Auto merge of #131628 - matthiaskrgr:rollup-imbojxz, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #128784 (Check ABI target compatibility for function pointers)
 - #130965 (make `Step` doc-comments more clear)
 - #131239 (Don't assume traits used as type are trait objs in 2021 edition)
 - #131277 (Handle `clippy` cases of `rustc::potential_query_instability` lint)
 - #131503 (More clearly document Stdin::read_line)
 - #131567 (Emit an error for unstable attributes that reference already stable features)
 - #131599 (Shallowly match opaque key in storage)
 - #131617 (remove const_cow_is_borrowed feature gate)

Failed merges:

 - #131616 (merge const_ipv4 / const_ipv6 feature gate into 'ip' feature gate)

r? `@ghost`
`@rustbot` modify labels: rollup

11 files changed, 54 insertions, 52 deletions

diff --git a/src/bootstrap/src/core/builder.rs b/src/bootstrap/src/core/builder.rs
index d32830c0a96..9ac0b0a01f7 100644
--- a/src/bootstrap/src/core/builder.rs
+++ b/src/bootstrap/src/core/builder.rs
@@ -72,36 +72,40 @@ impl<'a> Deref for Builder<'a> {
 }
 
 pub trait Step: 'static + Clone + Debug + PartialEq + Eq + Hash {
-    /// `PathBuf` when directories are created or to return a `Compiler` once
-    /// it's been assembled.
+    /// Result type of `Step::run`.
     type Output: Clone;
 
-    /// Whether this step is run by default as part of its respective phase.
-    /// `true` here can still be overwritten by `should_run` calling `default_condition`.
+    /// Whether this step is run by default as part of its respective phase, as defined by the `describe`
+    /// macro in [`Builder::get_step_descriptions`].
+    ///
+    /// Note: Even if set to `true`, it can still be overridden with [`ShouldRun::default_condition`]
+    /// by `Step::should_run`.
     const DEFAULT: bool = false;
 
     /// If true, then this rule should be skipped if --target was specified, but --host was not
     const ONLY_HOSTS: bool = false;
 
-    /// Primary function to execute this rule. Can call `builder.ensure()`
-    /// with other steps to run those.
+    /// Primary function to implement `Step` logic.
+    ///
+    /// This function can be triggered in two ways:
+    ///     1. Directly from [`Builder::execute_cli`].
+    ///     2. Indirectly by being called from other `Step`s using [`Builder::ensure`].
     ///
-    /// This gets called twice during a normal `./x.py` execution: first
-    /// with `dry_run() == true`, and then for real.
+    /// When called with [`Builder::execute_cli`] (as done by `Build::build`), this function executed twice:
+    ///     - First in "dry-run" mode to validate certain things (like cyclic Step invocations,
+    ///         directory creation, etc) super quickly.
+    ///     - Then it's called again to run the actual, very expensive process.
+    ///
+    /// When triggered indirectly from other `Step`s, it may still run twice (as dry-run and real mode)
+    /// depending on the `Step::run` implementation of the caller.
     fn run(self, builder: &Builder<'_>) -> Self::Output;
 
-    /// When bootstrap is passed a set of paths, this controls whether this rule
-    /// will execute. However, it does not get called in a "default" context
-    /// when we are not passed any paths; in that case, `make_run` is called
-    /// directly.
+    /// Determines if this `Step` should be run when given specific paths (e.g., `x build $path`).
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_>;
 
