Restrict sysroot crate imports to those defined in this repo.

compiler/rustc_codegen_cranelift/src/lib.rs

@@ -26,13 +26,12 @@ extern crate rustc_fs_util;
 extern crate rustc_hir;
 extern crate rustc_incremental;
 extern crate rustc_index;
+extern crate rustc_log;
 extern crate rustc_metadata;
 extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_symbol_mangling;
 extern crate rustc_target;
-#[macro_use]
-extern crate tracing;
 
 // This prevents duplicating functions and statics that are already part of the host rustc process.
 #[allow(unused_extern_crates)]
@@ -46,6 +45,7 @@ use cranelift_codegen::isa::TargetIsa;
 use cranelift_codegen::settings::{self, Configurable};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_codegen_ssa::{CodegenResults, TargetConfig};
+use rustc_log::tracing::info;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
 use rustc_session::Session;
 use rustc_session::config::OutputFilenames;

compiler/rustc_codegen_gcc/src/back/lto.rs

@@ -32,6 +32,7 @@ use rustc_codegen_ssa::{ModuleCodegen, ModuleKind, looks_like_rust_object_file};
 use rustc_data_structures::memmap::Mmap;
 use rustc_errors::{DiagCtxtHandle, FatalError};
 use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_log::tracing::info;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::WorkProduct;
 use rustc_middle::middle::exported_symbols::{SymbolExportInfo, SymbolExportLevel};

compiler/rustc_codegen_gcc/src/back/write.rs

@@ -6,6 +6,7 @@ use rustc_codegen_ssa::back::write::{BitcodeSection, CodegenContext, EmitObj, Mo
 use rustc_codegen_ssa::{CompiledModule, ModuleCodegen};
 use rustc_errors::DiagCtxtHandle;
 use rustc_fs_util::link_or_copy;
+use rustc_log::tracing::debug;
 use rustc_session::config::OutputType;
 use rustc_span::fatal_error::FatalError;
 use rustc_target::spec::SplitDebuginfo;

compiler/rustc_codegen_gcc/src/consts.rs

@@ -6,6 +6,7 @@ use rustc_codegen_ssa::traits::{
     BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
 };
 use rustc_hir::def::DefKind;
+use rustc_log::tracing::trace;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::mir::interpret::{
     self, ConstAllocation, ErrorHandled, Scalar as InterpScalar, read_target_uint,

compiler/rustc_codegen_gcc/src/gcc_util.rs

@@ -1,8 +1,8 @@
 #[cfg(feature = "master")]
 use gccjit::Context;
 use rustc_codegen_ssa::target_features;
+use rustc_data_structures::smallvec::{SmallVec, smallvec};
 use rustc_session::Session;
-use smallvec::{SmallVec, smallvec};
 
 fn gcc_features_by_flags(sess: &Session, features: &mut Vec<String>) {
     target_features::retpoline_features_by_flags(sess, features);

compiler/rustc_codegen_gcc/src/lib.rs

@@ -25,12 +25,6 @@
 #![deny(clippy::pattern_type_mismatch)]
 #![allow(clippy::needless_lifetimes, clippy::uninlined_format_args)]
 
-// These crates are pulled from the sysroot because they are part of
-// rustc's public API, so we need to ensure version compatibility.
-extern crate smallvec;
-#[macro_use]
-extern crate tracing;
-
 // The rustc crates we need
 extern crate rustc_abi;
 extern crate rustc_apfloat;
@@ -45,6 +39,7 @@ extern crate rustc_hir;
 extern crate rustc_index;
 #[cfg(feature = "master")]
 extern crate rustc_interface;
+extern crate rustc_log;
 extern crate rustc_macros;
 extern crate rustc_middle;
 extern crate rustc_session;

compiler/rustc_data_structures/src/lib.rs

@@ -43,6 +43,8 @@ use std::fmt;
 pub use atomic_ref::AtomicRef;
 pub use ena::{snapshot_vec, undo_log, unify};
 pub use rustc_index::static_assert_size;
+// Re-export some data-structure crates which are part of our public API.
+pub use {either, indexmap, smallvec, thin_vec};
 
 pub mod aligned;
 pub mod base_n;

compiler/rustc_lint/messages.ftl

@@ -207,6 +207,9 @@ lint_confusable_identifier_pair = found both `{$existing_sym}` and `{$sym}` as i
 
