Avoid Lrc<Box<dyn CodegenBackend>>.

Because `Lrc<Box<T>>` is silly. (Clippy warns about `Rc<Box<T>>` and
`Arc<Box<T>>`, and it would warn here if (a) we used Clippy with rustc,
and (b) Clippy knew about `Lrc`.)

Author: nnethercote

Diff for: compiler/rustc_driver_impl/src/lib.rs

@@ -329,7 +329,7 @@ fn run_compiler(
                         return;
                     }
                     let should_stop =
-                        print_crate_info(&***compiler.codegen_backend(), compiler.session(), false);
+                        print_crate_info(&**compiler.codegen_backend(), compiler.session(), false);
 
                     if should_stop == Compilation::Stop {
                         return;
@@ -351,7 +351,7 @@ fn run_compiler(
 
     interface::run_compiler(config, |compiler| {
         let sess = compiler.session();
-        let should_stop = print_crate_info(&***compiler.codegen_backend(), sess, true)
+        let should_stop = print_crate_info(&**compiler.codegen_backend(), sess, true)
             .and_then(|| list_metadata(sess, &*compiler.codegen_backend().metadata_loader()))
             .and_then(|| try_process_rlink(sess, compiler));
 

Diff for: compiler/rustc_interface/src/interface.rs

@@ -36,7 +36,7 @@ pub type Result<T> = result::Result<T, ErrorGuaranteed>;
 /// Created by passing [`Config`] to [`run_compiler`].
 pub struct Compiler {
     pub(crate) sess: Lrc<Session>,
-    codegen_backend: Lrc<Box<dyn CodegenBackend>>,
+    codegen_backend: Lrc<dyn CodegenBackend>,
     pub(crate) register_lints: Option<Box<dyn Fn(&Session, &mut LintStore) + Send + Sync>>,
     pub(crate) override_queries: Option<fn(&Session, &mut Providers, &mut ExternProviders)>,
 }
@@ -45,7 +45,7 @@ impl Compiler {
     pub fn session(&self) -> &Lrc<Session> {
         &self.sess
     }
-    pub fn codegen_backend(&self) -> &Lrc<Box<dyn CodegenBackend>> {
+    pub fn codegen_backend(&self) -> &Lrc<dyn CodegenBackend> {
         &self.codegen_backend
     }
     pub fn register_lints(&self) -> &Option<Box<dyn Fn(&Session, &mut LintStore) + Send + Sync>> {
@@ -318,7 +318,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
             let compiler = Compiler {
                 sess: Lrc::new(sess),
-                codegen_backend: Lrc::new(codegen_backend),
+                codegen_backend: Lrc::from(codegen_backend),
                 register_lints: config.register_lints,
                 override_queries: config.override_queries,
             };

Diff for: compiler/rustc_interface/src/queries.rs

@@ -115,7 +115,7 @@ impl<'tcx> Queries<'tcx> {
     fn session(&self) -> &Lrc<Session> {
         &self.compiler.sess
     }
-    fn codegen_backend(&self) -> &Lrc<Box<dyn CodegenBackend>> {
+    fn codegen_backend(&self) -> &Lrc<dyn CodegenBackend> {
         self.compiler.codegen_backend()
     }
 
@@ -259,7 +259,7 @@ impl<'tcx> Queries<'tcx> {
             // Hook for UI tests.
             Self::check_for_rustc_errors_attr(tcx);
 
-            Ok(passes::start_codegen(&***self.codegen_backend(), tcx))
+            Ok(passes::start_codegen(&**self.codegen_backend(), tcx))
         })
     }
 
@@ -324,7 +324,7 @@ impl<'tcx> Queries<'tcx> {
 pub struct Linker {
     // compilation inputs
     sess: Lrc<Session>,
-    codegen_backend: Lrc<Box<dyn CodegenBackend>>,
+    codegen_backend: Lrc<dyn CodegenBackend>,
 
     // compilation outputs
     dep_graph: DepGraph,