do minor cleanups

* ToString and AsRef are in prelude, no need to import them

17 files changed, 45 insertions, 74 deletions

diff --git a/clippy_dev/src/lib.rs b/clippy_dev/src/lib.rs
index f73e7b86720..3aae3e53317 100644
--- a/clippy_dev/src/lib.rs
+++ b/clippy_dev/src/lib.rs
@@ -50,7 +50,7 @@ impl Lint {
             name: name.to_lowercase(),
             group: group.to_string(),
             desc: NL_ESCAPE_RE.replace(&desc.replace("\\\"", "\""), "").to_string(),
-            deprecation: deprecation.map(std::string::ToString::to_string),
+            deprecation: deprecation.map(ToString::to_string),
             module: module.to_string(),
         }
     }
diff --git a/clippy_lints/src/cargo_common_metadata.rs b/clippy_lints/src/cargo_common_metadata.rs
index 4fc9c3e60e7..15457e57860 100644
--- a/clippy_lints/src/cargo_common_metadata.rs
+++ b/clippy_lints/src/cargo_common_metadata.rs
@@ -8,8 +8,6 @@ use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
 use rustc_session::declare_tool_lint;
 use syntax::{ast::*, source_map::DUMMY_SP};
 
-use cargo_metadata;
-
 declare_clippy_lint! {
     /// **What it does:** Checks to see if all common metadata is defined in
     /// `Cargo.toml`. See: https://rust-lang-nursery.github.io/api-guidelines/documentation.html#cargotoml-includes-all-common-metadata-c-metadata
@@ -56,7 +54,7 @@ fn is_empty_path(value: &Option<PathBuf>) -> bool {
 
 fn is_empty_vec(value: &[String]) -> bool {
     // This works because empty iterators return true
-    value.iter().all(std::string::String::is_empty)
+    value.iter().all(String::is_empty)
 }
 
 declare_lint_pass!(CargoCommonMetadata => [CARGO_COMMON_METADATA]);
diff --git a/clippy_lints/src/consts.rs b/clippy_lints/src/consts.rs
index d86766ee0a5..f1e488a7e6d 100644
--- a/clippy_lints/src/consts.rs
+++ b/clippy_lints/src/consts.rs
@@ -253,7 +253,7 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
                     let res = self.tables.qpath_res(qpath, callee.hir_id);
                     if let Some(def_id) = res.opt_def_id();
                     let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
-                    let def_path: Vec<&str> = def_path.iter().map(|s| &**s).collect();
+                    let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
                     if let ["core", "num", int_impl, "max_value"] = *def_path;
                     then {
                        let value = match int_impl {
diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs
index 327c18e855d..75e6cebb563 100644
--- a/clippy_lints/src/doc.rs
+++ b/clippy_lints/src/doc.rs
@@ -1,6 +1,5 @@
 use crate::utils::{match_type, paths, return_ty, span_lint};
 use itertools::Itertools;
-use pulldown_cmark;
 use rustc::hir;
 use rustc::impl_lint_pass;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
diff --git a/clippy_lints/src/eta_reduction.rs b/clippy_lints/src/eta_reduction.rs
index 54fdde67dec..0abe757e359 100644
--- a/clippy_lints/src/eta_reduction.rs
+++ b/clippy_lints/src/eta_reduction.rs
@@ -146,11 +146,7 @@ fn check_closure(cx: &LateContext<'_, '_>, expr: &Expr) {
 }
 
 /// Tries to determine the type for universal function call to be used instead of the closure
-fn get_ufcs_type_name(
-    cx: &LateContext<'_, '_>,
-    method_def_id: def_id::DefId,
-    self_arg: &Expr,
-) -> std::option::Option<String> {
+fn get_ufcs_type_name(cx: &LateContext<'_, '_>, method_def_id: def_id::DefId, self_arg: &Expr) -> Option<String> {
     let expected_type_of_self = &cx.tcx.fn_sig(method_def_id).inputs_and_output().skip_binder()[0];
     let actual_type_of_self = &cx.tables.node_type(self_arg.hir_id);
 
