Auto merge of rust-lang#124831 - nnethercote:rustc_data_structures-cleanups, r=michaelwoerister

`rustc_data_structures` cleanups

Some improvements I found while looking through this code.

r? `@michaelwoerister`

Author: bors

compiler/rustc_borrowck/src/type_check/liveness/local_use_map.rs

@@ -1,4 +1,3 @@
-use rustc_data_structures::vec_linked_list as vll;
 use rustc_index::IndexVec;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::{Body, Local, Location};
@@ -37,9 +36,12 @@ pub(crate) struct LocalUseMap {
     /// we add for each local variable.
     first_drop_at: IndexVec<Local, Option<AppearanceIndex>>,
 
-    appearances: IndexVec<AppearanceIndex, Appearance>,
+    appearances: Appearances,
 }
 
+// The `Appearance::next` field effectively embeds a linked list within `Appearances`.
+type Appearances = IndexVec<AppearanceIndex, Appearance>;
+
 struct Appearance {
     point_index: PointIndex,
     next: Option<AppearanceIndex>,
@@ -49,14 +51,34 @@ rustc_index::newtype_index! {
     pub struct AppearanceIndex {}
 }
 
-impl vll::LinkElem for Appearance {
-    type LinkIndex = AppearanceIndex;
+fn appearances_iter(
+    first: Option<AppearanceIndex>,
+    appearances: &Appearances,
+) -> impl Iterator<Item = AppearanceIndex> + '_ {
+    AppearancesIter { appearances, current: first }
+}
+
+// Iterates over `Appearances` by following `next` fields.
+struct AppearancesIter<'a> {
+    appearances: &'a Appearances,
+    current: Option<AppearanceIndex>,
+}
 
-    fn next(elem: &Self) -> Option<AppearanceIndex> {
-        elem.next
+impl<'a> Iterator for AppearancesIter<'a> {
+    type Item = AppearanceIndex;
+
+    fn next(&mut self) -> Option<AppearanceIndex> {
+        if let Some(c) = self.current {
+            self.current = self.appearances[c].next;
+            Some(c)
+        } else {
+            None
+        }
     }
 }
 
+//-----------------------------------------------------------------------------
+
 impl LocalUseMap {
     pub(crate) fn build(
         live_locals: &[Local],
@@ -86,17 +108,17 @@ impl LocalUseMap {
     }
 
     pub(crate) fn defs(&self, local: Local) -> impl Iterator<Item = PointIndex> + '_ {
-        vll::iter(self.first_def_at[local], &self.appearances)
+        appearances_iter(self.first_def_at[local], &self.appearances)
             .map(move |aa| self.appearances[aa].point_index)
     }
 
     pub(crate) fn uses(&self, local: Local) -> impl Iterator<Item = PointIndex> + '_ {
-        vll::iter(self.first_use_at[local], &self.appearances)
+        appearances_iter(self.first_use_at[local], &self.appearances)
             .map(move |aa| self.appearances[aa].point_index)
     }
 
     pub(crate) fn drops(&self, local: Local) -> impl Iterator<Item = PointIndex> + '_ {
-        vll::iter(self.first_drop_at[local], &self.appearances)
+        appearances_iter(self.first_drop_at[local], &self.appearances)
             .map(move |aa| self.appearances[aa].point_index)
     }
 }
@@ -146,7 +168,7 @@ impl LocalUseMapBuild<'_> {
     fn insert(
         elements: &DenseLocationMap,
         first_appearance: &mut Option<AppearanceIndex>,
-        appearances: &mut IndexVec<AppearanceIndex, Appearance>,
+        appearances: &mut Appearances,
         location: Location,
     ) {
         let point_index = elements.point_from_location(location);

compiler/rustc_data_structures/src/fingerprint.rs

@@ -1,3 +1,4 @@
+use crate::stable_hasher::impl_stable_traits_for_trivial_type;
 use crate::stable_hasher::{Hash64, StableHasher, StableHasherResult};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::hash::{Hash, Hasher};

compiler/rustc_data_structures/src/flock/windows.rs

@@ -2,6 +2,7 @@ use std::fs::{File, OpenOptions};
 use std::io;
 use std::os::windows::prelude::*;
 use std::path::Path;
+use tracing::debug;
 
 use windows::{
     Win32::Foundation::{ERROR_INVALID_FUNCTION, HANDLE},

compiler/rustc_data_structures/src/graph/implementation/mod.rs

@@ -22,6 +22,7 @@
 
 use rustc_index::bit_set::BitSet;
 use std::fmt::Debug;
+use tracing::debug;
 