-    /// Builds up a "root" rule, either as a default rule or from a path passed
-    /// to us.
-    ///
-    /// When path is `None`, we are executing in a context where no paths were
-    /// passed. When `./x.py build` is run, for example, this rule could get
-    /// called if it is in the correct list below with a path of `None`.
+    /// Called directly by the bootstrap `Step` handler when not triggered indirectly by other `Step`s using [`Builder::ensure`].
+    /// For example, `./x.py test bootstrap` runs this for `test::Bootstrap`. Similarly, `./x.py test` runs it for every step
+    /// that is listed by the `describe` macro in [`Builder::get_step_descriptions`].
     fn make_run(_run: RunConfig<'_>) {
         // It is reasonable to not have an implementation of make_run for rules
         // who do not want to get called from the root context. This means that
diff --git a/src/tools/clippy/clippy_lints/src/index_refutable_slice.rs b/src/tools/clippy/clippy_lints/src/index_refutable_slice.rs
index 73ebe6aec15..96550c4d1cb 100644
--- a/src/tools/clippy/clippy_lints/src/index_refutable_slice.rs
+++ b/src/tools/clippy/clippy_lints/src/index_refutable_slice.rs
@@ -5,7 +5,7 @@ use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::higher::IfLet;
 use clippy_utils::ty::is_copy;
 use clippy_utils::{is_expn_of, is_lint_allowed, path_to_local};
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_hir::HirId;
@@ -133,7 +133,7 @@ fn lint_slice(cx: &LateContext<'_>, slice: &SliceLintInformation) {
         .index_use
         .iter()
         .map(|(index, _)| *index)
-        .collect::<FxHashSet<_>>();
+        .collect::<FxIndexSet<_>>();
 
     let value_name = |index| format!("{}_{index}", slice.ident.name);
 
diff --git a/src/tools/clippy/clippy_lints/src/lib.rs b/src/tools/clippy/clippy_lints/src/lib.rs
index 012aa689d4b..6ee064a6124 100644
--- a/src/tools/clippy/clippy_lints/src/lib.rs
+++ b/src/tools/clippy/clippy_lints/src/lib.rs
@@ -26,8 +26,6 @@
     unused_qualifications,
     rustc::internal
 )]
-// Disable this rustc lint for now, as it was also done in rustc
-#![allow(rustc::potential_query_instability)]
 
 // FIXME: switch to something more ergonomic here, once available.
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
diff --git a/src/tools/clippy/clippy_lints/src/lifetimes.rs b/src/tools/clippy/clippy_lints/src/lifetimes.rs
index 7c3ef98fd74..ec28671a061 100644
--- a/src/tools/clippy/clippy_lints/src/lifetimes.rs
+++ b/src/tools/clippy/clippy_lints/src/lifetimes.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
 use clippy_utils::trait_ref_of_method;
 use itertools::Itertools;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::Applicability;
 use rustc_hir::FnRetTy::Return;
 use rustc_hir::intravisit::nested_filter::{self as hir_nested_filter, NestedFilter};
@@ -311,7 +311,7 @@ fn could_use_elision<'tcx>(
     Some((elidable_lts, usages))
 }
 
-fn allowed_lts_from(named_generics: &[GenericParam<'_>]) -> FxHashSet<LocalDefId> {
+fn allowed_lts_from(named_generics: &[GenericParam<'_>]) -> FxIndexSet<LocalDefId> {
     named_generics
         .iter()
         .filter_map(|par| {
@@ -497,7 +497,7 @@ struct Usage {
 
