diff --git a/crates/cargo-test-support/src/registry.rs b/crates/cargo-test-support/src/registry.rs
index cf6cff8d2c2..6d3db585a34 100644
--- a/crates/cargo-test-support/src/registry.rs
+++ b/crates/cargo-test-support/src/registry.rs
@@ -442,7 +442,7 @@ impl Package {
         } else {
             registry_path.join(&file)
         };
-        let prev = fs::read_to_string(&dst).unwrap_or(String::new());
+        let prev = fs::read_to_string(&dst).unwrap_or_default();
         t!(fs::create_dir_all(dst.parent().unwrap()));
         t!(fs::write(&dst, prev + &line[..] + "\n"));
 
diff --git a/src/bin/cargo/commands/tree.rs b/src/bin/cargo/commands/tree.rs
index b98ee5f7aad..9cfff98fe48 100644
--- a/src/bin/cargo/commands/tree.rs
+++ b/src/bin/cargo/commands/tree.rs
@@ -206,7 +206,7 @@ fn parse_edge_kinds(config: &Config, args: &ArgMatches<'_>) -> CargoResult<HashS
             .warn("the --no-dev-dependencies flag has changed to -e=no-dev")?;
         kinds.push("no-dev");
     }
-    if kinds.len() == 0 {
+    if kinds.is_empty() {
         kinds.extend(&["normal", "build", "dev"]);
     }
 
diff --git a/src/cargo/core/compiler/build_context/target_info.rs b/src/cargo/core/compiler/build_context/target_info.rs
index 28d9589e1ef..e0271fabf55 100644
--- a/src/cargo/core/compiler/build_context/target_info.rs
+++ b/src/cargo/core/compiler/build_context/target_info.rs
@@ -448,7 +448,7 @@ fn env_args(
     // This means that, e.g., even if the specified --target is the
     // same as the host, build scripts in plugins won't get
     // RUSTFLAGS.
-    if requested_kinds != &[CompileKind::Host] && kind.is_host() {
+    if requested_kinds != [CompileKind::Host] && kind.is_host() {
         // This is probably a build script or plugin and we're
         // compiling with --target. In this scenario there are
         // no rustflags we can apply.
diff --git a/src/cargo/core/compiler/compile_kind.rs b/src/cargo/core/compiler/compile_kind.rs
index 3f8d1e9d819..e2089d969bd 100644
--- a/src/cargo/core/compiler/compile_kind.rs
+++ b/src/cargo/core/compiler/compile_kind.rs
@@ -55,7 +55,7 @@ impl CompileKind {
         if targets.len() > 1 && !config.cli_unstable().multitarget {
             bail!("specifying multiple `--target` flags requires `-Zmultitarget`")
         }
-        if targets.len() != 0 {
+        if !targets.is_empty() {
             return Ok(targets
                 .iter()
                 .map(|value| Ok(CompileKind::Target(CompileTarget::new(value)?)))
diff --git a/src/cargo/core/compiler/standard_lib.rs b/src/cargo/core/compiler/standard_lib.rs
index 0ae0b651546..c1c7f875c65 100644
--- a/src/cargo/core/compiler/standard_lib.rs
+++ b/src/cargo/core/compiler/standard_lib.rs
@@ -161,7 +161,7 @@ pub fn generate_std_roots(
         let features = std_features.activated_features(pkg.package_id(), FeaturesFor::NormalOrDev);
 
         for kind in kinds {
-            let list = ret.entry(*kind).or_insert(Vec::new());
+            let list = ret.entry(*kind).or_insert_with(Vec::new);
             list.push(interner.intern(
                 pkg,
                 lib,
@@ -173,7 +173,7 @@ pub fn generate_std_roots(
             ));
         }
     }
-    return Ok(ret);
+    Ok(ret)
 }
 
