Change singleton returned type to a reference

Change singleton returned type to a reference

We do not need a raw pointer for this singleton,
nor we need having it on the heap through a
smart pointer.

gcc/rust/ChangeLog:

	* ast/rust-ast.h: Change dereference from a pointer to a reference
	accessor.
	* ast/rust-expr.h: Likewise.
	* ast/rust-item.h: Likewise.
	* ast/rust-macro.h: Likewise.
	* ast/rust-path.h: Likewise.
	* ast/rust-pattern.h: Likewise.
	* ast/rust-type.h: Likewise.
	* backend/rust-compile-base.cc (HIRCompileBase::resolve_method_address):
	Likewise.
	* backend/rust-compile-context.h: Likewise.
	* backend/rust-compile-expr.cc (CompileExpr::visit): Likewise.
	(CompileExpr::generate_closure_function): Likewise.
	* backend/rust-compile-extern.h: Likewise.
	* backend/rust-compile-implitem.cc (CompileTraitItem::visit): Likewise.
	* backend/rust-compile-intrinsic.cc (Intrinsics::compile): Likewise.
	* backend/rust-compile-item.cc (CompileItem::visit): Likewise.
	* backend/rust-compile-resolve-path.cc (ResolvePathRef::resolve):
	Likewise.
	(HIRCompileBase::query_compile): Likewise.
	* backend/rust-compile-type.cc (TyTyResolveCompile::visit): Likewise.
	(TyTyResolveCompile::create_dyn_obj_record): Likewise.
	* backend/rust-compile.cc (HIRCompileBase::coerce_to_dyn_object):
	Likewise.
	* backend/rust-mangle-v0.cc (v0_path): Likewise.
	(v0_mangle_item): Likewise.
	* checks/errors/borrowck/rust-borrow-checker.cc (BorrowChecker::go):
	Likewise.
	* checks/errors/privacy/rust-privacy-check.cc (Resolver::resolve):
	Likewise.
	* checks/errors/rust-const-checker.cc (ConstChecker::ConstChecker):
	Likewise.
	* checks/errors/rust-unsafe-checker.cc (UnsafeChecker::UnsafeChecker):
	Likewise.
	* checks/lints/rust-lint-marklive-base.h: Likewise.
	* checks/lints/rust-lint-marklive.cc (MarkLive::go): Likewise.
	(MarkLive::visit): Likewise.
	(MarkLive::visit_path_segment): Likewise.
	* checks/lints/rust-lint-marklive.h: Likewise.
	* checks/lints/rust-lint-scan-deadcode.h: Likewise.
	* expand/rust-macro-expand.cc (MacroExpander::expand_invoc): Likewise.
	* expand/rust-macro-expand.h (struct MacroExpander): Change mapping
	from pointer to a reference.
	* expand/rust-proc-macro.cc (BangProcMacro::BangProcMacro): Replace
	pointer accessor with reference accessor.
	(AttributeProcMacro::AttributeProcMacro): Likewise.
	(CustomDeriveProcMacro::CustomDeriveProcMacro): Likewise.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::lower_lifetime):
	Likewise.
	(ASTLoweringBase::lower_loop_label): Likewise.
	(ASTLoweringBase::lower_path_expr_seg): Likewise.
	(ASTLoweringBase::lower_self): Likewise.
	(ASTLoweringBase::handle_lang_item_attribute): Likewise.
	(ASTLoweringBase::lower_extern_block): Likewise.
	(ASTLoweringBase::lower_macro_definition): Likewise.
	* hir/rust-ast-lower-base.h: Likewise.
	* hir/rust-ast-lower-block.h: Likewise.
	* hir/rust-ast-lower-enumitem.h: Likewise.
	* hir/rust-ast-lower-expr.cc (ASTLoweringExpr::translate): Likewise.
	(ASTLoweringExpr::visit): Likewise.
	* hir/rust-ast-lower-extern.h: Likewise.
	* hir/rust-ast-lower-implitem.cc (ASTLowerImplItem::translate):
	Likewise.
	(ASTLowerImplItem::visit): Likewise.
	(ASTLowerTraitItem::translate): Likewise.
	(ASTLowerTraitItem::visit): Likewise.
	* hir/rust-ast-lower-item.cc (ASTLoweringItem::translate): Likewise.
	(ASTLoweringItem::visit): Likewise.
	(ASTLoweringSimplePath::lower): Likewise.
	* hir/rust-ast-lower-pattern.cc (ASTLoweringPattern::translate):
	Likewise.
