diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index 6e47ff7d74081..8a20dd7968590 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -34,7 +34,6 @@ macro_rules! unwrap_or {
 pub mod util {
     pub mod classify;
     pub mod comments;
-    pub mod lev_distance;
     pub mod literal;
     pub mod parser;
 }
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index f83fc29577bfb..314e5103cc2de 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -353,7 +353,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let else_arm = self.arm(else_pat, else_expr);
 
         // Handle then + scrutinee:
-        let then_expr = self.lower_block_expr(then);
         let (then_pat, scrutinee, desugar) = match cond.kind {
             // `<pat> => <then>`:
             ExprKind::Let(ref pat, ref scrutinee) => {
@@ -375,6 +374,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 (pat, cond, hir::MatchSource::IfDesugar { contains_else_clause })
             }
         };
+        let then_expr = self.lower_block_expr(then);
         let then_arm = self.arm(then_pat, self.arena.alloc(then_expr));
 
         hir::ExprKind::Match(scrutinee, arena_vec![self; then_arm, else_arm], desugar)
@@ -400,7 +400,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
 
         // Handle then + scrutinee:
-        let then_expr = self.lower_block_expr(body);
         let (then_pat, scrutinee, desugar, source) = match cond.kind {
             ExprKind::Let(ref pat, ref scrutinee) => {
                 // to:
@@ -440,6 +439,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 (pat, cond, hir::MatchSource::WhileDesugar, hir::LoopSource::While)
             }
         };
+        let then_expr = self.lower_block_expr(body);
         let then_arm = self.arm(then_pat, self.arena.alloc(then_expr));
 
         // `match <scrutinee> { ... }`
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index d93655e59050d..f7c693cc94d1f 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -425,7 +425,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         /// declared for every type and trait definition.
         struct MiscCollector<'tcx, 'lowering, 'hir> {
             lctx: &'tcx mut LoweringContext<'lowering, 'hir>,
-            hir_id_owner: Option<NodeId>,
         }
 
         impl MiscCollector<'_, '_, '_> {
@@ -452,30 +451,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     }
                 }
             }
-
-            fn with_hir_id_owner<T>(
-                &mut self,
-                owner: Option<NodeId>,
-                f: impl FnOnce(&mut Self) -> T,
-            ) -> T {
-                let old = mem::replace(&mut self.hir_id_owner, owner);
-                let r = f(self);
-                self.hir_id_owner = old;
-                r
-            }
         }
 
         impl<'tcx> Visitor<'tcx> for MiscCollector<'tcx, '_, '_> {
-            fn visit_pat(&mut self, p: &'tcx Pat) {
-                if let PatKind::Paren(..) | PatKind::Rest = p.kind {
-                    // Doesn't generate a HIR node
-                } else if let Some(owner) = self.hir_id_owner {
-                    self.lctx.lower_node_id_with_owner(p.id, owner);
-                }
-
-                visit::walk_pat(self, p)
-            }
-
             fn visit_item(&mut self, item: &'tcx Item) {
                 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
 
@@ -499,24 +477,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     _ => {}
                 }
 
-                self.with_hir_id_owner(Some(item.id), |this| {
-                    visit::walk_item(this, item);
-                });
+                visit::walk_item(self, item);
             }
 
             fn visit_assoc_item(&mut self, item: &'tcx AssocItem, ctxt: AssocCtxt) {
                 self.lctx.allocate_hir_id_counter(item.id);
-                let owner = match (&item.kind, ctxt) {
-                    // Ignore patterns in trait methods without bodies.
-                    (AssocItemKind::Fn(_, _, _, None), AssocCtxt::Trait) => None,
-                    _ => Some(item.id),
-                };
-                self.with_hir_id_owner(owner, |this| visit::walk_assoc_item(this, item, ctxt));
-            }
-
-            fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
-                // Ignore patterns in foreign items
-                self.with_hir_id_owner(None, |this| visit::walk_foreign_item(this, i));
+                visit::walk_assoc_item(self, item, ctxt);
             }
 
             fn visit_ty(&mut self, t: &'tcx Ty) {
@@ -527,18 +493,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         // Mirrors visit::walk_fn_decl
                         for parameter in &f.decl.inputs {
                             // We don't lower the ids of argument patterns
-                            self.with_hir_id_owner(None, |this| {
-                                this.visit_pat(&parameter.pat);
-                            });
+                            self.visit_pat(&parameter.pat);
                             self.visit_ty(&parameter.ty)
                         }
                         self.visit_fn_ret_ty(&f.decl.output)
                     }
                     TyKind::ImplTrait(def_node_id, _) => {
                         self.lctx.allocate_hir_id_counter(def_node_id);
-                        self.with_hir_id_owner(Some(def_node_id), |this| {
-                            visit::walk_ty(this, t);
-                        });
+                        visit::walk_ty(self, t);
                     }
                     _ => visit::walk_ty(self, t),
                 }
@@ -548,7 +510,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.lower_node_id(CRATE_NODE_ID);
         debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == Some(hir::CRATE_HIR_ID));
 
-        visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
+        visit::walk_crate(&mut MiscCollector { lctx: &mut self }, c);
         visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
 
         let module = self.lower_mod(&c.module);
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index 41827a91ba4be..85aaa7e8893bf 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -4,7 +4,7 @@ use crate::llvm;
 
 use llvm::coverageinfo::CounterMappingRegion;
 use rustc_codegen_ssa::coverageinfo::map::{Counter, CounterExpression};
-use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods};
+use rustc_codegen_ssa::traits::ConstMethods;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_llvm::RustString;
 use rustc_middle::mir::coverage::CodeRegion;
@@ -15,9 +15,9 @@ use tracing::debug;
 
 /// Generates and exports the Coverage Map.
 ///
-/// This Coverage Map complies with Coverage Mapping Format version 3 (zero-based encoded as 2),
-/// as defined at [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format)
-/// and published in Rust's current (July 2020) fork of LLVM. This version is supported by the
+/// This Coverage Map complies with Coverage Mapping Format version 4 (zero-based encoded as 3),
+/// as defined at [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format)
+/// and published in Rust's current (November 2020) fork of LLVM. This version is supported by the
 /// LLVM coverage tools (`llvm-profdata` and `llvm-cov`) bundled with Rust's fork of LLVM.
 ///
 /// Consequently, Rust's bundled version of Clang also generates Coverage Maps compliant with
@@ -26,6 +26,13 @@ use tracing::debug;
 /// undocumented details in Clang's implementation (that may or may not be important) were also
 /// replicated for Rust's Coverage Map.
 pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
+    // Ensure LLVM supports Coverage Map Version 4 (encoded as a zero-based value: 3).
+    // If not, the LLVM Version must be less than 11.
+    let version = coverageinfo::mapping_version();
+    if version != 3 {
+        cx.tcx.sess.fatal("rustc option `-Z instrument-coverage` requires LLVM 11 or higher.");
+    }
+
     let function_coverage_map = match cx.coverage_context() {
         Some(ctx) => ctx.take_function_coverage_map(),
         None => return,
@@ -38,46 +45,50 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
     let mut mapgen = CoverageMapGenerator::new();
 
     // Encode coverage mappings and generate function records
-    let mut function_records = Vec::<&'ll llvm::Value>::new();
-    let coverage_mappings_buffer = llvm::build_byte_buffer(|coverage_mappings_buffer| {
-        for (instance, function_coverage) in function_coverage_map.into_iter() {
-            debug!("Generate coverage map for: {:?}", instance);
-
-            let mangled_function_name = cx.tcx.symbol_name(instance).to_string();
-            let function_source_hash = function_coverage.source_hash();
-            let (expressions, counter_regions) =
-                function_coverage.get_expressions_and_counter_regions();
-
-            let old_len = coverage_mappings_buffer.len();
-            mapgen.write_coverage_mappings(expressions, counter_regions, coverage_mappings_buffer);
-            let mapping_data_size = coverage_mappings_buffer.len() - old_len;
-            debug_assert!(
-                mapping_data_size > 0,
-                "Every `FunctionCoverage` should have at least one counter"
-            );
-
-            let function_record = mapgen.make_function_record(
-                cx,
-                mangled_function_name,
-                function_source_hash,
-                mapping_data_size,
-            );
-            function_records.push(function_record);
-        }
-    });
+    let mut function_data = Vec::new();
+    for (instance, function_coverage) in function_coverage_map {
+        debug!("Generate coverage map for: {:?}", instance);
+
+        let mangled_function_name = cx.tcx.symbol_name(instance).to_string();
+        let function_source_hash = function_coverage.source_hash();
+        let (expressions, counter_regions) =
+            function_coverage.get_expressions_and_counter_regions();
+
+        let coverage_mapping_buffer = llvm::build_byte_buffer(|coverage_mapping_buffer| {
+            mapgen.write_coverage_mapping(expressions, counter_regions, coverage_mapping_buffer);
+        });
+        debug_assert!(
+            coverage_mapping_buffer.len() > 0,
+            "Every `FunctionCoverage` should have at least one counter"
+        );
+
+        function_data.push((mangled_function_name, function_source_hash, coverage_mapping_buffer));
+    }
 
     // Encode all filenames referenced by counters/expressions in this module
     let filenames_buffer = llvm::build_byte_buffer(|filenames_buffer| {
         coverageinfo::write_filenames_section_to_buffer(&mapgen.filenames, filenames_buffer);
     });
 
+    let filenames_size = filenames_buffer.len();
+    let filenames_val = cx.const_bytes(&filenames_buffer[..]);
+    let filenames_ref = coverageinfo::hash_bytes(filenames_buffer);
+
     // Generate the LLVM IR representation of the coverage map and store it in a well-known global
-    mapgen.save_generated_coverage_map(
-        cx,
-        function_records,
-        filenames_buffer,
-        coverage_mappings_buffer,
-    );
+    let cov_data_val = mapgen.generate_coverage_map(cx, version, filenames_size, filenames_val);
+
+    for (mangled_function_name, function_source_hash, coverage_mapping_buffer) in function_data {
+        save_function_record(
+            cx,
+            mangled_function_name,
+            function_source_hash,
+            filenames_ref,
+            coverage_mapping_buffer,
+        );
+    }
+
+    // Save the coverage data value to LLVM IR
+    coverageinfo::save_cov_data_to_mod(cx, cov_data_val);
 }
 
 struct CoverageMapGenerator {
@@ -92,12 +103,12 @@ impl CoverageMapGenerator {
     /// Using the `expressions` and `counter_regions` collected for the current function, generate
     /// the `mapping_regions` and `virtual_file_mapping`, and capture any new filenames. Then use
     /// LLVM APIs to encode the `virtual_file_mapping`, `expressions`, and `mapping_regions` into
-    /// the given `coverage_mappings` byte buffer, compliant with the LLVM Coverage Mapping format.
-    fn write_coverage_mappings(
+    /// the given `coverage_mapping` byte buffer, compliant with the LLVM Coverage Mapping format.
+    fn write_coverage_mapping(
         &mut self,
         expressions: Vec<CounterExpression>,
         counter_regions: impl Iterator<Item = (Counter, &'a CodeRegion)>,
-        coverage_mappings_buffer: &RustString,
+        coverage_mapping_buffer: &RustString,
     ) {
         let mut counter_regions = counter_regions.collect::<Vec<_>>();
         if counter_regions.is_empty() {
@@ -145,89 +156,75 @@ impl CoverageMapGenerator {
             virtual_file_mapping,
             expressions,
             mapping_regions,
-            coverage_mappings_buffer,
+            coverage_mapping_buffer,
         );
     }
 