 struct LifetimeChecker<'cx, 'tcx, F> {
     cx: &'cx LateContext<'tcx>,
-    map: FxHashMap<LocalDefId, Vec<Usage>>,
+    map: FxIndexMap<LocalDefId, Vec<Usage>>,
     where_predicate_depth: usize,
     generic_args_depth: usize,
     phantom: std::marker::PhantomData<F>,
@@ -619,7 +619,7 @@ fn report_extra_impl_lifetimes<'tcx>(cx: &LateContext<'tcx>, impl_: &'tcx Impl<'
 fn report_elidable_impl_lifetimes<'tcx>(
     cx: &LateContext<'tcx>,
     impl_: &'tcx Impl<'_>,
-    map: &FxHashMap<LocalDefId, Vec<Usage>>,
+    map: &FxIndexMap<LocalDefId, Vec<Usage>>,
 ) {
     let single_usages = map
         .iter()
diff --git a/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs b/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
index 745f070a577..214b8b0f379 100644
--- a/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
+++ b/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
@@ -5,7 +5,7 @@ use clippy_utils::ty::has_iter_method;
 use clippy_utils::visitors::is_local_used;
 use clippy_utils::{SpanlessEq, contains_name, higher, is_integer_const, sugg};
 use rustc_ast::ast;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{Visitor, walk_expr};
@@ -39,7 +39,7 @@ pub(super) fn check<'tcx>(
                 var: canonical_id,
                 indexed_mut: FxHashSet::default(),
                 indexed_indirectly: FxHashMap::default(),
-                indexed_directly: FxHashMap::default(),
+                indexed_directly: FxIndexMap::default(),
                 referenced: FxHashSet::default(),
                 nonindex: false,
                 prefer_mutable: false,
@@ -229,7 +229,7 @@ struct VarVisitor<'a, 'tcx> {
     indexed_indirectly: FxHashMap<Symbol, Option<region::Scope>>,
     /// subset of `indexed` of vars that are indexed directly: `v[i]`
     /// this will not contain cases like `v[calc_index(i)]` or `v[(i + 4) % N]`
-    indexed_directly: FxHashMap<Symbol, (Option<region::Scope>, Ty<'tcx>)>,
+    indexed_directly: FxIndexMap<Symbol, (Option<region::Scope>, Ty<'tcx>)>,
     /// Any names that are used outside an index operation.
     /// Used to detect things like `&mut vec` used together with `vec[i]`
     referenced: FxHashSet<Symbol>,
diff --git a/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs b/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
index 7372f52e1e5..2ce6a8a85a5 100644
--- a/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
@@ -7,6 +7,7 @@ use clippy_utils::ty::{for_each_top_level_late_bound_region, is_copy};
 use clippy_utils::{get_attr, is_lint_allowed};
 use itertools::Itertools;
 use rustc_ast::Mutability;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir::intravisit::{Visitor, walk_expr};
 use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
@@ -475,19 +476,19 @@ impl<'tcx> Visitor<'tcx> for SigDropHelper<'_, 'tcx> {
 
 struct ArmSigDropHelper<'a, 'tcx> {
     sig_drop_checker: SigDropChecker<'a, 'tcx>,
-    found_sig_drop_spans: FxHashSet<Span>,
+    found_sig_drop_spans: FxIndexSet<Span>,
 }
 
 impl<'a, 'tcx> ArmSigDropHelper<'a, 'tcx> {
     fn new(cx: &'a LateContext<'tcx>) -> ArmSigDropHelper<'a, 'tcx> {
         ArmSigDropHelper {
             sig_drop_checker: SigDropChecker::new(cx),
-            found_sig_drop_spans: FxHashSet::<Span>::default(),
+            found_sig_drop_spans: FxIndexSet::<Span>::default(),
         }
     }
 }
 
-fn has_significant_drop_in_arms<'tcx>(cx: &LateContext<'tcx>, arms: &[&'tcx Expr<'_>]) -> FxHashSet<Span> {
+fn has_significant_drop_in_arms<'tcx>(cx: &LateContext<'tcx>, arms: &[&'tcx Expr<'_>]) -> FxIndexSet<Span> {
     let mut helper = ArmSigDropHelper::new(cx);
     for arm in arms {
         helper.visit_expr(arm);
diff --git a/src/tools/clippy/clippy_lints/src/missing_asserts_for_indexing.rs b/src/tools/clippy/clippy_lints/src/missing_asserts_for_indexing.rs
index b40d7eba15e..c56a4014b34 100644
--- a/src/tools/clippy/clippy_lints/src/missing_asserts_for_indexing.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_asserts_for_indexing.rs
@@ -8,7 +8,7 @@ use clippy_utils::visitors::for_each_expr_without_closures;
 use clippy_utils::{eq_expr_value, hash_expr, higher};
 use rustc_ast::{LitKind, RangeLimits};
 use rustc_data_structures::packed::Pu128;
-use rustc_data_structures::unhash::UnhashMap;
+use rustc_data_structures::unhash::UnindexMap;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir::{BinOp, Block, Body, Expr, ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
@@ -226,7 +226,7 @@ fn upper_index_expr(expr: &Expr<'_>) -> Option<usize> {
 }
 
 /// Checks if the expression is an index into a slice and adds it to `indexes`
-fn check_index<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut UnhashMap<u64, Vec<IndexEntry<'hir>>>) {
+fn check_index<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut UnindexMap<u64, Vec<IndexEntry<'hir>>>) {
     if let ExprKind::Index(slice, index_lit, _) = expr.kind
         && cx.typeck_results().expr_ty_adjusted(slice).peel_refs().is_slice()
         && let Some(index) = upper_index_expr(index_lit)
@@ -274,7 +274,7 @@ fn check_index<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut Unh
 }
 
