diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index f5afea15d655e..c95f79472fe57 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -407,7 +407,7 @@ impl String {
     ///
     /// assert_eq!(s.capacity(), cap);
     ///
-    /// // ...but this may make the vector reallocate
+    /// // ...but this may make the string reallocate
     /// s.push('a');
     /// ```
     #[inline]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 9c0db5d98725d..6ad0e68a88f3b 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -2,7 +2,9 @@
 
 //! String manipulation.
 //!
-//! For more details, see the `std::str` module.
+//! For more details, see the [`std::str`] module.
+//!
+//! [`std::str`]: ../../std/str/index.html
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
diff --git a/src/librustc/dep_graph/graph.rs b/src/librustc/dep_graph/graph.rs
index 33902fe913a9c..d5cde7034116c 100644
--- a/src/librustc/dep_graph/graph.rs
+++ b/src/librustc/dep_graph/graph.rs
@@ -524,7 +524,7 @@ impl DepGraph {
             edge_list_indices.push((start, end));
         }
 
-        debug_assert!(edge_list_data.len() <= ::std::u32::MAX as usize);
+        debug_assert!(edge_list_data.len() <= u32::MAX as usize);
         debug_assert_eq!(edge_list_data.len(), total_edge_count);
 
         SerializedDepGraph { nodes, fingerprints, edge_list_indices, edge_list_data }
diff --git a/src/librustc/mir/interpret/allocation.rs b/src/librustc/mir/interpret/allocation.rs
index d3efe62e8c153..c8d35db0adeb2 100644
--- a/src/librustc/mir/interpret/allocation.rs
+++ b/src/librustc/mir/interpret/allocation.rs
@@ -818,9 +818,9 @@ impl UndefMask {
             // First set all bits except the first `bita`,
             // then unset the last `64 - bitb` bits.
             let range = if bitb == 0 {
-                u64::max_value() << bita
+                u64::MAX << bita
             } else {
-                (u64::max_value() << bita) & (u64::max_value() >> (64 - bitb))
+                (u64::MAX << bita) & (u64::MAX >> (64 - bitb))
             };
             if new_state {
                 self.blocks[blocka] |= range;
@@ -832,21 +832,21 @@ impl UndefMask {
         // across block boundaries
         if new_state {
             // Set `bita..64` to `1`.
-            self.blocks[blocka] |= u64::max_value() << bita;
+            self.blocks[blocka] |= u64::MAX << bita;
             // Set `0..bitb` to `1`.
             if bitb != 0 {
-                self.blocks[blockb] |= u64::max_value() >> (64 - bitb);
+                self.blocks[blockb] |= u64::MAX >> (64 - bitb);
             }
             // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1)..blockb {
-                self.blocks[block] = u64::max_value();
+                self.blocks[block] = u64::MAX;
             }
         } else {
             // Set `bita..64` to `0`.
-            self.blocks[blocka] &= !(u64::max_value() << bita);
+            self.blocks[blocka] &= !(u64::MAX << bita);
             // Set `0..bitb` to `0`.
             if bitb != 0 {
-                self.blocks[blockb] &= !(u64::max_value() >> (64 - bitb));
+                self.blocks[blockb] &= !(u64::MAX >> (64 - bitb));
             }
             // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1)..blockb {
diff --git a/src/librustc/mir/interpret/pointer.rs b/src/librustc/mir/interpret/pointer.rs
index a4974fb541b6b..cc3c50b7899f3 100644
--- a/src/librustc/mir/interpret/pointer.rs
+++ b/src/librustc/mir/interpret/pointer.rs
@@ -78,9 +78,9 @@ pub trait PointerArithmetic: layout::HasDataLayout {
     fn overflowing_signed_offset(&self, val: u64, i: i128) -> (u64, bool) {
         // FIXME: is it possible to over/underflow here?
         if i < 0 {
-            // Trickery to ensure that `i64::min_value()` works fine: compute `n = -i`.
+            // Trickery to ensure that `i64::MIN` works fine: compute `n = -i`.
             // This formula only works for true negative values; it overflows for zero!
-            let n = u64::max_value() - (i as u64) + 1;
+            let n = u64::MAX - (i as u64) + 1;
             let res = val.overflowing_sub(n);
             self.truncate_to_ptr(res)
         } else {
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 36818020569b0..51718592fd9db 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -1198,7 +1198,7 @@ impl<'tcx> TerminatorKind<'tcx> {
         t: BasicBlock,
         f: BasicBlock,
     ) -> TerminatorKind<'tcx> {
-        static BOOL_SWITCH_FALSE: &'static [u128] = &[0];
+        static BOOL_SWITCH_FALSE: &[u128] = &[0];
         TerminatorKind::SwitchInt {
             discr: cond,
             switch_ty: tcx.types.bool,
diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs
index f9c8b01571e04..63d7124ee91f9 100644
--- a/src/librustc/traits/structural_impls.rs
+++ b/src/librustc/traits/structural_impls.rs
@@ -415,9 +415,9 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
             super::ReferenceOutlivesReferent(ty) => {
                 tcx.lift(&ty).map(super::ReferenceOutlivesReferent)
             }
-            super::ObjectTypeBound(ty, r) => tcx
-                .lift(&ty)
-                .and_then(|ty| tcx.lift(&r).and_then(|r| Some(super::ObjectTypeBound(ty, r)))),
+            super::ObjectTypeBound(ty, r) => {
+                tcx.lift(&ty).and_then(|ty| tcx.lift(&r).map(|r| super::ObjectTypeBound(ty, r)))
+            }
             super::ObjectCastObligation(ty) => tcx.lift(&ty).map(super::ObjectCastObligation),
             super::Coercion { source, target } => {
                 Some(super::Coercion { source: tcx.lift(&source)?, target: tcx.lift(&target)? })
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index f1b4b828c71fa..7a5a417919d50 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -7,7 +7,6 @@ use rustc_span::DUMMY_SP;
 
 use std::cmp;
 use std::fmt;
-use std::i128;
 use std::iter;
 use std::mem;
 use std::ops::Bound;
@@ -1001,7 +1000,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     }
                 }
 