-    /// Generate and return the function record `Value`
-    fn make_function_record(
-        &mut self,
-        cx: &CodegenCx<'ll, 'tcx>,
-        mangled_function_name: String,
-        function_source_hash: u64,
-        mapping_data_size: usize,
-    ) -> &'ll llvm::Value {
-        let name_ref = coverageinfo::compute_hash(&mangled_function_name);
-        let name_ref_val = cx.const_u64(name_ref);
-        let mapping_data_size_val = cx.const_u32(mapping_data_size as u32);
-        let func_hash_val = cx.const_u64(function_source_hash);
-        cx.const_struct(
-            &[name_ref_val, mapping_data_size_val, func_hash_val],
-            /*packed=*/ true,
-        )
-    }
-
-    /// Combine the filenames and coverage mappings buffers, construct coverage map header and the
-    /// array of function records, and combine everything into the complete coverage map. Save the
-    /// coverage map data into the LLVM IR as a static global using a specific, well-known section
-    /// and name.
-    fn save_generated_coverage_map(
+    /// Construct coverage map header and the array of function records, and combine them into the
+    /// coverage map. Save the coverage map data into the LLVM IR as a static global using a
+    /// specific, well-known section and name.
+    fn generate_coverage_map(
         self,
         cx: &CodegenCx<'ll, 'tcx>,
-        function_records: Vec<&'ll llvm::Value>,
-        filenames_buffer: Vec<u8>,
-        mut coverage_mappings_buffer: Vec<u8>,
-    ) {
-        // Concatenate the encoded filenames and encoded coverage mappings, and add additional zero
-        // bytes as-needed to ensure 8-byte alignment.
-        let mut coverage_size = coverage_mappings_buffer.len();
-        let filenames_size = filenames_buffer.len();
-        let remaining_bytes =
-            (filenames_size + coverage_size) % coverageinfo::COVMAP_VAR_ALIGN_BYTES;
-        if remaining_bytes > 0 {
-            let pad = coverageinfo::COVMAP_VAR_ALIGN_BYTES - remaining_bytes;
-            coverage_mappings_buffer.append(&mut [0].repeat(pad));
-            coverage_size += pad;
-        }
-        let filenames_and_coverage_mappings = [filenames_buffer, coverage_mappings_buffer].concat();
-        let filenames_and_coverage_mappings_val =
-            cx.const_bytes(&filenames_and_coverage_mappings[..]);
-
-        debug!(
-            "cov map: n_records = {}, filenames_size = {}, coverage_size = {}, 0-based version = {}",
-            function_records.len(),
-            filenames_size,
-            coverage_size,
-            coverageinfo::mapping_version()
-        );
+        version: u32,
+        filenames_size: usize,
+        filenames_val: &'ll llvm::Value,
+    ) -> &'ll llvm::Value {
+        debug!("cov map: filenames_size = {}, 0-based version = {}", filenames_size, version);
 
-        // Create the coverage data header
-        let n_records_val = cx.const_u32(function_records.len() as u32);
+        // Create the coverage data header (Note, fields 0 and 2 are now always zero,
+        // as of `llvm::coverage::CovMapVersion::Version4`.)
+        let zero_was_n_records_val = cx.const_u32(0);
         let filenames_size_val = cx.const_u32(filenames_size as u32);
-        let coverage_size_val = cx.const_u32(coverage_size as u32);
-        let version_val = cx.const_u32(coverageinfo::mapping_version());
+        let zero_was_coverage_size_val = cx.const_u32(0);
+        let version_val = cx.const_u32(version);
         let cov_data_header_val = cx.const_struct(
-            &[n_records_val, filenames_size_val, coverage_size_val, version_val],
+            &[zero_was_n_records_val, filenames_size_val, zero_was_coverage_size_val, version_val],
             /*packed=*/ false,
         );
 
-        // Create the function records array
-        let name_ref_from_u64 = cx.type_i64();
-        let mapping_data_size_from_u32 = cx.type_i32();
-        let func_hash_from_u64 = cx.type_i64();
-        let function_record_ty = cx.type_struct(
-            &[name_ref_from_u64, mapping_data_size_from_u32, func_hash_from_u64],
-            /*packed=*/ true,
-        );
-        let function_records_val = cx.const_array(function_record_ty, &function_records[..]);
-
         // Create the complete LLVM coverage data value to add to the LLVM IR
-        let cov_data_val = cx.const_struct(
-            &[cov_data_header_val, function_records_val, filenames_and_coverage_mappings_val],
-            /*packed=*/ false,
-        );
-
-        // Save the coverage data value to LLVM IR
-        coverageinfo::save_map_to_mod(cx, cov_data_val);
+        cx.const_struct(&[cov_data_header_val, filenames_val], /*packed=*/ false)
     }
 }
+
+/// Construct a function record and combine it with the function's coverage mapping data.
+/// Save the function record into the LLVM IR as a static global using a
+/// specific, well-known section and name.
+fn save_function_record(
+    cx: &CodegenCx<'ll, 'tcx>,
+    mangled_function_name: String,
+    function_source_hash: u64,
+    filenames_ref: u64,
+    coverage_mapping_buffer: Vec<u8>,
+) {
+    // Concatenate the encoded coverage mappings
+    let coverage_mapping_size = coverage_mapping_buffer.len();
+    let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer[..]);
+
+    let func_name_hash = coverageinfo::hash_str(&mangled_function_name);
+    let func_name_hash_val = cx.const_u64(func_name_hash);
+    let coverage_mapping_size_val = cx.const_u32(coverage_mapping_size as u32);
+    let func_hash_val = cx.const_u64(function_source_hash);
+    let filenames_ref_val = cx.const_u64(filenames_ref);
+    let func_record_val = cx.const_struct(
+        &[
+            func_name_hash_val,
+            coverage_mapping_size_val,
+            func_hash_val,
+            filenames_ref_val,
+            coverage_mapping_val,
+        ],
+        /*packed=*/ true,
+    );
+
+    // At the present time, the coverage map for Rust assumes every instrumented function `is_used`.
+    // Note that Clang marks functions as "unused" in `CodeGenPGO::emitEmptyCounterMapping`. (See:
+    // https://github.com/rust-lang/llvm-project/blob/de02a75e398415bad4df27b4547c25b896c8bf3b/clang%2Flib%2FCodeGen%2FCodeGenPGO.cpp#L877-L878
+    // for example.)
+    //
+    // It's not yet clear if or how this may be applied to Rust in the future, but the `is_used`
+    // argument is available and handled similarly.
+    let is_used = true;
+    coverageinfo::save_func_record_to_mod(cx, func_name_hash, func_record_val, is_used);
+}
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index e21e03822ebb3..e777f363eb084 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -23,7 +23,7 @@ use tracing::debug;
 
 pub mod mapgen;
 
-const COVMAP_VAR_ALIGN_BYTES: usize = 8;
+const VAR_ALIGN_BYTES: usize = 8;
 
 /// A context object for maintaining all state needed by the coverageinfo module.
 pub struct CrateCoverageContext<'tcx> {
@@ -177,17 +177,20 @@ pub(crate) fn write_mapping_to_buffer(
         );
     }
 }
+pub(crate) fn hash_str(strval: &str) -> u64 {
+    let strval = CString::new(strval).expect("null error converting hashable str to C string");
+    unsafe { llvm::LLVMRustCoverageHashCString(strval.as_ptr()) }
+}
 
-pub(crate) fn compute_hash(name: &str) -> u64 {
-    let name = CString::new(name).expect("null error converting hashable name to C string");
-    unsafe { llvm::LLVMRustCoverageComputeHash(name.as_ptr()) }
+pub(crate) fn hash_bytes(bytes: Vec<u8>) -> u64 {
+    unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_ptr().cast(), bytes.len()) }
 }
 
 pub(crate) fn mapping_version() -> u32 {
     unsafe { llvm::LLVMRustCoverageMappingVersion() }
 }
 
-pub(crate) fn save_map_to_mod<'ll, 'tcx>(
+pub(crate) fn save_cov_data_to_mod<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     cov_data_val: &'ll llvm::Value,
 ) {
@@ -198,7 +201,7 @@ pub(crate) fn save_map_to_mod<'ll, 'tcx>(
     debug!("covmap var name: {:?}", covmap_var_name);
 
     let covmap_section_name = llvm::build_string(|s| unsafe {
-        llvm::LLVMRustCoverageWriteSectionNameToString(cx.llmod, s);
+        llvm::LLVMRustCoverageWriteMapSectionNameToString(cx.llmod, s);
     })
     .expect("Rust Coverage section name failed UTF-8 conversion");
     debug!("covmap section name: {:?}", covmap_section_name);
@@ -206,8 +209,43 @@ pub(crate) fn save_map_to_mod<'ll, 'tcx>(
     let llglobal = llvm::add_global(cx.llmod, cx.val_ty(cov_data_val), &covmap_var_name);
     llvm::set_initializer(llglobal, cov_data_val);
     llvm::set_global_constant(llglobal, true);
-    llvm::set_linkage(llglobal, llvm::Linkage::InternalLinkage);
+    llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
     llvm::set_section(llglobal, &covmap_section_name);
-    llvm::set_alignment(llglobal, COVMAP_VAR_ALIGN_BYTES);
+    llvm::set_alignment(llglobal, VAR_ALIGN_BYTES);
+    cx.add_used_global(llglobal);
+}
+
+pub(crate) fn save_func_record_to_mod<'ll, 'tcx>(
+    cx: &CodegenCx<'ll, 'tcx>,
+    func_name_hash: u64,
+    func_record_val: &'ll llvm::Value,
+    is_used: bool,
+) {
+    // Assign a name to the function record. This is used to merge duplicates.
+    //
+    // In LLVM, a "translation unit" (effectively, a `Crate` in Rust) can describe functions that
+    // are included-but-not-used. If (or when) Rust generates functions that are
+    // included-but-not-used, note that a dummy description for a function included-but-not-used
+    // in a Crate can be replaced by full description provided by a different Crate. The two kinds
+    // of descriptions play distinct roles in LLVM IR; therefore, assign them different names (by
+    // appending "u" to the end of the function record var name, to prevent `linkonce_odr` merging.
+    let func_record_var_name =
+        format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" });
+    debug!("function record var name: {:?}", func_record_var_name);
+
+    let func_record_section_name = llvm::build_string(|s| unsafe {
+        llvm::LLVMRustCoverageWriteFuncSectionNameToString(cx.llmod, s);
+    })
+    .expect("Rust Coverage function record section name failed UTF-8 conversion");
+    debug!("function record section name: {:?}", func_record_section_name);
+
+    let llglobal = llvm::add_global(cx.llmod, cx.val_ty(func_record_val), &func_record_var_name);
+    llvm::set_initializer(llglobal, func_record_val);
+    llvm::set_global_constant(llglobal, true);
+    llvm::set_linkage(llglobal, llvm::Linkage::LinkOnceODRLinkage);
+    llvm::set_visibility(llglobal, llvm::Visibility::Hidden);
+    llvm::set_section(llglobal, &func_record_section_name);
+    llvm::set_alignment(llglobal, VAR_ALIGN_BYTES);
+    llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name);
     cx.add_used_global(llglobal);
 }
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 8b15c8b0eb607..41482d18946ad 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -642,7 +642,7 @@ pub type InlineAsmDiagHandler = unsafe extern "C" fn(&SMDiagnostic, *const c_voi
 pub mod coverageinfo {
     use super::coverage_map;
 
-    /// Aligns with [llvm::coverage::CounterMappingRegion::RegionKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L205-L221)
+    /// Aligns with [llvm::coverage::CounterMappingRegion::RegionKind](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L206-L222)
     #[derive(Copy, Clone, Debug)]
     #[repr(C)]
     pub enum RegionKind {
@@ -665,13 +665,13 @@ pub mod coverageinfo {
 
     /// This struct provides LLVM's representation of a "CoverageMappingRegion", encoded into the
     /// coverage map, in accordance with the
-    /// [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format).
+    /// [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format).
     /// The struct composes fields representing the `Counter` type and value(s) (injected counter
     /// ID, or expression type and operands), the source file (an indirect index into a "filenames
     /// array", encoded separately), and source location (start and end positions of the represented
     /// code region).
     ///
-    /// Aligns with [llvm::coverage::CounterMappingRegion](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L223-L226)
+    /// Aligns with [llvm::coverage::CounterMappingRegion](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L224-L227)
     /// Important: The Rust struct layout (order and types of fields) must match its C++
     /// counterpart.
     #[derive(Copy, Clone, Debug)]
@@ -1791,10 +1791,14 @@ extern "C" {
 
     pub fn LLVMRustCoverageCreatePGOFuncNameVar(F: &'a Value, FuncName: *const c_char)
     -> &'a Value;
-    pub fn LLVMRustCoverageComputeHash(Name: *const c_char) -> u64;
+    pub fn LLVMRustCoverageHashCString(StrVal: *const c_char) -> u64;
+    pub fn LLVMRustCoverageHashByteArray(Bytes: *const c_char, NumBytes: size_t) -> u64;
 
