Rollup merge of rust-lang#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

Author: Centril

src/librustc/infer/canonical/query_response.rs

@@ -22,7 +22,7 @@ use crate::traits::{Obligation, ObligationCause, PredicateObligation};
 use crate::ty::fold::TypeFoldable;
 use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, BoundVar, Ty, TyCtxt};
-use crate::util::captures::Captures;
+use rustc_data_structures::captures::Captures;
 use rustc_index::vec::Idx;
 use rustc_index::vec::IndexVec;
 use rustc_span::DUMMY_SP;

src/librustc/infer/outlives/verify.rs

@@ -3,7 +3,7 @@ use crate::infer::{GenericKind, VerifyBound};
 use crate::traits;
 use crate::ty::subst::{InternalSubsts, Subst};
 use crate::ty::{self, Ty, TyCtxt};
-use crate::util::captures::Captures;
+use rustc_data_structures::captures::Captures;
 use rustc_hir::def_id::DefId;
 
 /// The `TypeOutlives` struct has the job of "lowering" a `T: 'a`

src/librustc/lib.rs

@@ -100,7 +100,6 @@ pub mod ty;
 
 pub mod util {
     pub mod bug;
-    pub mod captures;
     pub mod common;
 }
 

src/librustc/middle/cstore.rs

@@ -5,8 +5,8 @@
 use crate::hir::map as hir_map;
 use crate::hir::map::definitions::{DefKey, DefPathTable};
 use crate::session::search_paths::PathKind;
-use crate::session::{CrateDisambiguator, Session};
-use crate::ty::{self, TyCtxt};
+use crate::session::CrateDisambiguator;
+use crate::ty::TyCtxt;
 
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{self, MetadataRef};
@@ -208,7 +208,6 @@ pub trait CrateStore {
     fn crate_is_private_dep_untracked(&self, cnum: CrateNum) -> bool;
     fn crate_disambiguator_untracked(&self, cnum: CrateNum) -> CrateDisambiguator;
     fn crate_hash_untracked(&self, cnum: CrateNum) -> Svh;
-    fn item_generics_cloned_untracked(&self, def: DefId, sess: &Session) -> ty::Generics;
 
     // This is basically a 1-based range of ints, which is a little
     // silly - I may fix that.

src/librustc/traits/project.rs

@@ -17,7 +17,6 @@ use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
 use crate::ty::fold::{TypeFoldable, TypeFolder};
 use crate::ty::subst::{InternalSubsts, Subst};
 use crate::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt};
-use crate::util::common::FN_OUTPUT_NAME;
 use rustc_data_structures::snapshot_map::{Snapshot, SnapshotMap};
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
@@ -1364,7 +1363,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
         projection_ty: ty::ProjectionTy::from_ref_and_name(
             tcx,
             trait_ref,
-            Ident::with_dummy_span(FN_OUTPUT_NAME),
+            Ident::with_dummy_span(rustc_hir::FN_OUTPUT_NAME),
         ),
         ty: ret_type,
     });

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};

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};

src/librustc/util/common.rs

@@ -5,14 +5,9 @@ use rustc_data_structures::sync::Lock;
 use std::fmt::Debug;
 use std::time::{Duration, Instant};
 
-use rustc_span::symbol::{sym, Symbol};
-
 #[cfg(test)]
 mod tests;
 
-// The name of the associated type for `Fn` return types.
-pub const FN_OUTPUT_NAME: Symbol = sym::Output;
-
 pub use errors::ErrorReported;
 
 pub fn to_readable_str(mut val: usize) -> String {

src/librustc_ast_lowering/item.rs

@@ -25,19 +25,16 @@ pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
     pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
 }
 
-impl<'a, 'lowering, 'hir> ItemLowerer<'a, 'lowering, 'hir> {
-    fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
-    where
-        F: FnOnce(&mut Self),
-    {
+impl ItemLowerer<'_, '_, '_> {
+    fn with_trait_impl_ref(&mut self, impl_ref: &Option<TraitRef>, f: impl FnOnce(&mut Self)) {
         let old = self.lctx.is_in_trait_impl;
-        self.lctx.is_in_trait_impl = if let &None = trait_impl_ref { false } else { true };
+        self.lctx.is_in_trait_impl = if let &None = impl_ref { false } else { true };
         f(self);
         self.lctx.is_in_trait_impl = old;
     }
 }
 
-impl<'a, 'lowering, 'hir> Visitor<'a> for ItemLowerer<'a, 'lowering, 'hir> {
+impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
     fn visit_mod(&mut self, m: &'a Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
         let hir_id = self.lctx.lower_node_id(n);