	(ASTLoweringPattern::visit): Likewise.
	* hir/rust-ast-lower-stmt.cc (ASTLoweringStmt::translate): Likewise.
	(ASTLoweringStmt::visit): Likewise.
	* hir/rust-ast-lower-struct-field-expr.h: Likewise.
	* hir/rust-ast-lower-type.cc (ASTLowerTypePath::visit): Likewise.
	(ASTLowerQualifiedPathInType::visit): Likewise.
	(ASTLoweringType::translate): Likewise.
	(ASTLoweringType::visit): Likewise.
	(ASTLowerGenericParam::translate): Likewise.
	(ASTLowerGenericParam::visit): Likewise.
	(ASTLoweringTypeBounds::translate): Likewise.
	(ASTLoweringTypeBounds::visit): Likewise.
	(ASTLowerWhereClauseItem::translate): Likewise.
	(ASTLowerWhereClauseItem::visit): Likewise.
	* hir/rust-ast-lower.cc (ASTLowering::go): Likewise.
	(ASTLoweringBlock::visit): Likewise.
	(ASTLoweringIfBlock::visit): Likewise.
	(ASTLoweringIfLetBlock::visit): Likewise.
	(ASTLowerStructExprField::visit): Likewise.
	(ASTLoweringExprWithBlock::visit): Likewise.
	(ASTLowerPathInExpression::visit): Likewise.
	(ASTLoweringBase::lower_qual_path_type): Likewise.
	(ASTLowerQualPathInExpression::visit): Likewise.
	* metadata/rust-export-metadata.cc (ExportContext::emit_trait):
	Likewise.
	(ExportContext::emit_function): Likewise.
	(ExportContext::emit_macro): Likewise.
	(PublicInterface::PublicInterface): Likewise.
	(PublicInterface::expected_metadata_filename): Likewise.
	* metadata/rust-export-metadata.h: Likewise.
	* resolve/rust-ast-resolve-base.h: Likewise.
	* resolve/rust-ast-resolve-implitem.h: Likewise.
	* resolve/rust-ast-resolve-item.cc (ResolveTraitItems::visit):
	Likewise.
	(ResolveItem::visit): Likewise.
	(ResolveExternItem::visit): Likewise.
	* resolve/rust-ast-resolve-path.cc (ResolvePath::resolve_path):
	Likewise.
	* resolve/rust-ast-resolve-stmt.h: Likewise.
	* resolve/rust-ast-resolve-toplevel.h: Likewise.
	* resolve/rust-ast-resolve-type.cc (ResolveRelativeTypePath::go):
	Likewise.
	(ResolveTypeToCanonicalPath::visit): Likewise.
	* resolve/rust-ast-resolve-type.h: Likewise.
	* resolve/rust-ast-resolve.cc (NameResolution::NameResolution):
	Likewise.
	(NameResolution::go): Likewise.
	* resolve/rust-ast-resolve.h: Likewise.
	* resolve/rust-early-name-resolver-2.0.cc (Early::visit_attributes):
	Likewise.
	* resolve/rust-early-name-resolver.cc (EarlyNameResolver::EarlyNameResolver):
	Likewise.
	* resolve/rust-late-name-resolver-2.0.cc (next_node_id): Likewise.
	(next_hir_id): Likewise.
	* resolve/rust-name-resolution-context.cc (NameResolutionContext::NameResolutionContext):
	Likewise.
	* resolve/rust-name-resolver.cc (Resolver::Resolver): Likewise.
	(Resolver::generate_builtins): Likewise.
	(Resolver::setup_builtin): Likewise.
	* resolve/rust-name-resolver.h: Likewise.
	* resolve/rust-toplevel-name-resolver-2.0.cc (TopLevel::visit):
	Likewise.
	(TopLevel::handle_use_glob): Likewise.
	* rust-session-manager.cc (Session::get_instance): Likewise.
	(Session::handle_input_files): Likewise.
	(Session::handle_crate_name): Likewise.
	(Session::compile_crate): Likewise.
	(Session::load_extern_crate): Likewise.
	* rust-session-manager.h: Likewise.
	* typecheck/rust-autoderef.cc (Adjuster::try_unsize_type): Likewise.
	* typecheck/rust-coercion.cc (TypeCoercionRules::do_coercion):
	Likewise.
	(TypeCoercionRules::coerce_unsafe_ptr): Likewise.
	(TypeCoercionRules::coerce_borrowed_pointer): Likewise.