     #[allow(improper_ctypes)]
-    pub fn LLVMRustCoverageWriteSectionNameToString(M: &Module, Str: &RustString);
+    pub fn LLVMRustCoverageWriteMapSectionNameToString(M: &Module, Str: &RustString);
+
+    #[allow(improper_ctypes)]
+    pub fn LLVMRustCoverageWriteFuncSectionNameToString(M: &Module, Str: &RustString);
 
     #[allow(improper_ctypes)]
     pub fn LLVMRustCoverageWriteMappingVarNameToString(Str: &RustString);
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 53a404ee01944..fc40065a9664e 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -220,12 +220,24 @@ pub fn set_linkage(llglobal: &Value, linkage: Linkage) {
     }
 }
 
+pub fn set_visibility(llglobal: &Value, visibility: Visibility) {
+    unsafe {
+        LLVMRustSetVisibility(llglobal, visibility);
+    }
+}
+
 pub fn set_alignment(llglobal: &Value, bytes: usize) {
     unsafe {
         ffi::LLVMSetAlignment(llglobal, bytes as c_uint);
     }
 }
 
+pub fn set_comdat(llmod: &Module, llglobal: &Value, name: &str) {
+    unsafe {
+        LLVMRustSetComdat(llmod, llglobal, name.as_ptr().cast(), name.len());
+    }
+}
+
 /// Safe wrapper around `LLVMGetParam`, because segfaults are no fun.
 pub fn get_param(llfn: &Value, index: c_uint) -> &Value {
     unsafe {
diff --git a/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs b/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
index bcac2c90fdc20..af6c476292bd1 100644
--- a/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
+++ b/compiler/rustc_codegen_ssa/src/coverageinfo/ffi.rs
@@ -1,6 +1,6 @@
 use rustc_middle::mir::coverage::{CounterValueReference, MappedExpressionIndex};
 
-/// Aligns with [llvm::coverage::Counter::CounterKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L91)
+/// Aligns with [llvm::coverage::Counter::CounterKind](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L206-L222)
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub enum CounterKind {
@@ -17,7 +17,7 @@ pub enum CounterKind {
 ///     `instrprof.increment()`)
 ///   * For `CounterKind::Expression`, `id` is the index into the coverage map's array of
 ///     counter expressions.
-/// Aligns with [llvm::coverage::Counter](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L98-L99)
+/// Aligns with [llvm::coverage::Counter](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L99-L100)
 /// Important: The Rust struct layout (order and types of fields) must match its C++ counterpart.
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
@@ -41,7 +41,7 @@ impl Counter {
     }
 }
 
-/// Aligns with [llvm::coverage::CounterExpression::ExprKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L146)
+/// Aligns with [llvm::coverage::CounterExpression::ExprKind](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L147)
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
 pub enum ExprKind {
@@ -49,7 +49,7 @@ pub enum ExprKind {
     Add = 1,
 }
 
-/// Aligns with [llvm::coverage::CounterExpression](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L147-L148)
+/// Aligns with [llvm::coverage::CounterExpression](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L148-L149)
 /// Important: The Rust struct layout (order and types of fields) must match its C++
 /// counterpart.
 #[derive(Copy, Clone, Debug)]
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index fd8f46a6926c0..373f0a602c0ef 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -124,6 +124,11 @@ impl<'a, 'tcx> Visitor<'tcx> for FindHirNodeVisitor<'a, 'tcx> {
                 return;
             }
         }
+
+        // FIXME(const_generics): Currently, any uninferred `const` generics arguments
+        // are handled specially, but instead they should be handled in `annotate_method_call`,
+        // which currently doesn't work because this evaluates to `false` for const arguments.
+        // See https://github.com/rust-lang/rust/pull/77758 for more details.
         if self.node_ty_contains_target(expr.hir_id).is_some() {
             match expr.kind {
                 ExprKind::Closure(..) => self.found_closure = Some(&expr),
@@ -345,11 +350,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     ) -> DiagnosticBuilder<'tcx> {
         let arg = self.resolve_vars_if_possible(arg);
         let arg_data = self.extract_inference_diagnostics_data(arg, None);
-        let kind_str = match arg.unpack() {
-            GenericArgKind::Type(_) => "type",
-            GenericArgKind::Const(_) => "the value",
-            GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
-        };
 
         let mut local_visitor = FindHirNodeVisitor::new(&self, arg, span);
         let ty_to_string = |ty: Ty<'tcx>| -> String {
@@ -618,6 +618,28 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             .any(|span_label| span_label.label.is_some() && span_label.span == span)
             && local_visitor.found_arg_pattern.is_none()
         {
+            let (kind_str, const_value) = match arg.unpack() {
+                GenericArgKind::Type(_) => ("type", None),
+                GenericArgKind::Const(_) => ("the value", Some(())),
+                GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
+            };
+
+            // FIXME(const_generics): we would like to handle const arguments
+            // as part of the normal diagnostics flow below, but there appear to
+            // be subtleties in doing so, so for now we special-case const args
+            // here.
+            if let Some(suggestion) = const_value
+                .and_then(|_| arg_data.parent_name.as_ref())
+                .map(|parent| format!("{}::<{}>", parent, arg_data.name))
+            {
+                err.span_suggestion_verbose(
+                    span,
+                    "consider specifying the const argument",
+                    suggestion,
+                    Applicability::MaybeIncorrect,
+                );
+            }
+
             // Avoid multiple labels pointing at `span`.
             err.span_label(
                 span,
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 20a7b47313ecf..b43cbf46d61e3 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -1,6 +1,5 @@
 use rustc_ast::mut_visit::{visit_clobber, MutVisitor, *};
 use rustc_ast::ptr::P;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_ast::{self as ast, AttrVec, BlockCheckMode};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -20,6 +19,7 @@ use rustc_session::parse::CrateConfig;
 use rustc_session::CrateDisambiguator;
 use rustc_session::{early_error, filesearch, output, DiagnosticOutput, Session};
 use rustc_span::edition::Edition;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::FileLoader;
 use rustc_span::symbol::{sym, Symbol};
 use smallvec::SmallVec;
@@ -512,8 +512,11 @@ pub(crate) fn check_attr_crate_type(
 
                 if let ast::MetaItemKind::NameValue(spanned) = a.meta().unwrap().kind {
                     let span = spanned.span;
-                    let lev_candidate =
-                        find_best_match_for_name(CRATE_TYPES.iter().map(|(k, _)| k), n, None);
+                    let lev_candidate = find_best_match_for_name(
+                        &CRATE_TYPES.iter().map(|(k, _)| *k).collect::<Vec<_>>(),
+                        n,
+                        None,
+                    );
                     if let Some(candidate) = lev_candidate {
                         lint_buffer.buffer_lint_with_diagnostic(
                             lint::builtin::UNKNOWN_CRATE_TYPES,
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 4cfeb0d968b95..16563d21ff133 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -19,7 +19,6 @@ use self::TargetLint::*;
 use crate::levels::LintLevelsBuilder;
 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
 use rustc_ast as ast;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync;
 use rustc_errors::{add_elided_lifetime_in_path_suggestion, struct_span_err, Applicability};
@@ -37,6 +36,7 @@ use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
 use rustc_session::Session;
 use rustc_session::SessionLintStore;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
 use rustc_target::abi::LayoutOf;
 
@@ -411,7 +411,7 @@ impl LintStore {
                         self.by_name.keys().map(|name| Symbol::intern(&name)).collect::<Vec<_>>();
 
                     let suggestion = find_best_match_for_name(
-                        symbols.iter(),
+                        &symbols,
                         Symbol::intern(&lint_name.to_lowercase()),
                         None,
                     );
diff --git a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
index 2b1143a4ecff5..25badc3f4e17b 100644
--- a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
@@ -3,7 +3,6 @@
 #include "llvm/ProfileData/Coverage/CoverageMappingWriter.h"
 #include "llvm/ProfileData/InstrProf.h"
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/Support/LEB128.h"
 
 #include <iostream>
 
@@ -13,15 +12,14 @@ extern "C" void LLVMRustCoverageWriteFilenamesSectionToBuffer(
     const char* const Filenames[],
     size_t FilenamesLen,
     RustStringRef BufferOut) {
-  // LLVM 11's CoverageFilenamesSectionWriter uses its new `Version4` format,
-  // so we're manually writing the `Version3` format ourselves.
-  RawRustStringOstream OS(BufferOut);
-  encodeULEB128(FilenamesLen, OS);
+  SmallVector<StringRef,32> FilenameRefs;
   for (size_t i = 0; i < FilenamesLen; i++) {
-    StringRef Filename(Filenames[i]);
-    encodeULEB128(Filename.size(), OS);
-    OS << Filename;
+    FilenameRefs.push_back(StringRef(Filenames[i]));
   }
+  auto FilenamesWriter = coverage::CoverageFilenamesSectionWriter(
+    makeArrayRef(FilenameRefs));
+  RawRustStringOstream OS(BufferOut);
+  FilenamesWriter.write(OS);
 }
 
 extern "C" void LLVMRustCoverageWriteMappingToBuffer(
@@ -45,20 +43,40 @@ extern "C" LLVMValueRef LLVMRustCoverageCreatePGOFuncNameVar(LLVMValueRef F, con
   return wrap(createPGOFuncNameVar(*cast<Function>(unwrap(F)), FuncNameRef));
 }
 
-extern "C" uint64_t LLVMRustCoverageComputeHash(const char *Name) {
-  StringRef NameRef(Name);
-  return IndexedInstrProf::ComputeHash(NameRef);
+extern "C" uint64_t LLVMRustCoverageHashCString(const char *StrVal) {
+  StringRef StrRef(StrVal);
+  return IndexedInstrProf::ComputeHash(StrRef);
+}
+
+extern "C" uint64_t LLVMRustCoverageHashByteArray(
+    const char *Bytes,
+    unsigned NumBytes) {
+  StringRef StrRef(Bytes, NumBytes);
+  return IndexedInstrProf::ComputeHash(StrRef);
 }
 
-extern "C" void LLVMRustCoverageWriteSectionNameToString(LLVMModuleRef M,
-                                                         RustStringRef Str) {
+static void WriteSectionNameToString(LLVMModuleRef M,
+                                     InstrProfSectKind SK,
+                                     RustStringRef Str) {
   Triple TargetTriple(unwrap(M)->getTargetTriple());
-  auto name = getInstrProfSectionName(IPSK_covmap,
-                                      TargetTriple.getObjectFormat());
+  auto name = getInstrProfSectionName(SK, TargetTriple.getObjectFormat());
   RawRustStringOstream OS(Str);
   OS << name;
 }
 
+extern "C" void LLVMRustCoverageWriteMapSectionNameToString(LLVMModuleRef M,
+                                                            RustStringRef Str) {
+  WriteSectionNameToString(M, IPSK_covmap, Str);
+}
+
+extern "C" void LLVMRustCoverageWriteFuncSectionNameToString(LLVMModuleRef M,
+                                                             RustStringRef Str) {
+#if LLVM_VERSION_GE(11, 0)
+  WriteSectionNameToString(M, IPSK_covfun, Str);
+// else do nothing; the `Version` check will abort codegen on the Rust side
+#endif
+}
+
 extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
   auto name = getCoverageMappingVarName();
   RawRustStringOstream OS(Str);
@@ -66,5 +84,9 @@ extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
 }
 
 extern "C" uint32_t LLVMRustCoverageMappingVersion() {
+#if LLVM_VERSION_GE(11, 0)
+  return coverage::CovMapVersion::Version4;
+#else
   return coverage::CovMapVersion::Version3;
+#endif
 }
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 9b0c176b69203..e17f933932e6a 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -1462,7 +1462,7 @@ extern "C" void LLVMRustSetComdat(LLVMModuleRef M, LLVMValueRef V,
                                   const char *Name, size_t NameLen) {
   Triple TargetTriple(unwrap(M)->getTargetTriple());
   GlobalObject *GV = unwrap<GlobalObject>(V);
-  if (!TargetTriple.isOSBinFormatMachO()) {
+  if (TargetTriple.supportsCOMDAT()) {
     StringRef NameRef(Name, NameLen);
     GV->setComdat(unwrap(M)->getOrInsertComdat(NameRef));
   }
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index 6b46d7c497d3e..8a6bf9dff7b6f 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/compiler/rustc_middle/src/mir/coverage.rs
@@ -21,9 +21,9 @@ rustc_index::newtype_index! {
 impl ExpressionOperandId {
     /// An expression operand for a "zero counter", as described in the following references:
     ///
-    /// * <https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#counter>
-    /// * <https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#tag>
-    /// * <https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#counter-expressions>
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter>
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#tag>
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter-expressions>
     ///
     /// This operand can be used to count two or more separate code regions with a single counter,
     /// if they run sequentially with no branches, by injecting the `Counter` in a `BasicBlock` for
diff --git a/compiler/rustc_middle/src/ty/query/plumbing.rs b/compiler/rustc_middle/src/ty/query/plumbing.rs
index 9e97ed2fb2926..d0730bd121c98 100644
--- a/compiler/rustc_middle/src/ty/query/plumbing.rs
+++ b/compiler/rustc_middle/src/ty/query/plumbing.rs
@@ -128,7 +128,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn try_print_query_stack(handler: &Handler, num_frames: Option<usize>) {
         eprintln!("query stack during panic:");
 