-                let (mut min, mut max) = (i128::max_value(), i128::min_value());
+                let (mut min, mut max) = (i128::MAX, i128::MIN);
                 let discr_type = def.repr.discr_type();
                 let bits = Integer::from_attr(self, discr_type).size().bits();
                 for (i, discr) in def.discriminants(tcx) {
@@ -1021,7 +1020,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     }
                 }
                 // We might have no inhabited variants, so pretend there's at least one.
-                if (min, max) == (i128::max_value(), i128::min_value()) {
+                if (min, max) == (i128::MAX, i128::MIN) {
                     min = 0;
                     max = 0;
                 }
diff --git a/src/librustc/ty/print/pretty.rs b/src/librustc/ty/print/pretty.rs
index 3bf92552c8624..4829955cb70c4 100644
--- a/src/librustc/ty/print/pretty.rs
+++ b/src/librustc/ty/print/pretty.rs
@@ -920,7 +920,7 @@ pub trait PrettyPrinter<'tcx>:
             }
             (ConstValue::Scalar(Scalar::Raw { data, .. }), ty::Uint(ui)) => {
                 let bit_size = Integer::from_attr(&self.tcx(), UnsignedInt(*ui)).size();
-                let max = truncate(u128::max_value(), bit_size);
+                let max = truncate(u128::MAX, bit_size);
 
                 let ui_str = ui.name_str();
                 if data == max {
diff --git a/src/librustc/ty/query/on_disk_cache.rs b/src/librustc/ty/query/on_disk_cache.rs
index 109ac97fe6265..5e36e4df698ed 100644
--- a/src/librustc/ty/query/on_disk_cache.rs
+++ b/src/librustc/ty/query/on_disk_cache.rs
@@ -92,7 +92,7 @@ struct AbsoluteBytePos(u32);
 
 impl AbsoluteBytePos {
     fn new(pos: usize) -> AbsoluteBytePos {
-        debug_assert!(pos <= ::std::u32::MAX as usize);
+        debug_assert!(pos <= u32::MAX as usize);
         AbsoluteBytePos(pos as u32)
     }
 
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index 7b1f821877baa..62d2b4ae20397 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -50,11 +50,11 @@ fn signed_min(size: Size) -> i128 {
 }
 
 fn signed_max(size: Size) -> i128 {
-    i128::max_value() >> (128 - size.bits())
+    i128::MAX >> (128 - size.bits())
 }
 
 fn unsigned_max(size: Size) -> u128 {
-    u128::max_value() >> (128 - size.bits())
+    u128::MAX >> (128 - size.bits())
 }
 
 fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
@@ -77,7 +77,7 @@ impl<'tcx> Discr<'tcx> {
             let min = signed_min(size);
             let max = signed_max(size);
             let val = sign_extend(self.val, size) as i128;
-            assert!(n < (i128::max_value() as u128));
+            assert!(n < (i128::MAX as u128));
             let n = n as i128;
             let oflo = val > max - n;
             let val = if oflo { min + (n - (max - val) - 1) } else { val + n };
diff --git a/src/librustc_builtin_macros/format.rs b/src/librustc_builtin_macros/format.rs
index 3724a83a94981..d6b8b8cafb79c 100644
--- a/src/librustc_builtin_macros/format.rs
+++ b/src/librustc_builtin_macros/format.rs
@@ -284,7 +284,7 @@ impl<'a, 'b> Context<'a, 'b> {
                                 err.tool_only_span_suggestion(
                                     sp,
                                     &format!("use the `{}` trait", name),
-                                    fmt.to_string(),
+                                    (*fmt).to_string(),
                                     Applicability::MaybeIncorrect,
                                 );
                             }
@@ -476,7 +476,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 match ty {
                     Placeholder(_) => {
                         // record every (position, type) combination only once
-                        let ref mut seen_ty = self.arg_unique_types[arg];
+                        let seen_ty = &mut self.arg_unique_types[arg];
                         let i = seen_ty.iter().position(|x| *x == ty).unwrap_or_else(|| {
                             let i = seen_ty.len();
                             seen_ty.push(ty);
@@ -526,7 +526,7 @@ impl<'a, 'b> Context<'a, 'b> {
 
         // Map the arguments
         for i in 0..args_len {
-            let ref arg_types = self.arg_types[i];
+            let arg_types = &self.arg_types[i];
             let arg_offsets = arg_types.iter().map(|offset| sofar + *offset).collect::<Vec<_>>();
             self.arg_index_map.push(arg_offsets);
             sofar += self.arg_unique_types[i].len();
@@ -597,7 +597,7 @@ impl<'a, 'b> Context<'a, 'b> {
                             let arg_idx = match arg_index_consumed.get_mut(i) {
                                 None => 0, // error already emitted elsewhere
                                 Some(offset) => {
-                                    let ref idx_map = self.arg_index_map[i];
+                                    let idx_map = &self.arg_index_map[i];
                                     // unwrap_or branch: error already emitted elsewhere
                                     let arg_idx = *idx_map.get(*offset).unwrap_or(&0);
                                     *offset += 1;
@@ -721,7 +721,7 @@ impl<'a, 'b> Context<'a, 'b> {
             let name = names_pos[i];
             let span = self.ecx.with_def_site_ctxt(e.span);
             pats.push(self.ecx.pat_ident(span, name));
-            for ref arg_ty in self.arg_unique_types[i].iter() {
+            for arg_ty in self.arg_unique_types[i].iter() {
                 locals.push(Context::format_arg(self.ecx, self.macsp, e.span, arg_ty, name));
             }
             heads.push(self.ecx.expr_addr_of(e.span, e));
diff --git a/src/librustc_builtin_macros/global_allocator.rs b/src/librustc_builtin_macros/global_allocator.rs
index 8de7455a09a64..5d16be3206aaa 100644
--- a/src/librustc_builtin_macros/global_allocator.rs
+++ b/src/librustc_builtin_macros/global_allocator.rs
@@ -57,12 +57,12 @@ impl AllocFnFactory<'_, '_> {
     fn allocator_fn(&self, method: &AllocatorMethod) -> Stmt {
         let mut abi_args = Vec::new();
         let mut i = 0;
-        let ref mut mk = || {
+        let mut mk = || {
             let name = self.cx.ident_of(&format!("arg{}", i), self.span);
             i += 1;
             name
         };
-        let args = method.inputs.iter().map(|ty| self.arg_ty(ty, &mut abi_args, mk)).collect();
+        let args = method.inputs.iter().map(|ty| self.arg_ty(ty, &mut abi_args, &mut mk)).collect();
         let result = self.call_allocator(method.name, args);
         let (output_ty, output_expr) = self.ret_ty(&method.output, result);
         let decl = self.cx.fn_decl(abi_args, ast::FnRetTy::Ty(output_ty));
diff --git a/src/librustc_builtin_macros/test.rs b/src/librustc_builtin_macros/test.rs
index 7fe65f28532d0..bc194a3eec4c3 100644
--- a/src/librustc_builtin_macros/test.rs
+++ b/src/librustc_builtin_macros/test.rs
@@ -313,7 +313,7 @@ fn should_fail(i: &ast::Item) -> bool {
 fn should_panic(cx: &ExtCtxt<'_>, i: &ast::Item) -> ShouldPanic {
     match attr::find_by_name(&i.attrs, sym::should_panic) {
         Some(attr) => {
-            let ref sd = cx.parse_sess.span_diagnostic;
+            let sd = &cx.parse_sess.span_diagnostic;
 
