gccrs: ast: Change Identifier definition

Change Identifier type definition from a simple typedef to a whole class
with it's own node id.

gcc/rust/ChangeLog:

	* ast/rust-ast-collector.cc (TokenCollector::visit): Change with
	call to getter.
	* ast/rust-ast.cc (Module::as_string): Likewise.
	(StaticItem::as_string): Likewise.
	(TupleStruct::as_string): Likewise.
	(Method::as_string): Likewise.
	(StructStruct::as_string): Likewise.
	(UseTreeRebind::as_string): Likewise.
	(Enum::as_string): Likewise.
	(Trait::as_string): Likewise.
	(Union::as_string): Likewise.
	(Function::as_string): Likewise.
	(TypeAlias::as_string): Likewise.
	(MacroRulesDefinition::as_string): Likewise.
	(FieldAccessExpr::as_string): Likewise.
	(MacroMatchFragment::as_string): Likewise.
	(TypeParam::as_string): Likewise.
	(StructExprFieldIdentifierValue::as_string): Likewise.
	(EnumItem::as_string): Likewise.
	(StructField::as_string): Likewise.
	(ExternalTypeItem::as_string): Likewise.
	(ExternalStaticItem::as_string): Likewise.
	(ExternalFunctionItem::as_string): Likewise.
	(TraitFunctionDecl::as_string): Likewise.
	(TraitMethodDecl::as_string): Likewise.
	(TraitItemConst::as_string): Likewise.
	(TraitItemType::as_string): Likewise.
	(MaybeNamedParam::as_string): Likewise.
	(MetaListPaths::as_string): Likewise.
	(MetaListNameValueStr::as_string): Likewise.
	(Module::process_file_path): Likewise.
	(MetaListNameValueStr::check_cfg_predicate): Likewise.
	(MetaListPaths::check_cfg_predicate): Likewise.
	(MetaWord::check_cfg_predicate): Likewise.
	(MetaNameValueStr::check_cfg_predicate): Likewise.
	(MetaNameValueStr::to_attribute): Likewise.
	(MetaWord::to_attribute): Likewise.
	(MetaListPaths::to_attribute): Likewise.
	(MetaListNameValueStr::to_attribute): Likewise.
	(operator<<): Change Identifier class <<
	operator overload for standard output stream.
	* ast/rust-ast.h (class Identifier): Change typedef to proper
	class definition.
	(operator<<): Add prototype for operator overload.
	(class Token): Change getter identifier.
	(class MetaListNameValueStr): Likewise.
	(class PathExpr): Likewise.
	* ast/rust-expr.h: Likewise.
	* ast/rust-item.h: Likewise.
	* ast/rust-macro.h: Likewise.
	* ast/rust-path.cc (GenericArg::disambiguate_to_type): Likewise.
	(GenericArgsBinding::as_string): Likewise.
	(ConstGenericParam::as_string): Likewise.
	* ast/rust-path.h: Likewise.
	* ast/rust-pattern.cc (IdentifierPattern::as_string): Likewise.
	(StructPatternFieldIdentPat::as_string): Likewise.
	(StructPatternFieldIdent::as_string): Likewise.
	* ast/rust-type.h: Likewise.
	* backend/rust-compile-base.cc: Likewise.
	* backend/rust-compile-expr.cc (CompileExpr::visit): Likewise.
	* backend/rust-compile-extern.h: Likewise.
	* backend/rust-compile-fnparam.cc (CompileFnParam::visit):
	Likewise.
	* backend/rust-compile-implitem.cc (CompileTraitItem::visit):
	Likewise.
	* backend/rust-compile-item.cc (CompileItem::visit): Likewise.
	* backend/rust-compile-pattern.cc (CompilePatternBindings::visit): Likewise.
	* backend/rust-compile-struct-field-expr.cc (CompileStructExprField::visit):
	Likewise.
	* backend/rust-compile-var-decl.h: Likewise.
	* backend/rust-compile.cc: Likewise.
	* checks/errors/rust-unsafe-checker.cc (check_extern_call):
	Likewise.
	* checks/lints/rust-lint-marklive.cc (MarkLive::visit):
	Likewise.
	* checks/lints/rust-lint-scan-deadcode.h: Likewise.
	* expand/rust-derive-clone.cc (DeriveClone::clone_fn): Likewise.
	(DeriveClone::visit_tuple): Likewise.
	(DeriveClone::visit_struct): Likewise.
	(DeriveClone::visit_union): Likewise.
	* expand/rust-derive-copy.cc (DeriveCopy::visit_struct):
	Likewise.
	(DeriveCopy::visit_tuple): Likewise.
	(DeriveCopy::visit_enum): Likewise.
	(DeriveCopy::visit_union): Likewise.
	* expand/rust-macro-expand.cc (MacroExpander::match_matcher):
	Likewise.
	(MacroExpander::match_n_matches): Likewise.
	(MacroExpander::match_repetition): Likewise.