-        // Be careful reyling on global state here: this code is called from
+        // Be careful relying on global state here: this code is called from
         // a panic hook, which means that the global `Handler` may be in a weird
         // state if it was responsible for triggering the panic.
         let mut i = 0;
@@ -507,7 +507,7 @@ macro_rules! define_queries_struct {
     (tcx: $tcx:tt,
      input: ($(([$($modifiers:tt)*] [$($attr:tt)*] [$name:ident]))*)) => {
         pub struct Queries<$tcx> {
-            /// This provides access to the incremental comilation on-disk cache for query results.
+            /// This provides access to the incremental compilation on-disk cache for query results.
             /// Do not access this directly. It is only meant to be used by
             /// `DepGraph::try_mark_green()` and the query infrastructure.
             /// This is `None` if we are not incremental compilation mode
diff --git a/compiler/rustc_mir/src/transform/coverage/debug.rs b/compiler/rustc_mir/src/transform/coverage/debug.rs
index 7f1dc3844b21d..e9528557b3337 100644
--- a/compiler/rustc_mir/src/transform/coverage/debug.rs
+++ b/compiler/rustc_mir/src/transform/coverage/debug.rs
@@ -95,18 +95,18 @@
 //!
 //!     Depending on the values and combinations, counters can be labeled by:
 //!
-//!         * `id` - counter or expression ID (ascending counter IDs, starting at 1, or descending
-//!           expression IDs, starting at `u32:MAX`)
-//!         * `block` - the `BasicCoverageBlock` label (for example, `bcb0`) or edge label (for
-//!           example `bcb0->bcb1`), for counters or expressions assigned to count a
-//!           `BasicCoverageBlock` or edge. Intermediate expressions (not directly associated with
-//!           a BCB or edge) will be labeled by their expression ID, unless `operation` is also
-//!           specified.
-//!         * `operation` - applied to expressions only, labels include the left-hand-side counter
-//!           or expression label (lhs operand), the operator (`+` or `-`), and the right-hand-side
-//!           counter or expression (rhs operand). Expression operand labels are generated
-//!           recursively, generating labels with nested operations, enclosed in parentheses
-//!           (for example: `bcb2 + (bcb0 - bcb1)`).
+//!       * `id` - counter or expression ID (ascending counter IDs, starting at 1, or descending
+//!         expression IDs, starting at `u32:MAX`)
+//!       * `block` - the `BasicCoverageBlock` label (for example, `bcb0`) or edge label (for
+//!         example `bcb0->bcb1`), for counters or expressions assigned to count a
+//!         `BasicCoverageBlock` or edge. Intermediate expressions (not directly associated with
+//!         a BCB or edge) will be labeled by their expression ID, unless `operation` is also
+//!         specified.
+//!       * `operation` - applied to expressions only, labels include the left-hand-side counter
+//!         or expression label (lhs operand), the operator (`+` or `-`), and the right-hand-side
+//!         counter or expression (rhs operand). Expression operand labels are generated
+//!         recursively, generating labels with nested operations, enclosed in parentheses
+//!         (for example: `bcb2 + (bcb0 - bcb1)`).
 
 use super::graph::{BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph};
 use super::spans::CoverageSpan;
diff --git a/compiler/rustc_mir_build/src/thir/pattern/_match.rs b/compiler/rustc_mir_build/src/thir/pattern/_match.rs
index 79a74e387435c..f299663f67934 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/_match.rs
@@ -1,12 +1,16 @@
 //! Note: tests specific to this file can be found in:
-//!     - ui/pattern/usefulness
-//!     - ui/or-patterns
-//!     - ui/consts/const_in_pattern
-//!     - ui/rfc-2008-non-exhaustive
-//!     - ui/half-open-range-patterns
-//!     - probably many others
+//!
+//!   - `ui/pattern/usefulness`
+//!   - `ui/or-patterns`
+//!   - `ui/consts/const_in_pattern`
+//!   - `ui/rfc-2008-non-exhaustive`
+//!   - `ui/half-open-range-patterns`
+//!   - probably many others
+//!
 //! I (Nadrieril) prefer to put new tests in `ui/pattern/usefulness` unless there's a specific
-//! reason not to, for example if they depend on a particular feature like or_patterns.
+//! reason not to, for example if they depend on a particular feature like `or_patterns`.
+//!
+//! -----
 //!
 //! This file includes the logic for exhaustiveness and usefulness checking for
 //! pattern-matching. Specifically, given a list of patterns for a type, we can
@@ -14,8 +18,8 @@
 //! (a) the patterns cover every possible constructor for the type (exhaustiveness)
 //! (b) each pattern is necessary (usefulness)
 //!
-//! The algorithm implemented here is a modified version of the one described in:
-//! <http://moscova.inria.fr/~maranget/papers/warn/index.html>
+//! The algorithm implemented here is a modified version of the one described in
+//! [this paper](http://moscova.inria.fr/~maranget/papers/warn/index.html).
 //! However, to save future implementors from reading the original paper, we
 //! summarise the algorithm here to hopefully save time and be a little clearer
 //! (without being so rigorous).
@@ -131,18 +135,22 @@
 //!
 //!    This returns zero or more new pattern-stacks, as follows. We look at the pattern `p_1`
 //!    on top of the stack, and we have four cases:
-//!         1.1. `p_1 = c(r_1, .., r_a)`, i.e. the top of the stack has constructor `c`. We
-//!              push onto the stack the arguments of this constructor, and return the result:
-//!                 r_1, .., r_a, p_2, .., p_n
-//!         1.2. `p_1 = c'(r_1, .., r_a')` where `c ≠ c'`. We discard the current stack and
-//!              return nothing.
+//!
+//!      1.1. `p_1 = c(r_1, .., r_a)`, i.e. the top of the stack has constructor `c`. We
+//!           push onto the stack the arguments of this constructor, and return the result:
+//!              `r_1, .., r_a, p_2, .., p_n`
+//!
+//!      1.2. `p_1 = c'(r_1, .., r_a')` where `c ≠ c'`. We discard the current stack and
+//!           return nothing.
+//!
 //!         1.3. `p_1 = _`. We push onto the stack as many wildcards as the constructor `c` has
 //!              arguments (its arity), and return the resulting stack:
-//!                 _, .., _, p_2, .., p_n
+//!                 `_, .., _, p_2, .., p_n`
+//!
 //!         1.4. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting
 //!              stack:
-//!                 S(c, (r_1, p_2, .., p_n))
-//!                 S(c, (r_2, p_2, .., p_n))
+//!                 - `S(c, (r_1, p_2, .., p_n))`
+//!                 - `S(c, (r_2, p_2, .., p_n))`
 //!
 //! 2. We can pop a wildcard off the top of the stack. This is called `S(_, p)`, where `p` is
 //!    a pattern-stack. Note: the paper calls this `D(p)`.
@@ -157,8 +165,8 @@
 //!                 p_2, .., p_n
 //!         2.3. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting
 //!           stack.
-//!                 S(_, (r_1, p_2, .., p_n))
-//!                 S(_, (r_2, p_2, .., p_n))
+//!                 - `S(_, (r_1, p_2, .., p_n))`
+//!                 - `S(_, (r_2, p_2, .., p_n))`
 //!
 //! Note that the OR-patterns are not always used directly in Rust, but are used to derive the
 //! exhaustive integer matching rules, so they're written here for posterity.
@@ -198,7 +206,7 @@
 //! ]
 //! ```
 //!
-//! and `p` is [Some(false), 0], then we don't care about row 2 since we know `p` only
+//! and `p` is `[Some(false), 0]`, then we don't care about row 2 since we know `p` only
 //! matches values that row 2 doesn't. For row 1 however, we need to dig into the
 //! arguments of `Some` to know whether some new value is covered. So we compute
 //! `U([[true, _]], [false, 0])`.
@@ -222,7 +230,7 @@
 //! ]
 //! ```
 //!
-//! and `p` is [_, false, _], the `Some` constructor doesn't appear in `P`. So if we
+//! and `p` is `[_, false, _]`, the `Some` constructor doesn't appear in `P`. So if we
 //! only had row 2, we'd know that `p` is useful. However row 1 starts with a
 //! wildcard, so we need to check whether `U([[true, _]], [false, 1])`.
 //!
@@ -243,7 +251,7 @@
 //! ]
 //! ```
 //!
-//! and `p` is [_, false], both `None` and `Some` constructors appear in the first
+//! and `p` is `[_, false]`, both `None` and `Some` constructors appear in the first
 //! components of `P`. We will therefore try popping both constructors in turn: we
 //! compute `U([[true, _]], [_, false])` for the `Some` constructor, and `U([[false]],
 //! [false])` for the `None` constructor. The first case returns true, so we know that
@@ -294,6 +302,7 @@
 //!     + If some constructors are missing from the matrix, it turns out we don't need to do
 //!       anything special (because we know none of the integers are actually wildcards: i.e., we
 //!       can't span wildcards using ranges).
+
 use self::Constructor::*;
 use self::SliceKind::*;
 use self::Usefulness::*;
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index ffbf786491df2..93be478fc8c2c 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1450,10 +1450,10 @@ impl<'a> Parser<'a> {
                         .help("valid widths are 8, 16, 32, 64 and 128")
                         .emit();
                 } else {
-                    let msg = format!("invalid suffix `{}` for integer literal", suf);
+                    let msg = format!("invalid suffix `{}` for number literal", suf);
                     self.struct_span_err(span, &msg)
                         .span_label(span, format!("invalid suffix `{}`", suf))
-                        .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
+                        .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
                         .emit();
                 }
             }
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index a0d5b61e8bd1b..809de9beff625 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1,7 +1,6 @@
 use std::cmp::Reverse;
 use std::ptr;
 
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_ast::{self as ast, Path};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
@@ -14,6 +13,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::{self, DefIdTree};
 use rustc_session::Session;
 use rustc_span::hygiene::MacroKind;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, MultiSpan, Span};
@@ -716,7 +716,7 @@ impl<'a> Resolver<'a> {
         suggestions.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 
         match find_best_match_for_name(
-            suggestions.iter().map(|suggestion| &suggestion.candidate),
+            &suggestions.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
             ident.name,
             None,
         ) {
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 026cf8be73801..cb1f0834ce7ac 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -10,7 +10,6 @@ use crate::{CrateLint, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet
 use crate::{NameBinding, NameBindingKind, PathResult, PrivacyError, ToNameBinding};
 
 use rustc_ast::unwrap_or;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_ast::NodeId;
 use rustc_ast_lowering::ResolverAstLowering;
 use rustc_data_structures::fx::FxHashSet;
@@ -25,6 +24,7 @@ use rustc_session::lint::builtin::{PUB_USE_OF_PRIVATE_EXTERN_CRATE, UNUSED_IMPOR
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::DiagnosticMessageId;
 use rustc_span::hygiene::ExpnId;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::{MultiSpan, Span};
 
