Rollup merge of #67922 - Centril:lowering-cleanup, r=petrochenkov

rustc_ast_lowering: misc cleanup & rustc dep reductions

- The first two commits do some code simplification.
- The next three do some file splitting (getting `lib.rs` below the 3kloc tidy lint).
- The remaining commits reduce the number of `rustc::` imports. This works towards making lowering independent of the `rustc` crate.

r? @oli-obk cc @Zoxc

2 files changed, 3 insertions, 4 deletions

diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 2f51d21d24c..d1e37a4ea11 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -26,8 +26,8 @@ use crate::ty::layout::VariantIdx;
 use crate::ty::subst::{InternalSubsts, Subst, SubstsRef};
 use crate::ty::util::{Discr, IntTypeExt};
 use crate::ty::walk::TypeWalker;
-use crate::util::captures::Captures;
 use arena::SyncDroplessArena;
+use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index aeda2eb1a15..c89d045cebb 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -13,11 +13,10 @@ use crate::ty::layout::VariantIdx;
 use crate::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst, SubstsRef};
 use crate::ty::{self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable};
 use crate::ty::{List, ParamEnv, ParamEnvAnd, TyS};
-use crate::util::captures::Captures;
+use polonius_engine::Atom;
+use rustc_data_structures::captures::Captures;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-
-use polonius_engine::Atom;
 use rustc_index::vec::Idx;
 use rustc_macros::HashStable;
 use rustc_span::symbol::{kw, Symbol};