 fn detect_sysroot_src_path(target_data: &RustcTargetData) -> CargoResult<PathBuf> {
diff --git a/src/cargo/core/compiler/unit.rs b/src/cargo/core/compiler/unit.rs
index ebbba387983..84565a6517e 100644
--- a/src/cargo/core/compiler/unit.rs
+++ b/src/cargo/core/compiler/unit.rs
@@ -204,6 +204,6 @@ impl UnitInterner {
         }
         let item = Rc::new(item.clone());
         me.cache.insert(item.clone());
-        return item;
+        item
     }
 }
diff --git a/src/cargo/core/compiler/unit_graph.rs b/src/cargo/core/compiler/unit_graph.rs
index 2db9015058e..350c040abad 100644
--- a/src/cargo/core/compiler/unit_graph.rs
+++ b/src/cargo/core/compiler/unit_graph.rs
@@ -113,6 +113,6 @@ pub fn emit_serialized_unit_graph(root_units: &[Unit], unit_graph: &UnitGraph) -
     let stdout = std::io::stdout();
     let mut lock = stdout.lock();
     serde_json::to_writer(&mut lock, &s)?;
-    write!(lock, "\n")?;
+    writeln!(lock)?;
     Ok(())
 }
diff --git a/src/cargo/core/manifest.rs b/src/cargo/core/manifest.rs
index c5c15a4a8b0..646708e5901 100644
--- a/src/cargo/core/manifest.rs
+++ b/src/cargo/core/manifest.rs
@@ -669,7 +669,7 @@ impl Target {
             .set_name(name)
             .set_doctest(true)
             .set_doc(true);
-        return target;
+        target
     }
 
     pub fn bin_target(
@@ -684,7 +684,7 @@ impl Target {
             .set_name(name)
             .set_required_features(required_features)
             .set_doc(true);
-        return target;
+        target
     }
 
     /// Builds a `Target` corresponding to the `build = "build.rs"` entry.
@@ -696,7 +696,7 @@ impl Target {
             .set_for_host(true)
             .set_benched(false)
             .set_tested(false);
-        return target;
+        target
     }
 
     pub fn metabuild_target(name: &str) -> Target {
@@ -707,7 +707,7 @@ impl Target {
             .set_for_host(true)
             .set_benched(false)
             .set_tested(false);
-        return target;
+        target
     }
 
     pub fn example_target(
@@ -733,7 +733,7 @@ impl Target {
             .set_required_features(required_features)
             .set_tested(false)
             .set_benched(false);
-        return target;
+        target
     }
 
     pub fn test_target(
@@ -748,7 +748,7 @@ impl Target {
             .set_name(name)
             .set_required_features(required_features)
             .set_benched(false);
-        return target;
+        target
     }
 
     pub fn bench_target(
@@ -763,7 +763,7 @@ impl Target {
             .set_name(name)
             .set_required_features(required_features)
             .set_tested(false);
-        return target;
+        target
     }
 
     pub fn name(&self) -> &str {
diff --git a/src/cargo/core/registry.rs b/src/cargo/core/registry.rs
index 5b45a4bc501..8a05b4510d6 100644
--- a/src/cargo/core/registry.rs
+++ b/src/cargo/core/registry.rs
@@ -622,7 +622,7 @@ fn lock(
 
     // Lock the summary's ID if possible
     let summary = match pair {
-        Some((precise, _)) => summary.override_id(precise.clone()),
+        Some((precise, _)) => summary.override_id(*precise),
         None => summary,
     };
     summary.map_dependencies(|dep| {
diff --git a/src/cargo/core/resolver/conflict_cache.rs b/src/cargo/core/resolver/conflict_cache.rs
index c59e4117810..e0e64b96a5d 100644
--- a/src/cargo/core/resolver/conflict_cache.rs
+++ b/src/cargo/core/resolver/conflict_cache.rs
@@ -213,7 +213,7 @@ impl ConflictCache {
 
         for c in con.keys() {
             self.dep_from_pid
-                .entry(c.clone())
+                .entry(*c)
                 .or_insert_with(HashSet::new)
                 .insert(dep.clone());
         }
diff --git a/src/cargo/core/resolver/encode.rs b/src/cargo/core/resolver/encode.rs
index 5fb4631952f..4d711498235 100644
--- a/src/cargo/core/resolver/encode.rs
+++ b/src/cargo/core/resolver/encode.rs
@@ -260,7 +260,7 @@ impl EncodableResolve {
         let mut g = Graph::new();
 
