From 4f9b9a43c1c64781a19edeb58b4022df9ac0aafb Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 22 Jan 2025 13:58:47 +0000
Subject: [PATCH 1/4] Remove the need to manually call
 set_using_internal_features

---
 compiler/rustc_driver_impl/src/lib.rs     | 53 +++++------------------
 compiler/rustc_interface/src/interface.rs |  3 +-
 compiler/rustc_interface/src/tests.rs     |  6 ++-
 compiler/rustc_session/src/session.rs     |  4 +-
 src/librustdoc/core.rs                    |  7 ++-
 src/librustdoc/doctest.rs                 |  2 +-
 src/librustdoc/lib.rs                     | 17 +++-----
 src/tools/clippy/src/driver.rs            | 10 ++---
 src/tools/miri/src/bin/miri.rs            | 25 +++--------
 tests/ui-fulldeps/run-compiler-twice.rs   |  2 +-
 10 files changed, 36 insertions(+), 93 deletions(-)

diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 414d1205b0efa..e8bfe429585ff 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -28,8 +28,8 @@ use std::io::{self, IsTerminal, Read, Write};
 use std::panic::{self, PanicHookInfo, catch_unwind};
 use std::path::{Path, PathBuf};
 use std::process::{self, Command, Stdio};
+use std::sync::OnceLock;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::{Arc, OnceLock};
 use std::time::{Instant, SystemTime};
 use std::{env, str};
 
@@ -214,18 +214,11 @@ pub struct RunCompiler<'a> {
     file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
     make_codegen_backend:
         Option<Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>>,
-    using_internal_features: Arc<std::sync::atomic::AtomicBool>,
 }
 
 impl<'a> RunCompiler<'a> {
     pub fn new(at_args: &'a [String], callbacks: &'a mut (dyn Callbacks + Send)) -> Self {
-        Self {
-            at_args,
-            callbacks,
-            file_loader: None,
-            make_codegen_backend: None,
-            using_internal_features: Arc::default(),
-        }
+        Self { at_args, callbacks, file_loader: None, make_codegen_backend: None }
     }
 
     /// Set a custom codegen backend.
@@ -257,23 +250,9 @@ impl<'a> RunCompiler<'a> {
         self
     }
 
-    /// Set the session-global flag that checks whether internal features have been used,
-    /// suppressing the message about submitting an issue in ICEs when enabled.
-    #[must_use]
-    pub fn set_using_internal_features(mut self, using_internal_features: Arc<AtomicBool>) -> Self {
-        self.using_internal_features = using_internal_features;
-        self
-    }
-
     /// Parse args and run the compiler.
     pub fn run(self) {
-        run_compiler(
-            self.at_args,
-            self.callbacks,
-            self.file_loader,
-            self.make_codegen_backend,
-            self.using_internal_features,
-        );
+        run_compiler(self.at_args, self.callbacks, self.file_loader, self.make_codegen_backend);
     }
 }
 
@@ -284,7 +263,6 @@ fn run_compiler(
     make_codegen_backend: Option<
         Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>,
     >,
-    using_internal_features: Arc<std::sync::atomic::AtomicBool>,
 ) {
     let mut default_early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
 
@@ -331,7 +309,7 @@ fn run_compiler(
         override_queries: None,
         make_codegen_backend,
         registry: diagnostics_registry(),
-        using_internal_features,
+        using_internal_features: &USING_INTERNAL_FEATURES,
         expanded_args: args,
     };
 
@@ -1350,6 +1328,8 @@ fn ice_path_with_config(config: Option<&UnstableOptions>) -> &'static Option<Pat
     })
 }
 
+pub static USING_INTERNAL_FEATURES: AtomicBool = AtomicBool::new(false);
+
 /// Installs a panic hook that will print the ICE message on unexpected panics.
 ///
 /// The hook is intended to be useable even by external tools. You can pass a custom
@@ -1360,15 +1340,8 @@ fn ice_path_with_config(config: Option<&UnstableOptions>) -> &'static Option<Pat
 /// If you have no extra info to report, pass the empty closure `|_| ()` as the argument to
 /// extra_info.
 ///
-/// Returns a flag that can be set to disable the note for submitting a bug. This can be passed to
-/// [`RunCompiler::set_using_internal_features`] to let macro expansion set it when encountering
-/// internal features.
-///
 /// A custom rustc driver can skip calling this to set up a custom ICE hook.
-pub fn install_ice_hook(
-    bug_report_url: &'static str,
-    extra_info: fn(&DiagCtxt),
-) -> Arc<AtomicBool> {
+pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&DiagCtxt)) {
     // If the user has not explicitly overridden "RUST_BACKTRACE", then produce
     // full backtraces. When a compiler ICE happens, we want to gather
     // as much information as possible to present in the issue opened
@@ -1385,8 +1358,6 @@ pub fn install_ice_hook(
         }
     }
 