@@ -1096,33 +1096,37 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     _ => None,
                 };
                 let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter());
-                let names = resolutions.filter_map(|(BindingKey { ident: i, .. }, resolution)| {
-                    if *i == ident {
-                        return None;
-                    } // Never suggest the same name
-                    match *resolution.borrow() {
-                        NameResolution { binding: Some(name_binding), .. } => {
-                            match name_binding.kind {
-                                NameBindingKind::Import { binding, .. } => {
-                                    match binding.kind {
-                                        // Never suggest the name that has binding error
-                                        // i.e., the name that cannot be previously resolved
-                                        NameBindingKind::Res(Res::Err, _) => None,
-                                        _ => Some(&i.name),
+                let names = resolutions
+                    .filter_map(|(BindingKey { ident: i, .. }, resolution)| {
+                        if *i == ident {
+                            return None;
+                        } // Never suggest the same name
+                        match *resolution.borrow() {
+                            NameResolution { binding: Some(name_binding), .. } => {
+                                match name_binding.kind {
+                                    NameBindingKind::Import { binding, .. } => {
+                                        match binding.kind {
+                                            // Never suggest the name that has binding error
+                                            // i.e., the name that cannot be previously resolved
+                                            NameBindingKind::Res(Res::Err, _) => None,
+                                            _ => Some(i.name),
+                                        }
                                     }
+                                    _ => Some(i.name),
                                 }
-                                _ => Some(&i.name),
                             }
+                            NameResolution { ref single_imports, .. }
+                                if single_imports.is_empty() =>
+                            {
+                                None
+                            }
+                            _ => Some(i.name),
                         }
-                        NameResolution { ref single_imports, .. } if single_imports.is_empty() => {
-                            None
-                        }
-                        _ => Some(&i.name),
-                    }
-                });
+                    })
+                    .collect::<Vec<Symbol>>();
 
                 let lev_suggestion =
-                    find_best_match_for_name(names, ident.name, None).map(|suggestion| {
+                    find_best_match_for_name(&names, ident.name, None).map(|suggestion| {
                         (
                             vec![(ident.span, suggestion.to_string())],
                             String::from("a similar name exists in the module"),
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 2473436a91675..6ce299a941708 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -5,7 +5,6 @@ use crate::path_names_to_string;
 use crate::{CrateLint, Module, ModuleKind, ModuleOrUniformRoot};
 use crate::{PathResult, PathSource, Segment};
 
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_ast::visit::FnKind;
 use rustc_ast::{self as ast, Expr, ExprKind, Item, ItemKind, NodeId, Path, Ty, TyKind};
 use rustc_ast_pretty::pprust::path_segment_to_string;
@@ -18,6 +17,7 @@ use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::PrimTy;
 use rustc_session::parse::feature_err;
 use rustc_span::hygiene::MacroKind;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
 
@@ -1206,7 +1206,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
         names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 
         match find_best_match_for_name(
-            names.iter().map(|suggestion| &suggestion.candidate),
+            &names.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
             name,
             None,
         ) {
@@ -1592,9 +1592,10 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             .bindings
             .iter()
             .filter(|(id, _)| id.span.ctxt() == label.span.ctxt())
-            .map(|(id, _)| &id.name);
+            .map(|(id, _)| id.name)
+            .collect::<Vec<Symbol>>();
 
-        find_best_match_for_name(names, label.name, None).map(|symbol| {
+        find_best_match_for_name(&names, label.name, None).map(|symbol| {
             // Upon finding a similar name, get the ident that it was from - the span
             // contained within helps make a useful diagnostic. In addition, determine
             // whether this candidate is within scope.
diff --git a/compiler/rustc_ast/src/util/lev_distance.rs b/compiler/rustc_span/src/lev_distance.rs
similarity index 86%
rename from compiler/rustc_ast/src/util/lev_distance.rs
rename to compiler/rustc_span/src/lev_distance.rs
index 21c2c925bc479..edc6625a6ead7 100644
--- a/compiler/rustc_ast/src/util/lev_distance.rs
+++ b/compiler/rustc_span/src/lev_distance.rs
@@ -1,6 +1,4 @@
-// FIXME(Centril): Move to rustc_span?
-
-use rustc_span::symbol::Symbol;
+use crate::symbol::Symbol;
 use std::cmp;
 
 #[cfg(test)]
@@ -45,17 +43,14 @@ pub fn lev_distance(a: &str, b: &str) -> usize {
 ///
 /// Besides Levenshtein, we use case insensitive comparison to improve accuracy on an edge case with
 /// a lower(upper)case letters mismatch.
-pub fn find_best_match_for_name<'a, T>(
-    iter_names: T,
+#[cold]
+pub fn find_best_match_for_name(
+    name_vec: &[Symbol],
     lookup: Symbol,
     dist: Option<usize>,
-) -> Option<Symbol>
-where
-    T: Iterator<Item = &'a Symbol>,
-{
+) -> Option<Symbol> {
     let lookup = &lookup.as_str();
     let max_dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
-    let name_vec: Vec<&Symbol> = iter_names.collect();
 
     let (case_insensitive_match, levenshtein_match) = name_vec
         .iter()
@@ -83,18 +78,18 @@ where
     // 2. Levenshtein distance match
     // 3. Sorted word match
     if let Some(candidate) = case_insensitive_match {
-        Some(*candidate)
+        Some(candidate)
     } else if levenshtein_match.is_some() {
-        levenshtein_match.map(|(candidate, _)| *candidate)
+        levenshtein_match.map(|(candidate, _)| candidate)
     } else {
         find_match_by_sorted_words(name_vec, lookup)
     }
 }
 
-fn find_match_by_sorted_words<'a>(iter_names: Vec<&'a Symbol>, lookup: &str) -> Option<Symbol> {
+fn find_match_by_sorted_words(iter_names: &[Symbol], lookup: &str) -> Option<Symbol> {
     iter_names.iter().fold(None, |result, candidate| {
         if sort_by_words(&candidate.as_str()) == sort_by_words(lookup) {
-            Some(**candidate)
+            Some(*candidate)
         } else {
             result
         }
diff --git a/compiler/rustc_ast/src/util/lev_distance/tests.rs b/compiler/rustc_span/src/lev_distance/tests.rs
similarity index 69%
rename from compiler/rustc_ast/src/util/lev_distance/tests.rs
rename to compiler/rustc_span/src/lev_distance/tests.rs
index 7ebedbcb76a36..7aa01cb8efe7e 100644
--- a/compiler/rustc_ast/src/util/lev_distance/tests.rs
+++ b/compiler/rustc_span/src/lev_distance/tests.rs
@@ -21,38 +21,35 @@ fn test_lev_distance() {
 
 #[test]
 fn test_find_best_match_for_name() {
-    use rustc_span::with_default_session_globals;
+    use crate::with_default_session_globals;
     with_default_session_globals(|| {
         let input = vec![Symbol::intern("aaab"), Symbol::intern("aaabc")];
         assert_eq!(
-            find_best_match_for_name(input.iter(), Symbol::intern("aaaa"), None),
+            find_best_match_for_name(&input, Symbol::intern("aaaa"), None),
             Some(Symbol::intern("aaab"))
         );
 
-        assert_eq!(
-            find_best_match_for_name(input.iter(), Symbol::intern("1111111111"), None),
-            None
-        );
+        assert_eq!(find_best_match_for_name(&input, Symbol::intern("1111111111"), None), None);
 
         let input = vec![Symbol::intern("aAAA")];
         assert_eq!(
-            find_best_match_for_name(input.iter(), Symbol::intern("AAAA"), None),
+            find_best_match_for_name(&input, Symbol::intern("AAAA"), None),
             Some(Symbol::intern("aAAA"))
         );
 
         let input = vec![Symbol::intern("AAAA")];
         // Returns None because `lev_distance > max_dist / 3`
-        assert_eq!(find_best_match_for_name(input.iter(), Symbol::intern("aaaa"), None), None);
+        assert_eq!(find_best_match_for_name(&input, Symbol::intern("aaaa"), None), None);
 
         let input = vec![Symbol::intern("AAAA")];
         assert_eq!(
-            find_best_match_for_name(input.iter(), Symbol::intern("aaaa"), Some(4)),
+            find_best_match_for_name(&input, Symbol::intern("aaaa"), Some(4)),
             Some(Symbol::intern("AAAA"))
         );
 
         let input = vec![Symbol::intern("a_longer_variable_name")];
         assert_eq!(
-            find_best_match_for_name(input.iter(), Symbol::intern("a_variable_longer_name"), None),
+            find_best_match_for_name(&input, Symbol::intern("a_variable_longer_name"), None),
             Some(Symbol::intern("a_longer_variable_name"))
         );
     })
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 0926561f4c513..11a49d1ab887d 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -34,6 +34,7 @@ use hygiene::Transparency;
 pub use hygiene::{DesugaringKind, ExpnData, ExpnId, ExpnKind, ForLoopLoc, MacroKind};
 pub mod def_id;
 use def_id::{CrateNum, DefId, LOCAL_CRATE};
+pub mod lev_distance;
 mod span_encoding;
 pub use span_encoding::{Span, DUMMY_SP};
 
diff --git a/compiler/rustc_typeck/src/astconv/errors.rs b/compiler/rustc_typeck/src/astconv/errors.rs
index 685243f54cb90..b04acd9660d45 100644
--- a/compiler/rustc_typeck/src/astconv/errors.rs
+++ b/compiler/rustc_typeck/src/astconv/errors.rs
@@ -1,11 +1,11 @@
 use crate::astconv::AstConv;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{pluralize, struct_span_err, Applicability};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty;
 use rustc_session::parse::feature_err;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::{Span, DUMMY_SP};
 
@@ -180,7 +180,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             .collect();
 
         if let (Some(suggested_name), true) = (
-            find_best_match_for_name(all_candidate_names.iter(), assoc_name.name, None),
+            find_best_match_for_name(&all_candidate_names, assoc_name.name, None),
             assoc_name.span != DUMMY_SP,
         ) {
             err.span_suggestion(
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index b011e26d64b9a..9b814f6b7ee66 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -13,7 +13,6 @@ use crate::errors::{
 };
 use crate::middle::resolve_lifetime as rl;
 use crate::require_c_abi_if_c_variadic;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::{struct_span_err, Applicability, ErrorReported, FatalError};
 use rustc_hir as hir;
@@ -26,6 +25,7 @@ use rustc_middle::ty::subst::{self, InternalSubsts, Subst, SubstsRef};
 use rustc_middle::ty::GenericParamDefKind;
 use rustc_middle::ty::{self, Const, DefIdTree, Ty, TyCtxt, TypeFoldable};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::spec::abi;
@@ -1579,7 +1579,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
                     let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
                     if let Some(suggested_name) = find_best_match_for_name(
-                        adt_def.variants.iter().map(|variant| &variant.ident.name),
+                        &adt_def
+                            .variants
+                            .iter()
+                            .map(|variant| variant.ident.name)
+                            .collect::<Vec<Symbol>>(),
                         assoc_ident.name,
                         None,
                     ) {
diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs
index f7f9e607a7441..26962d2222d32 100644
--- a/compiler/rustc_typeck/src/check/expr.rs
+++ b/compiler/rustc_typeck/src/check/expr.rs
@@ -22,7 +22,6 @@ use crate::type_error_struct;
 
 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
 use rustc_ast as ast;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::ErrorReported;
@@ -40,6 +39,7 @@ use rustc_middle::ty::Ty;
 use rustc_middle::ty::TypeFoldable;
 use rustc_middle::ty::{AdtKind, Visibility};
 use rustc_span::hygiene::DesugaringKind;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::Span;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_trait_selection::traits::{self, ObligationCauseCode};
@@ -1441,18 +1441,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         field: Symbol,
         skip: Vec<Symbol>,
     ) -> Option<Symbol> {
-        let names = variant.fields.iter().filter_map(|field| {
-            // ignore already set fields and private fields from non-local crates
-            if skip.iter().any(|&x| x == field.ident.name)
-                || (!variant.def_id.is_local() && field.vis != Visibility::Public)
-            {
-                None
-            } else {
-                Some(&field.ident.name)
-            }
-        });
+        let names = variant
+            .fields
+            .iter()
+            .filter_map(|field| {
+                // ignore already set fields and private fields from non-local crates
+                if skip.iter().any(|&x| x == field.ident.name)
+                    || (!variant.def_id.is_local() && field.vis != Visibility::Public)
+                {
+                    None
+                } else {
+                    Some(field.ident.name)
+                }
+            })
+            .collect::<Vec<Symbol>>();
 