	(MacroExpander::match_repetition_skipped_metavars): Likewise.
	* hir/rust-ast-lower-base.cc (struct_field_name_exists):
	Likewise.
	* hir/rust-ast-lower-expr.cc (ASTLoweringExpr::visit): Likewise.
	* hir/rust-ast-lower-type.cc (ASTLowerGenericParam::visit):
	Likewise.
	* hir/rust-hir-dump.cc (Dump::visit): Likewise.
	* hir/tree/rust-hir-expr.h: Likewise.
	* hir/tree/rust-hir-item.h: Likewise.
	* hir/tree/rust-hir-path.h: Likewise.
	* hir/tree/rust-hir-type.h: Likewise.
	* hir/tree/rust-hir.cc (Module::as_string): Likewise.
	(StaticItem::as_string): Likewise.
	(TupleStruct::as_string): Likewise.
	(ConstantItem::as_string): Likewise.
	(StructStruct::as_string): Likewise.
	(UseTreeRebind::as_string): Likewise.
	(Enum::as_string): Likewise.
	(Trait::as_string): Likewise.
	(Union::as_string): Likewise.
	(Function::as_string): Likewise.
	(TypeAlias::as_string): Likewise.
	(FieldAccessExpr::as_string): Likewise.
	(TypeParam::as_string): Likewise.
	(GenericArgsBinding::as_string): Likewise.
	(StructPatternFieldIdent::as_string): Likewise.
	(StructPatternFieldIdentPat::as_string): Likewise.
	(IdentifierPattern::as_string): Likewise.
	(StructExprFieldIdentifierValue::as_string): Likewise.
	(EnumItem::as_string): Likewise.
	(StructField::as_string): Likewise.
	(ExternalStaticItem::as_string): Likewise.
	(ExternalFunctionItem::as_string): Likewise.
	(NamedFunctionParam::as_string): Likewise.
	(TraitFunctionDecl::as_string): Likewise.
	(TraitItemConst::as_string): Likewise.
	(TraitItemType::as_string): Likewise.
	(MaybeNamedParam::as_string): Likewise.
	* hir/tree/rust-hir.h: Likewise.
	* parse/rust-parse-impl.h (Parser::parse_macro_match_fragment):
	Likewise.
	(Parser::parse_module): Likewise.
	(Parser::parse_use_tree): Likewise.
	(Parser::parse_maybe_named_param): Likewise.
	* resolve/rust-ast-resolve-implitem.h: Likewise.
	* resolve/rust-ast-resolve-item.cc (ResolveTraitItems::visit):
	Likewise.
	(ResolveItem::visit): Likewise.
	(flatten_rebind): Likewise.
	(ResolveExternItem::visit): Likewise.
	(rust_flatten_rebind): Likewise.
	(rust_flatten_rebind_nested): Likewise.
	* resolve/rust-ast-resolve-pattern.cc (PatternDeclaration::go):
	Likewise.
	(PatternDeclaration::visit): Likewise.
	(PatternDeclaration::add_new_binding): Likewise.
	* resolve/rust-ast-resolve-stmt.h: Likewise.
	* resolve/rust-ast-resolve-toplevel.h: Likewise.
	* resolve/rust-ast-resolve-type.h: Likewise.
	* resolve/rust-early-name-resolver.cc (EarlyNameResolver::visit): Likewise.
	* typecheck/rust-autoderef.cc: Likewise.
	* typecheck/rust-hir-dot-operator.cc (MethodResolver::select):
	Likewise.
	* typecheck/rust-hir-path-probe.cc (PathProbeType::visit):
	Likewise.
	* typecheck/rust-hir-trait-reference.cc (TraitReference::get_name): Likewise.
	* typecheck/rust-hir-trait-resolve.cc (ResolveTraitItemToRef::visit): Likewise.
	(TraitResolver::resolve_trait): Likewise.
	(TraitItemReference::resolve_item): Likewise.
	(AssociatedImplTrait::setup_raw_associated_types): Likewise.
	* typecheck/rust-hir-type-check-enumitem.cc (TypeCheckEnumItem::visit): Likewise.
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit):
	Likewise.
	* typecheck/rust-hir-type-check-implitem.cc (TypeCheckTopLevelExternItem::visit): Likewise.
	(TypeCheckImplItem::visit): Likewise.
	(TypeCheckImplItemWithTrait::visit): Likewise.
	* typecheck/rust-hir-type-check-item.cc (TypeCheckItem::visit):
	Likewise.
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::visit): Likewise.
	* typecheck/rust-hir-type-check-struct.cc (TypeCheckStructExpr::visit): Likewise.
	* typecheck/rust-hir-type-check-type.cc (TypeResolveGenericParam::visit): Likewise.
	* typecheck/rust-hir-type-check.cc (TraitItemReference::get_type_from_fn): Likewise.
	* typecheck/rust-tyty-subst.cc (SubstitutionRef::get_mappings_from_generic_args): Likewise.
	* util/rust-attributes.cc (check_doc_attribute): Likewise.
	* util/rust-hir-map.cc (Mappings::insert_macro_def): Likewise.