-    let using_internal_features = Arc::new(std::sync::atomic::AtomicBool::default());
-    let using_internal_features_hook = Arc::clone(&using_internal_features);
     panic::update_hook(Box::new(
         move |default_hook: &(dyn Fn(&PanicHookInfo<'_>) + Send + Sync + 'static),
               info: &PanicHookInfo<'_>| {
@@ -1438,11 +1409,9 @@ pub fn install_ice_hook(
             }
 
             // Print the ICE message
-            report_ice(info, bug_report_url, extra_info, &using_internal_features_hook);
+            report_ice(info, bug_report_url, extra_info, &USING_INTERNAL_FEATURES);
         },
     ));
-
-    using_internal_features
 }
 
 /// Prints the ICE message, including query stack, but without backtrace.
@@ -1583,13 +1552,11 @@ pub fn main() -> ! {
     init_rustc_env_logger(&early_dcx);
     signal_handler::install();
     let mut callbacks = TimePassesCallbacks::default();
-    let using_internal_features = install_ice_hook(DEFAULT_BUG_REPORT_URL, |_| ());
+    install_ice_hook(DEFAULT_BUG_REPORT_URL, |_| ());
     install_ctrlc_handler();
 
     let exit_code = catch_with_exit_code(|| {
-        RunCompiler::new(&args::raw_args(&early_dcx)?, &mut callbacks)
-            .set_using_internal_features(using_internal_features)
-            .run();
+        RunCompiler::new(&args::raw_args(&early_dcx)?, &mut callbacks).run();
         Ok(())
     });
 
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 1971c63756386..6a6549a475397 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -1,6 +1,5 @@
 use std::path::PathBuf;
 use std::result;
-use std::sync::Arc;
 
 use rustc_ast::{LitKind, MetaItemKind, token};
 use rustc_codegen_ssa::traits::CodegenBackend;
@@ -347,7 +346,7 @@ pub struct Config {
     /// enabled. Makes it so that "please report a bug" is hidden, as ICEs with
     /// internal features are wontfix, and they are usually the cause of the ICEs.
     /// None signifies that this is not tracked.
-    pub using_internal_features: Arc<std::sync::atomic::AtomicBool>,
+    pub using_internal_features: &'static std::sync::atomic::AtomicBool,
 
     /// All commandline args used to invoke the compiler, with @file args fully expanded.
     /// This will only be used within debug info, e.g. in the pdb file on windows
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index d7370c1ff53f7..74d02ac22276c 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -2,7 +2,7 @@
 use std::collections::{BTreeMap, BTreeSet};
 use std::num::NonZero;
 use std::path::{Path, PathBuf};
-use std::sync::Arc;
+use std::sync::atomic::AtomicBool;
 
 use rustc_data_structures::profiling::TimePassesFormat;
 use rustc_errors::emitter::HumanReadableErrorType;
@@ -62,6 +62,8 @@ where
             temps_dir,
         };
 
+        static USING_INTERNAL_FEATURES: AtomicBool = AtomicBool::new(false);
+
         let sess = build_session(
             early_dcx,
             sessopts,
@@ -74,7 +76,7 @@ where
             sysroot,
             "",
             None,
-            Arc::default(),
+            &USING_INTERNAL_FEATURES,
             Default::default(),
         );
         let cfg = parse_cfg(sess.dcx(), matches.opt_strs("cfg"));
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 60f1154dc6d02..10f1ce376ef55 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -189,7 +189,7 @@ pub struct Session {
     /// enabled. Makes it so that "please report a bug" is hidden, as ICEs with
     /// internal features are wontfix, and they are usually the cause of the ICEs.
     /// None signifies that this is not tracked.
-    pub using_internal_features: Arc<AtomicBool>,
+    pub using_internal_features: &'static AtomicBool,
 
