintStyle {
+    /// The fingerprint is actually a DefPathHash.
+    DefPathHash,
+    /// Query key was `()` or equivalent, so fingerprint is just zero.
+    Unit,
+    /// Some opaque hash.
+    Opaque,
+}
+
+impl FingerprintStyle {
+    #[inline]
+    pub fn reconstructible(self) -> bool {
+        match self {
+            FingerprintStyle::DefPathHash | FingerprintStyle::Unit => true,
+            FingerprintStyle::Opaque => false,
+        }
+    }
+}
+
 /// Describe the different families of dependency nodes.
 pub trait DepKind: Copy + fmt::Debug + Eq + Hash + Send + Encodable<FileEncoder> + 'static {
     const NULL: Self;
@@ -73,5 +94,5 @@ pub trait DepKind: Copy + fmt::Debug + Eq + Hash + Send + Encodable<FileEncoder>
     where
         OP: for<'a> FnOnce(Option<&'a Lock<TaskDeps<Self>>>);
 
-    fn can_reconstruct_query_key(&self) -> bool;
+    fn fingerprint_style(&self) -> FingerprintStyle;
 }

compiler/rustc_query_system/src/query/plumbing.rs

@@ -26,24 +26,15 @@ use std::hash::{Hash, Hasher};
 use std::mem;
 use std::num::NonZeroU32;
 use std::ptr;
-#[cfg(debug_assertions)]
-use std::sync::atomic::{AtomicUsize, Ordering};
 
 pub struct QueryCacheStore<C: QueryCache> {
     cache: C,
     shards: Sharded<C::Sharded>,
-    #[cfg(debug_assertions)]
-    pub cache_hits: AtomicUsize,
 }
 
 impl<C: QueryCache + Default> Default for QueryCacheStore<C> {
     fn default() -> Self {
-        Self {
+        Self { cache: C::default(), shards: Default::default() }
-            cache: C::default(),
-            shards: Default::default(),
-            #[cfg(debug_assertions)]
-            cache_hits: AtomicUsize::new(0),
-        }
     }
 }
 
@@ -377,10 +368,6 @@ where
         if unlikely!(tcx.profiler().enabled()) {
             tcx.profiler().query_cache_hit(index.into());
         }
-        #[cfg(debug_assertions)]
-        {
-            cache.cache_hits.fetch_add(1, Ordering::Relaxed);
-        }
         tcx.dep_graph().read_index(index);
         on_hit(value)
     })
@@ -429,10 +416,6 @@ where
             if unlikely!(tcx.dep_context().profiler().enabled()) {
                 tcx.dep_context().profiler().query_cache_hit(index.into());
             }
-            #[cfg(debug_assertions)]
-            {
-                cache.cache_hits.fetch_add(1, Ordering::Relaxed);
-            }
             query_blocked_prof_timer.finish_with_query_invocation_id(index.into());
 
             (v, Some(index))
@@ -540,7 +523,7 @@ where
         // We always expect to find a cached result for things that
         // can be forced from `DepNode`.
         debug_assert!(
-            !dep_node.kind.can_reconstruct_query_key() || result.is_some(),
+            !dep_node.kind.fingerprint_style().reconstructible() || result.is_some(),
             "missing on-disk cache entry for {:?}",
             dep_node
         );
@@ -705,10 +688,6 @@ where
         if unlikely!(tcx.dep_context().profiler().enabled()) {
             tcx.dep_context().profiler().query_cache_hit(index.into());
         }
-        #[cfg(debug_assertions)]
-        {
-            cache.cache_hits.fetch_add(1, Ordering::Relaxed);
-        }
     });
 
     let lookup = match cached {
@@ -778,7 +757,7 @@ where
         return false;
     }
 
-    if !<Q::Key as DepNodeParams<CTX::DepContext>>::can_reconstruct_query_key() {
+    if !<Q::Key as DepNodeParams<CTX::DepContext>>::fingerprint_style().reconstructible() {
         return false;
     }
 

compiler/rustc_resolve/src/imports.rs

@@ -9,7 +9,6 @@ use crate::{BindingKey, ModuleKind, ResolutionError, Resolver, Segment};
 use crate::{CrateLint, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet, Weak};
 use crate::{NameBinding, NameBindingKind, PathResult, PrivacyError, ToNameBinding};
 