             match attr.meta_item_list() {
                 // Handle #[should_panic(expected = "foo")]
@@ -378,7 +378,7 @@ fn test_type(cx: &ExtCtxt<'_>) -> TestType {
 
 fn has_test_signature(cx: &ExtCtxt<'_>, i: &ast::Item) -> bool {
     let has_should_panic_attr = attr::contains_name(&i.attrs, sym::should_panic);
-    let ref sd = cx.parse_sess.span_diagnostic;
+    let sd = &cx.parse_sess.span_diagnostic;
     if let ast::ItemKind::Fn(_, ref sig, ref generics, _) = i.kind {
         if let ast::Unsafe::Yes(span) = sig.header.unsafety {
             sd.struct_span_err(i.span, "unsafe functions cannot be used for tests")
diff --git a/src/librustc_builtin_macros/test_harness.rs b/src/librustc_builtin_macros/test_harness.rs
index 51a2170280559..e7e1ad8eda784 100644
--- a/src/librustc_builtin_macros/test_harness.rs
+++ b/src/librustc_builtin_macros/test_harness.rs
@@ -326,7 +326,7 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 /// &[&test1, &test2]
 fn mk_tests_slice(cx: &TestCtxt<'_>, sp: Span) -> P<ast::Expr> {
     debug!("building test vector from {} tests", cx.test_cases.len());
-    let ref ecx = cx.ext_cx;
+    let ecx = &cx.ext_cx;
 
     ecx.expr_vec_slice(
         sp,
diff --git a/src/librustc_codegen_llvm/asm.rs b/src/librustc_codegen_llvm/asm.rs
index 8066136c2fe42..c8f0fe8c72395 100644
--- a/src/librustc_codegen_llvm/asm.rs
+++ b/src/librustc_codegen_llvm/asm.rs
@@ -60,7 +60,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
             .chain(ia.inputs.iter().map(|s| s.to_string()))
             .chain(ext_constraints)
             .chain(clobbers)
-            .chain(arch_clobbers.iter().map(|s| s.to_string()))
+            .chain(arch_clobbers.iter().map(|s| (*s).to_string()))
             .collect::<Vec<String>>()
             .join(",");
 
diff --git a/src/librustc_codegen_llvm/back/write.rs b/src/librustc_codegen_llvm/back/write.rs
index a215ef81bc9eb..0c243128104e7 100644
--- a/src/librustc_codegen_llvm/back/write.rs
+++ b/src/librustc_codegen_llvm/back/write.rs
@@ -725,7 +725,7 @@ pub(crate) unsafe fn codegen(
                         Err(_) => return 0,
                     };
 
-                    if let Err(_) = write!(cursor, "{:#}", demangled) {
+                    if write!(cursor, "{:#}", demangled).is_err() {
                         // Possible only if provided buffer is not big enough
                         return 0;
                     }
diff --git a/src/librustc_codegen_llvm/context.rs b/src/librustc_codegen_llvm/context.rs
index 46f461b98c8de..3466363ac7972 100644
--- a/src/librustc_codegen_llvm/context.rs
+++ b/src/librustc_codegen_llvm/context.rs
@@ -174,7 +174,6 @@ pub unsafe fn create_module(
 
         let llvm_data_layout = llvm::LLVMGetDataLayout(llmod);
         let llvm_data_layout = str::from_utf8(CStr::from_ptr(llvm_data_layout).to_bytes())
-            .ok()
             .expect("got a non-UTF8 data-layout from LLVM");
 
         // Unfortunately LLVM target specs change over time, and right now we
diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index 76728e9840616..b313bf57d4a9a 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -1257,7 +1257,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                 if main_thread_worker_state == MainThreadWorkerState::Idle {
                     if !queue_full_enough(work_items.len(), running, max_workers) {
                         // The queue is not full enough, codegen more items:
-                        if let Err(_) = codegen_worker_send.send(Message::CodegenItem) {
+                        if codegen_worker_send.send(Message::CodegenItem).is_err() {
                             panic!("Could not send Message::CodegenItem to main thread")
                         }
                         main_thread_worker_state = MainThreadWorkerState::Codegenning;
diff --git a/src/librustc_error_codes/error_codes/E0380.md b/src/librustc_error_codes/error_codes/E0380.md
index fe5de56933963..638f0c8ecc65f 100644
--- a/src/librustc_error_codes/error_codes/E0380.md
+++ b/src/librustc_error_codes/error_codes/E0380.md
@@ -1,4 +1,14 @@
-Auto traits cannot have methods or associated items.
-For more information see the [opt-in builtin traits RFC][RFC 19].
+An auto trait was declared with a method or an associated item.
+
+Erroneous code example:
+
+```compile_fail,E0380
+unsafe auto trait Trait {
+    type Output; // error!
+}
+```
+
+Auto traits cannot have methods or associated items. For more information see
+the [opt-in builtin traits RFC][RFC 19].
 