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 2e5ce50bf34..c3712e13d3f 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -47,7 +47,8 @@ extern crate syntax_pos;
 use rustc::lint::{self, LintId};
 use rustc::session::Session;
 use rustc_data_structures::fx::FxHashSet;
-use toml;
+
+use std::path::Path;
 
 /// Macro used to declare a Clippy lint.
 ///
@@ -349,16 +350,16 @@ pub fn read_conf(args: &[syntax::ast::NestedMetaItem], sess: &Session) -> Conf {
             let file_name = file_name.map(|file_name| {
                 if file_name.is_relative() {
                     sess.local_crate_source_file
-                        .as_ref()
-                        .and_then(|file| std::path::Path::new(&file).parent().map(std::path::Path::to_path_buf))
-                        .unwrap_or_default()
+                        .as_deref()
+                        .and_then(Path::parent)
+                        .unwrap_or_else(|| Path::new(""))
                         .join(file_name)
                 } else {
                     file_name
                 }
             });
 
-            let (conf, errors) = utils::conf::read(file_name.as_ref().map(std::convert::AsRef::as_ref));
+            let (conf, errors) = utils::conf::read(file_name.as_ref().map(AsRef::as_ref));
 
             // all conf errors are non-fatal, we just use the default conf in case of error
             for error in errors {
diff --git a/clippy_lints/src/literal_representation.rs b/clippy_lints/src/literal_representation.rs
index 24f40a161be..427243d4c62 100644
--- a/clippy_lints/src/literal_representation.rs
+++ b/clippy_lints/src/literal_representation.rs
@@ -8,7 +8,6 @@ use rustc::{declare_lint_pass, impl_lint_pass};
 use rustc_errors::Applicability;
 use rustc_session::declare_tool_lint;
 use syntax::ast::*;
-use syntax_pos;
 
 declare_clippy_lint! {
     /// **What it does:** Warns if a long integral or floating-point constant does
diff --git a/clippy_lints/src/multiple_crate_versions.rs b/clippy_lints/src/multiple_crate_versions.rs
index db22631104d..79caf4f5552 100644
--- a/clippy_lints/src/multiple_crate_versions.rs
+++ b/clippy_lints/src/multiple_crate_versions.rs
@@ -6,7 +6,6 @@ use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
 use rustc_session::declare_tool_lint;
 use syntax::{ast::*, source_map::DUMMY_SP};
 
-use cargo_metadata;
 use itertools::Itertools;
 
 declare_clippy_lint! {
diff --git a/clippy_lints/src/regex.rs b/clippy_lints/src/regex.rs
index e06ebe539e7..c60912ddb2c 100644
--- a/clippy_lints/src/regex.rs
+++ b/clippy_lints/src/regex.rs
@@ -1,7 +1,6 @@
 use crate::consts::{constant, Constant};
 use crate::utils::{is_expn_of, match_def_path, match_type, paths, span_help_and_lint, span_lint};
 use if_chain::if_chain;
-use regex_syntax;
 use rustc::hir::*;
 use rustc::impl_lint_pass;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
diff --git a/clippy_lints/src/utils/conf.rs b/clippy_lints/src/utils/conf.rs
index a3407d1e990..52223aa7a4b 100644
--- a/clippy_lints/src/utils/conf.rs
+++ b/clippy_lints/src/utils/conf.rs
@@ -8,7 +8,6 @@ use std::io::Read;
 use std::sync::Mutex;
 use std::{env, fmt, fs, io, path};
 use syntax::{ast, source_map};
-use toml;
 