-use rustc_ast::unwrap_or;
 use rustc_ast::NodeId;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::ptr_key::PtrKey;
@@ -349,10 +348,10 @@ impl<'a> Resolver<'a> {
             if !self.is_accessible_from(single_import.vis.get(), parent_scope.module) {
                 continue;
             }
-            let module = unwrap_or!(
+            let module = match single_import.imported_module.get() {
-                single_import.imported_module.get(),
+                Some(x) => x,
-                return Err((Undetermined, Weak::No))
+                None => return Err((Undetermined, Weak::No)),
-            );
+            };
             let ident = match single_import.kind {
                 ImportKind::Single { source, .. } => source,
                 _ => unreachable!(),

compiler/rustc_serialize/src/serialize.rs

@@ -500,8 +500,8 @@ impl<D: Decoder, const N: usize> Decodable<D> for [u8; N] {
         d.read_seq(|d, len| {
             assert!(len == N);
             let mut v = [0u8; N];
-            for i in 0..len {
+            for x in &mut v {
-                v[i] = d.read_seq_elt(|d| Decodable::decode(d))?;
+                *x = d.read_seq_elt(|d| Decodable::decode(d))?;
             }
             Ok(v)
         })

compiler/rustc_span/src/symbol.rs

@@ -816,6 +816,7 @@ symbols! {
         mem_size_of,
         mem_size_of_val,
         mem_uninitialized,
+        mem_variant_count,
         mem_zeroed,
         member_constraints,
         memory,
@@ -893,6 +894,7 @@ symbols! {
         nomem,
         non_ascii_idents,
         non_exhaustive,
+        non_exhaustive_omitted_patterns_lint,
         non_modrs_mods,
         none_error,
         nontemporal_store,

compiler/rustc_target/src/spec/armv7_unknown_linux_uclibceabihf.rs

@@ -0,0 +1,24 @@
+use crate::spec::{Target, TargetOptions};
+
+// This target is for uclibc Linux on ARMv7 without NEON or
+// thumb-mode. See the thumbv7neon variant for enabling both.
+
+pub fn target() -> Target {
+    let base = super::linux_uclibc_base::opts();
+    Target {
+        llvm_target: "armv7-unknown-linux-gnueabihf".to_string(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        arch: "arm".to_string(),
+
+        options: TargetOptions {
+            // Info about features at https://wiki.debian.org/ArmHardFloatPort
+            features: "+v7,+vfp3,-d32,+thumb2,-neon".to_string(),
+            cpu: "generic".to_string(),
+            max_atomic_width: Some(64),
+            mcount: "_mcount".to_string(),
+            abi: "eabihf".to_string(),
+            ..base
+        },
+    }
+}

compiler/rustc_target/src/spec/mod.rs

@@ -952,6 +952,8 @@ supported_targets! {
     ("bpfel-unknown-none", bpfel_unknown_none),
 
     ("armv6k-nintendo-3ds", armv6k_nintendo_3ds),
+
+    ("armv7-unknown-linux-uclibceabihf", armv7_unknown_linux_uclibceabihf),
 }
 
 /// Warnings encountered when parsing the target `json`.

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -278,14 +278,14 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
 
             fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) {
                 self.is_poly |= expr.ty.definitely_has_param_types_or_consts(self.tcx);
-                if self.is_poly == false {
+                if !self.is_poly {
                     visit::walk_expr(self, expr)
                 }
             }
 
             fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) {
                 self.is_poly |= pat.ty.definitely_has_param_types_or_consts(self.tcx);
-                if self.is_poly == false {
+                if !self.is_poly {
                     visit::walk_pat(self, pat);
                 }
             }
@@ -298,7 +298,7 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
         let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body, tcx };
         visit::walk_expr(&mut is_poly_vis, &body[body_id]);
         debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly);
-        if is_poly_vis.is_poly == false {
+        if !is_poly_vis.is_poly {
             return Ok(None);
         }
 

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -704,7 +704,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 .filter_map(|lang_item| self.tcx.lang_items().require(*lang_item).ok())
                 .collect();
 
-        never_suggest_borrow.push(self.tcx.get_diagnostic_item(sym::Send).unwrap());
+        if let Some(def_id) = self.tcx.get_diagnostic_item(sym::Send) {
+            never_suggest_borrow.push(def_id);
+        }
 
         let param_env = obligation.param_env;
         let trait_ref = poly_trait_ref.skip_binder();

compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs

@@ -83,10 +83,10 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
     ) -> EvaluationResult {
         match self.evaluate_obligation(obligation) {
             Ok(result) => result,
-            Err(OverflowError::Cannonical) => {
+            Err(OverflowError::Canonical) => {
                 let mut selcx = SelectionContext::with_query_mode(&self, TraitQueryMode::Standard);
                 selcx.evaluate_root_obligation(obligation).unwrap_or_else(|r| match r {
-                    OverflowError::Cannonical => {
+                    OverflowError::Canonical => {
                         span_bug!(
                             obligation.cause.span,
                             "Overflow should be caught earlier in standard query mode: {:?}, {:?}",