     /// All commandline args used to invoke the compiler, with @file args fully expanded.
     /// This will only be used within debug info, e.g. in the pdb file on windows
@@ -966,7 +966,7 @@ pub fn build_session(
     sysroot: PathBuf,
     cfg_version: &'static str,
     ice_file: Option<PathBuf>,
-    using_internal_features: Arc<AtomicBool>,
+    using_internal_features: &'static AtomicBool,
     expanded_args: Vec<String>,
 ) -> Session {
     // FIXME: This is not general enough to make the warning lint completely override
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 0dda3466a7173..ad67c2ba24536 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -1,10 +1,10 @@
-use std::sync::atomic::AtomicBool;
-use std::sync::{Arc, LazyLock};
+use std::sync::LazyLock;
 use std::{io, mem};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::unord::UnordSet;
+use rustc_driver::USING_INTERNAL_FEATURES;
 use rustc_errors::TerminalUrl;
 use rustc_errors::codes::*;
 use rustc_errors::emitter::{
@@ -221,7 +221,6 @@ pub(crate) fn create_config(
         ..
     }: RustdocOptions,
     RenderOptions { document_private, .. }: &RenderOptions,
-    using_internal_features: Arc<AtomicBool>,
 ) -> rustc_interface::Config {
     // Add the doc cfg into the doc build.
     cfgs.push("doc".to_string());
@@ -316,7 +315,7 @@ pub(crate) fn create_config(
         make_codegen_backend: None,
         registry: rustc_driver::diagnostics_registry(),
         ice_file: None,
-        using_internal_features,
+        using_internal_features: &USING_INTERNAL_FEATURES,
         expanded_args,
     }
 }
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 009e9662933ae..8c3e28ecec38c 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -193,7 +193,7 @@ pub(crate) fn run(dcx: DiagCtxtHandle<'_>, input: Input, options: RustdocOptions
         make_codegen_backend: None,
         registry: rustc_driver::diagnostics_registry(),
         ice_file: None,
-        using_internal_features: Arc::default(),
+        using_internal_features: &rustc_driver::USING_INTERNAL_FEATURES,
         expanded_args: options.expanded_args.clone(),
     };
 
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index ba620b6cb6bef..7861a01ba855c 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -73,8 +73,6 @@ extern crate tikv_jemalloc_sys as jemalloc_sys;
 use std::env::{self, VarError};
 use std::io::{self, IsTerminal};
 use std::process;
-use std::sync::Arc;
-use std::sync::atomic::AtomicBool;
 
 use rustc_errors::DiagCtxtHandle;
 use rustc_interface::interface;
@@ -158,7 +156,7 @@ pub fn main() {
 
     let mut early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
 
-    let using_internal_features = rustc_driver::install_ice_hook(
+    rustc_driver::install_ice_hook(
         "https://github.com/rust-lang/rust/issues/new\
     ?labels=C-bug%2C+I-ICE%2C+T-rustdoc&template=ice.md",
         |_| (),
@@ -179,7 +177,7 @@ pub fn main() {
 
     let exit_code = rustc_driver::catch_with_exit_code(|| {
         let at_args = rustc_driver::args::raw_args(&early_dcx)?;
-        main_args(&mut early_dcx, &at_args, using_internal_features);
+        main_args(&mut early_dcx, &at_args);
         Ok(())
     });
     process::exit(exit_code);
@@ -768,11 +766,7 @@ fn run_merge_finalize(opt: config::RenderOptions) -> Result<(), error::Error> {
     Ok(())
 }
 
-fn main_args(
-    early_dcx: &mut EarlyDiagCtxt,
-    at_args: &[String],
-    using_internal_features: Arc<AtomicBool>,
-) {
+fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
     // Throw away the first argument, the name of the binary.
     // In case of at_args being empty, as might be the case by
     // passing empty argument array to execve under some platforms,
@@ -825,8 +819,7 @@ fn main_args(
         (false, Some(md_input)) => {
             let md_input = md_input.to_owned();
             let edition = options.edition;
-            let config =
-                core::create_config(input, options, &render_options, using_internal_features);
+            let config = core::create_config(input, options, &render_options);
 
             // `markdown::render` can invoke `doctest::make_test`, which
             // requires session globals and a thread pool, so we use
@@ -859,7 +852,7 @@ fn main_args(
     let scrape_examples_options = options.scrape_examples_options.clone();
     let bin_crate = options.bin_crate;
 
-    let config = core::create_config(input, options, &render_options, using_internal_features);
+    let config = core::create_config(input, options, &render_options);
 
     let registered_lints = config.register_lints.is_some();
 
diff --git a/src/tools/clippy/src/driver.rs b/src/tools/clippy/src/driver.rs
index 75ef60a5dc8ac..b3bfec4272004 100644
--- a/src/tools/clippy/src/driver.rs
+++ b/src/tools/clippy/src/driver.rs
@@ -186,7 +186,7 @@ pub fn main() {
 
     rustc_driver::init_rustc_env_logger(&early_dcx);
 