 /// Gets the configuration file from arguments.
 pub fn file_from_args(args: &[ast::NestedMetaItem]) -> Result<Option<path::PathBuf>, (&'static str, source_map::Span)> {
@@ -77,7 +76,6 @@ macro_rules! define_Conf {
             }
             $(
                 mod $rust_name {
-                    use serde;
                     use serde::Deserialize;
                     crate fn deserialize<'de, D: serde::Deserializer<'de>>(deserializer: D)
                     -> Result<define_Conf!(TY $($ty)+), D::Error> {
diff --git a/clippy_lints/src/utils/sugg.rs b/clippy_lints/src/utils/sugg.rs
index 228fda9eec0..7050ea4cb2d 100644
--- a/clippy_lints/src/utils/sugg.rs
+++ b/clippy_lints/src/utils/sugg.rs
@@ -5,9 +5,7 @@ use crate::utils::{higher, snippet, snippet_opt, snippet_with_macro_callsite};
 use matches::matches;
 use rustc::hir;
 use rustc::lint::{EarlyContext, LateContext, LintContext};
-use rustc_errors;
 use rustc_errors::Applicability;
-use std;
 use std::borrow::Cow;
 use std::convert::TryInto;
 use std::fmt::Display;
diff --git a/clippy_lints/src/wildcard_dependencies.rs b/clippy_lints/src/wildcard_dependencies.rs
index bd865bf495c..0a302ce04ca 100644
--- a/clippy_lints/src/wildcard_dependencies.rs
+++ b/clippy_lints/src/wildcard_dependencies.rs
@@ -4,9 +4,7 @@ use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
 use rustc_session::declare_tool_lint;
 use syntax::{ast::*, source_map::DUMMY_SP};
 
-use cargo_metadata;
 use if_chain::if_chain;
-use semver;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for wildcard dependencies in the `Cargo.toml`.
diff --git a/src/driver.rs b/src/driver.rs
index 4cdff783788..4a080c12e44 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -1,5 +1,6 @@
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
 #![feature(rustc_private)]
+#![feature(str_strip)]
 
 // FIXME: switch to something more ergonomic here, once available.
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
@@ -18,6 +19,8 @@ use rustc_tools_util::*;
 
 use lazy_static::lazy_static;
 use std::borrow::Cow;
+use std::env;
+use std::ops::Deref;
 use std::panic;
 use std::path::{Path, PathBuf};
 use std::process::{exit, Command};
@@ -26,22 +29,21 @@ mod lintlist;
 
 /// If a command-line option matches `find_arg`, then apply the predicate `pred` on its value. If
 /// true, then return it. The parameter is assumed to be either `--arg=value` or `--arg value`.
-fn arg_value<'a>(
-    args: impl IntoIterator<Item = &'a String>,
+fn arg_value<'a, T: Deref<Target = str>>(
+    args: &'a [T],
     find_arg: &str,
     pred: impl Fn(&str) -> bool,
 ) -> Option<&'a str> {
-    let mut args = args.into_iter().map(String::as_str);
-
+    let mut args = args.iter().map(Deref::deref);
     while let Some(arg) = args.next() {
-        let arg: Vec<_> = arg.splitn(2, '=').collect();
-        if arg.get(0) != Some(&find_arg) {
+        let mut arg = arg.splitn(2, '=');
+        if arg.next() != Some(find_arg) {
             continue;
         }
 
-        let value = arg.get(1).cloned().or_else(|| args.next());
-        if value.as_ref().map_or(false, |p| pred(p)) {
-            return value;
+        match arg.next().or_else(|| args.next()) {
+            Some(v) if pred(v) => return Some(v),
+            _ => {},
         }
     }
     None
@@ -49,19 +51,16 @@ fn arg_value<'a>(
 
 #[test]
 fn test_arg_value() {
-    let args: Vec<_> = ["--bar=bar", "--foobar", "123", "--foo"]
-        .iter()
-        .map(std::string::ToString::to_string)
-        .collect();
-
-    assert_eq!(arg_value(None, "--foobar", |_| true), None);
-    assert_eq!(arg_value(&args, "--bar", |_| false), None);
-    assert_eq!(arg_value(&args, "--bar", |_| true), Some("bar"));
-    assert_eq!(arg_value(&args, "--bar", |p| p == "bar"), Some("bar"));
-    assert_eq!(arg_value(&args, "--bar", |p| p == "foo"), None);
-    assert_eq!(arg_value(&args, "--foobar", |p| p == "foo"), None);
-    assert_eq!(arg_value(&args, "--foobar", |p| p == "123"), Some("123"));
-    assert_eq!(arg_value(&args, "--foo", |_| true), None);
+    let args = &["--bar=bar", "--foobar", "123", "--foo"];
+
+    assert_eq!(arg_value(&[] as &[&str], "--foobar", |_| true), None);
+    assert_eq!(arg_value(args, "--bar", |_| false), None);
+    assert_eq!(arg_value(args, "--bar", |_| true), Some("bar"));
+    assert_eq!(arg_value(args, "--bar", |p| p == "bar"), Some("bar"));
+    assert_eq!(arg_value(args, "--bar", |p| p == "foo"), None);
+    assert_eq!(arg_value(args, "--foobar", |p| p == "foo"), None);
+    assert_eq!(arg_value(args, "--foobar", |p| p == "123"), Some("123"));
+    assert_eq!(arg_value(args, "--foo", |_| true), None);
 }
 
