Construct SourceMap at the same time as SessionGlobals.

Currently `SourceMap` is constructed slightly later than
`SessionGlobals`, and inserted. This commit changes things so they are
done at the same time.

Benefits:
- `SessionGlobals::source_map` changes from
  `Lock<Option<Lrc<SourceMap>>>` to `Option<Lrc<SourceMap>>`. It's still
  optional, but mutability isn't required because it's initialized at
  construction.
- `set_source_map` is removed, simplifying `run_compiler`, which is
  good because that's a critical function and it's nice to make it
  simpler.

This requires moving things around a bit, so the necessary inputs are
available when `SessionGlobals` is created, in particular the `loader`
and `hash_kind`, which are no longer computed by `build_session`. These
inputs are captured by the new `SourceMapInputs` type, which is threaded
through various places.

compiler/rustc_hir/src/tests.rs

@@ -14,7 +14,7 @@ fn def_path_hash_depends_on_crate_id() {
     // the crate by changing the crate disambiguator (e.g. via bumping the
     // crate's version number).
 
-    create_session_globals_then(Edition::Edition2024, || {
+    create_session_globals_then(Edition::Edition2024, None, || {
         let id0 = StableCrateId::new(Symbol::intern("foo"), false, vec!["1".to_string()], "");
         let id1 = StableCrateId::new(Symbol::intern("foo"), false, vec!["2".to_string()], "");
 

compiler/rustc_interface/src/interface.rs

@@ -21,7 +21,7 @@
 use rustc_session::filesearch::{self, sysroot_candidates};
 use rustc_session::parse::ParseSess;
 use rustc_session::{lint, CompilerIO, EarlyDiagCtxt, Session};
-use rustc_span::source_map::FileLoader;
+use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
 use rustc_span::symbol::sym;
 use rustc_span::FileName;
 use std::path::PathBuf;
@@ -336,18 +336,23 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
     let early_dcx = EarlyDiagCtxt::new(config.opts.error_format);
     early_dcx.initialize_checked_jobserver();
 
+    crate::callbacks::setup_callbacks();
+
+    let sysroot = filesearch::materialize_sysroot(config.opts.maybe_sysroot.clone());
+    let target = config::build_target_config(&early_dcx, &config.opts, &sysroot);
+    let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
+    let path_mapping = config.opts.file_path_mapping();
+    let hash_kind = config.opts.unstable_opts.src_hash_algorithm(&target);
+
     util::run_in_thread_pool_with_globals(
         config.opts.edition,
         config.opts.unstable_opts.threads,
+        SourceMapInputs { file_loader, path_mapping, hash_kind },
         |current_gcx| {
-            crate::callbacks::setup_callbacks();
+            // The previous `early_dcx` can't be reused here because it doesn't
-
+            // impl `Send`. Creating a new one is fine.
             let early_dcx = EarlyDiagCtxt::new(config.opts.error_format);
 
-            let sysroot = filesearch::materialize_sysroot(config.opts.maybe_sysroot.clone());
-
-            let target = config::build_target_config(&early_dcx, &config.opts, &sysroot);
-
             let codegen_backend = match config.make_codegen_backend {
                 None => util::get_codegen_backend(
                     &early_dcx,
@@ -372,9 +377,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 config.opts.unstable_opts.translate_directionality_markers,
             ) {
                 Ok(bundle) => bundle,
-                Err(e) => {
+                Err(e) => early_dcx.early_fatal(format!("failed to load fluent bundle: {e}")),
-                    early_dcx.early_fatal(format!("failed to load fluent bundle: {e}"));
-                }
             };
 
             let mut locale_resources = Vec::from(config.locale_resources);
@@ -393,7 +396,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 config.registry.clone(),
                 locale_resources,
                 config.lint_caps,
-                config.file_loader,
                 target,
                 sysroot,
                 util::rustc_version_str().unwrap_or("unknown"),
@@ -440,7 +442,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 current_gcx,
             };
 
