Import rustc_plugin from its new location

Depends on https://github.com/rust-lang/rust/pull/62727

CONTRIBUTING.md

@@ -90,7 +90,7 @@ Clippy is a [rustc compiler plugin][compiler_plugin]. The main entry point is at
 pub mod else_if_without_else;
 // ...
 
-pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
+pub fn register_plugins(reg: &mut rustc_driver::plugin::Registry) {
     // ...
     reg.register_early_lint_pass(box else_if_without_else::ElseIfWithoutElse);
     // ...
@@ -103,7 +103,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
 }
 ```
 
-The [`rustc_plugin::PluginRegistry`][plugin_registry] provides two methods to register lints: [register_early_lint_pass][reg_early_lint_pass] and [register_late_lint_pass][reg_late_lint_pass].
+The [`plugin::PluginRegistry`][plugin_registry] provides two methods to register lints: [register_early_lint_pass][reg_early_lint_pass] and [register_late_lint_pass][reg_late_lint_pass].
 Both take an object that implements an [`EarlyLintPass`][early_lint_pass] or [`LateLintPass`][late_lint_pass] respectively. This is done in every single lint.
 It's worth noting that the majority of `clippy_lints/src/lib.rs` is autogenerated by `util/dev update_lints` and you don't have to add anything by hand. When you are writing your own lint, you can use that script to save you some time.
 
@@ -193,9 +193,9 @@ or the [MIT](http://opensource.org/licenses/MIT) license.
 [lint_crate_entry]: https://github.com/rust-lang/rust-clippy/blob/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/clippy_lints/src/lib.rs
 [else_if_without_else]: https://github.com/rust-lang/rust-clippy/blob/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/clippy_lints/src/else_if_without_else.rs
 [compiler_plugin]: https://doc.rust-lang.org/unstable-book/language-features/plugin.html#lint-plugins
-[plugin_registry]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin/registry/struct.Registry.html
-[reg_early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin/registry/struct.Registry.html#method.register_early_lint_pass
-[reg_late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin/registry/struct.Registry.html#method.register_late_lint_pass
+[plugin_registry]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html
+[reg_early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html#method.register_early_lint_pass
+[reg_late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html#method.register_late_lint_pass
 [early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/lint/trait.EarlyLintPass.html
 [late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/lint/trait.LateLintPass.html
 [toolstate_commit_history]: https://github.com/rust-lang-nursery/rust-toolstate/commits/master

clippy_lints/src/lib.rs

@@ -23,12 +23,12 @@ extern crate rustc;
 #[allow(unused_extern_crates)]
 extern crate rustc_data_structures;
 #[allow(unused_extern_crates)]
+extern crate rustc_driver;
+#[allow(unused_extern_crates)]
 extern crate rustc_errors;
 #[allow(unused_extern_crates)]
 extern crate rustc_mir;
 #[allow(unused_extern_crates)]
-extern crate rustc_plugin;
-#[allow(unused_extern_crates)]
 extern crate rustc_target;
 #[allow(unused_extern_crates)]
 extern crate rustc_typeck;
@@ -320,7 +320,7 @@ pub fn register_pre_expansion_lints(
 }
 
 #[doc(hidden)]
-pub fn read_conf(reg: &rustc_plugin::Registry<'_>) -> Conf {
+pub fn read_conf(reg: &rustc_driver::plugin::Registry<'_>) -> Conf {
     match utils::conf::file_from_args(reg.args()) {
         Ok(file_name) => {
             // if the user specified a file, it must exist, otherwise default to `clippy.toml` but
@@ -382,7 +382,7 @@ pub fn read_conf(reg: &rustc_plugin::Registry<'_>) -> Conf {
 /// Used in `./src/driver.rs`.
 #[allow(clippy::too_many_lines)]
 #[rustfmt::skip]
-pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
+pub fn register_plugins(reg: &mut rustc_driver::plugin::Registry<'_>, conf: &Conf) {
     let mut store = reg.sess.lint_store.borrow_mut();
     register_removed_non_tool_lints(&mut store);
 

src/driver.rs

@@ -7,8 +7,6 @@
 extern crate rustc_driver;
 #[allow(unused_extern_crates)]
 extern crate rustc_interface;
-#[allow(unused_extern_crates)]
-extern crate rustc_plugin;
 
 use rustc_interface::interface;
 use rustc_tools_util::*;
@@ -65,7 +63,7 @@ struct ClippyCallbacks;
 impl rustc_driver::Callbacks for ClippyCallbacks {
     fn after_parsing(&mut self, compiler: &interface::Compiler) -> rustc_driver::Compilation {
         let sess = compiler.session();
-        let mut registry = rustc_plugin::registry::Registry::new(
+        let mut registry = rustc_driver::plugin::registry::Registry::new(
             sess,
             compiler
                 .parse()
@@ -81,7 +79,7 @@ impl rustc_driver::Callbacks for ClippyCallbacks {
         let conf = clippy_lints::read_conf(&registry);
         clippy_lints::register_plugins(&mut registry, &conf);
 
-        let rustc_plugin::registry::Registry {
+        let rustc_driver::plugin::registry::Registry {
             early_lint_passes,
             late_lint_passes,
             lint_groups,

src/lib.rs

@@ -7,9 +7,7 @@
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
 #[allow(unused_extern_crates)]
 extern crate rustc_driver;
-#[allow(unused_extern_crates)]
-extern crate rustc_plugin;
-use self::rustc_plugin::Registry;
+use self::rustc_driver::plugin::Registry;
 
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry<'_>) {