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

10 files changed, 207 insertions, 159 deletions

diff --git a/gcc/rust/ast/rust-ast-collector.cc b/gcc/rust/ast/rust-ast-collector.cc
index e261849..d851066 100644
--- a/gcc/rust/ast/rust-ast-collector.cc
+++ b/gcc/rust/ast/rust-ast-collector.cc
@@ -296,7 +296,7 @@ TokenCollector::visit (StructField &field)
       visit (attr);
     }
   visit (field.get_visibility ());
-  auto name = field.get_field_name ();
+  auto name = field.get_field_name ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (field.get_locus (), std::move (name)));
   tokens.push_back (Rust::Token::make (COLON, Location ()));
@@ -358,7 +358,7 @@ TokenCollector::visit (MaybeNamedParam &param)
     {
       visit (attr);
     }
-  auto param_name = param.get_name ();
+  auto param_name = param.get_name ().as_string ();
   switch (param.get_param_kind ())
     {
     case MaybeNamedParam::UNNAMED:
@@ -458,7 +458,7 @@ TokenCollector::visit (AttrInputMetaItemContainer &container)
 void
 TokenCollector::visit (IdentifierExpr &ident_expr)
 {
-  auto ident = ident_expr.get_ident ();
+  auto ident = ident_expr.get_ident ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (ident_expr.get_locus (), std::move (ident)));
 }
@@ -520,7 +520,7 @@ TokenCollector::visit (ConstGenericParam &param)
   // const IDENTIFIER : Type ( = Block | IDENTIFIER | -?LITERAL )?
 