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -161,7 +161,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     Ok(Some(EvaluatedCandidate { candidate: c, evaluation: eval }))
                 }
                 Ok(_) => Ok(None),
-                Err(OverflowError::Cannonical) => Err(Overflow),
+                Err(OverflowError::Canonical) => Err(Overflow),
                 Err(OverflowError::ErrorReporting) => Err(ErrorReporting),
             })
             .flat_map(Result::transpose)

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -900,7 +900,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         match self.candidate_from_obligation(stack) {
             Ok(Some(c)) => self.evaluate_candidate(stack, &c),
             Ok(None) => Ok(EvaluatedToAmbig),
-            Err(Overflow) => Err(OverflowError::Cannonical),
+            Err(Overflow) => Err(OverflowError::Canonical),
             Err(ErrorReporting) => Err(OverflowError::ErrorReporting),
             Err(..) => Ok(EvaluatedToErr),
         }
@@ -1064,7 +1064,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     self.infcx.report_overflow_error(error_obligation, true);
                 }
                 TraitQueryMode::Canonical => {
-                    return Err(OverflowError::Cannonical);
+                    return Err(OverflowError::Canonical);
                 }
             }
         }

compiler/rustc_traits/src/chalk/lowering.rs

@@ -892,7 +892,7 @@ impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> {
         match r {
             ty::ReLateBound(index, br) if *index == self.binder_index => match br.kind {
                 ty::BoundRegionKind::BrNamed(def_id, _name) => {
-                    if self.named_parameters.iter().find(|d| **d == def_id).is_none() {
+                    if !self.named_parameters.iter().any(|d| *d == def_id) {
                         self.named_parameters.push(def_id);
                     }
                 }

compiler/rustc_typeck/src/check/callee.rs

@@ -329,7 +329,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let obligation = Obligation::new(
                             ObligationCause::dummy_with_span(callee_expr.span),
                             self.param_env,
-                            predicate.clone(),
+                            *predicate,
                         );
                         let result = self.infcx.evaluate_obligation(&obligation);
                         self.tcx

compiler/rustc_typeck/src/check/cast.rs

@@ -431,7 +431,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                         .sess
                         .source_map()
                         .span_to_snippet(self.expr.span)
-                        .map_or(false, |snip| snip.starts_with("("));
+                        .map_or(false, |snip| snip.starts_with('('));
 
                     // Very crude check to see whether the expression must be wrapped
                     // in parentheses for the suggestion to work (issue #89497).

compiler/rustc_typeck/src/check/expr.rs

@@ -1887,7 +1887,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             };
         let expr_snippet =
             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
-        let is_wrapped = expr_snippet.starts_with("(") && expr_snippet.ends_with(")");
+        let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
         let after_open = expr.span.lo() + rustc_span::BytePos(1);
         let before_close = expr.span.hi() - rustc_span::BytePos(1);
 

compiler/rustc_typeck/src/check/method/probe.rs

@@ -753,17 +753,27 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
             let impl_ty = impl_ty.subst(self.tcx, impl_substs);
 
+            debug!("impl_ty: {:?}", impl_ty);
+
             // Determine the receiver type that the method itself expects.
-            let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs);
+            let (xform_self_ty, xform_ret_ty) = self.xform_self_ty(&item, impl_ty, impl_substs);
+            debug!("xform_self_ty: {:?}, xform_ret_ty: {:?}", xform_self_ty, xform_ret_ty);
 
             // We can't use normalize_associated_types_in as it will pollute the
             // fcx's fulfillment context after this probe is over.
+            // Note: we only normalize `xform_self_ty` here since the normalization
+            // of the return type can lead to inference results that prohibit
+            // valid canidates from being found, see issue #85671
+            // FIXME Postponing the normalization of the return type likely only hides a deeper bug,
+            // which might be caused by the `param_env` itself. The clauses of the `param_env`
+            // maybe shouldn't include `Param`s, but rather fresh variables or be canonicalized,
+            // see isssue #89650
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
             let selcx = &mut traits::SelectionContext::new(self.fcx);
-            let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } =
+            let traits::Normalized { value: xform_self_ty, obligations } =
-                traits::normalize(selcx, self.param_env, cause, xform_tys);
+                traits::normalize(selcx, self.param_env, cause, xform_self_ty);
             debug!(
-                "assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}",
+                "assemble_inherent_impl_probe after normalization: xform_self_ty = {:?}/{:?}",
                 xform_self_ty, xform_ret_ty
             );
 