-    let using_internal_features = rustc_driver::install_ice_hook(BUG_REPORT_URL, |dcx| {
+    rustc_driver::install_ice_hook(BUG_REPORT_URL, |dcx| {
         // FIXME: this macro calls unwrap internally but is called in a panicking context!  It's not
         // as simple as moving the call from the hook to main, because `install_ice_hook` doesn't
         // accept a generic closure.
@@ -295,13 +295,9 @@ pub fn main() {
         let clippy_enabled = !cap_lints_allow && relevant_package && !info_query;
         if clippy_enabled {
             args.extend(clippy_args);
-            rustc_driver::RunCompiler::new(&args, &mut ClippyCallbacks { clippy_args_var })
-                .set_using_internal_features(using_internal_features)
-                .run();
+            rustc_driver::RunCompiler::new(&args, &mut ClippyCallbacks { clippy_args_var }).run();
         } else {
-            rustc_driver::RunCompiler::new(&args, &mut RustcCallbacks { clippy_args_var })
-                .set_using_internal_features(using_internal_features)
-                .run();
+            rustc_driver::RunCompiler::new(&args, &mut RustcCallbacks { clippy_args_var }).run();
         }
         Ok(())
     }))
diff --git a/src/tools/miri/src/bin/miri.rs b/src/tools/miri/src/bin/miri.rs
index 22c15c8405fdf..e03088917597e 100644
--- a/src/tools/miri/src/bin/miri.rs
+++ b/src/tools/miri/src/bin/miri.rs
@@ -30,7 +30,7 @@ use std::ops::Range;
 use std::path::PathBuf;
 use std::str::FromStr;
 use std::sync::atomic::{AtomicI32, Ordering};
-use std::sync::{Arc, Once};
+use std::sync::Once;
 
 use miri::{
     BacktraceStyle, BorrowTrackerMethod, MiriConfig, MiriEntryFnType,ProvenanceMode, RetagFields, ValidationMode,
@@ -370,13 +370,10 @@ fn init_late_loggers(early_dcx: &EarlyDiagCtxt, tcx: TyCtxt<'_>) {
 fn run_compiler_and_exit(
     args: &[String],
     callbacks: &mut (dyn rustc_driver::Callbacks + Send),
-    using_internal_features: Arc<std::sync::atomic::AtomicBool>,
 ) -> ! {
     // Invoke compiler, and handle return code.
     let exit_code = rustc_driver::catch_with_exit_code(move || {
-        rustc_driver::RunCompiler::new(args, callbacks)
-            .set_using_internal_features(using_internal_features)
-            .run();
+        rustc_driver::RunCompiler::new(args, callbacks).run();
         Ok(())
     });
     std::process::exit(exit_code)
@@ -467,8 +464,7 @@ fn main() {
     // If the environment asks us to actually be rustc, then do that.
     if let Some(crate_kind) = env::var_os("MIRI_BE_RUSTC") {
         // Earliest rustc setup.
-        let using_internal_features =
-            rustc_driver::install_ice_hook(rustc_driver::DEFAULT_BUG_REPORT_URL, |_| ());
+        rustc_driver::install_ice_hook(rustc_driver::DEFAULT_BUG_REPORT_URL, |_| ());
         rustc_driver::init_rustc_env_logger(&early_dcx);
 
         let target_crate = if crate_kind == "target" {
@@ -492,16 +488,11 @@ fn main() {
         }
 
         // We cannot use `rustc_driver::main` as we want it to use `args` as the CLI arguments.
-        run_compiler_and_exit(
-            &args,
-            &mut MiriBeRustCompilerCalls { target_crate },
-            using_internal_features,
-        )
+        run_compiler_and_exit(&args, &mut MiriBeRustCompilerCalls { target_crate })
     }
 
     // Add an ICE bug report hook.
-    let using_internal_features =
-        rustc_driver::install_ice_hook("https://github.com/rust-lang/miri/issues/new", |_| ());
+    rustc_driver::install_ice_hook("https://github.com/rust-lang/miri/issues/new", |_| ());
 
     // Init loggers the Miri way.
     init_early_loggers(&early_dcx);
@@ -735,9 +726,5 @@ fn main() {
 
     debug!("rustc arguments: {:?}", rustc_args);
     debug!("crate arguments: {:?}", miri_config.args);
-    run_compiler_and_exit(
-        &rustc_args,
-        &mut MiriCompilerCalls::new(miri_config, many_seeds),
-        using_internal_features,
-    )
+    run_compiler_and_exit(&rustc_args, &mut MiriCompilerCalls::new(miri_config, many_seeds))
 }
diff --git a/tests/ui-fulldeps/run-compiler-twice.rs b/tests/ui-fulldeps/run-compiler-twice.rs
index bcc235e58ed33..f414c961627dd 100644
--- a/tests/ui-fulldeps/run-compiler-twice.rs
+++ b/tests/ui-fulldeps/run-compiler-twice.rs
@@ -72,7 +72,7 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf, linker: Option<&Path
         override_queries: None,
         make_codegen_backend: None,
         registry: rustc_driver::diagnostics_registry(),
-        using_internal_features: std::sync::Arc::default(),
+        using_internal_features: &rustc_driver::USING_INTERNAL_FEATURES,
         expanded_args: Default::default(),
     };
 