-        find_best_match_for_name(names, field, None)
+        find_best_match_for_name(&names, field, None)
     }
 
     fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<Symbol> {
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index 478f8a16169ed..39a79893b6441 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -9,7 +9,6 @@ use crate::hir::def::DefKind;
 use crate::hir::def_id::DefId;
 
 use rustc_ast as ast;
-use rustc_ast::util::lev_distance::{find_best_match_for_name, lev_distance};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
@@ -27,6 +26,7 @@ use rustc_middle::ty::{
 };
 use rustc_session::lint;
 use rustc_span::def_id::LocalDefId;
+use rustc_span::lev_distance::{find_best_match_for_name, lev_distance};
 use rustc_span::{symbol::Ident, Span, Symbol, DUMMY_SP};
 use rustc_trait_selection::autoderef::{self, Autoderef};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
@@ -1538,8 +1538,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 Ok(None)
             } else {
                 let best_name = {
-                    let names = applicable_close_candidates.iter().map(|cand| &cand.ident.name);
-                    find_best_match_for_name(names, self.method_name.unwrap().name, None)
+                    let names = applicable_close_candidates
+                        .iter()
+                        .map(|cand| cand.ident.name)
+                        .collect::<Vec<Symbol>>();
+                    find_best_match_for_name(&names, self.method_name.unwrap().name, None)
                 }
                 .unwrap();
                 Ok(applicable_close_candidates
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 3d5ce57a491c5..a979bc470d8db 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -2,7 +2,6 @@
 //! found or is otherwise invalid.
 
 use crate::check::FnCtxt;
-use rustc_ast::util::lev_distance;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
@@ -17,6 +16,7 @@ use rustc_middle::ty::print::with_crate_prefix;
 use rustc_middle::ty::{
     self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
 };
+use rustc_span::lev_distance;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{source_map, FileName, Span};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
@@ -744,7 +744,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if actual.is_enum() {
                     let adt_def = actual.ty_adt_def().expect("enum is not an ADT");
                     if let Some(suggestion) = lev_distance::find_best_match_for_name(
-                        adt_def.variants.iter().map(|s| &s.ident.name),
+                        &adt_def.variants.iter().map(|s| s.ident.name).collect::<Vec<_>>(),
                         item_name.name,
                         None,
                     ) {
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index a729912126e4f..bcb73e1b4e74e 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -1,7 +1,6 @@
 use crate::check::FnCtxt;
 use rustc_ast as ast;
 
-use rustc_ast::util::lev_distance::find_best_match_for_name;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
@@ -13,6 +12,7 @@ use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKi
 use rustc_middle::ty::subst::GenericArg;
 use rustc_middle::ty::{self, Adt, BindingMode, Ty, TypeFoldable};
 use rustc_span::hygiene::DesugaringKind;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::{Span, Spanned};
 use rustc_span::symbol::Ident;
 use rustc_trait_selection::traits::{ObligationCause, Pattern};
@@ -1302,8 +1302,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ),
             );
             if plural == "" {
-                let input = unmentioned_fields.iter().map(|(_, field)| &field.name);
-                let suggested_name = find_best_match_for_name(input, ident.name, None);
+                let input =
+                    unmentioned_fields.iter().map(|(_, field)| field.name).collect::<Vec<_>>();
+                let suggested_name = find_best_match_for_name(&input, ident.name, None);
                 if let Some(suggested_name) = suggested_name {
                     err.span_suggestion(
                         ident.span,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 9f35e57df418b..a615701f253d3 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -754,12 +754,14 @@ impl Tester for Collector {
             let folder_name = filename
                 .to_string()
                 .chars()
-                .map(|c| if c == '/' || c == '.' { '_' } else { c })
+                .map(|c| if c == '\\' || c == '/' || c == '.' { '_' } else { c })
                 .collect::<String>();
 
             path.push(format!(
-                "{name}_{line}_{number}",
-                name = folder_name,
+                "{krate}_{file}_{line}_{number}",
+                krate = cratename,
+                file = folder_name,
+                line = line,
                 number = {
                     // Increases the current test number, if this file already
                     // exists or it creates a new entry with a test number of 0.
@@ -768,7 +770,6 @@ impl Tester for Collector {
                         .and_modify(|v| *v += 1)
                         .or_insert(0)
                 },
-                line = line,
             ));
 
             std::fs::create_dir_all(&path)
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index a88efba77b41c..751f230105392 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -513,7 +513,7 @@ fn main_options(options: config::Options) -> MainResult {
     }
 
     // need to move these items separately because we lose them by the time the closure is called,
-    // but we can't crates the Handler ahead of time because it's not Send
+    // but we can't create the Handler ahead of time because it's not Send
     let diag_opts = (options.error_format, options.edition, options.debugging_opts.clone());
     let show_coverage = options.show_coverage;
     let run_check = options.run_check;
diff --git a/src/test/run-make-fulldeps/coverage-llvmir-base/Makefile b/src/test/run-make-fulldeps/coverage-llvmir-base/Makefile
index e84642922d934..219ba15ad116d 100644
--- a/src/test/run-make-fulldeps/coverage-llvmir-base/Makefile
+++ b/src/test/run-make-fulldeps/coverage-llvmir-base/Makefile
@@ -12,10 +12,12 @@ ifeq ($(UNAME),Darwin)
 	INSTR_PROF_DATA_SUFFIX=,regular,live_support
 	DATA_SECTION_PREFIX=__DATA,
 	LLVM_COV_SECTION_PREFIX=__LLVM_COV,
+	COMDAT_IF_SUPPORTED=
 else
 	INSTR_PROF_DATA_SUFFIX=
 	DATA_SECTION_PREFIX=
 	LLVM_COV_SECTION_PREFIX=
+	COMDAT_IF_SUPPORTED=, comdat
 endif
 
 ifeq ($(LINK_DEAD_CODE),yes)
@@ -29,28 +31,39 @@ ifdef IS_WINDOWS
 		-check-prefixes=CHECK,WINDOWS \
 		-DPRIVATE_GLOBAL='internal global' \
 		-DDEFINE_INTERNAL='$(DEFINE_INTERNAL)' \
+		-DCOMDAT_IF_SUPPORTED='$(COMDAT_IF_SUPPORTED)' \
 		-DINSTR_PROF_DATA='.lprfd$$M' \
 		-DINSTR_PROF_NAME='.lprfn$$M' \
 		-DINSTR_PROF_CNTS='.lprfc$$M' \
 		-DINSTR_PROF_VALS='.lprfv$$M' \
 		-DINSTR_PROF_VNODES='.lprfnd$$M' \
 		-DINSTR_PROF_COVMAP='.lcovmap$$M' \
+		-DINSTR_PROF_COVFUN='.lcovfun$$M' \
 		-DINSTR_PROF_ORDERFILE='.lorderfile$$M'
 else
 	LLVM_FILECHECK_OPTIONS=\
 		-check-prefixes=CHECK \
 		-DPRIVATE_GLOBAL='private global' \
 		-DDEFINE_INTERNAL='$(DEFINE_INTERNAL)' \
+		-DCOMDAT_IF_SUPPORTED='$(COMDAT_IF_SUPPORTED)' \
 		-DINSTR_PROF_DATA='$(DATA_SECTION_PREFIX)__llvm_prf_data$(INSTR_PROF_DATA_SUFFIX)' \
 		-DINSTR_PROF_NAME='$(DATA_SECTION_PREFIX)__llvm_prf_names' \
 		-DINSTR_PROF_CNTS='$(DATA_SECTION_PREFIX)__llvm_prf_cnts' \
 		-DINSTR_PROF_VALS='$(DATA_SECTION_PREFIX)__llvm_prf_vals' \
 		-DINSTR_PROF_VNODES='$(DATA_SECTION_PREFIX)__llvm_prf_vnds' \
 		-DINSTR_PROF_COVMAP='$(LLVM_COV_SECTION_PREFIX)__llvm_covmap' \
+		-DINSTR_PROF_COVFUN='$(LLVM_COV_SECTION_PREFIX)__llvm_covfun' \
 		-DINSTR_PROF_ORDERFILE='$(DATA_SECTION_PREFIX)__llvm_orderfile'
 endif
 
+ifeq ($(LLVM_VERSION_11_PLUS),true)
+all: test_llvm_ir
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
 all:
+endif
+
+test_llvm_ir:
 	# Compile the test program with non-experimental coverage instrumentation, and generate LLVM IR
 	#
 	# Note: `-Clink-dead-code=no` disables the option, needed because the option is automatically
@@ -62,4 +75,5 @@ all:
 			-Clink-dead-code=$(LINK_DEAD_CODE) \
 			--emit=llvm-ir
 
-	cat "$(TMPDIR)"/testprog.ll | "$(LLVM_FILECHECK)" $(BASEDIR)/filecheck.testprog.txt $(LLVM_FILECHECK_OPTIONS)
+	cat "$(TMPDIR)"/testprog.ll | \
+			"$(LLVM_FILECHECK)" $(BASEDIR)/filecheck.testprog.txt $(LLVM_FILECHECK_OPTIONS)
diff --git a/src/test/run-make-fulldeps/coverage-llvmir-base/filecheck.testprog.txt b/src/test/run-make-fulldeps/coverage-llvmir-base/filecheck.testprog.txt
index bd2a2475d9e10..a312ec48e8498 100644
--- a/src/test/run-make-fulldeps/coverage-llvmir-base/filecheck.testprog.txt
+++ b/src/test/run-make-fulldeps/coverage-llvmir-base/filecheck.testprog.txt
@@ -3,7 +3,10 @@
 
 WINDOWS:      $__llvm_profile_runtime_user = comdat any
 
-CHECK:        @__llvm_coverage_mapping = internal constant
+CHECK:        @__covrec_{{[A-F0-9]+}}u = linkonce_odr hidden constant
+CHECK-SAME:   section "[[INSTR_PROF_COVFUN]]"[[COMDAT_IF_SUPPORTED]], align 8
+
+CHECK:        @__llvm_coverage_mapping = private constant
 CHECK-SAME:   section "[[INSTR_PROF_COVMAP]]", align 8
 
 WINDOWS:      @__llvm_profile_runtime = external global i32
diff --git a/src/test/run-make-fulldeps/coverage-reports-base/Makefile b/src/test/run-make-fulldeps/coverage-reports-base/Makefile
index 1e2aa056e4008..2dac8fc2225bf 100644
--- a/src/test/run-make-fulldeps/coverage-reports-base/Makefile
+++ b/src/test/run-make-fulldeps/coverage-reports-base/Makefile
@@ -18,7 +18,10 @@ SOURCEDIR=../coverage
 # `llvm/release_debuginfo`. Note that some CI builds disable debug assertions (by setting
 # `NO_LLVM_ASSERTIONS=1`), so it is not OK to fail the test, but `bless`ed test results cannot be
 # generated without debug assertions.
-LLVM_COV_DEBUG := $(shell "$(LLVM_BIN_DIR)"/llvm-cov show --debug 2>&1 | grep -q "Unknown command line argument '--debug'"; echo $$?)
+LLVM_COV_DEBUG := $(shell \
+		"$(LLVM_BIN_DIR)"/llvm-cov show --debug 2>&1 | \
+		grep -q "Unknown command line argument '--debug'"; \
+		echo $$?)
 ifeq ($(LLVM_COV_DEBUG), 1)
 DEBUG_FLAG=--debug
 endif
@@ -30,7 +33,12 @@ ifdef RUSTC_BLESS_TEST
 DEBUG_FLAG=--debug
 endif
 
+ifeq ($(LLVM_VERSION_11_PLUS),true)
 all: $(patsubst $(SOURCEDIR)/%.rs,%,$(wildcard $(SOURCEDIR)/*.rs))
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
+all:
+endif
 
 # Ensure there are no `expected` results for tests that may have been removed or renamed
 .PHONY: clear_expected_if_blessed
diff --git a/src/test/run-make-fulldeps/coverage-spanview-base/Makefile b/src/test/run-make-fulldeps/coverage-spanview-base/Makefile
index 03ef04776a03b..9f9440340e0ed 100644
--- a/src/test/run-make-fulldeps/coverage-spanview-base/Makefile
+++ b/src/test/run-make-fulldeps/coverage-spanview-base/Makefile
@@ -24,7 +24,12 @@ For revisions in Pull Requests (PR):
 endef
 export SPANVIEW_HEADER
 
+ifeq ($(LLVM_VERSION_11_PLUS),true)
 all: $(patsubst $(SOURCEDIR)/%.rs,%,$(wildcard $(SOURCEDIR)/*.rs))
+else
+$(info Rust option `-Z instrument-coverage` requires LLVM 11 or higher. Test skipped.)
+all:
+endif
 