@@ -1420,6 +1430,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             };
 
             let mut result = ProbeResult::Match;
+            let mut xform_ret_ty = probe.xform_ret_ty;
+            debug!(?xform_ret_ty);
+
             let selcx = &mut traits::SelectionContext::new(self);
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
 
@@ -1428,7 +1441,17 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             // match as well (or at least may match, sometimes we
             // don't have enough information to fully evaluate).
             match probe.kind {
-                InherentImplCandidate(substs, ref ref_obligations) => {
+                InherentImplCandidate(ref substs, ref ref_obligations) => {
+                    // `xform_ret_ty` hasn't been normalized yet, only `xform_self_ty`,
+                    // see the reasons mentioned in the comments in `assemble_inherent_impl_probe`
+                    // for why this is necessary
+                    let traits::Normalized {
+                        value: normalized_xform_ret_ty,
+                        obligations: normalization_obligations,
+                    } = traits::normalize(selcx, self.param_env, cause.clone(), probe.xform_ret_ty);
+                    xform_ret_ty = normalized_xform_ret_ty;
+                    debug!("xform_ret_ty after normalization: {:?}", xform_ret_ty);
+
                     // Check whether the impl imposes obligations we have to worry about.
                     let impl_def_id = probe.item.container.id();
                     let impl_bounds = self.tcx.predicates_of(impl_def_id);
@@ -1442,7 +1465,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
                     let candidate_obligations = impl_obligations
                         .chain(norm_obligations.into_iter())
-                        .chain(ref_obligations.iter().cloned());
+                        .chain(ref_obligations.iter().cloned())
+                        .chain(normalization_obligations.into_iter());
+
                     // Evaluate those obligations to see if they might possibly hold.
                     for o in candidate_obligations {
                         let o = self.resolve_vars_if_possible(o);
@@ -1527,9 +1552,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             }
 
             if let ProbeResult::Match = result {
-                if let (Some(return_ty), Some(xform_ret_ty)) =
+                if let (Some(return_ty), Some(xform_ret_ty)) = (self.return_type, xform_ret_ty) {
-                    (self.return_type, probe.xform_ret_ty)
-                {
                     let xform_ret_ty = self.resolve_vars_if_possible(xform_ret_ty);
                     debug!(
                         "comparing return_ty {:?} with xform ret ty {:?}",
@@ -1669,6 +1692,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         self.static_candidates.push(source);
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn xform_self_ty(
         &self,
         item: &ty::AssocItem,
@@ -1683,9 +1707,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn xform_method_sig(&self, method: DefId, substs: SubstsRef<'tcx>) -> ty::FnSig<'tcx> {
         let fn_sig = self.tcx.fn_sig(method);
-        debug!("xform_self_ty(fn_sig={:?}, substs={:?})", fn_sig, substs);
+        debug!(?fn_sig);
 
         assert!(!substs.has_escaping_bound_vars());
 

compiler/rustc_typeck/src/check/regionck.rs

@@ -413,7 +413,7 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionCtxt<'a, 'tcx> {
             }
 
             hir::ExprKind::Match(ref discr, arms, _) => {
-                self.link_match(discr, &arms[..]);
+                self.link_match(discr, arms);
 
                 intravisit::walk_expr(self, expr);
             }

compiler/rustc_typeck/src/check/upvar.rs

@@ -65,6 +65,7 @@ use std::iter;
 enum PlaceAncestryRelation {
     Ancestor,
     Descendant,
+    SamePlace,
     Divergent,
 }
 
@@ -564,7 +565,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 for possible_ancestor in min_cap_list.iter_mut() {
                     match determine_place_ancestry_relation(&place, &possible_ancestor.place) {
                         // current place is descendant of possible_ancestor
-                        PlaceAncestryRelation::Descendant => {
+                        PlaceAncestryRelation::Descendant | PlaceAncestryRelation::SamePlace => {
                             ancestor_found = true;
                             let backup_path_expr_id = possible_ancestor.info.path_expr_id;
 