From 974db1a6e444e2b053f49a8d3242db335669acef Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 22 Jan 2025 14:00:36 +0000
Subject: [PATCH 2/4] Remove set_make_codegen_backend and set_file_loader

They can both be set inside the config callback too.
---
 compiler/rustc_driver_impl/src/lib.rs         | 50 ++-----------------
 compiler/rustc_interface/src/interface.rs     | 10 ++++
 .../examples/rustc-driver-example.rs          | 13 +++--
 .../rustc-driver-interacting-with-the-ast.rs  | 13 +++--
 4 files changed, 27 insertions(+), 59 deletions(-)

diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index e8bfe429585ff..c0c4debcda3b1 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -60,7 +60,6 @@ use rustc_session::lint::{Lint, LintId};
 use rustc_session::output::collect_crate_types;
 use rustc_session::{EarlyDiagCtxt, Session, config, filesearch};
 use rustc_span::FileName;
-use rustc_span::source_map::FileLoader;
 use rustc_target::json::ToJson;
 use rustc_target::spec::{Target, TargetTuple};
 use time::OffsetDateTime;
@@ -211,59 +210,20 @@ pub fn diagnostics_registry() -> Registry {
 pub struct RunCompiler<'a> {
     at_args: &'a [String],
     callbacks: &'a mut (dyn Callbacks + Send),
-    file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
-    make_codegen_backend:
-        Option<Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>>,
 }
 
 impl<'a> RunCompiler<'a> {
     pub fn new(at_args: &'a [String], callbacks: &'a mut (dyn Callbacks + Send)) -> Self {
-        Self { at_args, callbacks, file_loader: None, make_codegen_backend: None }
-    }
-
-    /// Set a custom codegen backend.
-    ///
-    /// Has no uses within this repository, but is used by bjorn3 for "the
-    /// hotswapping branch of cg_clif" for "setting the codegen backend from a
-    /// custom driver where the custom codegen backend has arbitrary data."
-    /// (See #102759.)
-    pub fn set_make_codegen_backend(
-        &mut self,
-        make_codegen_backend: Option<
-            Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>,
-        >,
-    ) -> &mut Self {
-        self.make_codegen_backend = make_codegen_backend;
-        self
-    }
-
-    /// Load files from sources other than the file system.
-    ///
-    /// Has no uses within this repository, but may be used in the future by
-    /// bjorn3 for "hooking rust-analyzer's VFS into rustc at some point for
-    /// running rustc without having to save". (See #102759.)
-    pub fn set_file_loader(
-        &mut self,
-        file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
-    ) -> &mut Self {
-        self.file_loader = file_loader;
-        self
+        Self { at_args, callbacks }
     }
 
     /// Parse args and run the compiler.
     pub fn run(self) {
-        run_compiler(self.at_args, self.callbacks, self.file_loader, self.make_codegen_backend);
+        run_compiler(self.at_args, self.callbacks);
     }
 }
 
-fn run_compiler(
-    at_args: &[String],
-    callbacks: &mut (dyn Callbacks + Send),
-    file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
-    make_codegen_backend: Option<
-        Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>,
-    >,
-) {
+fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send)) {
     let mut default_early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
 
     // Throw away the first argument, the name of the binary.
@@ -300,14 +260,14 @@ fn run_compiler(
         output_file: ofile,
         output_dir: odir,
         ice_file,
-        file_loader,
+        file_loader: None,
         locale_resources: DEFAULT_LOCALE_RESOURCES.to_vec(),
         lint_caps: Default::default(),
         psess_created: None,
         hash_untracked_state: None,
         register_lints: None,
         override_queries: None,
-        make_codegen_backend,
+        make_codegen_backend: None,
         registry: diagnostics_registry(),
         using_internal_features: &USING_INTERNAL_FEATURES,
         expanded_args: args,
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 6a6549a475397..900c6ef1147a4 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -308,6 +308,11 @@ pub struct Config {
     pub output_dir: Option<PathBuf>,
     pub output_file: Option<OutFileName>,
     pub ice_file: Option<PathBuf>,
+    /// Load files from sources other than the file system.
+    ///
+    /// Has no uses within this repository, but may be used in the future by
+    /// bjorn3 for "hooking rust-analyzer's VFS into rustc at some point for
+    /// running rustc without having to save". (See #102759.)
     pub file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
     /// The list of fluent resources, used for lints declared with
     /// [`Diagnostic`](rustc_errors::Diagnostic) and [`LintDiagnostic`](rustc_errors::LintDiagnostic).
@@ -336,6 +341,11 @@ pub struct Config {
     pub override_queries: Option<fn(&Session, &mut Providers)>,
 