-            rustc_span::set_source_map(compiler.sess.psess.clone_source_map(), move || {
             // There are two paths out of `f`.
             // - Normal exit.
             // - Panic, e.g. triggered by `abort_if_errors`.
@@ -478,7 +479,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             prof.generic_activity("drop_compiler").run(move || drop(compiler));
 
             res
-            })
         },
     )
 }

compiler/rustc_interface/src/tests.rs

@@ -16,6 +16,7 @@
 use rustc_session::utils::{CanonicalizedPath, NativeLib, NativeLibKind};
 use rustc_session::{build_session, filesearch, getopts, CompilerIO, EarlyDiagCtxt, Session};
 use rustc_span::edition::{Edition, DEFAULT_EDITION};
+use rustc_span::source_map::{RealFileLoader, SourceMapInputs};
 use rustc_span::symbol::sym;
 use rustc_span::{FileName, SourceFileHashAlgorithm};
 use rustc_target::spec::{CodeModel, LinkerFlavorCli, MergeFunctions, PanicStrategy, RelocModel};
@@ -36,8 +37,14 @@ fn sess_and_cfg<F>(args: &[&'static str], f: F)
     let sessopts = build_session_options(&mut early_dcx, &matches);
     let sysroot = filesearch::materialize_sysroot(sessopts.maybe_sysroot.clone());
     let target = rustc_session::config::build_target_config(&early_dcx, &sessopts, &sysroot);
+    let hash_kind = sessopts.unstable_opts.src_hash_algorithm(&target);
+    let sm_inputs = Some(SourceMapInputs {
+        file_loader: Box::new(RealFileLoader) as _,
+        path_mapping: sessopts.file_path_mapping(),
+        hash_kind,
+    });
 
-    rustc_span::create_default_session_globals_then(|| {
+    rustc_span::create_session_globals_then(DEFAULT_EDITION, sm_inputs, || {
         let temps_dir = sessopts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);
         let io = CompilerIO {
             input: Input::Str { name: FileName::Custom(String::new()), input: String::new() },
@@ -45,6 +52,7 @@ fn sess_and_cfg<F>(args: &[&'static str], f: F)
             output_file: None,
             temps_dir,
         };
+
         let sess = build_session(
             early_dcx,
             sessopts,
@@ -53,7 +61,6 @@ fn sess_and_cfg<F>(args: &[&'static str], f: F)
             registry::Registry::new(&[]),
             vec![],
             Default::default(),
-            None,
             target,
             sysroot,
             "",

compiler/rustc_interface/src/util.rs

@@ -14,6 +14,7 @@
 use rustc_session::{filesearch, Session};
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
+use rustc_span::source_map::SourceMapInputs;
 use rustc_span::symbol::sym;
 use rustc_target::spec::Target;
 use session::output::{categorize_crate_type, CRATE_TYPES};
@@ -65,8 +66,9 @@ fn init_stack_size() -> usize {
     })
 }
 
-pub(crate) fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
+fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
     edition: Edition,
+    sm_inputs: SourceMapInputs,
     f: F,
 ) -> R {
     // The "thread pool" is a single spawned thread in the non-parallel
@@ -84,7 +86,9 @@ pub(crate) fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: S
         // name contains null bytes.
         let r = builder
             .spawn_scoped(s, move || {
-                rustc_span::create_session_globals_then(edition, || f(CurrentGcx::new()))
+                rustc_span::create_session_globals_then(edition, Some(sm_inputs), || {
+                    f(CurrentGcx::new())
+                })
             })
             .unwrap()
             .join();
@@ -100,15 +104,17 @@ pub(crate) fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: S
 pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
     edition: Edition,
     _threads: usize,
+    sm_inputs: SourceMapInputs,
     f: F,
 ) -> R {
-    run_in_thread_with_globals(edition, f)
+    run_in_thread_with_globals(edition, sm_inputs, f)
 }
 
 #[cfg(parallel_compiler)]
 pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
     edition: Edition,
     threads: usize,
+    sm_inputs: SourceMapInputs,
     f: F,
 ) -> R {
     use rustc_data_structures::{defer, jobserver, sync::FromDyn};
@@ -120,7 +126,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     let registry = sync::Registry::new(std::num::NonZero::new(threads).unwrap());
 
     if !sync::is_dyn_thread_safe() {
-        return run_in_thread_with_globals(edition, |current_gcx| {
+        return run_in_thread_with_globals(edition, sm_inputs, |current_gcx| {
             // Register the thread for use with the `WorkerLocal` type.
             registry.register();
 