 [RFC 19]: https://github.com/rust-lang/rfcs/blob/master/text/0019-opt-in-builtin-traits.md
diff --git a/src/librustc_error_codes/error_codes/E0382.md b/src/librustc_error_codes/error_codes/E0382.md
index f2356583cce1c..d1408a0629630 100644
--- a/src/librustc_error_codes/error_codes/E0382.md
+++ b/src/librustc_error_codes/error_codes/E0382.md
@@ -1,5 +1,4 @@
-This error occurs when an attempt is made to use a variable after its contents
-have been moved elsewhere.
+A variable was used after its contents have been moved elsewhere.
 
 Erroneous code example:
 
diff --git a/src/librustc_error_codes/error_codes/E0384.md b/src/librustc_error_codes/error_codes/E0384.md
index 7c7ee744a8c89..e21fac0797cb9 100644
--- a/src/librustc_error_codes/error_codes/E0384.md
+++ b/src/librustc_error_codes/error_codes/E0384.md
@@ -1,4 +1,4 @@
-This error occurs when an attempt is made to reassign an immutable variable.
+An immutable variable was reassigned.
 
 Erroneous code example:
 
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 5b00087de6fb7..f0e388a597b40 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -163,7 +163,7 @@ impl CodeSuggestion {
                         None => buf.push_str(&line[lo..]),
                     }
                 }
-                if let None = hi_opt {
+                if hi_opt.is_none() {
                     buf.push('\n');
                 }
             }
diff --git a/src/librustc_errors/registry.rs b/src/librustc_errors/registry.rs
index c92a9d04775d1..32700c6500bc8 100644
--- a/src/librustc_errors/registry.rs
+++ b/src/librustc_errors/registry.rs
@@ -27,6 +27,6 @@ impl Registry {
         if !self.long_descriptions.contains_key(code) {
             return Err(InvalidErrorCode);
         }
-        Ok(self.long_descriptions.get(code).unwrap().clone())
+        Ok(*self.long_descriptions.get(code).unwrap())
     }
 }
diff --git a/src/librustc_incremental/persist/dirty_clean.rs b/src/librustc_incremental/persist/dirty_clean.rs
index f304292d922e5..e212dc81070ac 100644
--- a/src/librustc_incremental/persist/dirty_clean.rs
+++ b/src/librustc_incremental/persist/dirty_clean.rs
@@ -343,7 +343,8 @@ impl DirtyCleanVisitor<'tcx> {
                 &format!("clean/dirty auto-assertions not yet defined for {:?}", node),
             ),
         };
-        let labels = Labels::from_iter(labels.iter().flat_map(|s| s.iter().map(|l| l.to_string())));
+        let labels =
+            Labels::from_iter(labels.iter().flat_map(|s| s.iter().map(|l| (*l).to_string())));
         (name, labels)
     }
 
diff --git a/src/librustc_infer/traits/auto_trait.rs b/src/librustc_infer/traits/auto_trait.rs
index 1a4f899ac8592..3166fe0657697 100644
--- a/src/librustc_infer/traits/auto_trait.rs
+++ b/src/librustc_infer/traits/auto_trait.rs
@@ -150,7 +150,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
             // SelectionContext to return it back to us.
 
             let (new_env, user_env) = match self.evaluate_predicates(
-                &mut infcx,
+                &infcx,
                 trait_did,
                 ty,
                 orig_env,
diff --git a/src/librustc_infer/traits/select.rs b/src/librustc_infer/traits/select.rs
index 4c312c9fce259..fd94e3b69940c 100644
--- a/src/librustc_infer/traits/select.rs
+++ b/src/librustc_infer/traits/select.rs
@@ -1341,7 +1341,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         stack: &TraitObligationStack<'o, 'tcx>,
     ) -> Result<SelectionCandidateSet<'tcx>, SelectionError<'tcx>> {
         let TraitObligationStack { obligation, .. } = *stack;
-        let ref obligation = Obligation {
+        let obligation = &Obligation {
             param_env: obligation.param_env,
             cause: obligation.cause.clone(),
             recursion_depth: obligation.recursion_depth,
diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
index 10a8c0a63f188..7866ddbd4ccd8 100644
--- a/src/librustc_interface/util.rs
+++ b/src/librustc_interface/util.rs
@@ -426,7 +426,7 @@ pub(crate) fn check_attr_crate_type(attrs: &[ast::Attribute], lint_buffer: &mut
     for a in attrs.iter() {
         if a.check_name(sym::crate_type) {
             if let Some(n) = a.value_str() {
-                if let Some(_) = categorize_crate_type(n) {
+                if categorize_crate_type(n).is_some() {
                     return;
                 }
 
