diff --git a/src/librustc/infer/opaque_types/mod.rs b/src/librustc/infer/opaque_types/mod.rs
index 8e9af8b3938..1c52b5775a0 100644
--- a/src/librustc/infer/opaque_types/mod.rs
+++ b/src/librustc/infer/opaque_types/mod.rs
@@ -307,7 +307,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
             let required_region_bounds = tcx.required_region_bounds(
                 opaque_type,
-                bounds.predicates.clone(),
+                bounds.predicates,
             );
             debug_assert!(!required_region_bounds.is_empty());
 
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 260935a38d6..29c624575c3 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -1617,7 +1617,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                     self.ir.tcx.lint_hir_note(
                         lint::builtin::UNUSED_VARIABLES,
                         hir_id,
-                        spans.clone(),
+                        spans,
                         &format!("variable `{}` is assigned to, but never used", name),
                         &format!("consider using `_{}` instead", name),
                     );
diff --git a/src/librustc_borrowck/borrowck/check_loans.rs b/src/librustc_borrowck/borrowck/check_loans.rs
index 4a36d441d3d..54989db46c1 100644
--- a/src/librustc_borrowck/borrowck/check_loans.rs
+++ b/src/librustc_borrowck/borrowck/check_loans.rs
@@ -36,7 +36,7 @@ fn owned_ptr_base_path<'a, 'tcx>(loan_path: &'a LoanPath<'tcx>) -> &'a LoanPath<
 
     return match helper(loan_path) {
         Some(new_loan_path) => new_loan_path,
-        None => loan_path.clone()
+        None => loan_path,
     };
 
     fn helper<'a, 'tcx>(loan_path: &'a LoanPath<'tcx>) -> Option<&'a LoanPath<'tcx>> {
diff --git a/src/librustc_codegen_llvm/back/lto.rs b/src/librustc_codegen_llvm/back/lto.rs
index 74cda2d2fd1..5d3cc0c0a25 100644
--- a/src/librustc_codegen_llvm/back/lto.rs
+++ b/src/librustc_codegen_llvm/back/lto.rs
@@ -279,7 +279,7 @@ fn fat_lto(cgcx: &CodegenContext<LlvmCodegenBackend>,
             }
         }));
         serialized_modules.extend(cached_modules.into_iter().map(|(buffer, wp)| {
-            (buffer, CString::new(wp.cgu_name.clone()).unwrap())
+            (buffer, CString::new(wp.cgu_name).unwrap())
         }));
 
         // For all serialized bitcode files we parse them and link them in as we did
diff --git a/src/librustc_codegen_llvm/context.rs b/src/librustc_codegen_llvm/context.rs
index 967fe877fd1..588f7481cc0 100644
--- a/src/librustc_codegen_llvm/context.rs
+++ b/src/librustc_codegen_llvm/context.rs
@@ -459,7 +459,7 @@ impl CodegenCx<'b, 'tcx> {
         };
         let f = self.declare_cfn(name, fn_ty);
         llvm::SetUnnamedAddr(f, false);
-        self.intrinsics.borrow_mut().insert(name, f.clone());
+        self.intrinsics.borrow_mut().insert(name, f);
         f
     }
 