@@ -169,7 +175,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     // pool. Upon creation, each worker thread created gets a copy of the
     // session globals in TLS. This is possible because `SessionGlobals` impls
     // `Send` in the parallel compiler.
-    rustc_span::create_session_globals_then(edition, || {
+    rustc_span::create_session_globals_then(edition, Some(sm_inputs), || {
         rustc_span::with_session_globals(|session_globals| {
             let session_globals = FromDyn::from(session_globals);
             builder

compiler/rustc_log/src/lib.rs

@@ -17,7 +17,7 @@
 //!     rustc_log::init_logger(rustc_log::LoggerConfig::from_env("LOG")).unwrap();
 //!
 //!     let edition = rustc_span::edition::Edition::Edition2021;
-//!     rustc_span::create_session_globals_then(edition, || {
+//!     rustc_span::create_session_globals_then(edition, None, || {
 //!         /* ... */
 //!     });
 //! }

compiler/rustc_session/src/config.rs

@@ -1125,7 +1125,7 @@ pub fn build_dep_graph(&self) -> bool {
             || self.unstable_opts.query_dep_graph
     }
 
-    pub(crate) fn file_path_mapping(&self) -> FilePathMapping {
+    pub fn file_path_mapping(&self) -> FilePathMapping {
         file_path_mapping(self.remap_path_prefix.clone(), &self.unstable_opts)
     }
 
@@ -1162,6 +1162,16 @@ pub fn dcx_flags(&self, can_emit_warnings: bool) -> DiagCtxtFlags {
             track_diagnostics: self.track_diagnostics,
         }
     }
+
+    pub fn src_hash_algorithm(&self, target: &Target) -> SourceFileHashAlgorithm {
+        self.src_hash_algorithm.unwrap_or_else(|| {
+            if target.is_like_msvc {
+                SourceFileHashAlgorithm::Sha256
+            } else {
+                SourceFileHashAlgorithm::Md5
+            }
+        })
+    }
 }
 
 // The type of entry function, so users can have their own entry functions

compiler/rustc_session/src/session.rs

@@ -28,9 +28,9 @@
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
 use rustc_span::edition::Edition;
-use rustc_span::source_map::{FileLoader, FilePathMapping, RealFileLoader, SourceMap};
+use rustc_span::source_map::{FilePathMapping, SourceMap};
 use rustc_span::{FileNameDisplayPreference, RealFileName};
-use rustc_span::{SourceFileHashAlgorithm, Span, Symbol};
+use rustc_span::{Span, Symbol};
 use rustc_target::asm::InlineAsmArch;
 use rustc_target::spec::{CodeModel, PanicStrategy, RelocModel, RelroLevel};
 use rustc_target::spec::{
@@ -988,7 +988,6 @@ pub fn build_session(
     registry: rustc_errors::registry::Registry,
     fluent_resources: Vec<&'static str>,
     driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
-    file_loader: Option<Box<dyn FileLoader + Send + Sync + 'static>>,
     target: Target,
     sysroot: PathBuf,
     cfg_version: &'static str,
@@ -1015,24 +1014,11 @@ pub fn build_session(
         early_dcx.early_warn(warning)
     }
 
-    let loader = file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
-    let hash_kind = sopts.unstable_opts.src_hash_algorithm.unwrap_or_else(|| {
-        if target.is_like_msvc {
-            SourceFileHashAlgorithm::Sha256
-        } else {
-            SourceFileHashAlgorithm::Md5
-        }
-    });
-    let source_map = Lrc::new(SourceMap::with_file_loader_and_hash_kind(
-        loader,
-        sopts.file_path_mapping(),
-        hash_kind,
-    ));
-
     let fallback_bundle = fallback_fluent_bundle(
         fluent_resources,
         sopts.unstable_opts.translate_directionality_markers,
     );
+    let source_map = rustc_span::source_map::get_source_map().unwrap();
     let emitter = default_emitter(&sopts, registry, source_map.clone(), bundle, fallback_bundle);
 