 lint_custom_inner_attribute_unstable = custom inner attributes are unstable
 
+lint_dangerous_extern_crate = dangerous use of `extern crate {$name}` which is not guaranteed to exist exactly once in the sysroot
+    .help = try using a cargo dependency or using a re-export of the dependency provided by a rustc_* crate
+
 lint_dangling_pointers_from_temporaries = a dangling pointer will be produced because the temporary `{$ty}` will be dropped
     .label_ptr = this pointer will immediately be invalid
     .label_temporary = this `{$ty}` is deallocated at the end of the statement, bind it to a variable to extend its lifetime

compiler/rustc_lint/src/internal.rs

@@ -12,10 +12,10 @@ use tracing::debug;
 use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::lints::{
-    BadOptAccessDiag, DefaultHashTypesDiag, DiagOutOfImpl, LintPassByHand,
-    NonGlobImportTypeIrInherent, QueryInstability, QueryUntracked, SpanUseEqCtxtDiag,
-    SymbolInternStringLiteralDiag, TyQualified, TykindDiag, TykindKind, TypeIrDirectUse,
-    TypeIrInherentUsage, TypeIrTraitUsage, UntranslatableDiag,
+    BadOptAccessDiag, DangerousExternCrateDiag, DefaultHashTypesDiag, DiagOutOfImpl,
+    LintPassByHand, NonGlobImportTypeIrInherent, QueryInstability, QueryUntracked,
+    SpanUseEqCtxtDiag, SymbolInternStringLiteralDiag, TyQualified, TykindDiag, TykindKind,
+    TypeIrDirectUse, TypeIrInherentUsage, TypeIrTraitUsage, UntranslatableDiag,
 };
 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
 
@@ -703,3 +703,37 @@ impl<'tcx> LateLintPass<'tcx> for SymbolInternStringLiteral {
         }
     }
 }
+
+declare_tool_lint! {
+    /// The `dangerous_extern_crate` detects use of `extern crate` to import non-whitelisted crates
+    /// from the sysroot, which is dangerous because these crates are not guaranteed to exist
+    /// exactly once, and so may be missing entirely or appear multiple times resulting in ambiguity.
+    pub rustc::DANGEROUS_EXTERN_CRATE,
+    Allow,
+    "Forbid uses of non-whitelisted crates in `extern crate`",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(DangerousExternCrate => [DANGEROUS_EXTERN_CRATE]);
+
+impl EarlyLintPass for DangerousExternCrate {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        fn is_whitelisted(crate_name: &str) -> bool {
+            // Whitelist of allowed crates.
+            crate_name.starts_with("rustc_")
+                || matches!(crate_name, "test" | "self" | "core" | "alloc" | "std" | "proc_macro")
+        }
+
+        if let ast::ItemKind::ExternCrate(original_name, imported_name) = &item.kind {
+            let name = original_name.as_ref().unwrap_or(&imported_name.name).as_str();
+            let externs = &cx.builder.sess().opts.externs;
+            if externs.get(name).is_none() && !is_whitelisted(name) {
+                cx.emit_span_lint(
+                    DANGEROUS_EXTERN_CRATE,
+                    item.span,
+                    DangerousExternCrateDiag { name },
+                );
+            }
+        }
+    }
+}

compiler/rustc_lint/src/lib.rs

@@ -648,6 +648,8 @@ fn register_internals(store: &mut LintStore) {
     store.register_late_mod_pass(|_| Box::new(SpanUseEqCtxt));
     store.register_lints(&SymbolInternStringLiteral::lint_vec());
     store.register_late_mod_pass(|_| Box::new(SymbolInternStringLiteral));
+    store.register_lints(&DangerousExternCrate::lint_vec());
+    store.register_early_pass(|| Box::new(DangerousExternCrate));
     // FIXME(davidtwco): deliberately do not include `UNTRANSLATABLE_DIAGNOSTIC` and
     // `DIAGNOSTIC_OUTSIDE_OF_IMPL` here because `-Wrustc::internal` is provided to every crate and
     // these lints will trigger all of the time - change this once migration to diagnostic structs
@@ -670,6 +672,7 @@ fn register_internals(store: &mut LintStore) {
             LintId::of(BAD_OPT_ACCESS),
             LintId::of(SPAN_USE_EQ_CTXT),
             LintId::of(DIRECT_USE_OF_RUSTC_TYPE_IR),
+            LintId::of(DANGEROUS_EXTERN_CRATE),
         ],
     );
 }