diff --git a/src/librustc_lint/context.rs b/src/librustc_lint/context.rs
index 29a6b8c693ff3..5b7b73b48ec5b 100644
--- a/src/librustc_lint/context.rs
+++ b/src/librustc_lint/context.rs
@@ -335,7 +335,7 @@ impl LintStore {
             lint_name.to_string()
         };
         // If the lint was scoped with `tool::` check if the tool lint exists
-        if let Some(_) = tool_name {
+        if tool_name.is_some() {
             match self.by_name.get(&complete_name) {
                 None => match self.lint_groups.get(&*complete_name) {
                     None => return CheckLintNameResult::Tool(Err((None, String::new()))),
@@ -369,7 +369,7 @@ impl LintStore {
                         return if *silent {
                             CheckLintNameResult::Ok(&lint_ids)
                         } else {
-                            CheckLintNameResult::Tool(Err((Some(&lint_ids), name.to_string())))
+                            CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
                         };
                     }
                     CheckLintNameResult::Ok(&lint_ids)
@@ -404,7 +404,7 @@ impl LintStore {
                         return if *silent {
                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
                         } else {
-                            CheckLintNameResult::Tool(Err((Some(&lint_ids), name.to_string())))
+                            CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
                         };
                     }
                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
diff --git a/src/librustc_mir/borrow_check/type_check/mod.rs b/src/librustc_mir/borrow_check/type_check/mod.rs
index f4e1bce462f55..652de6c7b6fdf 100644
--- a/src/librustc_mir/borrow_check/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/type_check/mod.rs
@@ -1905,7 +1905,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             // expressions evaluate through `as_temp` or `into` a return
             // slot or local, so to find all unsized rvalues it is enough
             // to check all temps, return slots and locals.
-            if let None = self.reported_errors.replace((ty, span)) {
+            if self.reported_errors.replace((ty, span)).is_none() {
                 let mut diag = struct_span_err!(
                     self.tcx().sess,
                     span,
diff --git a/src/librustc_mir/borrow_check/type_check/relate_tys.rs b/src/librustc_mir/borrow_check/type_check/relate_tys.rs
index 31507a184d8f9..b0f048ff1a6fd 100644
--- a/src/librustc_mir/borrow_check/type_check/relate_tys.rs
+++ b/src/librustc_mir/borrow_check/type_check/relate_tys.rs
@@ -64,7 +64,7 @@ impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
     }
 
     fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> {
-        if let Some(_) = &mut self.borrowck_context {
+        if self.borrowck_context.is_some() {
             let origin = NLLRegionVariableOrigin::Existential { from_forall };
             self.infcx.next_nll_region_var(origin)
         } else {
diff --git a/src/librustc_mir/dataflow/generic/graphviz.rs b/src/librustc_mir/dataflow/generic/graphviz.rs
index 157526d3c51ad..f8e1d3e9fe8c6 100644
--- a/src/librustc_mir/dataflow/generic/graphviz.rs
+++ b/src/librustc_mir/dataflow/generic/graphviz.rs
@@ -604,8 +604,8 @@ fn write_diff<A: Analysis<'tcx>>(
     Ok(())
 }
 
-const BR_LEFT: &'static str = r#"<br align="left"/>"#;
-const BR_LEFT_SPACE: &'static str = r#"<br align="left"/> "#;
+const BR_LEFT: &str = r#"<br align="left"/>"#;
+const BR_LEFT_SPACE: &str = r#"<br align="left"/> "#;
 
 /// Line break policy that breaks at 40 characters and starts the next line with a single space.
 const LIMIT_30_ALIGN_1: Option<LineBreak> = Some(LineBreak { sequence: BR_LEFT_SPACE, limit: 30 });
diff --git a/src/librustc_mir/dataflow/generic/visitor.rs b/src/librustc_mir/dataflow/generic/visitor.rs
index 5bad8c61a0cd7..6e1513bcd1dd0 100644
--- a/src/librustc_mir/dataflow/generic/visitor.rs
+++ b/src/librustc_mir/dataflow/generic/visitor.rs
@@ -22,20 +22,20 @@ pub fn visit_results<F>(
             let loc = Location { block, statement_index };
 
             results.reconstruct_before_statement_effect(&mut state, stmt, loc);
-            vis.visit_statement(&mut state, stmt, loc);
+            vis.visit_statement(&state, stmt, loc);
 
             results.reconstruct_statement_effect(&mut state, stmt, loc);
-            vis.visit_statement_exit(&mut state, stmt, loc);
+            vis.visit_statement_exit(&state, stmt, loc);
         }
 
         let loc = body.terminator_loc(block);
         let term = block_data.terminator();
 
         results.reconstruct_before_terminator_effect(&mut state, term, loc);
-        vis.visit_terminator(&mut state, term, loc);
+        vis.visit_terminator(&state, term, loc);
 
         results.reconstruct_terminator_effect(&mut state, term, loc);
-        vis.visit_terminator_exit(&mut state, term, loc);
+        vis.visit_terminator_exit(&state, term, loc);
     }
 }
 
diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs
index 25463f31867df..b4e33b9502e69 100644
--- a/src/librustc_mir/dataflow/mod.rs
+++ b/src/librustc_mir/dataflow/mod.rs
@@ -16,7 +16,6 @@ use std::borrow::Borrow;
 use std::fmt;
 use std::io;
 use std::path::PathBuf;
-use std::usize;
 
 pub use self::at_location::{FlowAtLocation, FlowsAtLocation};
 pub(crate) use self::drop_flag_effects::*;
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index d63abdc356234..891afbf437f2b 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -203,7 +203,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         if is_add {
                             // max unsigned
                             Scalar::from_uint(
-                                u128::max_value() >> (128 - num_bits),
+                                u128::MAX >> (128 - num_bits),
                                 Size::from_bits(num_bits),
                             )
                         } else {
@@ -381,11 +381,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
         // Performs an exact division, resulting in undefined behavior where
-        // `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`.
+        // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`.
         // First, check x % y != 0 (or if that computation overflows).
         let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, a, b)?;
         if overflow || res.assert_bits(a.layout.size) != 0 {
-            // Then, check if `b` is -1, which is the "min_value / -1" case.
+            // Then, check if `b` is -1, which is the "MIN / -1" case.
             let minus1 = Scalar::from_int(-1, dest.layout.size);
             let b_scalar = b.to_scalar().unwrap();
             if b_scalar == minus1 {
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index 6517ae5d0f30f..3c4a1857f9690 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -565,7 +565,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
 