@@ -2278,15 +2279,17 @@ fn determine_place_ancestry_relation(
     let projections_b = &place_b.projections;
 
     let same_initial_projections =
-        iter::zip(projections_a, projections_b).all(|(proj_a, proj_b)| proj_a == proj_b);
+        iter::zip(projections_a, projections_b).all(|(proj_a, proj_b)| proj_a.kind == proj_b.kind);
 
     if same_initial_projections {
+        use std::cmp::Ordering;
+
         // First min(n, m) projections are the same
         // Select Ancestor/Descendant
-        if projections_b.len() >= projections_a.len() {
+        match projections_b.len().cmp(&projections_a.len()) {
-            PlaceAncestryRelation::Ancestor
+            Ordering::Greater => PlaceAncestryRelation::Ancestor,
-        } else {
+            Ordering::Equal => PlaceAncestryRelation::SamePlace,
-            PlaceAncestryRelation::Descendant
+            Ordering::Less => PlaceAncestryRelation::Descendant,
         }
     } else {
         PlaceAncestryRelation::Divergent

compiler/rustc_typeck/src/coherence/inherent_impls_overlap.rs

@@ -3,6 +3,7 @@ use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
+use rustc_index::vec::IndexVec;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::Symbol;
 use rustc_trait_selection::traits::{self, SkipLeakCheck};
@@ -158,14 +159,18 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                     // This is advantageous to running the algorithm over the
                     // entire graph when there are many connected regions.
 
+                    rustc_index::newtype_index! {
+                        pub struct RegionId {
+                            ENCODABLE = custom
+                        }
+                    }
                     struct ConnectedRegion {
                         idents: SmallVec<[Symbol; 8]>,
                         impl_blocks: FxHashSet<usize>,
                     }
-                    // Highest connected region id
+                    let mut connected_regions: IndexVec<RegionId, _> = Default::default();
-                    let mut highest_region_id = 0;
+                    // Reverse map from the Symbol to the connected region id.
                     let mut connected_region_ids = FxHashMap::default();
-                    let mut connected_regions = FxHashMap::default();
 
                     for (i, &(&_impl_def_id, impl_items)) in impls_items.iter().enumerate() {
                         if impl_items.len() == 0 {
@@ -173,7 +178,7 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                         }
                         // First obtain a list of existing connected region ids
                         let mut idents_to_add = SmallVec::<[Symbol; 8]>::new();
-                        let ids = impl_items
+                        let mut ids = impl_items
                             .in_definition_order()
                             .filter_map(|item| {
                                 let entry = connected_region_ids.entry(item.ident.name);
@@ -184,62 +189,64 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                                     None
                                 }
                             })
-                            .collect::<FxHashSet<usize>>();
+                            .collect::<SmallVec<[RegionId; 8]>>();
-                        match ids.len() {
+                        // Sort the id list so that the algorithm is deterministic
-                            0 | 1 => {
+                        ids.sort_unstable();
-                                let id_to_set = if ids.is_empty() {
+                        let ids = ids;
+                        match &ids[..] {
                             // Create a new connected region
-                                    let region = ConnectedRegion {
+                            [] => {
+                                let id_to_set = connected_regions.next_index();
+                                // Update the connected region ids
+                                for ident in &idents_to_add {
+                                    connected_region_ids.insert(*ident, id_to_set);
+                                }
+                                connected_regions.insert(
+                                    id_to_set,
+                                    ConnectedRegion {
                                         idents: idents_to_add,
                                         impl_blocks: std::iter::once(i).collect(),
-                                    };
+                                    },
-                                    connected_regions.insert(highest_region_id, region);
+                                );
-                                    (highest_region_id, highest_region_id += 1).0
+                            }
-                                } else {
                             // Take the only id inside the list
-                                    let id_to_set = *ids.iter().next().unwrap();
+                            &[id_to_set] => {
-                                    let region = connected_regions.get_mut(&id_to_set).unwrap();
+                                let region = connected_regions[id_to_set].as_mut().unwrap();
                                 region.impl_blocks.insert(i);
                                 region.idents.extend_from_slice(&idents_to_add);
-                                    id_to_set
-                                };
-                                let (_id, region) = connected_regions.iter().next().unwrap();
                                 // Update the connected region ids
-                                for ident in region.idents.iter() {
+                                for ident in &idents_to_add {
                                     connected_region_ids.insert(*ident, id_to_set);
                                 }
                             }
-                            _ => {
                             // We have multiple connected regions to merge.
                             // In the worst case this might add impl blocks
                             // one by one and can thus be O(n^2) in the size
                             // of the resulting final connected region, but
                             // this is no issue as the final step to check
                             // for overlaps runs in O(n^2) as well.
-
+                            &[id_to_set, ..] => {
-                                // Take the smallest id from the list
+                                let mut region = connected_regions.remove(id_to_set).unwrap();
-                                let id_to_set = *ids.iter().min().unwrap();
-
-                                // Sort the id list so that the algorithm is deterministic
-                                let mut ids = ids.into_iter().collect::<SmallVec<[usize; 8]>>();
-                                ids.sort_unstable();
-
-                                let mut region = connected_regions.remove(&id_to_set).unwrap();
-                                region.idents.extend_from_slice(&idents_to_add);
                                 region.impl_blocks.insert(i);
+                                region.idents.extend_from_slice(&idents_to_add);
+                                // Update the connected region ids
+                                for ident in &idents_to_add {
+                                    connected_region_ids.insert(*ident, id_to_set);
+                                }
 