 #[allow(clippy::too_many_lines)]
@@ -276,7 +275,7 @@ fn report_clippy_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     }
 
     // If backtraces are enabled, also print the query stack
-    let backtrace = std::env::var_os("RUST_BACKTRACE").map_or(false, |x| &x != "0");
+    let backtrace = env::var_os("RUST_BACKTRACE").map_or(false, |x| &x != "0");
 
     if backtrace {
         TyCtxt::try_print_query_stack(&handler);
@@ -288,16 +287,14 @@ pub fn main() {
     lazy_static::initialize(&ICE_HOOK);
     exit(
         rustc_driver::catch_fatal_errors(move || {
-            use std::env;
+            let mut orig_args: Vec<String> = env::args().collect();
 
-            if std::env::args().any(|a| a == "--version" || a == "-V") {
+            if orig_args.iter().any(|a| a == "--version" || a == "-V") {
                 let version_info = rustc_tools_util::get_version_info!();
                 println!("{}", version_info);
                 exit(0);
             }
 
-            let mut orig_args: Vec<String> = env::args().collect();
-
             // Get the sysroot, looking from most specific to this invocation to the least:
             // - command line
             // - runtime environment
@@ -350,7 +347,7 @@ pub fn main() {
             }
 
             let should_describe_lints = || {
-                let args: Vec<_> = std::env::args().collect();
+                let args: Vec<_> = env::args().collect();
                 args.windows(2).any(|args| {
                     args[1] == "help"
                         && match args[0].as_str() {
@@ -368,15 +365,9 @@ pub fn main() {
             // this conditional check for the --sysroot flag is there so users can call
             // `clippy_driver` directly
             // without having to pass --sysroot or anything
-            let mut args: Vec<String> = if have_sys_root_arg {
-                orig_args.clone()
-            } else {
-                orig_args
-                    .clone()
-                    .into_iter()
-                    .chain(Some("--sysroot".to_owned()))
-                    .chain(Some(sys_root))
-                    .collect()
+            let mut args: Vec<String> = orig_args.clone();
+            if !have_sys_root_arg {
+                args.extend(vec!["--sysroot".into(), sys_root]);
             };
 
             // this check ensures that dependencies are built but not linted and the final
@@ -385,7 +376,7 @@ pub fn main() {
                 || arg_value(&orig_args, "--cap-lints", |val| val == "allow").is_none();
 
             if clippy_enabled {
-                args.extend_from_slice(&["--cfg".to_owned(), r#"feature="cargo-clippy""#.to_owned()]);
+                args.extend(vec!["--cfg".into(), r#"feature="cargo-clippy""#.into()]);
                 if let Ok(extra_args) = env::var("CLIPPY_ARGS") {
                     args.extend(extra_args.split("__CLIPPY_HACKERY__").filter_map(|s| {
                         if s.is_empty() {
@@ -396,12 +387,10 @@ pub fn main() {
                     }));
                 }
             }
-
             let mut clippy = ClippyCallbacks;
             let mut default = rustc_driver::DefaultCallbacks;
             let callbacks: &mut (dyn rustc_driver::Callbacks + Send) =
                 if clippy_enabled { &mut clippy } else { &mut default };
-            let args = args;
             rustc_driver::run_compiler(&args, callbacks, None, None)
         })
         .and_then(|result| result)
diff --git a/tests/integration.rs b/tests/integration.rs
index 455965436d6..d14ced8ad4e 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -1,7 +1,6 @@
 #![cfg(feature = "integration")]
 
 use git2::Repository;
-use tempfile;
 