     let mut dcx =

compiler/rustc_span/src/lib.rs

@@ -49,7 +49,7 @@
 mod caching_source_map_view;
 pub mod source_map;
 pub use self::caching_source_map_view::CachingSourceMapView;
-use source_map::SourceMap;
+use source_map::{SourceMap, SourceMapInputs};
 
 pub mod edition;
 use edition::Edition;
@@ -104,35 +104,35 @@ pub struct SessionGlobals {
     metavar_spans: Lock<FxHashMap<Span, Span>>,
     hygiene_data: Lock<hygiene::HygieneData>,
 
-    /// A reference to the source map in the `Session`. It's an `Option`
+    /// The session's source map, if there is one. This field should only be
-    /// because it can't be initialized until `Session` is created, which
+    /// used in places where the `Session` is truly not available, such as
-    /// happens after `SessionGlobals`. `set_source_map` does the
+    /// `<Span as Debug>::fmt`.
-    /// initialization.
+    source_map: Option<Lrc<SourceMap>>,
-    ///
-    /// This field should only be used in places where the `Session` is truly
-    /// not available, such as `<Span as Debug>::fmt`.
-    source_map: Lock<Option<Lrc<SourceMap>>>,
 }
 
 impl SessionGlobals {
-    pub fn new(edition: Edition) -> SessionGlobals {
+    pub fn new(edition: Edition, sm_inputs: Option<SourceMapInputs>) -> SessionGlobals {
         SessionGlobals {
             symbol_interner: symbol::Interner::fresh(),
             span_interner: Lock::new(span_encoding::SpanInterner::default()),
             metavar_spans: Default::default(),
             hygiene_data: Lock::new(hygiene::HygieneData::new(edition)),
-            source_map: Lock::new(None),
+            source_map: sm_inputs.map(|inputs| Lrc::new(SourceMap::with_inputs(inputs))),
         }
     }
 }
 
-pub fn create_session_globals_then<R>(edition: Edition, f: impl FnOnce() -> R) -> R {
+pub fn create_session_globals_then<R>(
+    edition: Edition,
+    sm_inputs: Option<SourceMapInputs>,
+    f: impl FnOnce() -> R,
+) -> R {
     assert!(
         !SESSION_GLOBALS.is_set(),
         "SESSION_GLOBALS should never be overwritten! \
          Use another thread if you need another SessionGlobals"
     );
-    let session_globals = SessionGlobals::new(edition);
+    let session_globals = SessionGlobals::new(edition, sm_inputs);
     SESSION_GLOBALS.set(&session_globals, f)
 }
 
@@ -145,12 +145,13 @@ pub fn set_session_globals_then<R>(session_globals: &SessionGlobals, f: impl FnO
     SESSION_GLOBALS.set(session_globals, f)
 }
 
+/// No source map.
 pub fn create_session_if_not_set_then<R, F>(edition: Edition, f: F) -> R
 where
     F: FnOnce(&SessionGlobals) -> R,
 {
     if !SESSION_GLOBALS.is_set() {
-        let session_globals = SessionGlobals::new(edition);
+        let session_globals = SessionGlobals::new(edition, None);
         SESSION_GLOBALS.set(&session_globals, || SESSION_GLOBALS.with(f))
     } else {
         SESSION_GLOBALS.with(f)
@@ -164,8 +165,9 @@ pub fn with_session_globals<R, F>(f: F) -> R
     SESSION_GLOBALS.with(f)
 }
 
+/// Default edition, no source map.
 pub fn create_default_session_globals_then<R>(f: impl FnOnce() -> R) -> R {
-    create_session_globals_then(edition::DEFAULT_EDITION, f)
+    create_session_globals_then(edition::DEFAULT_EDITION, None, f)
 }
 
 // If this ever becomes non thread-local, `decode_syntax_context`
@@ -1318,25 +1320,6 @@ fn decode(s: &mut D) -> AttrId {
     }
 }
 