 # Ensure there are no `expected` results for tests that may have been removed or renamed
 .PHONY: clear_expected_if_blessed
diff --git a/src/test/run-make-fulldeps/coverage/coverage_tools.mk b/src/test/run-make-fulldeps/coverage/coverage_tools.mk
index 17f7696a8cf1d..99a2e0ba9523e 100644
--- a/src/test/run-make-fulldeps/coverage/coverage_tools.mk
+++ b/src/test/run-make-fulldeps/coverage/coverage_tools.mk
@@ -38,6 +38,13 @@ endif
 
 UNAME = $(shell uname)
 
+# Rust option `-Z instrument-coverage` uses LLVM Coverage Mapping Format version 4,
+# which requires LLVM 11 or greater.
+LLVM_VERSION_11_PLUS := $(shell \
+		LLVM_VERSION=$$("$(LLVM_BIN_DIR)"/llvm-config --version) && \
+		LLVM_VERSION_MAJOR=$${LLVM_VERSION/.*/} && \
+		[ $$LLVM_VERSION_MAJOR -ge 11 ] && echo true || echo false)
+
 # FIXME(richkadel): Can any of the features tested by `run-make-fulldeps/coverage-*` tests be tested
 # just as completely by more focused unit tests of the code logic itself, to reduce the number of
 # test result files generated and maintained, and to help identify specific test failures and root
diff --git a/src/test/rustdoc-js/doc-alias-filter-out.rs b/src/test/rustdoc-js/doc-alias-filter-out.rs
index 815e8cedd16da..3f0c094794e41 100644
--- a/src/test/rustdoc-js/doc-alias-filter-out.rs
+++ b/src/test/rustdoc-js/doc-alias-filter-out.rs
@@ -1,4 +1,2 @@
-#![feature(doc_alias)]
-
 #[doc(alias = "true")]
 pub struct Foo;
diff --git a/src/test/rustdoc-js/doc-alias-filter.rs b/src/test/rustdoc-js/doc-alias-filter.rs
index 8887f8c2b0149..d5227814c06a8 100644
--- a/src/test/rustdoc-js/doc-alias-filter.rs
+++ b/src/test/rustdoc-js/doc-alias-filter.rs
@@ -1,5 +1,3 @@
-#![feature(doc_alias)]
-
 #[doc(alias = "true")]
 pub struct Foo;
 
diff --git a/src/test/rustdoc-js/doc-alias-whitespace.rs b/src/test/rustdoc-js/doc-alias-whitespace.rs
index bea3e382ae4b0..16c022c749890 100644
--- a/src/test/rustdoc-js/doc-alias-whitespace.rs
+++ b/src/test/rustdoc-js/doc-alias-whitespace.rs
@@ -1,4 +1,2 @@
-#![feature(doc_alias)]
-
 #[doc(alias = "Demon Lord")]
 pub struct Struct;
diff --git a/src/test/rustdoc-js/doc-alias.rs b/src/test/rustdoc-js/doc-alias.rs
index 41caa98643cdd..750b7b757bc35 100644
--- a/src/test/rustdoc-js/doc-alias.rs
+++ b/src/test/rustdoc-js/doc-alias.rs
@@ -1,5 +1,3 @@
-#![feature(doc_alias)]
-
 #[doc(alias = "StructItem")]
 pub struct Struct {
     #[doc(alias = "StructFieldItem")]
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr-location.rs b/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
index 545964c7bd61b..7de2caa189dc7 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
+++ b/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
@@ -1,5 +1,3 @@
-#![feature(doc_alias)]
-
 pub struct Bar;
 pub trait Foo {
     type X;
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr-location.stderr b/src/test/rustdoc-ui/check-doc-alias-attr-location.stderr
index a66e9939eaf18..175626f49dcac 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr-location.stderr
+++ b/src/test/rustdoc-ui/check-doc-alias-attr-location.stderr
@@ -1,23 +1,23 @@
 error: `#[doc(alias = "...")]` isn't allowed on extern block
-  --> $DIR/check-doc-alias-attr-location.rs:9:7
+  --> $DIR/check-doc-alias-attr-location.rs:7:7
    |
 LL | #[doc(alias = "foo")]
    |       ^^^^^^^^^^^^^
 
 error: `#[doc(alias = "...")]` isn't allowed on implementation block
-  --> $DIR/check-doc-alias-attr-location.rs:12:7
+  --> $DIR/check-doc-alias-attr-location.rs:10:7
    |
 LL | #[doc(alias = "bar")]
    |       ^^^^^^^^^^^^^
 
 error: `#[doc(alias = "...")]` isn't allowed on implementation block
-  --> $DIR/check-doc-alias-attr-location.rs:18:7
+  --> $DIR/check-doc-alias-attr-location.rs:16:7
    |
 LL | #[doc(alias = "foobar")]
    |       ^^^^^^^^^^^^^^^^
 
 error: `#[doc(alias = "...")]` isn't allowed on type alias in implementation block
-  --> $DIR/check-doc-alias-attr-location.rs:20:11
+  --> $DIR/check-doc-alias-attr-location.rs:18:11
    |
 LL |     #[doc(alias = "assoc")]
    |           ^^^^^^^^^^^^^^^
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr.rs b/src/test/rustdoc-ui/check-doc-alias-attr.rs
index 0ca2349a43b0f..912e35f916545 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr.rs
+++ b/src/test/rustdoc-ui/check-doc-alias-attr.rs
@@ -1,5 +1,4 @@
 #![crate_type = "lib"]
-#![feature(doc_alias)]
 
 #[doc(alias = "foo")] // ok!
 pub struct Bar;
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr.stderr b/src/test/rustdoc-ui/check-doc-alias-attr.stderr
index 2c417a3bb65b5..8a729b02e72bf 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr.stderr
+++ b/src/test/rustdoc-ui/check-doc-alias-attr.stderr
@@ -1,35 +1,35 @@
 error: doc alias attribute expects a string: #[doc(alias = "0")]
-  --> $DIR/check-doc-alias-attr.rs:7:7
+  --> $DIR/check-doc-alias-attr.rs:6:7
    |
 LL | #[doc(alias)]
    |       ^^^^^
 
 error: doc alias attribute expects a string: #[doc(alias = "0")]
-  --> $DIR/check-doc-alias-attr.rs:8:7
+  --> $DIR/check-doc-alias-attr.rs:7:7
    |
 LL | #[doc(alias = 0)]
    |       ^^^^^^^^^
 
 error: doc alias attribute expects a string: #[doc(alias = "0")]
-  --> $DIR/check-doc-alias-attr.rs:9:7
+  --> $DIR/check-doc-alias-attr.rs:8:7
    |
 LL | #[doc(alias("bar"))]
    |       ^^^^^^^^^^^^
 
 error: '\"' character isn't allowed in `#[doc(alias = "...")]`
-  --> $DIR/check-doc-alias-attr.rs:10:7
+  --> $DIR/check-doc-alias-attr.rs:9:7
    |
 LL | #[doc(alias = "\"")]
    |       ^^^^^^^^^^^^
 
 error: '\n' character isn't allowed in `#[doc(alias = "...")]`
-  --> $DIR/check-doc-alias-attr.rs:11:7
+  --> $DIR/check-doc-alias-attr.rs:10:7
    |
 LL | #[doc(alias = "\n")]
    |       ^^^^^^^^^^^^
 
 error: '\n' character isn't allowed in `#[doc(alias = "...")]`
-  --> $DIR/check-doc-alias-attr.rs:12:7
+  --> $DIR/check-doc-alias-attr.rs:11:7
    |
 LL |   #[doc(alias = "
    |  _______^
@@ -37,19 +37,19 @@ LL | | ")]
    | |_^
 
 error: '\t' character isn't allowed in `#[doc(alias = "...")]`
-  --> $DIR/check-doc-alias-attr.rs:14:7
+  --> $DIR/check-doc-alias-attr.rs:13:7
    |
 LL | #[doc(alias = "\t")]
    |       ^^^^^^^^^^^^
 
 error: `#[doc(alias = "...")]` cannot start or end with ' '
-  --> $DIR/check-doc-alias-attr.rs:15:7
+  --> $DIR/check-doc-alias-attr.rs:14:7
    |
 LL | #[doc(alias = " hello")]
    |       ^^^^^^^^^^^^^^^^
 
 error: `#[doc(alias = "...")]` cannot start or end with ' '
-  --> $DIR/check-doc-alias-attr.rs:16:7
+  --> $DIR/check-doc-alias-attr.rs:15:7
    |
 LL | #[doc(alias = "hello ")]
    |       ^^^^^^^^^^^^^^^^
diff --git a/src/test/rustdoc-ui/doc-alias-assoc-const.rs b/src/test/rustdoc-ui/doc-alias-assoc-const.rs
index 73e23c152f268..d95324734be47 100644
--- a/src/test/rustdoc-ui/doc-alias-assoc-const.rs
+++ b/src/test/rustdoc-ui/doc-alias-assoc-const.rs
@@ -1,4 +1,3 @@
-#![feature(doc_alias)]
 #![feature(trait_alias)]
 
 pub struct Foo;
diff --git a/src/test/rustdoc-ui/doc-alias-assoc-const.stderr b/src/test/rustdoc-ui/doc-alias-assoc-const.stderr
index 3c64548cc204d..cbca40e1364fa 100644
--- a/src/test/rustdoc-ui/doc-alias-assoc-const.stderr
+++ b/src/test/rustdoc-ui/doc-alias-assoc-const.stderr
@@ -1,5 +1,5 @@
 error: `#[doc(alias = "...")]` isn't allowed on associated constant in trait implementation block
-  --> $DIR/doc-alias-assoc-const.rs:11:11
+  --> $DIR/doc-alias-assoc-const.rs:10:11
    |
 LL |     #[doc(alias = "CONST_BAZ")]
    |           ^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/rustdoc-ui/doc-test-doctest-feature.rs b/src/test/rustdoc-ui/doc-test-doctest-feature.rs
index 9a79fb8838351..2798804880ad0 100644
--- a/src/test/rustdoc-ui/doc-test-doctest-feature.rs
+++ b/src/test/rustdoc-ui/doc-test-doctest-feature.rs
@@ -2,13 +2,10 @@
 // compile-flags:--test
 // normalize-stdout-test: "src/test/rustdoc-ui" -> "$$DIR"
 
-#![feature(cfg_doctest)]
-
 // Make sure `cfg(doctest)` is set when finding doctests but not inside
 // the doctests.
 
 /// ```
-/// #![feature(cfg_doctest)]
 /// assert!(!cfg!(doctest));
 /// ```
 #[cfg(doctest)]
diff --git a/src/test/rustdoc-ui/doc-test-doctest-feature.stdout b/src/test/rustdoc-ui/doc-test-doctest-feature.stdout
index 75d29fab17d0d..b1cd74bf8520a 100644
--- a/src/test/rustdoc-ui/doc-test-doctest-feature.stdout
+++ b/src/test/rustdoc-ui/doc-test-doctest-feature.stdout
@@ -1,6 +1,6 @@
 
 running 1 test
-test $DIR/doc-test-doctest-feature.rs - Foo (line 10) ... ok
+test $DIR/doc-test-doctest-feature.rs - Foo (line 8) ... ok
 