 /// Checks if the expression is an `assert!` expression and adds it to `asserts`
-fn check_assert<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut UnhashMap<u64, Vec<IndexEntry<'hir>>>) {
+fn check_assert<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut UnindexMap<u64, Vec<IndexEntry<'hir>>>) {
     if let Some((comparison, asserted_len, slice)) = assert_len_expr(cx, expr) {
         let hash = hash_expr(cx, slice);
         let indexes = map.entry(hash).or_default();
@@ -311,7 +311,7 @@ fn check_assert<'hir>(cx: &LateContext<'_>, expr: &'hir Expr<'hir>, map: &mut Un
 /// Inspects indexes and reports lints.
 ///
 /// Called at the end of this lint after all indexing and `assert!` expressions have been collected.
-fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>>) {
+fn report_indexes(cx: &LateContext<'_>, map: &UnindexMap<u64, Vec<IndexEntry<'_>>>) {
     for bucket in map.values() {
         for entry in bucket {
             let Some(full_span) = entry
@@ -403,7 +403,7 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
 
 impl LateLintPass<'_> for MissingAssertsForIndexing {
     fn check_body(&mut self, cx: &LateContext<'_>, body: &Body<'_>) {
-        let mut map = UnhashMap::default();
+        let mut map = UnindexMap::default();
 
         for_each_expr_without_closures(body.value, |expr| {
             check_index(cx, expr, &mut map);
diff --git a/src/tools/clippy/clippy_lints/src/module_style.rs b/src/tools/clippy/clippy_lints/src/module_style.rs
index e9c5f64a255..676d608eb31 100644
--- a/src/tools/clippy/clippy_lints/src/module_style.rs
+++ b/src/tools/clippy/clippy_lints/src/module_style.rs
@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use rustc_ast::ast;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_lint::{EarlyContext, EarlyLintPass, Level, LintContext};
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::LOCAL_CRATE;
@@ -87,7 +87,7 @@ impl EarlyLintPass for ModStyle {
 
         // `folder_segments` is all unique folder path segments `path/to/foo.rs` gives
         // `[path, to]` but not foo
-        let mut folder_segments = FxHashSet::default();
+        let mut folder_segments = FxIndexSet::default();
         // `mod_folders` is all the unique folder names that contain a mod.rs file
         let mut mod_folders = FxHashSet::default();
         // `file_map` maps file names to the full path including the file name
@@ -144,7 +144,7 @@ impl EarlyLintPass for ModStyle {
 /// is `mod.rs` we add it's parent folder to `mod_folders`.
 fn process_paths_for_mod_files<'a>(
     path: &'a Path,
-    folder_segments: &mut FxHashSet<&'a OsStr>,
+    folder_segments: &mut FxIndexSet<&'a OsStr>,
     mod_folders: &mut FxHashSet<&'a OsStr>,
 ) {
     let mut comp = path.components().rev().peekable();
diff --git a/src/tools/clippy/clippy_lints/src/needless_pass_by_ref_mut.rs b/src/tools/clippy/clippy_lints/src/needless_pass_by_ref_mut.rs
index c2facb2fcf6..5c631a176c4 100644
--- a/src/tools/clippy/clippy_lints/src/needless_pass_by_ref_mut.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_pass_by_ref_mut.rs
@@ -5,7 +5,7 @@ use clippy_utils::source::snippet;
 use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{inherits_cfg, is_from_proc_macro, is_self};
 use core::ops::ControlFlow;
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{
@@ -101,7 +101,7 @@ fn check_closures<'tcx>(
     ctx: &mut MutablyUsedVariablesCtxt<'tcx>,
     cx: &LateContext<'tcx>,
     checked_closures: &mut FxHashSet<LocalDefId>,
-    closures: FxHashSet<LocalDefId>,
+    closures: FxIndexSet<LocalDefId>,
 ) {
     let hir = cx.tcx.hir();
     for closure in closures {
@@ -196,7 +196,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
                 prev_bind: None,
                 prev_move_to_closure: HirIdSet::default(),
                 aliases: HirIdMap::default(),
-                async_closures: FxHashSet::default(),
+                async_closures: FxIndexSet::default(),
                 tcx: cx.tcx,
             };
             euv::ExprUseVisitor::for_clippy(cx, fn_def_id, &mut ctx)
@@ -207,7 +207,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
 