-/// Insert `source_map` into the session globals for the duration of the
-/// closure's execution.
-pub fn set_source_map<T, F: FnOnce() -> T>(source_map: Lrc<SourceMap>, f: F) -> T {
-    with_session_globals(|session_globals| {
-        *session_globals.source_map.borrow_mut() = Some(source_map);
-    });
-    struct ClearSourceMap;
-    impl Drop for ClearSourceMap {
-        fn drop(&mut self) {
-            with_session_globals(|session_globals| {
-                session_globals.source_map.borrow_mut().take();
-            });
-        }
-    }
-
-    let _guard = ClearSourceMap;
-    f()
-}
-
 impl fmt::Debug for Span {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // Use the global `SourceMap` to print the span. If that's not
@@ -1352,7 +1335,7 @@ fn fallback(span: Span, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 
         if SESSION_GLOBALS.is_set() {
             with_session_globals(|session_globals| {
-                if let Some(source_map) = &*session_globals.source_map.borrow() {
+                if let Some(source_map) = &session_globals.source_map {
                     write!(f, "{} ({:?})", source_map.span_to_diagnostic_string(*self), self.ctxt())
                 } else {
                     fallback(*self, f)

compiler/rustc_span/src/source_map.rs

@@ -167,9 +167,17 @@ struct SourceMapFiles {
     stable_id_to_source_file: UnhashMap<StableSourceFileId, Lrc<SourceFile>>,
 }
 
+/// Used to construct a `SourceMap` with `SourceMap::with_inputs`.
+pub struct SourceMapInputs {
+    pub file_loader: Box<dyn FileLoader + Send + Sync>,
+    pub path_mapping: FilePathMapping,
+    pub hash_kind: SourceFileHashAlgorithm,
+}
+
 pub struct SourceMap {
     files: RwLock<SourceMapFiles>,
     file_loader: IntoDynSyncSend<Box<dyn FileLoader + Sync + Send>>,
+
     // This is used to apply the file path remapping as specified via
     // `--remap-path-prefix` to all `SourceFile`s allocated within this `SourceMap`.
     path_mapping: FilePathMapping,
@@ -180,17 +188,15 @@ pub struct SourceMap {
 
 impl SourceMap {
     pub fn new(path_mapping: FilePathMapping) -> SourceMap {
-        Self::with_file_loader_and_hash_kind(
+        Self::with_inputs(SourceMapInputs {
-            Box::new(RealFileLoader),
+            file_loader: Box::new(RealFileLoader),
             path_mapping,
-            SourceFileHashAlgorithm::Md5,
+            hash_kind: SourceFileHashAlgorithm::Md5,
-        )
+        })
     }
 
-    pub fn with_file_loader_and_hash_kind(
+    pub fn with_inputs(
-        file_loader: Box<dyn FileLoader + Sync + Send>,
+        SourceMapInputs { file_loader, path_mapping, hash_kind }: SourceMapInputs,
-        path_mapping: FilePathMapping,
-        hash_kind: SourceFileHashAlgorithm,
     ) -> SourceMap {
         SourceMap {
             files: Default::default(),
@@ -1054,6 +1060,10 @@ pub fn mac_call_stmt_semi_span(&self, mac_call: Span) -> Option<Span> {
     }
 }
 
+pub fn get_source_map() -> Option<Lrc<SourceMap>> {
+    with_session_globals(|session_globals| session_globals.source_map.clone())
+}
+
 #[derive(Clone)]
 pub struct FilePathMapping {
     mapping: Vec<(PathBuf, PathBuf)>,

src/tools/clippy/clippy_lints/src/doc/needless_doctest_main.rs

@@ -38,7 +38,7 @@ pub fn check(
     // of all `#[test]` attributes in not ignored code examples
     fn check_code_sample(code: String, edition: Edition, ignore: bool) -> (bool, Vec<Range<usize>>) {
         rustc_driver::catch_fatal_errors(|| {
-            rustc_span::create_session_globals_then(edition, || {
+            rustc_span::create_session_globals_then(edition, None, || {
                 let mut test_attr_spans = vec![];
                 let filename = FileName::anon_source_code(&code);