   tokens.push_back (Rust::Token::make (CONST, param.get_locus ()));
-  auto id = param.get_name ();
+  auto id = param.get_name ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (COLON, Location ()));
   visit (param.get_type ());
@@ -632,7 +632,7 @@ TokenCollector::visit (GenericArgsBinding &binding)
 {
   // Syntax:
   //    IDENTIFIER `=` Type
-  auto identifier = binding.get_identifier ();
+  auto identifier = binding.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (binding.get_locus (),
 						  std::move (identifier)));
 
@@ -1128,7 +1128,7 @@ TokenCollector::visit (StructExprFieldIdentifier &expr)
 {
   // TODO: Add attributes
   // visit_items_as_lines (expr.get_attrs ());
-  auto id = expr.get_field_name ();
+  auto id = expr.get_field_name ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (expr.get_locus (), std::move (id)));
 }
@@ -1217,7 +1217,7 @@ TokenCollector::visit (FieldAccessExpr &expr)
 {
   visit (expr.get_receiver_expr ());
   tokens.push_back (Rust::Token::make (DOT, expr.get_locus ()));
-  auto field_name = expr.get_field_name ();
+  auto field_name = expr.get_field_name ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (field_name)));
 }
@@ -1524,7 +1524,7 @@ TokenCollector::visit (TypeParam &param)
   // TypeParamBounds :
   //    TypeParamBound ( + TypeParamBound )* +?
 
-  auto id = param.get_type_representation ();
+  auto id = param.get_type_representation ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (param.get_locus (), std::move (id)));
   if (param.has_type_param_bounds ())
@@ -1591,7 +1591,7 @@ void
 TokenCollector::visit (Method &method)
 {
   visit (method.get_visibility ());
-  auto method_name = method.get_method_name ();
+  auto method_name = method.get_method_name ().as_string ();
   tokens.push_back (Rust::Token::make (FN_TOK, method.get_locus ()));
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (method_name)));
@@ -1632,7 +1632,7 @@ TokenCollector::visit (Module &module)
 
   visit_items_as_lines (module.get_outer_attrs ());
   visit (module.get_visibility ());
-  auto name = module.get_name ();
+  auto name = module.get_name ().as_string ();
   tokens.push_back (Rust::Token::make (MOD, module.get_locus ()));
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (name)));
@@ -1733,7 +1733,7 @@ TokenCollector::visit (UseTreeRebind &use_tree)
     {
       case UseTreeRebind::NewBindType::IDENTIFIER: {
 	tokens.push_back (Rust::Token::make (AS, Location ()));
-	auto id = use_tree.get_identifier ();
+	auto id = use_tree.get_identifier ().as_string ();
 	tokens.push_back (
 	  Rust::Token::make_identifier (use_tree.get_locus (), std::move (id)));
       }
@@ -1770,7 +1770,7 @@ TokenCollector::visit (Function &function)
   visit (function.get_visibility ());
 