         // # Function pointers
         // (both global from `alloc_map` and local from `extra_fn_ptr_map`)
-        if let Some(_) = self.get_fn_alloc(id) {
+        if self.get_fn_alloc(id).is_some() {
             return if let AllocCheck::Dereferenceable = liveness {
                 // The caller requested no function pointers.
                 throw_unsup!(DerefFunctionPointer)
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index 08d4ae34afbfa..ea8378574a3e0 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -311,9 +311,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         // taking into account the `spread_arg`.  If we could write
                         // this is a single iterator (that handles `spread_arg`), then
                         // `pass_argument` would be the loop body. It takes care to
-                        // not advance `caller_iter` for ZSTs.
-                        let mut locals_iter = body.args_iter();
-                        while let Some(local) = locals_iter.next() {
+                        // not advance `caller_iter` for ZSTs
+                        for local in body.args_iter() {
                             let dest = self.eval_place(&mir::Place::from(local))?;
                             if Some(local) == body.spread_arg {
                                 // Must be a tuple
diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 731dcc6a25f14..4f99bfe8a852a 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -463,7 +463,7 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
         let (lo, hi) = valid_range.clone().into_inner();
         // Determine the allowed range
         // `max_hi` is as big as the size fits
-        let max_hi = u128::max_value() >> (128 - op.layout.size.bits());
+        let max_hi = u128::MAX >> (128 - op.layout.size.bits());
         assert!(hi <= max_hi);
         // We could also write `(hi + 1) % (max_hi + 1) == lo` but `max_hi + 1` overflows for `u128`
         if (lo == 0 && hi == max_hi) || (hi + 1 == lo) {
diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs
index 286740f99dde6..9fe21964b9888 100644
--- a/src/librustc_mir/transform/promote_consts.rs
+++ b/src/librustc_mir/transform/promote_consts.rs
@@ -920,7 +920,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
             let (blocks, local_decls) = self.source.basic_blocks_and_local_decls_mut();
             match candidate {
                 Candidate::Ref(loc) => {
-                    let ref mut statement = blocks[loc.block].statements[loc.statement_index];
+                    let statement = &mut blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
                         StatementKind::Assign(box (
                             _,
@@ -971,7 +971,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                     }
                 }
                 Candidate::Repeat(loc) => {
-                    let ref mut statement = blocks[loc.block].statements[loc.statement_index];
+                    let statement = &mut blocks[loc.block].statements[loc.statement_index];
                     match statement.kind {
                         StatementKind::Assign(box (_, Rvalue::Repeat(ref mut operand, _))) => {
                             let ty = operand.ty(local_decls, self.tcx);
diff --git a/src/librustc_mir_build/hair/pattern/_match.rs b/src/librustc_mir_build/hair/pattern/_match.rs
index 4c7e6e1754aa1..5b054c0452243 100644
--- a/src/librustc_mir_build/hair/pattern/_match.rs
+++ b/src/librustc_mir_build/hair/pattern/_match.rs
@@ -2331,7 +2331,7 @@ fn specialize_one_pattern<'p, 'tcx>(
         PatKind::Binding { .. } | PatKind::Wild => Some(ctor_wild_subpatterns.iter().collect()),
 
         PatKind::Variant { adt_def, variant_index, ref subpatterns, .. } => {
-            let ref variant = adt_def.variants[variant_index];
+            let variant = &adt_def.variants[variant_index];
             let is_non_exhaustive = cx.is_foreign_non_exhaustive_variant(pat.ty, variant);
             Some(Variant(variant.def_id))
                 .filter(|variant_constructor| variant_constructor == constructor)
diff --git a/src/librustc_parse/parser/attr.rs b/src/librustc_parse/parser/attr.rs
index c5f8b2dd862a5..2dccb04f6cce1 100644
--- a/src/librustc_parse/parser/attr.rs
+++ b/src/librustc_parse/parser/attr.rs
@@ -37,7 +37,7 @@ impl<'a> Parser<'a> {
                     let inner_parse_policy = InnerAttributeParsePolicy::NotPermitted {
                         reason: inner_error_reason,
                         saw_doc_comment: just_parsed_doc_comment,
-                        prev_attr_sp: attrs.last().and_then(|a| Some(a.span)),
+                        prev_attr_sp: attrs.last().map(|a| a.span),
                     };
                     let attr = self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?;
                     attrs.push(attr);
diff --git a/src/librustc_parse/parser/diagnostics.rs b/src/librustc_parse/parser/diagnostics.rs
index 0759c43d45206..8b43b424f5502 100644
--- a/src/librustc_parse/parser/diagnostics.rs
+++ b/src/librustc_parse/parser/diagnostics.rs
@@ -19,7 +19,7 @@ use rustc_span::{MultiSpan, Span, SpanSnippetError, DUMMY_SP};
 use log::{debug, trace};
 use std::mem;
 
-const TURBOFISH: &'static str = "use `::<...>` instead of `<...>` to specify type arguments";
+const TURBOFISH: &str = "use `::<...>` instead of `<...>` to specify type arguments";
 
 /// Creates a placeholder argument.
 pub(super) fn dummy_arg(ident: Ident) -> Param {
diff --git a/src/librustc_passes/entry.rs b/src/librustc_passes/entry.rs
index f2239ad16eeb3..86596e205562e 100644
--- a/src/librustc_passes/entry.rs
+++ b/src/librustc_passes/entry.rs
@@ -196,7 +196,7 @@ fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
     // The file may be empty, which leads to the diagnostic machinery not emitting this
     // note. This is a relatively simple way to detect that case and emit a span-less
     // note instead.
-    if let Ok(_) = tcx.sess.source_map().lookup_line(sp.lo()) {
+    if tcx.sess.source_map().lookup_line(sp.lo()).is_ok() {
         err.set_span(sp);
         err.span_label(sp, &note);
     } else {
diff --git a/src/librustc_resolve/imports.rs b/src/librustc_resolve/imports.rs
index 73bc038ea15f9..3b018005a88d2 100644
--- a/src/librustc_resolve/imports.rs
+++ b/src/librustc_resolve/imports.rs
@@ -1432,7 +1432,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                             }
                             msg
                         }
-                        ref s @ _ => bug!("unexpected import subclass {:?}", s),
+                        ref s => bug!("unexpected import subclass {:?}", s),
                     };
                     let mut err = this.session.struct_span_err(binding.span, &msg);
 
diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs
index 817a276ff3e73..fd62c80293425 100644
--- a/src/librustc_resolve/late/diagnostics.rs
+++ b/src/librustc_resolve/late/diagnostics.rs
@@ -1086,7 +1086,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                     for param in params {
                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(param.span)
                         {
-                            if snippet.starts_with("&") && !snippet.starts_with("&'") {
+                            if snippet.starts_with('&') && !snippet.starts_with("&'") {
                                 introduce_suggestion
                                     .push((param.span, format!("&'a {}", &snippet[1..])));
                             } else if snippet.starts_with("&'_ ") {
@@ -1118,7 +1118,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                 (1, Some(name), Some("'_")) => {
                     suggest_existing(err, name.to_string());
                 }
-                (1, Some(name), Some(snippet)) if !snippet.ends_with(">") => {
+                (1, Some(name), Some(snippet)) if !snippet.ends_with('>') => {
                     suggest_existing(err, format!("{}<{}>", snippet, name));
                 }
                 (0, _, Some("&")) => {
@@ -1127,7 +1127,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                 (0, _, Some("'_")) => {
                     suggest_new(err, "'a");
                 }
-                (0, _, Some(snippet)) if !snippet.ends_with(">") => {
+                (0, _, Some(snippet)) if !snippet.ends_with('>') => {
                     suggest_new(err, &format!("{}<'a>", snippet));
                 }
                 _ => {
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 4f65b0e87a18c..40cafb626d7c2 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -1550,21 +1550,18 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
             let method_names = pcx.candidate_method_names();
             pcx.allow_similar_names = false;
-            let applicable_close_candidates: Vec<ty::AssocItem> =
-                method_names
-                    .iter()
-                    .filter_map(|&method_name| {
-                        pcx.reset();
-                        pcx.method_name = Some(method_name);
-                        pcx.assemble_inherent_candidates();
-                        pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)
-                            .map_or(None, |_| {
-                                pcx.pick_core()
-                                    .and_then(|pick| pick.ok())
-                                    .and_then(|pick| Some(pick.item))
-                            })
-                    })
-                    .collect();
+            let applicable_close_candidates: Vec<ty::AssocItem> = method_names
+                .iter()
+                .filter_map(|&method_name| {
+                    pcx.reset();
+                    pcx.method_name = Some(method_name);
+                    pcx.assemble_inherent_candidates();
+                    pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)
+                        .map_or(None, |_| {
+                            pcx.pick_core().and_then(|pick| pick.ok()).map(|pick| pick.item)
+                        })
+                })
+                .collect();
 
             if applicable_close_candidates.is_empty() {
                 Ok(None)
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index b7353c6af267a..d8b23998e727f 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -737,8 +737,8 @@ impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
 }
 
 pub fn check_wf_new(tcx: TyCtxt<'_>) {
-    let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
-    tcx.hir().krate().par_visit_all_item_likes(&mut visit);
+    let visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
+    tcx.hir().krate().par_visit_all_item_likes(&visit);
 }
 
 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 2dad3d1d6d708..26462e61e5d57 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -151,7 +151,7 @@ crate fn placeholder_type_error(
         .unwrap_or(&"ParamName");
 
     let mut sugg: Vec<_> =
-        placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
+        placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
     if generics.is_empty() {
         sugg.push((span, format!("<{}>", type_name)));
     } else if let Some(arg) = generics.iter().find(|arg| match arg.name {
@@ -160,7 +160,7 @@ crate fn placeholder_type_error(
     }) {
         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
-        sugg.push((arg.span, type_name.to_string()));
+        sugg.push((arg.span, (*type_name).to_string()));
     } else {
         sugg.push((
             generics.iter().last().unwrap().span.shrink_to_hi(),
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 7c845a9b66bbd..4c7765b296500 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -50,7 +50,7 @@ pub use self::types::Type::*;
 pub use self::types::Visibility::{Inherited, Public};
 pub use self::types::*;
 
-const FN_OUTPUT_NAME: &'static str = "Output";
+const FN_OUTPUT_NAME: &str = "Output";
 
 pub trait Clean<T> {
     fn clean(&self, cx: &DocContext<'_>) -> T;
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 99e3d731d0d6f..21e3d24cc968b 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -121,9 +121,7 @@ pub fn external_generic_args(
     let args: Vec<_> = substs
         .iter()
         .filter_map(|kind| match kind.unpack() {
-            GenericArgKind::Lifetime(lt) => {
-                lt.clean(cx).and_then(|lt| Some(GenericArg::Lifetime(lt)))
-            }
+            GenericArgKind::Lifetime(lt) => lt.clean(cx).map(|lt| GenericArg::Lifetime(lt)),
             GenericArgKind::Type(_) if skip_self => {
                 skip_self = false;
                 None
diff --git a/src/librustdoc/docfs.rs b/src/librustdoc/docfs.rs
index ecc394a2bc992..9c9a00295c3fa 100644
--- a/src/librustdoc/docfs.rs
+++ b/src/librustdoc/docfs.rs
@@ -90,14 +90,14 @@ impl DocFS {
             let sender = self.errors.sender.clone().unwrap();
             rayon::spawn(move || match fs::write(&path, &contents) {
                 Ok(_) => {
-                    sender
-                        .send(None)
-                        .expect(&format!("failed to send error on \"{}\"", path.display()));
+                    sender.send(None).unwrap_or_else(|_| {
+                        panic!("failed to send error on \"{}\"", path.display())
+                    });
                 }
                 Err(e) => {
-                    sender
-                        .send(Some(format!("\"{}\": {}", path.display(), e)))
-                        .expect(&format!("failed to send non-error on \"{}\"", path.display()));
+                    sender.send(Some(format!("\"{}\": {}", path.display(), e))).unwrap_or_else(
+                        |_| panic!("failed to send non-error on \"{}\"", path.display()),
+                    );
                 }
             });
             Ok(())
diff --git a/src/librustdoc/html/item_type.rs b/src/librustdoc/html/item_type.rs
index 4a0f4e5a4c9c8..0b2b0cdc18b09 100644
--- a/src/librustdoc/html/item_type.rs
+++ b/src/librustdoc/html/item_type.rs
@@ -62,7 +62,7 @@ impl<'a> From<&'a clean::Item> for ItemType {
     fn from(item: &'a clean::Item) -> ItemType {
         let inner = match item.inner {
             clean::StrippedItem(box ref item) => item,
-            ref inner @ _ => inner,
+            ref inner => inner,
         };
 