	(TypeCoercionRules::coerce_unsized): Likewise.
	* typecheck/rust-coercion.h: Likewise.
	* typecheck/rust-hir-dot-operator.cc (MethodResolver::select):
	Likewise.
	* typecheck/rust-hir-inherent-impl-overlap.h: Likewise.
	* typecheck/rust-hir-path-probe.cc (PathProbeType::process_enum_item_for_candiates):
	Likewise.
	(PathProbeType::process_impl_items_for_candidates): Likewise.
	(PathProbeImplTrait::process_trait_impl_items_for_candidates):
	Likewise.
	* typecheck/rust-hir-trait-resolve.cc (TraitResolver::resolve_path_to_trait):
	Likewise.
	(TraitItemReference::get_parent_trait_mappings): Likewise.
	* typecheck/rust-hir-type-check-base.cc (TypeCheckBase::resolve_literal):
	Likewise.
	(TypeCheckBase::get_marker_predicate): Likewise.
	* typecheck/rust-hir-type-check-base.h: Likewise.
	* typecheck/rust-hir-type-check-enumitem.cc (TypeCheckEnumItem::visit):
	Likewise.
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit):
	Likewise.
	(TypeCheckExpr::resolve_operator_overload): Likewise.
	(TypeCheckExpr::resolve_fn_trait_call): Likewise.
	* typecheck/rust-hir-type-check-implitem.cc (TypeCheckTopLevelExternItem::visit):
	Likewise.
	(TypeCheckImplItem::visit): Likewise.
	* typecheck/rust-hir-type-check-item.cc (TypeCheckItem::visit):
	Likewise.
	* typecheck/rust-hir-type-check-path.cc (TypeCheckExpr::resolve_root_path):
	Likewise.
	(TypeCheckExpr::resolve_segments): Likewise.
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::emit_pattern_size_error):
	Likewise.
	(ClosureParamInfer::Resolve): Likewise.
	* typecheck/rust-hir-type-check-struct.cc (TypeCheckStructExpr::resolve):
	Likewise.
	* typecheck/rust-hir-type-check-type.cc (TypeCheckType::visit): Likewise.
	(TypeCheckType::resolve_root_path): Likewise.
	(TypeResolveGenericParam::visit): Likewise.
	(ResolveWhereClauseItem::visit): Likewise.
	* typecheck/rust-hir-type-check.cc (TraitItemReference::get_type_from_fn):
	Likewise.
	* typecheck/rust-type-util.cc (query_type): Likewise.
	* typecheck/rust-typecheck-context.cc (TypeCheckContext::compute_inference_variables):
	Likewise.
	* typecheck/rust-tyty-bounds.cc (TypeBoundsProbe::scan): Likewise.
	(TypeBoundsProbe::assemble_builtin_candidate): Likewise.
	(TypeCheckBase::get_predicate_from_bound): Likewise.
	* typecheck/rust-tyty-call.cc (TypeCheckCallExpr::visit): Likewise.
	(TypeCheckMethodCallExpr::check): Likewise.
	* typecheck/rust-tyty-call.h: Likewise.
	* typecheck/rust-tyty-cmp.h: Likewise.
	* typecheck/rust-tyty-subst.cc (SubstitutionParamMapping::override_context):
	Likewise.
	(SubstitutionRef::monomorphize): Likewise.
	* typecheck/rust-tyty-util.cc (TyVar::get_implicit_infer_var):
	Likewise.
	(TyVar::monomorphized_clone): Likewise.
	(TyWithLocation::TyWithLocation): Likewise.
	* typecheck/rust-tyty.cc (BaseType::satisfies_bound): Likewise.
	(InferType::clone): Likewise.
	(ADTType::handle_substitions): Likewise.
	(TupleType::handle_substitions): Likewise.
	(FnType::handle_substitions): Likewise.
	(ClosureType::setup_fn_once_output): Likewise.
	(ArrayType::handle_substitions): Likewise.
	(SliceType::handle_substitions): Likewise.
	(ReferenceType::handle_substitions): Likewise.
	(PointerType::handle_substitions): Likewise.
	(ParamType::handle_substitions): Likewise.
	* typecheck/rust-tyty.h: Likewise.
	* typecheck/rust-unify.cc (UnifyRules::UnifyRules): Likewise.
	(UnifyRules::commit): Likewise.
	* util/rust-hir-map.cc: Change getter return type to a reference.
	* util/rust-hir-map.h: Update function's prototype.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>