diff --git a/src/librustc_codegen_llvm/debuginfo/metadata.rs b/src/librustc_codegen_llvm/debuginfo/metadata.rs
index d43adc9cb92..fbeda43af42 100644
--- a/src/librustc_codegen_llvm/debuginfo/metadata.rs
+++ b/src/librustc_codegen_llvm/debuginfo/metadata.rs
@@ -1609,7 +1609,7 @@ impl<'tcx> VariantInfo<'tcx> {
                 // with every variant, make each variant name be just the value
                 // of the discriminant. The struct name for the variant includes
                 // the actual variant description.
-                format!("{}", variant_index.as_usize()).to_string()
+                format!("{}", variant_index.as_usize())
             }
         }
     }
diff --git a/src/librustc_errors/annotate_snippet_emitter_writer.rs b/src/librustc_errors/annotate_snippet_emitter_writer.rs
index 9f9c7588d97..7ed2fddf72d 100644
--- a/src/librustc_errors/annotate_snippet_emitter_writer.rs
+++ b/src/librustc_errors/annotate_snippet_emitter_writer.rs
@@ -194,7 +194,7 @@ impl AnnotateSnippetEmitterWriter {
         let converter = DiagnosticConverter {
             source_map: self.source_map.clone(),
             level: level.clone(),
-            message: message.clone(),
+            message,
             code: code.clone(),
             msp: msp.clone(),
             children,
diff --git a/src/librustc_metadata/creader.rs b/src/librustc_metadata/creader.rs
index 7ffba41e256..5fef8e53e1d 100644
--- a/src/librustc_metadata/creader.rs
+++ b/src/librustc_metadata/creader.rs
@@ -236,7 +236,7 @@ impl<'a> CrateLoader<'a> {
                 let host_lib = host_lib.unwrap();
                 self.load_derive_macros(
                     &host_lib.metadata.get_root(),
-                    host_lib.dylib.clone().map(|p| p.0),
+                    host_lib.dylib.map(|p| p.0),
                     span
                 )
             } else {
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index 4f73c92be50..f9e503ee69b 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -1737,7 +1737,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 pat_span,
             }))),
         };
-        let for_arm_body = self.local_decls.push(local.clone());
+        let for_arm_body = self.local_decls.push(local);
         let locals = if has_guard.0 {
             let ref_for_guard = self.local_decls.push(LocalDecl::<'tcx> {
                 // This variable isn't mutated but has a name, so has to be
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 77ac2b96160..bf64643e5a7 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -922,7 +922,7 @@ fn receiver_is_valid<'fcx, 'tcx>(
         };
 
         let obligation = traits::Obligation::new(
-            cause.clone(),
+            cause,
             fcx.param_env,
             trait_ref.to_predicate()
         );
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 985bb02614b..20a4f86aedb 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -317,7 +317,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         // Ensure that rustdoc works even if rustc is feature-staged
         unstable_features: UnstableFeatures::Allow,
         actually_rustdoc: true,
-        debugging_opts: debugging_options.clone(),
+        debugging_opts: debugging_options,
         error_format,
         edition,
         describe_lints,
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 5bce5d6ba5d..baf99bacb8e 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -740,7 +740,7 @@ impl Tester for Collector {
         debug!("Creating test {}: {}", name, test);
         self.tests.push(testing::TestDescAndFn {
             desc: testing::TestDesc {
-                name: testing::DynTestName(name.clone()),
+                name: testing::DynTestName(name),
                 ignore: config.ignore,
                 // compiler failures are test failures
                 should_panic: testing::ShouldPanic::No,
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 6b699464ba9..22745a1a76d 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -23,6 +23,7 @@ use log::debug;
 use rustc_data_structures::fx::{FxHashMap};
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
+use std::slice;
 
 use rustc_data_structures::sync::Lrc;
 use errors::Applicability;
@@ -359,10 +360,10 @@ pub fn compile(
 
     // don't abort iteration early, so that errors for multiple lhses can be reported
     for lhs in &lhses {
-        valid &= check_lhs_no_empty_seq(sess, &[lhs.clone()]);
+        valid &= check_lhs_no_empty_seq(sess, slice::from_ref(lhs));
         valid &= check_lhs_duplicate_matcher_bindings(
             sess,
-            &[lhs.clone()],
+            slice::from_ref(lhs),
             &mut FxHashMap::default(),
             def.id
         );
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 85b524786b2..f44a6e7efa4 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -887,7 +887,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt<'_>,
     };
 
     let fmt_str = &*fmt.node.0.as_str();  // for the suggestions below
-    let mut parser = parse::Parser::new(fmt_str, str_style, skips.clone(), append_newline);
+    let mut parser = parse::Parser::new(fmt_str, str_style, skips, append_newline);
 
     let mut unverified_pieces = Vec::new();
     while let Some(piece) = parser.next() {
diff --git a/src/libsyntax_ext/proc_macro_server.rs b/src/libsyntax_ext/proc_macro_server.rs
index 00a420d3fa8..b5d5a38ce5b 100644
--- a/src/libsyntax_ext/proc_macro_server.rs
+++ b/src/libsyntax_ext/proc_macro_server.rs
@@ -409,7 +409,7 @@ impl server::TokenStream for Rustc<'_> {
     }
     fn from_str(&mut self, src: &str) -> Self::TokenStream {
         parse::parse_stream_from_source_str(
-            FileName::proc_macro_source_code(src.clone()),
+            FileName::proc_macro_source_code(src),
             src.to_string(),
             self.sess,
             Some(self.call_site),