     /// This is a callback from the driver that is called to create a codegen backend.
+    ///
+    /// Has no uses within this repository, but is used by bjorn3 for "the
+    /// hotswapping branch of cg_clif" for "setting the codegen backend from a
+    /// custom driver where the custom codegen backend has arbitrary data."
+    /// (See #102759.)
     pub make_codegen_backend:
         Option<Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>>,
 
diff --git a/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs b/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
index 576bbcea965d9..b77172841da03 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
@@ -19,7 +19,7 @@ use std::path::Path;
 use rustc_ast_pretty::pprust::item_to_string;
 use rustc_data_structures::sync::Lrc;
 use rustc_driver::{Compilation, RunCompiler};
-use rustc_interface::interface::Compiler;
+use rustc_interface::interface::{Compiler, Config};
 use rustc_middle::ty::TyCtxt;
 
 struct MyFileLoader;
@@ -51,6 +51,10 @@ fn main() {
 struct MyCallbacks;
 
 impl rustc_driver::Callbacks for MyCallbacks {
+    fn config(&mut self, config: &mut Config) {
+        config.file_loader = Some(Box::new(MyFileLoader));
+    }
+
     fn after_crate_root_parsing(
         &mut self,
         _compiler: &Compiler,
@@ -83,10 +87,5 @@ impl rustc_driver::Callbacks for MyCallbacks {
 }
 
 fn main() {
-    match RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks) {
-        mut compiler => {
-            compiler.set_file_loader(Some(Box::new(MyFileLoader)));
-            compiler.run();
-        }
-    }
+    RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks).run();
 }
diff --git a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
index 90a85d5db2108..6c06bbed50b18 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
@@ -19,7 +19,7 @@ use std::path::Path;
 use rustc_ast_pretty::pprust::item_to_string;
 use rustc_data_structures::sync::Lrc;
 use rustc_driver::{Compilation, RunCompiler};
-use rustc_interface::interface::Compiler;
+use rustc_interface::interface::{Compiler, Config};
 use rustc_middle::ty::TyCtxt;
 
 struct MyFileLoader;
@@ -51,6 +51,10 @@ fn main() {
 struct MyCallbacks;
 
 impl rustc_driver::Callbacks for MyCallbacks {
+    fn config(&mut self, config: &mut Config) {
+        config.file_loader = Some(Box::new(MyFileLoader));
+    }
+
     fn after_crate_root_parsing(
         &mut self,
         _compiler: &Compiler,
@@ -90,10 +94,5 @@ impl rustc_driver::Callbacks for MyCallbacks {
 }
 
 fn main() {
-    match RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks) {
-        mut compiler => {
-            compiler.set_file_loader(Some(Box::new(MyFileLoader)));
-            compiler.run();
-        }
-    }
+    RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks).run();
 }

From a77776cc1d7c599f4ff9355ffe01bad2e2b5bbad Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 22 Jan 2025 14:13:14 +0000
Subject: [PATCH 3/4] Remove RunCompiler

It has become nothing other than a wrapper around run_compiler.
---
 compiler/rustc_driver_impl/src/lib.rs         | 20 ++-----------------
 compiler/rustc_smir/src/rustc_internal/mod.rs |  4 ++--
 .../examples/rustc-driver-example.rs          |  4 ++--
 .../rustc-driver-interacting-with-the-ast.rs  |  4 ++--
 .../rustc-dev-guide/src/rustc-driver/intro.md |  4 ++--
 src/tools/clippy/src/driver.rs                |  6 +++---
 src/tools/miri/src/bin/miri.rs                |  2 +-
 tests/ui-fulldeps/compiler-calls.rs           |  2 +-
 tests/ui-fulldeps/obtain-borrowck.rs          |  2 +-
 9 files changed, 16 insertions(+), 32 deletions(-)

diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index c0c4debcda3b1..3501668afb68b 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -207,23 +207,7 @@ pub fn diagnostics_registry() -> Registry {
 }
 
 /// This is the primary entry point for rustc.
-pub struct RunCompiler<'a> {
-    at_args: &'a [String],
-    callbacks: &'a mut (dyn Callbacks + Send),
-}
-
-impl<'a> RunCompiler<'a> {
-    pub fn new(at_args: &'a [String], callbacks: &'a mut (dyn Callbacks + Send)) -> Self {
-        Self { at_args, callbacks }
-    }
-
-    /// Parse args and run the compiler.
-    pub fn run(self) {
-        run_compiler(self.at_args, self.callbacks);
-    }
-}
-
-fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send)) {
+pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send)) {
     let mut default_early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
 