             // We retrieve all the closures declared in the function because they will not be found
             // by `euv::Delegate`.
-            let mut closures: FxHashSet<LocalDefId> = FxHashSet::default();
+            let mut closures: FxIndexSet<LocalDefId> = FxIndexSet::default();
             for_each_expr(cx, body, |expr| {
                 if let ExprKind::Closure(closure) = expr.kind {
                     closures.insert(closure.def_id);
@@ -307,7 +307,7 @@ struct MutablyUsedVariablesCtxt<'tcx> {
     /// use of a variable.
     prev_move_to_closure: HirIdSet,
     aliases: HirIdMap<HirId>,
-    async_closures: FxHashSet<LocalDefId>,
+    async_closures: FxIndexSet<LocalDefId>,
     tcx: TyCtxt<'tcx>,
 }
 
diff --git a/src/tools/clippy/clippy_lints/src/swap.rs b/src/tools/clippy/clippy_lints/src/swap.rs
index a3145c4647c..6cba560393d 100644
--- a/src/tools/clippy/clippy_lints/src/swap.rs
+++ b/src/tools/clippy/clippy_lints/src/swap.rs
@@ -6,9 +6,9 @@ use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::{can_mut_borrow_both, eq_expr_value, is_in_const_context, std_or_core};
 use itertools::Itertools;
 
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::intravisit::{Visitor, walk_expr};
 
-use crate::FxHashSet;
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Block, Expr, ExprKind, LetStmt, PatKind, QPath, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
@@ -334,7 +334,7 @@ struct IndexBinding<'a, 'tcx> {
 
 impl<'tcx> IndexBinding<'_, 'tcx> {
     fn snippet_index_bindings(&mut self, exprs: &[&'tcx Expr<'tcx>]) -> String {
-        let mut bindings = FxHashSet::default();
+        let mut bindings = FxIndexSet::default();
         for expr in exprs {
             bindings.insert(self.snippet_index_binding(expr));
         }
diff --git a/src/tools/clippy/clippy_lints/src/trait_bounds.rs b/src/tools/clippy/clippy_lints/src/trait_bounds.rs
index 00277593622..3c3973857e7 100644
--- a/src/tools/clippy/clippy_lints/src/trait_bounds.rs
+++ b/src/tools/clippy/clippy_lints/src/trait_bounds.rs
@@ -5,7 +5,7 @@ use clippy_utils::source::{SpanRangeExt, snippet, snippet_with_applicability};
 use clippy_utils::{SpanlessEq, SpanlessHash, is_from_proc_macro};
 use core::hash::{Hash, Hasher};
 use itertools::Itertools;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, IndexEntry};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
@@ -16,7 +16,6 @@ use rustc_hir::{
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
 use rustc_span::{BytePos, Span};
-use std::collections::hash_map::Entry;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -427,7 +426,7 @@ fn rollup_traits(
     bounds: &[GenericBound<'_>],
     msg: &'static str,
 ) -> Vec<(ComparableTraitRef, Span)> {
-    let mut map = FxHashMap::default();
+    let mut map = FxIndexMap::default();
     let mut repeated_res = false;
 
     let only_comparable_trait_refs = |bound: &GenericBound<'_>| {
@@ -442,8 +441,8 @@ fn rollup_traits(
     for bound in bounds.iter().filter_map(only_comparable_trait_refs) {
         let (comparable_bound, span_direct) = bound;
         match map.entry(comparable_bound) {
-            Entry::Occupied(_) => repeated_res = true,
-            Entry::Vacant(e) => {
+            IndexEntry::Occupied(_) => repeated_res = true,
+            IndexEntry::Vacant(e) => {
                 e.insert((span_direct, i));
                 i += 1;
             },