+                                // Remove other regions from ids.
                                 for &id in ids.iter() {
                                     if id == id_to_set {
                                         continue;
                                     }
-                                    let r = connected_regions.remove(&id).unwrap();
+                                    let r = connected_regions.remove(id).unwrap();
-                                    // Update the connected region ids
                                     for ident in r.idents.iter() {
                                         connected_region_ids.insert(*ident, id_to_set);
                                     }
                                     region.idents.extend_from_slice(&r.idents);
                                     region.impl_blocks.extend(r.impl_blocks);
                                 }
+
                                 connected_regions.insert(id_to_set, region);
                             }
                         }
@@ -254,16 +261,22 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
                             let avg = impls.len() / connected_regions.len();
                             let s = connected_regions
                                 .iter()
-                                .map(|r| r.1.impl_blocks.len() as isize - avg as isize)
+                                .flatten()
+                                .map(|r| r.impl_blocks.len() as isize - avg as isize)
                                 .map(|v| v.abs() as usize)
                                 .sum::<usize>();
                             s / connected_regions.len()
                         },
-                        connected_regions.iter().map(|r| r.1.impl_blocks.len()).max().unwrap()
+                        connected_regions
+                            .iter()
+                            .flatten()
+                            .map(|r| r.impl_blocks.len())
+                            .max()
+                            .unwrap()
                     );
                     // List of connected regions is built. Now, run the overlap check
                     // for each pair of impl blocks in the same connected region.
-                    for (_id, region) in connected_regions.into_iter() {
+                    for region in connected_regions.into_iter().flatten() {
                         let mut impl_blocks =
                             region.impl_blocks.into_iter().collect::<SmallVec<[usize; 8]>>();
                         impl_blocks.sort_unstable();

compiler/rustc_typeck/src/lib.rs

@@ -63,6 +63,7 @@ This API is completely unstable and subject to change.
 #![feature(in_band_lifetimes)]
 #![feature(is_sorted)]
 #![feature(iter_zip)]
+#![feature(min_specialization)]
 #![feature(nll)]
 #![feature(try_blocks)]
 #![feature(never_type)]