         for &(ref id, _) in live_pkgs.values() {
-            g.add(id.clone());
+            g.add(*id);
         }
 
         for &(ref id, pkg) in live_pkgs.values() {
@@ -271,7 +271,7 @@ impl EncodableResolve {
 
             for edge in deps.iter() {
                 if let Some(to_depend_on) = lookup_id(edge) {
-                    g.link(id.clone(), to_depend_on);
+                    g.link(*id, to_depend_on);
                 }
             }
         }
@@ -282,7 +282,7 @@ impl EncodableResolve {
                 if let Some(ref replace) = pkg.replace {
                     assert!(pkg.dependencies.is_none());
                     if let Some(replace_id) = lookup_id(replace) {
-                        replacements.insert(id.clone(), replace_id);
+                        replacements.insert(*id, replace_id);
                     }
                 }
             }
diff --git a/src/cargo/lib.rs b/src/cargo/lib.rs
index a5c94f73fa8..b386ee7f558 100644
--- a/src/cargo/lib.rs
+++ b/src/cargo/lib.rs
@@ -144,7 +144,7 @@ pub fn display_error(err: &Error, shell: &mut Shell) {
 /// and context.
 pub fn display_warning_with_error(warning: &str, err: &Error, shell: &mut Shell) {
     drop(shell.warn(warning));
-    drop(writeln!(shell.err(), ""));
+    drop(writeln!(shell.err()));
     _display_error(err, shell, false);
 }
 
diff --git a/src/cargo/ops/cargo_fetch.rs b/src/cargo/ops/cargo_fetch.rs
index a21c9443eb0..1e0d855d0d1 100644
--- a/src/cargo/ops/cargo_fetch.rs
+++ b/src/cargo/ops/cargo_fetch.rs
@@ -39,7 +39,7 @@ pub fn fetch<'a>(
                 deps.iter().any(|d| {
                     // If no target was specified then all dependencies are
                     // fetched.
-                    if options.targets.len() == 0 {
+                    if options.targets.is_empty() {
                         return true;
                     }
 
diff --git a/src/cargo/ops/cargo_output_metadata.rs b/src/cargo/ops/cargo_output_metadata.rs
index d10a6a4f3c9..e6261d3a927 100644
--- a/src/cargo/ops/cargo_output_metadata.rs
+++ b/src/cargo/ops/cargo_output_metadata.rs
@@ -176,7 +176,7 @@ fn build_resolve_graph_r(
     let deps: Vec<Dep> = resolve
         .deps(pkg_id)
         .filter(|(_dep_id, deps)| {
-            if requested_kinds == &[CompileKind::Host] {
+            if requested_kinds == [CompileKind::Host] {
                 true
             } else {
                 requested_kinds.iter().any(|kind| {
diff --git a/src/cargo/ops/registry.rs b/src/cargo/ops/registry.rs
index 4d47bc45342..570e6f522bd 100644
--- a/src/cargo/ops/registry.rs
+++ b/src/cargo/ops/registry.rs
@@ -378,7 +378,7 @@ fn registry(
         token: token_config,
         index: index_config,
     } = registry_configuration(config, registry.clone())?;
-    let opt_index = index_config.as_ref().or(index.as_ref());
+    let opt_index = index_config.as_ref().or_else(|| index.as_ref());
     let sid = get_source_id(config, opt_index, registry.as_ref())?;
     if !sid.is_remote_registry() {
         bail!(
diff --git a/tests/testsuite/multitarget.rs b/tests/testsuite/multitarget.rs
index 1235642cb56..a72203c5779 100644
--- a/tests/testsuite/multitarget.rs
+++ b/tests/testsuite/multitarget.rs
@@ -35,7 +35,7 @@ fn simple_build() {
         .masquerade_as_nightly_cargo()
         .run();
 
-    assert!(p.target_bin(&t1, "foo").is_file());
+    assert!(p.target_bin(t1, "foo").is_file());
     assert!(p.target_bin(&t2, "foo").is_file());
 }