   tokens.push_back (Rust::Token::make (FN_TOK, function.get_locus ()));
-  auto name = function.get_function_name ();
+  auto name = function.get_function_name ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (name)));
   if (function.has_generics ())
@@ -1808,7 +1808,7 @@ TokenCollector::visit (TypeAlias &type_alias)
   visit_items_as_lines (type_alias.get_outer_attrs ());
   if (type_alias.has_visibility ())
     visit (type_alias.get_visibility ());
-  auto alias_name = type_alias.get_new_type_name ();
+  auto alias_name = type_alias.get_new_type_name ().as_string ();
   tokens.push_back (Rust::Token::make (TYPE, type_alias.get_locus ()));
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (alias_name)));
@@ -1827,7 +1827,7 @@ TokenCollector::visit (StructStruct &struct_item)
   visit_items_as_lines (struct_item.get_outer_attrs ());
   if (struct_item.has_visibility ())
     visit (struct_item.get_visibility ());
-  auto struct_name = struct_item.get_identifier ();
+  auto struct_name = struct_item.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (STRUCT_TOK, struct_item.get_locus ()));
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (struct_name)));
@@ -1850,7 +1850,7 @@ void
 TokenCollector::visit (TupleStruct &tuple_struct)
 {
   visit_items_as_lines (tuple_struct.get_outer_attrs ());
-  auto struct_name = tuple_struct.get_identifier ();
+  auto struct_name = tuple_struct.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (STRUCT_TOK, tuple_struct.get_locus ()));
   tokens.push_back (
     Rust::Token::make_identifier (Location (), std::move (struct_name)));
@@ -1870,7 +1870,7 @@ void
 TokenCollector::visit (EnumItem &item)
 {
   visit_items_as_lines (item.get_outer_attrs ());
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (item.get_locus (), std::move (id)));
 }
@@ -1878,7 +1878,7 @@ TokenCollector::visit (EnumItem &item)
 void
 TokenCollector::visit (EnumItemTuple &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (item.get_locus (), std::move (id)));
   tokens.push_back (Rust::Token::make (LEFT_PAREN, Location ()));
@@ -1889,7 +1889,7 @@ TokenCollector::visit (EnumItemTuple &item)
 void
 TokenCollector::visit (EnumItemStruct &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (item.get_locus (), std::move (id)));
   visit_items_as_block (item.get_struct_fields (),
@@ -1899,7 +1899,7 @@ TokenCollector::visit (EnumItemStruct &item)
 void
 TokenCollector::visit (EnumItemDiscriminant &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (item.get_locus (), std::move (id)));
   tokens.push_back (Rust::Token::make (EQUAL, Location ()));
@@ -1913,7 +1913,7 @@ TokenCollector::visit (Enum &enumeration)
   if (enumeration.has_visibility ())
     visit (enumeration.get_visibility ());
   tokens.push_back (Rust::Token::make (ENUM_TOK, enumeration.get_locus ()));
-  auto id = enumeration.get_identifier ();
+  auto id = enumeration.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (enumeration.get_locus (), std::move (id)));
   if (enumeration.has_generics ())
@@ -1929,7 +1929,7 @@ void
 TokenCollector::visit (Union &union_item)
 {
   visit_items_as_lines (union_item.get_outer_attrs ());
-  auto id = union_item.get_identifier ();
+  auto id = union_item.get_identifier ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (union_item.get_locus (), "union"));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
@@ -1974,7 +1974,7 @@ TokenCollector::visit (StaticItem &item)
   tokens.push_back (Rust::Token::make (STATIC_TOK, item.get_locus ()));
   if (item.is_mutable ())
     tokens.push_back (Rust::Token::make (MUT, Location ()));
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (COLON, Location ()));
   visit (item.get_type ());
@@ -2012,7 +2012,7 @@ void
 TokenCollector::visit (TraitItemFunc &item)
 {
   auto func = item.get_trait_function_decl ();
-  auto id = func.get_identifier ();
+  auto id = func.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (FN_TOK, item.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (LEFT_PAREN, Location ()));
@@ -2049,7 +2049,7 @@ void
 TokenCollector::visit (TraitItemMethod &item)
 {
   auto method = item.get_trait_method_decl ();
-  auto id = method.get_identifier ();
+  auto id = method.get_identifier ().as_string ();
 
   tokens.push_back (Rust::Token::make (FN_TOK, item.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
@@ -2071,7 +2071,7 @@ TokenCollector::visit (TraitItemMethod &item)
 void
 TokenCollector::visit (TraitItemConst &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   indentation ();
   tokens.push_back (Rust::Token::make (CONST, item.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
@@ -2084,7 +2084,7 @@ TokenCollector::visit (TraitItemConst &item)
 void
 TokenCollector::visit (TraitItemType &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   indentation ();
   tokens.push_back (Rust::Token::make (TYPE, item.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
@@ -2104,7 +2104,7 @@ TokenCollector::visit (Trait &trait)
 
   visit (trait.get_visibility ());
 
