remove redundant imports

detects redundant imports that can be eliminated.

for #117772 :

In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.

3 files changed, 18 insertions, 47 deletions

diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 5725a759fef..89d10fea729 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1,44 +1,34 @@
 // Decoding metadata from a single crate's metadata
 
-use crate::creader::{CStore, CrateMetadataRef};
+use crate::creader::CStore;
 use crate::rmeta::table::IsDefault;
 use crate::rmeta::*;
 
 use rustc_ast as ast;
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::owned_slice::OwnedSlice;
-use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{AppendOnlyVec, AtomicBool, Lock, Lrc, OnceLock};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};
-use rustc_hir::def::{CtorKind, DefKind, DocLinkResMap, Res};
-use rustc_hir::def_id::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX, LOCAL_CRATE};
-use rustc_hir::definitions::{DefKey, DefPath, DefPathData, DefPathHash};
+use rustc_hir::def::Res;
+use rustc_hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::definitions::{DefPath, DefPathData};
 use rustc_hir::diagnostic_items::DiagnosticItems;
-use rustc_index::{Idx, IndexVec};
-use rustc_middle::metadata::ModChild;
-use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
-use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
+use rustc_index::Idx;
 use rustc_middle::middle::lib_features::LibFeatures;
 use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
 use rustc_middle::ty::codec::TyDecoder;
-use rustc_middle::ty::fast_reject::SimplifiedType;
-use rustc_middle::ty::{self, ParameterizedOverTcx, Ty, TyCtxt, Visibility};
+use rustc_middle::ty::Visibility;
 use rustc_serialize::opaque::MemDecoder;
 use rustc_serialize::{Decodable, Decoder};
-use rustc_session::cstore::{
-    CrateSource, ExternCrate, ForeignModule, LinkagePreference, NativeLib,
-};
+use rustc_session::cstore::{CrateSource, ExternCrate};
 use rustc_session::Session;
-use rustc_span::hygiene::ExpnIndex;
-use rustc_span::symbol::{kw, Ident, Symbol};
-use rustc_span::{self, BytePos, ExpnId, Pos, Span, SpanData, SyntaxContext, DUMMY_SP};
+use rustc_span::symbol::kw;
+use rustc_span::{BytePos, Pos, SpanData, SyntaxContext, DUMMY_SP};
 
 use proc_macro::bridge::client::ProcMacro;
 use std::iter::TrustedLen;
-use std::num::NonZeroUsize;
 use std::path::Path;
 use std::sync::atomic::Ordering;
 use std::{io, iter, mem};
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index ffb2375a734..ab18b6412b8 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1,51 +1,37 @@
 use crate::errors::{FailCreateFileEncoder, FailWriteFile};
-use crate::rmeta::def_path_hash_map::DefPathHashMapRef;
-use crate::rmeta::table::TableBuilder;
 use crate::rmeta::*;
 
-use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::Attribute;
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::memmap::{Mmap, MmapMut};
 use rustc_data_structures::stable_hasher::{Hash128, HashStable, StableHasher};
 use rustc_data_structures::sync::{join, par_for_each_in, Lrc};
 use rustc_data_structures::temp_dir::MaybeTempDir;
 use rustc_hir as hir;
-use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{
-    CrateNum, DefId, DefIndex, LocalDefId, LocalDefIdSet, CRATE_DEF_ID, CRATE_DEF_INDEX,
-    LOCAL_CRATE,
-};
+use rustc_hir::def_id::{LocalDefId, LocalDefIdSet, CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::DefPathData;
-use rustc_hir::lang_items::LangItem;
 use rustc_hir_pretty::id_to_string;
-use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::dependency_format::Linkage;
-use rustc_middle::middle::exported_symbols::{
-    metadata_symbol_name, ExportedSymbol, SymbolExportInfo,
-};
-use rustc_middle::middle::lib_features::FeatureStability;
+use rustc_middle::middle::exported_symbols::metadata_symbol_name;
 use rustc_middle::mir::interpret;
 use rustc_middle::query::LocalCrate;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::specialization_graph;
 use rustc_middle::ty::codec::TyEncoder;
-use rustc_middle::ty::fast_reject::{self, SimplifiedType, TreatParams};
-use rustc_middle::ty::{self, AssocItemContainer, SymbolName, Ty, TyCtxt};
+use rustc_middle::ty::fast_reject::{self, TreatParams};
+use rustc_middle::ty::{AssocItemContainer, SymbolName};
 use rustc_middle::util::common::to_readable_str;
 use rustc_serialize::{opaque, Decodable, Decoder, Encodable, Encoder};
 use rustc_session::config::{CrateType, OptLevel};
-use rustc_session::cstore::{ForeignModule, LinkagePreference, NativeLib};
-use rustc_span::hygiene::{ExpnIndex, HygieneEncodeContext, MacroKind};
-use rustc_span::symbol::{sym, Symbol};
-use rustc_span::{self, ExternalSource, FileName, SourceFile, Span, SpanData, SyntaxContext};
+use rustc_span::hygiene::HygieneEncodeContext;
+use rustc_span::symbol::sym;
+use rustc_span::{ExternalSource, FileName, SourceFile, SpanData, SyntaxContext};
 use std::borrow::Borrow;
 use std::collections::hash_map::Entry;
 use std::fs::File;
 use std::hash::Hash;
 use std::io::{Read, Seek, Write};
-use std::num::NonZeroUsize;
 use std::path::{Path, PathBuf};
 
 pub(super) struct EncodeContext<'a, 'tcx> {
diff --git a/compiler/rustc_metadata/src/rmeta/table.rs b/compiler/rustc_metadata/src/rmeta/table.rs
index 7cdbcd9193c..3fc6d9db331 100644
--- a/compiler/rustc_metadata/src/rmeta/table.rs
+++ b/compiler/rustc_metadata/src/rmeta/table.rs
@@ -1,13 +1,8 @@
 use crate::rmeta::*;
 
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_hir::def::{CtorKind, CtorOf};
+use rustc_hir::def::CtorOf;
 use rustc_index::Idx;
-use rustc_middle::ty::{ParameterizedOverTcx, UnusedGenericParams};
-use rustc_serialize::opaque::FileEncoder;
-use rustc_span::hygiene::MacroKind;
-use std::marker::PhantomData;
-use std::num::NonZeroUsize;
 
 pub(super) trait IsDefault: Default {
     fn is_default(&self) -> bool;