compiler/rustc_lint/src/lints.rs

@@ -1000,6 +1000,13 @@ pub(crate) struct BadOptAccessDiag<'a> {
     pub msg: &'a str,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(lint_dangerous_extern_crate)]
+#[help]
+pub(crate) struct DangerousExternCrateDiag<'a> {
+    pub name: &'a str,
+}
+
 // let_underscore.rs
 #[derive(LintDiagnostic)]
 pub(crate) enum NonBindingLet {

compiler/rustc_log/src/lib.rs

@@ -44,6 +44,8 @@ use tracing_subscriber::fmt::FmtContext;
 use tracing_subscriber::fmt::format::{self, FormatEvent, FormatFields};
 use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::{Layer, Registry};
+// Re-export tracing
+pub use {tracing, tracing_core, tracing_subscriber};
 
 /// The values of all the environment variables that matter for configuring a logger.
 /// Errors are explicitly preserved so that we can share error handling.

compiler/rustc_resolve/src/rustdoc.rs

@@ -2,6 +2,8 @@ use std::mem;
 use std::ops::Range;
 
 use itertools::Itertools;
+/// Re-export the markdown parser used by rustdoc.
+pub use pulldown_cmark;
 use pulldown_cmark::{
     BrokenLink, BrokenLinkCallback, CowStr, Event, LinkType, Options, Parser, Tag,
 };

src/librustdoc/clean/auto_trait.rs

@@ -1,12 +1,12 @@
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_hir as hir;
 use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
 use rustc_middle::bug;
 use rustc_middle::ty::{self, Region, Ty, fold_regions};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{Symbol, kw};
 use rustc_trait_selection::traits::auto_trait::{self, RegionTarget};
-use thin_vec::ThinVec;
 use tracing::{debug, instrument};
 
 use crate::clean::{

src/librustdoc/clean/blanket_impl.rs

@@ -1,11 +1,11 @@
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_hir as hir;
 use rustc_infer::infer::{DefineOpaqueTypes, InferOk, TyCtxtInferExt};
 use rustc_infer::traits;
 use rustc_middle::ty::{self, TypingMode, Upcast};
 use rustc_span::DUMMY_SP;
 use rustc_span::def_id::DefId;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
-use thin_vec::ThinVec;
 use tracing::{debug, instrument, trace};
 
 use crate::clean;

src/librustdoc/clean/cfg/tests.rs

@@ -1,8 +1,8 @@
 use rustc_ast::ast::LitIntType;
 use rustc_ast::{MetaItemInner, MetaItemLit, Path, Safety, StrStyle};
+use rustc_data_structures::thin_vec::thin_vec;
 use rustc_span::symbol::{Ident, kw};
 use rustc_span::{DUMMY_SP, create_default_session_globals_then};
-use thin_vec::thin_vec;
 
 use super::*;
 

src/librustdoc/clean/inline.rs

@@ -4,6 +4,7 @@ use std::iter::once;
 use std::sync::Arc;
 
 use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::thin_vec::{ThinVec, thin_vec};
 use rustc_hir as hir;
 use rustc_hir::Mutability;
 use rustc_hir::def::{DefKind, Res};
@@ -14,7 +15,6 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{Symbol, sym};
-use thin_vec::{ThinVec, thin_vec};
 use tracing::{debug, trace};
 
 use super::{Item, extract_cfg_from_attrs};

src/librustdoc/clean/mod.rs

@@ -37,6 +37,7 @@ use std::mem;
 use rustc_ast::token::{Token, TokenKind};
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet, IndexEntry};
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_errors::codes::*;
 use rustc_errors::{FatalError, struct_span_code_err};
 use rustc_hir::def::{CtorKind, DefKind, Res};
@@ -52,7 +53,6 @@ use rustc_span::ExpnKind;
 use rustc_span::hygiene::{AstPass, MacroKind};
 use rustc_span::symbol::{Ident, Symbol, kw, sym};
 use rustc_trait_selection::traits::wf::object_region_bounds;
-use thin_vec::ThinVec;
 use tracing::{debug, instrument};
 use utils::*;
 use {rustc_ast as ast, rustc_hir as hir};

src/librustdoc/clean/simplify.rs

@@ -12,9 +12,9 @@
 //! bounds by special casing scenarios such as these. Fun!
 