 test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
 
diff --git a/src/test/rustdoc/deprecated-future.rs b/src/test/rustdoc/deprecated-future.rs
index c5248c52fb973..7db8cc6028179 100644
--- a/src/test/rustdoc/deprecated-future.rs
+++ b/src/test/rustdoc/deprecated-future.rs
@@ -1,5 +1,3 @@
-#![feature(deprecated)]
-
 // @has deprecated_future/index.html '//*[@class="stab deprecated"]' \
 //      'Deprecated'
 // @has deprecated_future/struct.S.html '//*[@class="stab deprecated"]' \
diff --git a/src/test/rustdoc/deprecated.rs b/src/test/rustdoc/deprecated.rs
index 18a33438a2346..a286856b2c3c1 100644
--- a/src/test/rustdoc/deprecated.rs
+++ b/src/test/rustdoc/deprecated.rs
@@ -1,5 +1,3 @@
-#![feature(deprecated)]
-
 // @has deprecated/index.html '//*[@class="docblock-short"]/span[@class="stab deprecated"]' \
 //      'Deprecated'
 // @has - '//*[@class="docblock-short"]' 'Deprecated docs'
diff --git a/src/test/rustdoc/issue-76501.rs b/src/test/rustdoc/issue-76501.rs
index 605059fe0dd8d..d468f35e28003 100644
--- a/src/test/rustdoc/issue-76501.rs
+++ b/src/test/rustdoc/issue-76501.rs
@@ -1,5 +1,3 @@
-#![feature(const_fn)]
-
 // @has 'issue_76501/fn.bloop.html' '//pre' 'pub const fn bloop() -> i32'
 /// A useless function that always returns 1.
 pub const fn bloop() -> i32 {
diff --git a/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr b/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
index b438ed3ad6508..05bf67a5ff7c6 100644
--- a/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
+++ b/src/test/ui/const-generics/infer/cannot-infer-const-args.full.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
    |
 LL |     foo();
    |     ^^^ cannot infer the value of const parameter `X` declared on the function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     foo::<X>();
+   |     ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr b/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
index b438ed3ad6508..05bf67a5ff7c6 100644
--- a/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
+++ b/src/test/ui/const-generics/infer/cannot-infer-const-args.min.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
    |
 LL |     foo();
    |     ^^^ cannot infer the value of const parameter `X` declared on the function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     foo::<X>();
+   |     ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/issue-77092.stderr b/src/test/ui/const-generics/infer/issue-77092.stderr
index 63facbf3b8c0f..99894173bc8f6 100644
--- a/src/test/ui/const-generics/infer/issue-77092.stderr
+++ b/src/test/ui/const-generics/infer/issue-77092.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
    |
 LL |         println!("{:?}", take_array_from_mut(&mut arr, i));
    |                          ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `take_array_from_mut`
+   |
+help: consider specifying the const argument
+   |
+LL |         println!("{:?}", take_array_from_mut::<N>(&mut arr, i));
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/method-chain.full.stderr b/src/test/ui/const-generics/infer/method-chain.full.stderr
index 1fb0b23cf1157..7aa3bd44df844 100644
--- a/src/test/ui/const-generics/infer/method-chain.full.stderr
+++ b/src/test/ui/const-generics/infer/method-chain.full.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
    |
 LL |     Foo.bar().bar().bar().bar().baz();
    |                                 ^^^ cannot infer the value of const parameter `N` declared on the associated function `baz`
+   |
+help: consider specifying the const argument
+   |
+LL |     Foo.bar().bar().bar().bar().baz::<N>();
+   |                                 ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/method-chain.min.stderr b/src/test/ui/const-generics/infer/method-chain.min.stderr
index 1fb0b23cf1157..7aa3bd44df844 100644
--- a/src/test/ui/const-generics/infer/method-chain.min.stderr
+++ b/src/test/ui/const-generics/infer/method-chain.min.stderr
@@ -3,6 +3,11 @@ error[E0282]: type annotations needed
    |
 LL |     Foo.bar().bar().bar().bar().baz();
    |                                 ^^^ cannot infer the value of const parameter `N` declared on the associated function `baz`
+   |
+help: consider specifying the const argument
+   |
+LL |     Foo.bar().bar().bar().bar().baz::<N>();
+   |                                 ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr b/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr
new file mode 100644
index 0000000000000..cc6c9a475104c
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.full.stderr
@@ -0,0 +1,14 @@
+error[E0282]: type annotations needed
+  --> $DIR/one-param-uninferred.rs:15:23
+   |
+LL |     let _: [u8; 17] = foo();
+   |                       ^^^ cannot infer the value of const parameter `M` declared on the function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     let _: [u8; 17] = foo::<M>();
+   |                       ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr b/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr
new file mode 100644
index 0000000000000..cc6c9a475104c
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.min.stderr
@@ -0,0 +1,14 @@
+error[E0282]: type annotations needed
+  --> $DIR/one-param-uninferred.rs:15:23
+   |
+LL |     let _: [u8; 17] = foo();
+   |                       ^^^ cannot infer the value of const parameter `M` declared on the function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     let _: [u8; 17] = foo::<M>();
+   |                       ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.
diff --git a/src/test/ui/const-generics/infer/one-param-uninferred.rs b/src/test/ui/const-generics/infer/one-param-uninferred.rs
new file mode 100644
index 0000000000000..0e947131f4cdb
--- /dev/null
+++ b/src/test/ui/const-generics/infer/one-param-uninferred.rs
@@ -0,0 +1,17 @@
+// Test that we emit an error if we cannot properly infer a constant.
+// revisions: full min
+
+#![cfg_attr(full, feature(const_generics))]
+#![cfg_attr(full, allow(incomplete_features))]
+#![cfg_attr(min, feature(min_const_generics))]
+
+fn foo<const N: usize, const M: usize>() -> [u8; N] {
+    todo!()
+}
+
+fn main() {
+    // FIXME(const_generics): Currently this only suggests one const parameter,
+    // but instead it should suggest to provide all parameters.
+    let _: [u8; 17] = foo();
+                  //~^ ERROR type annotations needed
+}
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.full.stderr b/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
index 7a451903e9630..4be625ba90930 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
+++ b/src/test/ui/const-generics/infer/uninferred-consts.full.stderr
@@ -2,7 +2,12 @@ error[E0282]: type annotations needed
   --> $DIR/uninferred-consts.rs:14:9
    |
 LL |     Foo.foo();
-   |         ^^^ cannot infer the value of const parameter `N` declared on the associated function `foo`
+   |         ^^^ cannot infer the value of const parameter `A` declared on the associated function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     Foo.foo::<A>();
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.min.stderr b/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
index 7a451903e9630..4be625ba90930 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
+++ b/src/test/ui/const-generics/infer/uninferred-consts.min.stderr
@@ -2,7 +2,12 @@ error[E0282]: type annotations needed
   --> $DIR/uninferred-consts.rs:14:9
    |
 LL |     Foo.foo();
-   |         ^^^ cannot infer the value of const parameter `N` declared on the associated function `foo`
+   |         ^^^ cannot infer the value of const parameter `A` declared on the associated function `foo`
+   |
+help: consider specifying the const argument
+   |
+LL |     Foo.foo::<A>();
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/const-generics/infer/uninferred-consts.rs b/src/test/ui/const-generics/infer/uninferred-consts.rs
index ec5b3ffe5440b..00fb6eac99208 100644
--- a/src/test/ui/const-generics/infer/uninferred-consts.rs
+++ b/src/test/ui/const-generics/infer/uninferred-consts.rs
@@ -8,7 +8,7 @@
 // taken from https://github.com/rust-lang/rust/issues/70507#issuecomment-615268893
 struct Foo;
 impl Foo {
-    fn foo<const N: usize>(self) {}
+    fn foo<const A: usize, const B: usize>(self) {}
 }
 fn main() {
     Foo.foo();
diff --git a/src/test/ui/old-suffixes-are-really-forbidden.stderr b/src/test/ui/old-suffixes-are-really-forbidden.stderr
index ccfe60e964b2e..fb309793b34b4 100644
--- a/src/test/ui/old-suffixes-are-really-forbidden.stderr
+++ b/src/test/ui/old-suffixes-are-really-forbidden.stderr
@@ -1,18 +1,18 @@
-error: invalid suffix `is` for integer literal
+error: invalid suffix `is` for number literal
   --> $DIR/old-suffixes-are-really-forbidden.rs:2:13
    |
 LL |     let a = 1_is;
    |             ^^^^ invalid suffix `is`
    |
-   = help: the suffix must be one of the integral types (`u32`, `isize`, etc)
+   = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
-error: invalid suffix `us` for integer literal
+error: invalid suffix `us` for number literal
   --> $DIR/old-suffixes-are-really-forbidden.rs:3:13
    |
 LL |     let b = 2_us;
    |             ^^^^ invalid suffix `us`
    |
-   = help: the suffix must be one of the integral types (`u32`, `isize`, etc)
+   = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/bad-lit-suffixes.rs b/src/test/ui/parser/bad-lit-suffixes.rs
index 7db83674efc60..446a0940559b3 100644
--- a/src/test/ui/parser/bad-lit-suffixes.rs
+++ b/src/test/ui/parser/bad-lit-suffixes.rs
@@ -19,8 +19,8 @@ fn main() {
     1234f1024; //~ ERROR invalid width `1024` for float literal
     1234.5f1024; //~ ERROR invalid width `1024` for float literal
 
-    1234suffix; //~ ERROR invalid suffix `suffix` for integer literal
-    0b101suffix; //~ ERROR invalid suffix `suffix` for integer literal
+    1234suffix; //~ ERROR invalid suffix `suffix` for number literal
+    0b101suffix; //~ ERROR invalid suffix `suffix` for number literal
     1.0suffix; //~ ERROR invalid suffix `suffix` for float literal
     1.0e10suffix; //~ ERROR invalid suffix `suffix` for float literal
 }
diff --git a/src/test/ui/parser/bad-lit-suffixes.stderr b/src/test/ui/parser/bad-lit-suffixes.stderr
index 6b0049298ffd2..9b596571481b9 100644
--- a/src/test/ui/parser/bad-lit-suffixes.stderr
+++ b/src/test/ui/parser/bad-lit-suffixes.stderr
@@ -78,21 +78,21 @@ LL |     1234.5f1024;
    |
    = help: valid widths are 32 and 64
 
-error: invalid suffix `suffix` for integer literal
+error: invalid suffix `suffix` for number literal
   --> $DIR/bad-lit-suffixes.rs:22:5
    |
 LL |     1234suffix;
    |     ^^^^^^^^^^ invalid suffix `suffix`
    |
-   = help: the suffix must be one of the integral types (`u32`, `isize`, etc)
+   = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
-error: invalid suffix `suffix` for integer literal
+error: invalid suffix `suffix` for number literal
   --> $DIR/bad-lit-suffixes.rs:23:5
    |
 LL |     0b101suffix;
    |     ^^^^^^^^^^^ invalid suffix `suffix`
    |
-   = help: the suffix must be one of the integral types (`u32`, `isize`, etc)
+   = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
 error: invalid suffix `suffix` for float literal
   --> $DIR/bad-lit-suffixes.rs:24:5
diff --git a/src/test/ui/parser/no-binary-float-literal.rs b/src/test/ui/parser/no-binary-float-literal.rs
index 052cb4934f503..e07ff6518eeed 100644
--- a/src/test/ui/parser/no-binary-float-literal.rs
+++ b/src/test/ui/parser/no-binary-float-literal.rs
@@ -4,5 +4,5 @@ fn main() {
     0b101.010;
     //~^ ERROR binary float literal is not supported
     0b101p4f64;
-    //~^ ERROR invalid suffix `p4f64` for integer literal
+    //~^ ERROR invalid suffix `p4f64` for number literal
 }
diff --git a/src/test/ui/parser/no-binary-float-literal.stderr b/src/test/ui/parser/no-binary-float-literal.stderr
index 65b129b5827ce..cfd448684590f 100644
--- a/src/test/ui/parser/no-binary-float-literal.stderr
+++ b/src/test/ui/parser/no-binary-float-literal.stderr
@@ -10,13 +10,13 @@ error: binary float literal is not supported
 LL |     0b101010f64;
    |     ^^^^^^^^^^^ not supported
 
-error: invalid suffix `p4f64` for integer literal
+error: invalid suffix `p4f64` for number literal
   --> $DIR/no-binary-float-literal.rs:6:5
    |
 LL |     0b101p4f64;
    |     ^^^^^^^^^^ invalid suffix `p4f64`
    |
-   = help: the suffix must be one of the integral types (`u32`, `isize`, etc)
+   = help: the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)
 
 error: aborting due to 3 previous errors
 
diff --git a/src/tools/clippy/clippy_lints/src/attrs.rs b/src/tools/clippy/clippy_lints/src/attrs.rs
index 9a667aa61b4f5..15505fd79f4a1 100644
--- a/src/tools/clippy/clippy_lints/src/attrs.rs
+++ b/src/tools/clippy/clippy_lints/src/attrs.rs
@@ -5,7 +5,7 @@ use crate::utils::{
     span_lint_and_sugg, span_lint_and_then, without_block_comments,
 };
 use if_chain::if_chain;
-use rustc_ast::util::lev_distance::find_best_match_for_name;
+use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
 use rustc_errors::Applicability;
 use rustc_hir::{
@@ -427,7 +427,7 @@ fn check_clippy_lint_names(cx: &LateContext<'_>, ident: &str, items: &[NestedMet
                             .map(|l| Symbol::intern(&l.name_lower()))
                             .collect::<Vec<_>>();
                         let sugg = find_best_match_for_name(
-                            symbols.iter(),
+                            &symbols,
                             Symbol::intern(&format!("clippy::{}", name_lower)),
                             None,
                         );