     // Throw away the first argument, the name of the binary.
@@ -1516,7 +1500,7 @@ pub fn main() -> ! {
     install_ctrlc_handler();
 
     let exit_code = catch_with_exit_code(|| {
-        RunCompiler::new(&args::raw_args(&early_dcx)?, &mut callbacks).run();
+        run_compiler(&args::raw_args(&early_dcx)?, &mut callbacks);
         Ok(())
     });
 
diff --git a/compiler/rustc_smir/src/rustc_internal/mod.rs b/compiler/rustc_smir/src/rustc_internal/mod.rs
index dc63ea1999e5b..ad38ea228bf53 100644
--- a/compiler/rustc_smir/src/rustc_internal/mod.rs
+++ b/compiler/rustc_smir/src/rustc_internal/mod.rs
@@ -316,7 +316,7 @@ macro_rules! optional {
 #[doc(hidden)]
 macro_rules! run_driver {
     ($args:expr, $callback:expr $(, $with_tcx:ident)?) => {{
-        use rustc_driver::{Callbacks, Compilation, RunCompiler};
+        use rustc_driver::{Callbacks, Compilation, run_compiler};
         use rustc_middle::ty::TyCtxt;
         use rustc_interface::interface;
         use stable_mir::CompilerError;
@@ -347,7 +347,7 @@ macro_rules! run_driver {
             /// Runs the compiler against given target and tests it with `test_function`
             pub fn run(&mut self) -> Result<C, CompilerError<B>> {
                 let compiler_result = rustc_driver::catch_fatal_errors(|| -> interface::Result::<()> {
-                    RunCompiler::new(&self.args.clone(), self).run();
+                    run_compiler(&self.args.clone(), self);
                     Ok(())
                 });
                 match (compiler_result, self.result.take()) {
diff --git a/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs b/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
index b77172841da03..8983915d78a9c 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-driver-example.rs
@@ -18,7 +18,7 @@ use std::path::Path;
 
 use rustc_ast_pretty::pprust::item_to_string;
 use rustc_data_structures::sync::Lrc;
-use rustc_driver::{Compilation, RunCompiler};
+use rustc_driver::{Compilation, run_compiler};
 use rustc_interface::interface::{Compiler, Config};
 use rustc_middle::ty::TyCtxt;
 
@@ -87,5 +87,5 @@ impl rustc_driver::Callbacks for MyCallbacks {
 }
 
 fn main() {
-    RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks).run();
+    run_compiler(&["main.rs".to_string()], &mut MyCallbacks);
 }
diff --git a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
index 6c06bbed50b18..c894b60444ac4 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
@@ -18,7 +18,7 @@ use std::path::Path;
 
 use rustc_ast_pretty::pprust::item_to_string;
 use rustc_data_structures::sync::Lrc;
-use rustc_driver::{Compilation, RunCompiler};
+use rustc_driver::{Compilation, run_compiler};
 use rustc_interface::interface::{Compiler, Config};
 use rustc_middle::ty::TyCtxt;
 
@@ -94,5 +94,5 @@ impl rustc_driver::Callbacks for MyCallbacks {
 }
 
 fn main() {
-    RunCompiler::new(&["main.rs".to_string()], &mut MyCallbacks).run();
+    run_compiler(&["main.rs".to_string()], &mut MyCallbacks);
 }
diff --git a/src/doc/rustc-dev-guide/src/rustc-driver/intro.md b/src/doc/rustc-dev-guide/src/rustc-driver/intro.md
index a6234dc129ffe..40500e6bc7a5f 100644
--- a/src/doc/rustc-dev-guide/src/rustc-driver/intro.md
+++ b/src/doc/rustc-dev-guide/src/rustc-driver/intro.md
@@ -6,7 +6,7 @@ The [`rustc_driver`] is essentially `rustc`'s `main` function.
 It acts as the glue for running the various phases of the compiler in the correct order,
 using the interface defined in the [`rustc_interface`] crate. Where possible, using [`rustc_driver`] rather than [`rustc_interface`] is recommended.
 