library/alloc/src/boxed.rs

@@ -187,6 +187,7 @@ impl<T> Box<T> {
     #[cfg(not(no_global_oom_handling))]
     #[inline(always)]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn new(x: T) -> Self {
         box x
     }
@@ -211,6 +212,7 @@ impl<T> Box<T> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     #[inline]
     pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
         Self::new_uninit_in(Global)
@@ -237,6 +239,7 @@ impl<T> Box<T> {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_zeroed() -> Box<mem::MaybeUninit<T>> {
         Self::new_zeroed_in(Global)
     }
@@ -245,6 +248,7 @@ impl<T> Box<T> {
     /// `x` will be pinned in memory and unable to be moved.
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "pin", since = "1.33.0")]
+    #[must_use]
     #[inline(always)]
     pub fn pin(x: T) -> Pin<Box<T>> {
         (box x).into()
@@ -339,6 +343,7 @@ impl<T, A: Allocator> Box<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
+    #[must_use]
     #[inline]
     pub fn new_in(x: T, alloc: A) -> Self {
         let mut boxed = Self::new_uninit_in(alloc);
@@ -395,6 +400,7 @@ impl<T, A: Allocator> Box<T, A> {
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[cfg(not(no_global_oom_handling))]
+    #[must_use]
     // #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
@@ -459,6 +465,7 @@ impl<T, A: Allocator> Box<T, A> {
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[cfg(not(no_global_oom_handling))]
     // #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A> {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
         // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
@@ -503,6 +510,7 @@ impl<T, A: Allocator> Box<T, A> {
     /// `x` will be pinned in memory and unable to be moved.
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
+    #[must_use]
     #[inline(always)]
     pub fn pin_in(x: T, alloc: A) -> Pin<Self>
     where
@@ -561,6 +569,7 @@ impl<T> Box<[T]> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
         unsafe { RawVec::with_capacity(len).into_box(len) }
     }
@@ -585,6 +594,7 @@ impl<T> Box<[T]> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_zeroed_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
         unsafe { RawVec::with_capacity_zeroed(len).into_box(len) }
     }
@@ -681,6 +691,7 @@ impl<T, A: Allocator> Box<[T], A> {
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
     // #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_uninit_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
         unsafe { RawVec::with_capacity_in(len, alloc).into_box(len) }
     }
@@ -708,6 +719,7 @@ impl<T, A: Allocator> Box<[T], A> {
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
     // #[unstable(feature = "new_uninit", issue = "63291")]
+    #[must_use]
     pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Box<[mem::MaybeUninit<T>], A> {
         unsafe { RawVec::with_capacity_zeroed_in(len, alloc).into_box(len) }
     }
@@ -1277,6 +1289,7 @@ impl<T> From<T> for Box<T> {
     /// from the stack into it.
     ///
     /// # Examples
+    ///
     /// ```rust
     /// let x = 5;
     /// let boxed = Box::new(5);
@@ -1330,6 +1343,12 @@ impl<T: Copy> From<&[T]> for Box<[T]> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_cow", since = "1.45.0")]
 impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
+    /// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
+    ///
+    /// When `cow` is the `Cow::Borrowed` variant, this
+    /// conversion allocates on the heap and copies the
+    /// underlying slice. Otherwise, it will try to reuse the owned
+    /// `Vec`'s allocation.
     #[inline]
     fn from(cow: Cow<'_, [T]>) -> Box<[T]> {
         match cow {
@@ -1348,6 +1367,7 @@ impl From<&str> for Box<str> {
     /// and performs a copy of `s`.
     ///
     /// # Examples
+    ///
     /// ```rust
     /// let boxed: Box<str> = Box::from("hello");
     /// println!("{}", boxed);
@@ -1361,6 +1381,29 @@ impl From<&str> for Box<str> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_cow", since = "1.45.0")]
 impl From<Cow<'_, str>> for Box<str> {
+    /// Converts a `Cow<'_, str>` into a `Box<str>`
+    ///
+    /// When `cow` is the `Cow::Borrowed` variant, this
+    /// conversion allocates on the heap and copies the
+    /// underlying `str`. Otherwise, it will try to reuse the owned
+    /// `String`'s allocation.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use std::borrow::Cow;
+    ///
+    /// let unboxed = Cow::Borrowed("hello");
+    /// let boxed: Box<str> = Box::from(unboxed);
+    /// println!("{}", boxed);
+    /// ```
+    ///
+    /// ```rust
+    /// # use std::borrow::Cow;
+    /// let unboxed = Cow::Owned("hello".to_string());
+    /// let boxed: Box<str> = Box::from(unboxed);
+    /// println!("{}", boxed);
+    /// ```
     #[inline]
     fn from(cow: Cow<'_, str>) -> Box<str> {
         match cow {
@@ -1403,6 +1446,7 @@ impl<T, const N: usize> From<[T; N]> for Box<[T]> {
     /// This conversion moves the array to newly heap-allocated memory.
     ///
     /// # Examples
+    ///
     /// ```rust
     /// let boxed: Box<[u8]> = Box::from([4, 2]);
     /// println!("{:?}", boxed);
@@ -1416,6 +1460,15 @@ impl<T, const N: usize> From<[T; N]> for Box<[T]> {
 impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> {
     type Error = Box<[T]>;
 
+    /// Attempts to convert a `Box<[T]>` into a `Box<[T; N]>`.
+    ///
+    /// The conversion occurs in-place and does not require a
+    /// new memory allocation.
+    ///
+    /// # Errors
+    ///
+    /// Returns the old `Box<[T]>` in the `Err` variant if
+    /// `boxed_slice.len()` does not equal `N`.
     fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> {
         if boxed_slice.len() == N {
             Ok(unsafe { Box::from_raw(Box::into_raw(boxed_slice) as *mut [T; N]) })