 use std::env;
 use std::process::Command;
diff --git a/tests/ui/inefficient_to_string.fixed b/tests/ui/inefficient_to_string.fixed
index 32bc7574a52..c972b9419ef 100644
--- a/tests/ui/inefficient_to_string.fixed
+++ b/tests/ui/inefficient_to_string.fixed
@@ -2,7 +2,6 @@
 #![deny(clippy::inefficient_to_string)]
 
 use std::borrow::Cow;
-use std::string::ToString;
 
 fn main() {
     let rstr: &str = "hello";
diff --git a/tests/ui/inefficient_to_string.rs b/tests/ui/inefficient_to_string.rs
index 2741565e50d..acdc55aa0d6 100644
--- a/tests/ui/inefficient_to_string.rs
+++ b/tests/ui/inefficient_to_string.rs
@@ -2,7 +2,6 @@
 #![deny(clippy::inefficient_to_string)]
 
 use std::borrow::Cow;
-use std::string::ToString;
 
 fn main() {
     let rstr: &str = "hello";
diff --git a/tests/ui/inefficient_to_string.stderr b/tests/ui/inefficient_to_string.stderr
index 20788f6f6cc..08592e7d588 100644
--- a/tests/ui/inefficient_to_string.stderr
+++ b/tests/ui/inefficient_to_string.stderr
@@ -1,5 +1,5 @@
 error: calling `to_string` on `&&str`
-  --> $DIR/inefficient_to_string.rs:12:21
+  --> $DIR/inefficient_to_string.rs:11:21
    |
 LL |     let _: String = rrstr.to_string();
    |                     ^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(*rrstr).to_string()`
@@ -12,7 +12,7 @@ LL | #![deny(clippy::inefficient_to_string)]
    = help: `&str` implements `ToString` through a slower blanket impl, but `str` has a fast specialization of `ToString`
 
 error: calling `to_string` on `&&&str`
-  --> $DIR/inefficient_to_string.rs:13:21
+  --> $DIR/inefficient_to_string.rs:12:21
    |
 LL |     let _: String = rrrstr.to_string();
    |                     ^^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(**rrrstr).to_string()`
@@ -20,7 +20,7 @@ LL |     let _: String = rrrstr.to_string();
    = help: `&&str` implements `ToString` through a slower blanket impl, but `str` has a fast specialization of `ToString`
 
 error: calling `to_string` on `&&std::string::String`
-  --> $DIR/inefficient_to_string.rs:21:21
+  --> $DIR/inefficient_to_string.rs:20:21
    |
 LL |     let _: String = rrstring.to_string();
    |                     ^^^^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(*rrstring).to_string()`
@@ -28,7 +28,7 @@ LL |     let _: String = rrstring.to_string();
    = help: `&std::string::String` implements `ToString` through a slower blanket impl, but `std::string::String` has a fast specialization of `ToString`
 
 error: calling `to_string` on `&&&std::string::String`
-  --> $DIR/inefficient_to_string.rs:22:21
+  --> $DIR/inefficient_to_string.rs:21:21
    |
 LL |     let _: String = rrrstring.to_string();
    |                     ^^^^^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(**rrrstring).to_string()`
@@ -36,7 +36,7 @@ LL |     let _: String = rrrstring.to_string();
    = help: `&&std::string::String` implements `ToString` through a slower blanket impl, but `std::string::String` has a fast specialization of `ToString`
 
 error: calling `to_string` on `&&std::borrow::Cow<'_, str>`
-  --> $DIR/inefficient_to_string.rs:30:21
+  --> $DIR/inefficient_to_string.rs:29:21
    |
 LL |     let _: String = rrcow.to_string();
    |                     ^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(*rrcow).to_string()`
@@ -44,7 +44,7 @@ LL |     let _: String = rrcow.to_string();
    = help: `&std::borrow::Cow<'_, str>` implements `ToString` through a slower blanket impl, but `std::borrow::Cow<'_, str>` has a fast specialization of `ToString`
 
 error: calling `to_string` on `&&&std::borrow::Cow<'_, str>`
-  --> $DIR/inefficient_to_string.rs:31:21
+  --> $DIR/inefficient_to_string.rs:30:21
    |
 LL |     let _: String = rrrcow.to_string();
    |                     ^^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(**rrrcow).to_string()`