-  auto id = trait.get_identifier ();
+  auto id = trait.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (TRAIT, trait.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
 
@@ -2168,7 +2168,7 @@ TokenCollector::visit (ExternalTypeItem &type)
 {
   visit (type.get_visibility ());
 
-  auto id = type.get_identifier ();
+  auto id = type.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (TYPE, Location ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (SEMICOLON, Location ()));
@@ -2177,7 +2177,7 @@ TokenCollector::visit (ExternalTypeItem &type)
 void
 TokenCollector::visit (ExternalStaticItem &item)
 {
-  auto id = item.get_identifier ();
+  auto id = item.get_identifier ().as_string ();
   visit_items_as_lines (item.get_outer_attrs ());
   if (item.has_visibility ())
     visit (item.get_visibility ());
@@ -2197,7 +2197,7 @@ TokenCollector::visit (ExternalFunctionItem &function)
 {
   visit (function.get_visibility ());
 
-  auto id = function.get_identifier ();
+  auto id = function.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make (FN_TOK, function.get_locus ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (LEFT_PAREN, Location ()));
@@ -2247,7 +2247,7 @@ get_delimiters (DelimType delim)
 void
 TokenCollector::visit (MacroMatchFragment &match)
 {
-  auto id = match.get_ident ();
+  auto id = match.get_ident ().as_string ();
   auto frag_spec = match.get_frag_spec ().as_string ();
   tokens.push_back (Rust::Token::make (DOLLAR_SIGN, Location ()));
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
@@ -2318,7 +2318,7 @@ TokenCollector::visit (MacroRulesDefinition &rules_def)
   for (auto &outer_attr : rules_def.get_outer_attrs ())
     visit (outer_attr);
 
-  auto rule_name = rules_def.get_rule_name ();
+  auto rule_name = rules_def.get_rule_name ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (rules_def.get_locus (), "macro_rules"));
   tokens.push_back (Rust::Token::make (EXCLAM, Location ()));
@@ -2361,7 +2361,7 @@ TokenCollector::visit (MetaItemSeq &item)
 void
 TokenCollector::visit (MetaWord &word)
 {
-  auto id = word.get_ident ();
+  auto id = word.get_ident ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (word.get_locus (), std::move (id)));
 }
@@ -2370,7 +2370,7 @@ void
 TokenCollector::visit (MetaNameValueStr &name)
 {
   auto pair = name.get_name_value_pair ();
-  auto id = std::get<0> (pair);
+  auto id = std::get<0> (pair).as_string ();
   auto value = std::get<1> (pair);
   tokens.push_back (
     Rust::Token::make_identifier (name.get_locus (), std::move (id)));
@@ -2384,7 +2384,7 @@ TokenCollector::visit (MetaNameValueStr &name)
 void
 TokenCollector::visit (MetaListPaths &list)
 {
-  auto id = list.get_ident ();
+  auto id = list.get_ident ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (list.get_locus (), std::move (id)));
   tokens.push_back (Rust::Token::make (LEFT_PAREN, Location ()));
@@ -2395,7 +2395,7 @@ TokenCollector::visit (MetaListPaths &list)
 void
 TokenCollector::visit (MetaListNameValueStr &list)
 {
-  auto id = list.get_ident ();
+  auto id = list.get_ident ().as_string ();
   tokens.push_back (
     Rust::Token::make_identifier (list.get_locus (), std::move (id)));
   tokens.push_back (Rust::Token::make (LEFT_PAREN, Location ()));
@@ -2421,7 +2421,7 @@ TokenCollector::visit (IdentifierPattern &pattern)
     {
       tokens.push_back (Rust::Token::make (MUT, Location ()));
     }
-  auto id = pattern.get_ident ();
+  auto id = pattern.get_ident ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   if (pattern.has_pattern_to_bind ())
     {
@@ -2528,7 +2528,7 @@ void
 TokenCollector::visit (StructPatternFieldIdentPat &pattern)
 {
   visit_items_as_lines (pattern.get_outer_attrs ());
-  auto id = pattern.get_identifier ();
+  auto id = pattern.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
   tokens.push_back (Rust::Token::make (COLON, pattern.get_locus ()));
   visit (pattern.get_ident_pattern ());
@@ -2543,7 +2543,7 @@ TokenCollector::visit (StructPatternFieldIdent &pattern)
   if (pattern.is_mut ())
     tokens.push_back (Rust::Token::make (MUT, Location ()));
 