 use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_data_structures::unord::UnordSet;
 use rustc_hir::def_id::DefId;
-use thin_vec::ThinVec;
 
 use crate::clean;
 use crate::clean::{GenericArgs as PP, WherePredicate as WP};

src/librustdoc/clean/types.rs

@@ -10,6 +10,7 @@ use rustc_attr_data_structures::{
     AttributeKind, ConstStability, Deprecation, Stability, StableSince, find_attr,
 };
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::lang_items::LangItem;
@@ -26,7 +27,6 @@ use rustc_session::Session;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{Symbol, kw, sym};
 use rustc_span::{DUMMY_SP, FileName, Loc};
-use thin_vec::ThinVec;
 use tracing::{debug, trace};
 use {rustc_ast as ast, rustc_hir as hir};
 

src/librustdoc/clean/utils.rs

@@ -4,13 +4,13 @@ use std::sync::LazyLock as Lazy;
 use std::{ascii, mem};
 
 use rustc_ast::tokenstream::TokenTree;
+use rustc_data_structures::thin_vec::{ThinVec, thin_vec};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_metadata::rendered_const;
 use rustc_middle::mir;
 use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, TyCtxt, TypeVisitableExt};
 use rustc_span::symbol::{Symbol, kw, sym};
-use thin_vec::{ThinVec, thin_vec};
 use tracing::{debug, warn};
 use {rustc_ast as ast, rustc_hir as hir};
 

src/librustdoc/html/markdown.rs

@@ -36,15 +36,15 @@ use std::str::{self, CharIndices};
 use std::sync::atomic::AtomicUsize;
 use std::sync::{Arc, Weak};
 
-use pulldown_cmark::{
-    BrokenLink, CodeBlockKind, CowStr, Event, LinkType, Options, Parser, Tag, TagEnd, html,
-};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{Diag, DiagMessage};
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::TyCtxt;
 pub(crate) use rustc_resolve::rustdoc::main_body_opts;
 use rustc_resolve::rustdoc::may_be_doc_link;
+use rustc_resolve::rustdoc::pulldown_cmark::{
+    self, BrokenLink, CodeBlockKind, CowStr, Event, LinkType, Options, Parser, Tag, TagEnd, html,
+};
 use rustc_span::edition::Edition;
 use rustc_span::{Span, Symbol};
 use tracing::{debug, trace};

src/librustdoc/html/markdown/footnotes.rs

@@ -4,8 +4,8 @@ use std::fmt::Write as _;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Weak};
 
-use pulldown_cmark::{CowStr, Event, Tag, TagEnd, html};
 use rustc_data_structures::fx::FxIndexMap;
+use rustc_resolve::rustdoc::pulldown_cmark::{CowStr, Event, Tag, TagEnd, html};
 
 use super::SpannedEvent;
 

src/librustdoc/html/render/search_index.rs

@@ -5,12 +5,12 @@ use std::collections::{BTreeMap, VecDeque};
 
 use encode::{bitmap_to_string, write_vlqhex_to_string};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::DefId;
 use rustc_span::sym;
 use rustc_span::symbol::{Symbol, kw};
 use serde::ser::{Serialize, SerializeSeq, SerializeStruct, Serializer};
-use thin_vec::ThinVec;
 use tracing::instrument;
 
 use crate::clean::types::{Function, Generics, ItemId, Type, WherePredicate};

src/librustdoc/json/conversions.rs

@@ -5,14 +5,14 @@
 use rustc_abi::ExternAbi;
 use rustc_ast::ast;
 use rustc_attr_data_structures::{self as attrs, DeprecatedSince};
+use rustc_data_structures::thin_vec::ThinVec;
 use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{HeaderSafety, Safety};
 use rustc_metadata::rendered_const;
 use rustc_middle::{bug, ty};
 use rustc_span::{Pos, kw, sym};
 use rustdoc_json_types::*;
-use thin_vec::ThinVec;
 
 use crate::clean::{self, ItemId};
 use crate::formats::item_type::ItemType;

src/librustdoc/lib.rs

@@ -18,8 +18,6 @@
 #![warn(rustc::internal)]
 // tidy-alphabetical-end
 
-extern crate thin_vec;
-
 // N.B. these need `extern crate` even in 2018 edition
 // because they're loaded implicitly from the sysroot.
 // The reason they're loaded from the sysroot is because
@@ -28,7 +26,6 @@ extern crate thin_vec;
 //
 // Dependencies listed in Cargo.toml do not need `extern crate`.
 
-extern crate pulldown_cmark;
 extern crate rustc_abi;
 extern crate rustc_ast;
 extern crate rustc_ast_pretty;