library/alloc/src/collections/binary_heap.rs

@@ -364,6 +364,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// heap.push(4);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn new() -> BinaryHeap<T> {
         BinaryHeap { data: vec![] }
     }
@@ -383,6 +384,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// heap.push(4);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn with_capacity(capacity: usize) -> BinaryHeap<T> {
         BinaryHeap { data: Vec::with_capacity(capacity) }
     }
@@ -848,6 +850,7 @@ impl<T> BinaryHeap<T> {
     ///
     /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), vec![5, 4]);
     /// ```
+    #[must_use = "`self` will be dropped if the result is not used"]
     #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
     pub fn into_iter_sorted(self) -> IntoIterSorted<T> {
         IntoIterSorted { inner: self }
@@ -1006,6 +1009,7 @@ impl<T> BinaryHeap<T> {
     ///
     /// io::sink().write(heap.as_slice()).unwrap();
     /// ```
+    #[must_use]
     #[unstable(feature = "binary_heap_as_slice", issue = "83659")]
     pub fn as_slice(&self) -> &[T] {
         self.data.as_slice()
@@ -1028,6 +1032,7 @@ impl<T> BinaryHeap<T> {
     ///     println!("{}", x);
     /// }
     /// ```
+    #[must_use = "`self` will be dropped if the result is not used"]
     #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
     pub fn into_vec(self) -> Vec<T> {
         self.into()

library/alloc/src/collections/btree/map.rs

@@ -502,6 +502,7 @@ impl<K, V> BTreeMap<K, V> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[must_use]
     pub const fn new() -> BTreeMap<K, V> {
         BTreeMap { root: None, length: 0 }
     }
@@ -1264,6 +1265,7 @@ impl<K, V> BTreeMap<K, V> {
     /// assert_eq!(keys, [1, 2]);
     /// ```
     #[inline]
+    #[must_use = "`self` will be dropped if the result is not used"]
     #[stable(feature = "map_into_keys_values", since = "1.54.0")]
     pub fn into_keys(self) -> IntoKeys<K, V> {
         IntoKeys { inner: self.into_iter() }
@@ -1286,6 +1288,7 @@ impl<K, V> BTreeMap<K, V> {
     /// assert_eq!(values, ["hello", "goodbye"]);
     /// ```
     #[inline]
+    #[must_use = "`self` will be dropped if the result is not used"]
     #[stable(feature = "map_into_keys_values", since = "1.54.0")]
     pub fn into_values(self) -> IntoValues<K, V> {
         IntoValues { inner: self.into_iter() }

library/alloc/src/collections/btree/map/entry.rs

@@ -448,6 +448,7 @@ impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
     /// }
     /// assert_eq!(map["poneyland"], 22);
     /// ```
+    #[must_use = "`self` will be dropped if the result is not used"]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_mut(self) -> &'a mut V {
         self.handle.into_val_mut()

library/alloc/src/collections/btree/map/tests.rs

@@ -1755,20 +1755,20 @@ fn test_send() {
 #[test]
 fn test_ord_absence() {
     fn map<K>(mut map: BTreeMap<K, ()>) {
-        map.is_empty();
+        let _ = map.is_empty();
-        map.len();
+        let _ = map.len();
         map.clear();
-        map.iter();
+        let _ = map.iter();
-        map.iter_mut();
+        let _ = map.iter_mut();
-        map.keys();
+        let _ = map.keys();
-        map.values();
+        let _ = map.values();
-        map.values_mut();
+        let _ = map.values_mut();
         if true {
-            map.into_values();
+            let _ = map.into_values();
         } else if true {
-            map.into_iter();
+            let _ = map.into_iter();
         } else {
-            map.into_keys();
+            let _ = map.into_keys();
         }
     }
 

library/alloc/src/collections/btree/set.rs

@@ -248,6 +248,7 @@ impl<T> BTreeSet<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[must_use]
     pub const fn new() -> BTreeSet<T> {
         BTreeSet { map: BTreeMap::new() }
     }
@@ -534,6 +535,7 @@ impl<T> BTreeSet<T> {
     /// b.insert(1);
     /// assert_eq!(a.is_disjoint(&b), false);
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_disjoint(&self, other: &BTreeSet<T>) -> bool
     where
@@ -559,6 +561,7 @@ impl<T> BTreeSet<T> {
     /// set.insert(4);
     /// assert_eq!(set.is_subset(&sup), false);
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_subset(&self, other: &BTreeSet<T>) -> bool
     where
@@ -638,6 +641,7 @@ impl<T> BTreeSet<T> {
     /// set.insert(2);
     /// assert_eq!(set.is_superset(&sub), true);
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_superset(&self, other: &BTreeSet<T>) -> bool
     where