         match *inner {
@@ -194,7 +194,7 @@ impl fmt::Display for ItemType {
     }
 }
 
-pub const NAMESPACE_TYPE: &'static str = "t";
-pub const NAMESPACE_VALUE: &'static str = "v";
-pub const NAMESPACE_MACRO: &'static str = "m";
-pub const NAMESPACE_KEYWORD: &'static str = "k";
+pub const NAMESPACE_TYPE: &str = "t";
+pub const NAMESPACE_VALUE: &str = "v";
+pub const NAMESPACE_MACRO: &str = "m";
+pub const NAMESPACE_KEYWORD: &str = "k";
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index ed007fe383c1d..42529a6682ec1 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -296,7 +296,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
                         ""
                     }
                 )),
-                playground_button.as_ref().map(String::as_str),
+                playground_button.as_deref(),
                 Some((s1.as_str(), s2)),
             ));
             Some(Event::Html(s.into()))
@@ -315,7 +315,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
                         ""
                     }
                 )),
-                playground_button.as_ref().map(String::as_str),
+                playground_button.as_deref(),
                 None,
             ));
             Some(Event::Html(s.into()))
@@ -869,12 +869,8 @@ pub fn plain_summary_line(md: &str) -> String {
         }
     }
     let mut s = String::with_capacity(md.len() * 3 / 2);
-    let mut p = ParserWrapper { inner: Parser::new(md), is_in: 0, is_first: true };
-    while let Some(t) = p.next() {
-        if !t.is_empty() {
-            s.push_str(&t);
-        }
-    }
+    let p = ParserWrapper { inner: Parser::new(md), is_in: 0, is_first: true };
+    p.into_iter().filter(|t| !t.is_empty()).for_each(|i| s.push_str(&i));
     s
 }
 
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 4dd2a6562a4cd..07fe439ace226 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -2727,7 +2727,7 @@ fn naive_assoc_href(it: &clean::Item, link: AssocItemLink<'_>) -> String {
     let name = it.name.as_ref().unwrap();
     let ty = match it.type_() {
         Typedef | AssocType => AssocType,
-        s @ _ => s,
+        s => s,
     };
 
     let anchor = format!("#{}.{}", ty, name);
@@ -3150,7 +3150,7 @@ fn render_attribute(attr: &ast::MetaItem) -> Option<String> {
     }
 }
 
-const ATTRIBUTE_WHITELIST: &'static [Symbol] = &[
+const ATTRIBUTE_WHITELIST: &[Symbol] = &[
     sym::export_name,
     sym::lang,
     sym::link_section,
@@ -4610,7 +4610,7 @@ fn item_keyword(w: &mut Buffer, cx: &Context, it: &clean::Item) {
     document(w, cx, it)
 }
 
-crate const BASIC_KEYWORDS: &'static str = "rust, rustlang, rust-lang";
+crate const BASIC_KEYWORDS: &str = "rust, rustlang, rust-lang";
 
 fn make_item_keywords(it: &clean::Item) -> String {
     format!("{}, {}", BASIC_KEYWORDS, it.name.as_ref().unwrap())
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 9e1ac8754d9b0..7fd7de56f4615 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -185,7 +185,7 @@ macro_rules! eprintln {
 /// builds or when debugging in release mode is significantly faster.
 ///
 /// Note that the macro is intended as a debugging tool and therefore you
-/// should avoid having uses of it in version control for longer periods.
+/// should avoid having uses of it in version control for long periods.
 /// Use cases involving debug output that should be added to version control
 /// are better served by macros such as [`debug!`] from the [`log`] crate.
 ///
diff --git a/src/libstd/sys/unix/process/process_common.rs b/src/libstd/sys/unix/process/process_common.rs
index 83f052c898ba3..859da691ad278 100644
--- a/src/libstd/sys/unix/process/process_common.rs
+++ b/src/libstd/sys/unix/process/process_common.rs
@@ -19,9 +19,9 @@ cfg_if::cfg_if! {
     if #[cfg(target_os = "fuchsia")] {
         // fuchsia doesn't have /dev/null
     } else if #[cfg(target_os = "redox")] {
-        const DEV_NULL: &'static str = "null:\0";
+        const DEV_NULL: &str = "null:\0";
     } else {
-        const DEV_NULL: &'static str = "/dev/null\0";
+        const DEV_NULL: &str = "/dev/null\0";
     }
 }
 
diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
index b42e41cbfe6f0..55f9df9caafb2 100644
--- a/src/libtest/lib.rs
+++ b/src/libtest/lib.rs
@@ -96,7 +96,7 @@ use time::TestExecTime;
 // Process exit code to be used to indicate test failures.
 const ERROR_EXIT_CODE: i32 = 101;
 
-const SECONDARY_TEST_INVOKER_VAR: &'static str = "__RUST_TEST_INVOKE";
+const SECONDARY_TEST_INVOKER_VAR: &str = "__RUST_TEST_INVOKE";
 
 // The default console test runner. It accepts the command line
 // arguments and a vector of test_descs.
@@ -158,7 +158,7 @@ pub fn test_main_static_abort(tests: &[&TestDescAndFn]) {
             .filter(|test| test.desc.name.as_slice() == name)
             .map(make_owned_test)
             .next()
-            .expect(&format!("couldn't find a test with the provided name '{}'", name));
+            .unwrap_or_else(|| panic!("couldn't find a test with the provided name '{}'", name));
         let TestDescAndFn { desc, testfn } = test;
         let testfn = match testfn {
             StaticTestFn(f) => f,