 #[cfg(test)]
 mod tests;

compiler/rustc_data_structures/src/graph/implementation/tests.rs

@@ -1,4 +1,5 @@
 use crate::graph::implementation::*;
+use tracing::debug;
 
 type TestGraph = Graph<&'static str, &'static str>;
 

compiler/rustc_data_structures/src/graph/scc/mod.rs

@@ -10,6 +10,7 @@ use crate::graph::vec_graph::VecGraph;
 use crate::graph::{DirectedGraph, NumEdges, Successors};
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use std::ops::Range;
+use tracing::{debug, instrument};
 
 #[cfg(test)]
 mod tests;

compiler/rustc_data_structures/src/lib.rs

@@ -42,66 +42,59 @@
 #![feature(unwrap_infallible)]
 // tidy-alphabetical-end
 
-#[macro_use]
-extern crate tracing;
-
-use std::fmt;
-
+pub use atomic_ref::AtomicRef;
+pub use ena::snapshot_vec;
+pub use ena::undo_log;
+pub use ena::unify;
 pub use rustc_index::static_assert_size;
 
-/// This calls the passed function while ensuring it won't be inlined into the caller.
-#[inline(never)]
-#[cold]
-pub fn outline<F: FnOnce() -> R, R>(f: F) -> R {
-    f()
-}
+use std::fmt;
 
+pub mod aligned;
 pub mod base_n;
 pub mod binary_search_util;
 pub mod captures;
+pub mod fingerprint;
 pub mod flat_map_in_place;
 pub mod flock;
+pub mod frozen;
 pub mod fx;
 pub mod graph;
 pub mod intern;
 pub mod jobserver;
-pub mod macros;
+pub mod marker;
+pub mod memmap;
 pub mod obligation_forest;
+pub mod owned_slice;
+pub mod packed;
+pub mod profiling;
+pub mod sharded;
 pub mod sip128;
 pub mod small_c_str;
 pub mod snapshot_map;
-pub mod svh;
-pub use ena::snapshot_vec;
-pub mod memmap;
 pub mod sorted_map;
-#[macro_use]
+pub mod sso;
 pub mod stable_hasher;
-mod atomic_ref;
-pub mod fingerprint;
-pub mod marker;
-pub mod profiling;
-pub mod sharded;
 pub mod stack;
-pub mod sync;
-pub mod tiny_list;
-pub mod transitive_relation;
-pub mod vec_linked_list;
-pub mod work_queue;
-pub use atomic_ref::AtomicRef;
-pub mod aligned;
-pub mod frozen;
-mod hashes;
-pub mod owned_slice;
-pub mod packed;
-pub mod sso;
 pub mod steal;
+pub mod svh;
+pub mod sync;
 pub mod tagged_ptr;
 pub mod temp_dir;
+pub mod transitive_relation;
 pub mod unhash;
 pub mod unord;
+pub mod work_queue;
 
-pub use ena::undo_log;
-pub use ena::unify;
+mod atomic_ref;
+mod hashes;
+
+/// This calls the passed function while ensuring it won't be inlined into the caller.
+#[inline(never)]
+#[cold]
+pub fn outline<F: FnOnce() -> R, R>(f: F) -> R {
+    f()
+}
 
 /// Returns a structure that calls `f` when dropped.
 pub fn defer<F: FnOnce()>(f: F) -> OnDrop<F> {

compiler/rustc_data_structures/src/macros.rs

@@ -70,12 +70,12 @@
 //! aren't needed anymore.
 
 use crate::fx::{FxHashMap, FxHashSet};
-
 use std::cell::Cell;
 use std::collections::hash_map::Entry;
 use std::fmt::Debug;
 use std::hash;
 use std::marker::PhantomData;
+use tracing::debug;
 
 mod graphviz;
 

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -3,8 +3,10 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::cmp::Ordering;
 use std::fmt;
 
-#[repr(packed(8))]
+/// A packed 128-bit integer. Useful for reducing the size of structures in
+/// some cases.
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(packed(8))]
 pub struct Pu128(pub u128);
 
 impl Pu128 {