-The main entry point of [`rustc_driver`] is [`rustc_driver::RunCompiler`][rd_rc].
+The main entry point of [`rustc_driver`] is [`rustc_driver::run_compiler`][rd_rc].
 This builder accepts the same command-line args as rustc as well as an implementation of [`Callbacks`][cb] and a couple of other optional options.
 [`Callbacks`][cb] is a `trait` that allows for custom compiler configuration,
 as well as allowing custom code to run after different phases of the compilation.
@@ -40,7 +40,7 @@ specifically [`rustc_driver_impl::run_compiler`][rdi_rc]
 [cb]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/trait.Callbacks.html
 [example]: https://github.com/rust-lang/rustc-dev-guide/blob/master/examples/rustc-interface-example.rs
 [i_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/fn.run_compiler.html
-[rd_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/struct.RunCompiler.html
+[rd_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/fn.run_compiler.html
 [rdi_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver_impl/fn.run_compiler.html
 [stupid-stats]: https://github.com/nrc/stupid-stats
 [`nightly-rustc`]: https://doc.rust-lang.org/nightly/nightly-rustc/
diff --git a/src/tools/clippy/src/driver.rs b/src/tools/clippy/src/driver.rs
index b3bfec4272004..68edefd3095cf 100644
--- a/src/tools/clippy/src/driver.rs
+++ b/src/tools/clippy/src/driver.rs
@@ -236,7 +236,7 @@ pub fn main() {
             let mut args: Vec<String> = orig_args.clone();
             pass_sysroot_env_if_given(&mut args, sys_root_env);
 
-            rustc_driver::RunCompiler::new(&args, &mut DefaultCallbacks).run();
+            rustc_driver::run_compiler(&args, &mut DefaultCallbacks);
             return Ok(());
         }
 
@@ -295,9 +295,9 @@ pub fn main() {
         let clippy_enabled = !cap_lints_allow && relevant_package && !info_query;
         if clippy_enabled {
             args.extend(clippy_args);
-            rustc_driver::RunCompiler::new(&args, &mut ClippyCallbacks { clippy_args_var }).run();
+            rustc_driver::run_compiler(&args, &mut ClippyCallbacks { clippy_args_var });
         } else {
-            rustc_driver::RunCompiler::new(&args, &mut RustcCallbacks { clippy_args_var }).run();
+            rustc_driver::run_compiler(&args, &mut RustcCallbacks { clippy_args_var });
         }
         Ok(())
     }))
diff --git a/src/tools/miri/src/bin/miri.rs b/src/tools/miri/src/bin/miri.rs
index e03088917597e..a2e9c63f79e13 100644
--- a/src/tools/miri/src/bin/miri.rs
+++ b/src/tools/miri/src/bin/miri.rs
@@ -373,7 +373,7 @@ fn run_compiler_and_exit(
 ) -> ! {
     // Invoke compiler, and handle return code.
     let exit_code = rustc_driver::catch_with_exit_code(move || {
-        rustc_driver::RunCompiler::new(args, callbacks).run();
+        rustc_driver::run_compiler(args, callbacks);
         Ok(())
     });
     std::process::exit(exit_code)
diff --git a/tests/ui-fulldeps/compiler-calls.rs b/tests/ui-fulldeps/compiler-calls.rs
index 5fb47c87e501f..d6148dfec43ce 100644
--- a/tests/ui-fulldeps/compiler-calls.rs
+++ b/tests/ui-fulldeps/compiler-calls.rs
@@ -25,7 +25,7 @@ fn main() {
     let mut count = 1;
     let args = vec!["compiler-calls".to_string(), "foo.rs".to_string()];
     rustc_driver::catch_fatal_errors(|| -> interface::Result<()> {
-        rustc_driver::RunCompiler::new(&args, &mut TestCalls { count: &mut count }).run();
+        rustc_driver::run_compiler(&args, &mut TestCalls { count: &mut count });
         Ok(())
     })
     .ok();
diff --git a/tests/ui-fulldeps/obtain-borrowck.rs b/tests/ui-fulldeps/obtain-borrowck.rs
index 8ea2ac6197199..f8064c245a872 100644
--- a/tests/ui-fulldeps/obtain-borrowck.rs
+++ b/tests/ui-fulldeps/obtain-borrowck.rs
@@ -47,7 +47,7 @@ fn main() {
         rustc_args.push("-Zpolonius".to_owned());
         let mut callbacks = CompilerCalls::default();
         // Call the Rust compiler with our callbacks.
-        rustc_driver::RunCompiler::new(&rustc_args, &mut callbacks).run();
+        rustc_driver::run_compiler(&rustc_args, &mut callbacks);
         Ok(())
     });
     std::process::exit(exit_code);

From 241f8244e8ca1c6a86c08b4803d0394058aa28ca Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 22 Jan 2025 14:49:37 +0000
Subject: [PATCH 4/4] Remove outdated sentence

---
 compiler/rustc_interface/src/interface.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 900c6ef1147a4..01b6f1c853365 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -355,7 +355,6 @@ pub struct Config {
     /// The inner atomic value is set to true when a feature marked as `internal` is
     /// enabled. Makes it so that "please report a bug" is hidden, as ICEs with
     /// internal features are wontfix, and they are usually the cause of the ICEs.
-    /// None signifies that this is not tracked.
     pub using_internal_features: &'static std::sync::atomic::AtomicBool,
 
     /// All commandline args used to invoke the compiler, with @file args fully expanded.