Auto merge of #100869 - nnethercote:replace-ThinVec, r=spastorino

Replace `rustc_data_structures::thin_vec::ThinVec` with `thin_vec::ThinVec`

`rustc_data_structures::thin_vec::ThinVec` looks like this:
```
pub struct ThinVec<T>(Option<Box<Vec<T>>>);
```
It's just a zero word if the vector is empty, but requires two
allocations if it is non-empty. So it's only usable in cases where the
vector is empty most of the time.

This commit removes it in favour of `thin_vec::ThinVec`, which is also
word-sized, but stores the length and capacity in the same allocation as
the elements. It's good in a wider variety of situation, e.g. in enum
variants where the vector is usually/always non-empty.

The commit also:
- Sorts some `Cargo.toml` dependency lists, to make additions easier.
- Sorts some `use` item lists, to make additions easier.
- Changes `clean_trait_ref_with_bindings` to take a
  `ThinVec<TypeBinding>` rather than a `&[TypeBinding]`, because this
  avoid some unnecessary allocations.

r? `@spastorino`

3 files changed, 6 insertions, 6 deletions

diff --git a/compiler/rustc_query_system/Cargo.toml b/compiler/rustc_query_system/Cargo.toml
index b7787aeb8f7..bafc6b0a082 100644
--- a/compiler/rustc_query_system/Cargo.toml
+++ b/compiler/rustc_query_system/Cargo.toml
@@ -7,9 +7,8 @@ edition = "2021"
 doctest = false
 
 [dependencies]
+parking_lot = "0.11"
 rustc_arena = { path = "../rustc_arena" }
-tracing = "0.1"
-rustc-rayon-core = { version = "0.4.0", optional = true }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -17,12 +16,14 @@ rustc_feature = { path = "../rustc_feature" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
+rustc-rayon-core = { version = "0.4.0", optional = true }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-parking_lot = "0.11"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
+thin-vec = "0.2.8"
+tracing = "0.1"
 
 [features]
 rustc_use_parallel_compiler = ["rustc-rayon-core"]
diff --git a/compiler/rustc_query_system/src/query/mod.rs b/compiler/rustc_query_system/src/query/mod.rs
index c6197b9fedb..0b07bb64b6a 100644
--- a/compiler/rustc_query_system/src/query/mod.rs
+++ b/compiler/rustc_query_system/src/query/mod.rs
@@ -15,12 +15,11 @@ mod config;
 pub use self::config::{QueryConfig, QueryDescription, QueryVTable};
 
 use crate::dep_graph::{DepContext, DepNodeIndex, HasDepContext, SerializedDepNodeIndex};
-
 use rustc_data_structures::sync::Lock;
-use rustc_data_structures::thin_vec::ThinVec;
 use rustc_errors::Diagnostic;
 use rustc_hir::def::DefKind;
 use rustc_span::Span;
+use thin_vec::ThinVec;
 
 /// Description of a frame in the query stack.
 ///
diff --git a/compiler/rustc_query_system/src/query/plumbing.rs b/compiler/rustc_query_system/src/query/plumbing.rs
index e97411b777b..7bbc22e8293 100644
--- a/compiler/rustc_query_system/src/query/plumbing.rs
+++ b/compiler/rustc_query_system/src/query/plumbing.rs
@@ -14,7 +14,6 @@ use rustc_data_structures::profiling::TimingGuard;
 #[cfg(parallel_compiler)]
 use rustc_data_structures::sharded::Sharded;
 use rustc_data_structures::sync::Lock;
-use rustc_data_structures::thin_vec::ThinVec;
 use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed, FatalError};
 use rustc_session::Session;
 use rustc_span::{Span, DUMMY_SP};
@@ -24,6 +23,7 @@ use std::fmt::Debug;
 use std::hash::Hash;
 use std::mem;
 use std::ptr;
+use thin_vec::ThinVec;
 
 pub struct QueryState<K> {
     #[cfg(parallel_compiler)]