-  auto id = pattern.get_identifier ();
+  auto id = pattern.get_identifier ().as_string ();
   tokens.push_back (Rust::Token::make_identifier (Location (), std::move (id)));
 }
 
diff --git a/gcc/rust/ast/rust-ast.cc b/gcc/rust/ast/rust-ast.cc
index 14ad3a0..24e719c 100644
--- a/gcc/rust/ast/rust-ast.cc
+++ b/gcc/rust/ast/rust-ast.cc
@@ -251,7 +251,7 @@ VisItem::as_string () const
 std::string
 Module::as_string () const
 {
-  std::string str = VisItem::as_string () + "mod " + module_name;
+  std::string str = VisItem::as_string () + "mod " + module_name.as_string ();
 
   // Return early if we're dealing with an unloaded module as their body resides
   // in a different file
@@ -298,7 +298,7 @@ StaticItem::as_string () const
   if (has_mut)
     str += " mut";
 
-  str += " " + name;
+  str += " " + name.as_string ();
 
   // DEBUG: null pointer check
   if (type == nullptr)
@@ -339,7 +339,7 @@ TupleStruct::as_string () const
 {
   std::string str = VisItem::as_string ();
 
-  str += "struct " + struct_name;
+  str += "struct " + struct_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -476,7 +476,7 @@ Method::as_string () const
 
   str += vis.as_string () + " " + qualifiers.as_string ();
 
-  str += " fn " + method_name;
+  str += " fn " + method_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -537,7 +537,7 @@ StructStruct::as_string () const
 {
   std::string str = VisItem::as_string ();
 
-  str += "struct " + struct_name;
+  str += "struct " + struct_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -686,7 +686,7 @@ UseTreeRebind::as_string () const
       // nothing to add, just path
       break;
     case IDENTIFIER:
-      path_str += " as " + identifier;
+      path_str += " as " + identifier.as_string ();
       break;
     case WILDCARD:
       path_str += " as _";
@@ -703,7 +703,7 @@ std::string
 Enum::as_string () const
 {
   std::string str = VisItem::as_string ();
-  str += enum_name;
+  str += enum_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -768,7 +768,7 @@ Trait::as_string () const
   if (has_unsafe)
     str += "unsafe ";
 
-  str += "trait " + name;
+  str += "trait " + name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -851,7 +851,7 @@ Union::as_string () const
 {
   std::string str = VisItem::as_string ();
 
-  str += "union " + union_name;
+  str += "union " + union_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -923,7 +923,7 @@ Function::as_string () const
       str += "void ";
     }
 
-  str += function_name;
+  str += function_name.as_string ();
 
   if (has_generics ())
     {
@@ -1110,7 +1110,7 @@ TypeAlias::as_string () const
 {
   std::string str = VisItem::as_string ();
 
-  str += " " + new_type_name;
+  str += " " + new_type_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -1192,7 +1192,7 @@ MacroRulesDefinition::as_string () const
   // TODO: deal with macro_2_0
   str += "macro_rules!";
 
