Restrict sysroot crate imports to those defined in this repo.

It's common to import dependencies from the sysroot via `extern crate`
rather than use an explicit cargo dependency, when it's necessary to use
the same dependency version as used by rustc itself. However, this is
dangerous for crates.io crates, since rustc may not pull in the
dependency on some targets, or may pull in multiple versions. In both
cases, the `extern crate` fails to resolve.

To address this, re-export all such dependencies from the appropriate
`rustc_*` crates, and use this alias from crates which would otherwise
need to use `extern crate`.

clippy_lints/src/doc/broken_link.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint;
-use pulldown_cmark::BrokenLink as PullDownBrokenLink;
 use rustc_lint::LateContext;
+use rustc_resolve::rustdoc::pulldown_cmark::BrokenLink as PullDownBrokenLink;
 use rustc_resolve::rustdoc::{DocFragment, source_span_for_markdown_range};
 use rustc_span::{BytePos, Pos, Span};
 

clippy_lints/src/doc/mod.rs

@@ -4,19 +4,21 @@ use clippy_config::Conf;
 use clippy_utils::attrs::is_doc_hidden;
 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_then};
 use clippy_utils::{is_entrypoint_fn, is_trait_impl_item};
-use pulldown_cmark::Event::{
-    Code, DisplayMath, End, FootnoteReference, HardBreak, Html, InlineHtml, InlineMath, Rule, SoftBreak, Start,
-    TaskListMarker, Text,
-};
-use pulldown_cmark::Tag::{BlockQuote, CodeBlock, FootnoteDefinition, Heading, Item, Link, Paragraph};
-use pulldown_cmark::{BrokenLink, CodeBlockKind, CowStr, Options, TagEnd};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Applicability;
 use rustc_hir::{Attribute, ImplItemKind, ItemKind, Node, Safety, TraitItemKind};
 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
+use rustc_resolve::rustdoc::pulldown_cmark::Event::{
+    Code, DisplayMath, End, FootnoteReference, HardBreak, Html, InlineHtml, InlineMath, Rule, SoftBreak, Start,
+    TaskListMarker, Text,
+};
+use rustc_resolve::rustdoc::pulldown_cmark::Tag::{
+    BlockQuote, CodeBlock, FootnoteDefinition, Heading, Item, Link, Paragraph,
+};
+use rustc_resolve::rustdoc::pulldown_cmark::{BrokenLink, CodeBlockKind, CowStr, Options, TagEnd};
 use rustc_resolve::rustdoc::{
-    DocFragment, add_doc_fragment, attrs_to_doc_fragments, main_body_opts, source_span_for_markdown_range,
-    span_of_fragments,
+    DocFragment, add_doc_fragment, attrs_to_doc_fragments, main_body_opts, pulldown_cmark,
+    source_span_for_markdown_range, span_of_fragments,
 };
 use rustc_session::impl_lint_pass;
 use rustc_span::Span;

clippy_lints/src/lib.rs

@@ -27,9 +27,6 @@
     rustc::internal
 )]
 
-// FIXME: switch to something more ergonomic here, once available.
-// (Currently there is no way to opt into sysroot crates without `extern crate`.)
-extern crate pulldown_cmark;
 extern crate rustc_abi;
 extern crate rustc_arena;
 extern crate rustc_ast;
@@ -53,8 +50,6 @@ extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_target;
 extern crate rustc_trait_selection;
-extern crate smallvec;
-extern crate thin_vec;
 
 #[macro_use]
 extern crate clippy_utils;

clippy_lints/src/methods/ip_constant.rs

@@ -1,10 +1,10 @@
 use clippy_utils::consts::{ConstEvalCtxt, Constant};
 use clippy_utils::diagnostics::span_lint_and_then;
+use rustc_data_structures::smallvec::SmallVec;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, QPath, TyKind};
 use rustc_lint::LateContext;
 use rustc_span::sym;
-use smallvec::SmallVec;
 
 use super::IP_CONSTANT;
 

clippy_lints/src/unnested_or_patterns.rs

@@ -9,6 +9,7 @@ use rustc_ast::PatKind::*;
 use rustc_ast::mut_visit::*;
 use rustc_ast::{self as ast, DUMMY_NODE_ID, Mutability, Pat, PatKind};
 use rustc_ast_pretty::pprust;
+use rustc_data_structures::thin_vec::{ThinVec, thin_vec};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::impl_lint_pass;
@@ -17,7 +18,6 @@ use rustc_span::DUMMY_SP;
 use std::boxed::Box;
 use std::cell::Cell;
 use std::mem;
-use thin_vec::{ThinVec, thin_vec};
 
 declare_clippy_lint! {
     /// ### What it does

clippy_utils/src/lib.rs

@@ -25,7 +25,6 @@
 
 // FIXME: switch to something more ergonomic here, once available.
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
-extern crate indexmap;
 extern crate rustc_abi;
 extern crate rustc_ast;
 extern crate rustc_attr_parsing;
@@ -47,7 +46,6 @@ extern crate rustc_mir_dataflow;
 extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_trait_selection;
-extern crate smallvec;
 
 pub mod ast_utils;
 pub mod attrs;
@@ -90,6 +88,7 @@ use rustc_abi::Integer;
 use rustc_ast::ast::{self, LitKind, RangeLimits};
 use rustc_ast::join_path_syms;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::indexmap;
 use rustc_data_structures::packed::Pu128;
 use rustc_data_structures::unhash::UnindexMap;
 use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk};

clippy_utils/src/msrvs.rs

@@ -2,12 +2,12 @@ use crate::sym;
 use rustc_ast::Attribute;
 use rustc_ast::attr::AttributeExt;
 use rustc_attr_parsing::parse_version;
+use rustc_data_structures::smallvec::SmallVec;
 use rustc_hir::RustcVersion;
 use rustc_lint::LateContext;
 use rustc_session::Session;
 use rustc_span::Symbol;
 use serde::Deserialize;
-use smallvec::SmallVec;
 use std::iter::once;
 use std::sync::atomic::{AtomicBool, Ordering};
 
@@ -192,12 +192,12 @@ fn parse_attrs(sess: &Session, attrs: &[impl AttributeExt]) -> Option<RustcVersi
 
     let msrv_attr = msrv_attrs.next()?;
 
-    if let Some(duplicate) = msrv_attrs.next_back() {
-        sess.dcx()
-            .struct_span_err(duplicate.span(), "`clippy::msrv` is defined multiple times")
-            .with_span_note(msrv_attr.span(), "first definition found here")
-            .emit();
-    }
+        if let Some(duplicate) = msrv_attrs.next_back() {
+            sess.dcx()
+                .struct_span_err(duplicate.span(), "`clippy::msrv` is defined multiple times")
+                .with_span_note(msrv_attr.span(), "first definition found here")
+                .emit();
+        }
 
     let Some(msrv) = msrv_attr.value_str() else {
         sess.dcx().span_err(msrv_attr.span(), "bad clippy attribute");
@@ -205,8 +205,8 @@ fn parse_attrs(sess: &Session, attrs: &[impl AttributeExt]) -> Option<RustcVersi
     };
 
     let Some(version) = parse_version(msrv) else {
-        sess.dcx()
-            .span_err(msrv_attr.span(), format!("`{msrv}` is not a valid Rust version"));
+            sess.dcx()
+                .span_err(msrv_attr.span(), format!("`{msrv}` is not a valid Rust version"));
         return None;
     };