-  str += rule_name;
+  str += rule_name.as_string ();
 
   str += "\n Macro rules: ";
   if (rules.empty ())
@@ -1559,7 +1559,7 @@ std::string
 FieldAccessExpr::as_string () const
 {
   // TODO: rewrite dump to better reflect non-literal exprs
-  return receiver->as_string () + "." + field;
+  return receiver->as_string () + "." + field.as_string ();
 }
 
 std::string
@@ -2179,7 +2179,7 @@ LifetimeParam::as_string () const
 std::string
 MacroMatchFragment::as_string () const
 {
-  return "$" + ident + ": " + frag_spec.as_string ();
+  return "$" + ident.as_string () + ": " + frag_spec.as_string ();
 }
 
 std::string
@@ -2256,7 +2256,7 @@ TypeParam::as_string () const
   else
     str += outer_attr.as_string ();
 
-  str += "\n Identifier: " + type_representation;
+  str += "\n Identifier: " + type_representation.as_string ();
 
   str += "\n Type param bounds: ";
   if (!has_type_param_bounds ())
@@ -2565,7 +2565,7 @@ std::string
 StructExprFieldIdentifierValue::as_string () const
 {
   // TODO: rewrite to work with non-linearisable exprs
-  return field_name + " : " + StructExprFieldWithVal::as_string ();
+  return field_name.as_string () + " : " + StructExprFieldWithVal::as_string ();
 }
 
 std::string
@@ -2604,7 +2604,7 @@ std::string
 EnumItem::as_string () const
 {
   std::string str = VisItem::as_string ();
-  str += variant_name;
+  str += variant_name.as_string ();
 
   return str;
 }
@@ -2691,7 +2691,7 @@ StructField::as_string () const
   if (has_visibility ())
     str += "\n" + visibility.as_string ();
 
-  str += " " + field_name + " : " + field_type->as_string ();
+  str += " " + field_name.as_string () + " : " + field_type->as_string ();
 
   return str;
 }
@@ -2713,7 +2713,7 @@ ExternalTypeItem::as_string () const
 {
   auto str = append_attributes (outer_attrs, OUTER);
 
-  str += "type " + item_name + ";";
+  str += "type " + item_name.as_string () + ";";
 
   return str;
 }
@@ -2733,7 +2733,7 @@ ExternalStaticItem::as_string () const
     str += "mut ";
 
   // add name
-  str += item_name;
+  str += item_name.as_string ();
 
   // add type on new line
   str += "\n Type: " + item_type->as_string ();
@@ -2753,7 +2753,7 @@ ExternalFunctionItem::as_string () const
   str += "fn ";
 
   // add name
-  str += item_name;
+  str += item_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -2850,7 +2850,8 @@ TraitItemFunc::as_string () const
 std::string
 TraitFunctionDecl::as_string () const
 {
-  std::string str = qualifiers.as_string () + "fn " + function_name;
+  std::string str
+    = qualifiers.as_string () + "fn " + function_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -2920,7 +2921,8 @@ TraitItemMethod::as_string () const
 std::string
 TraitMethodDecl::as_string () const
 {
-  std::string str = qualifiers.as_string () + "fn " + function_name;
+  std::string str
+    = qualifiers.as_string () + "fn " + function_name.as_string ();
 
   // generic params
   str += "\n Generic params: ";
@@ -2979,7 +2981,7 @@ TraitItemConst::as_string () const
   // TODO: rewrite to work with non-linearisable exprs
   std::string str = append_attributes (outer_attrs, OUTER);
 
-  str += "\nconst " + name + " : " + type->as_string ();
+  str += "\nconst " + name.as_string () + " : " + type->as_string ();
 
   if (has_expression ())
     str += " = " + expr->as_string ();
@@ -2992,7 +2994,7 @@ TraitItemType::as_string () const
 {
   std::string str = append_attributes (outer_attrs, OUTER);
 
-  str += "\ntype " + name;
+  str += "\ntype " + name.as_string ();
 
   str += "\n Type param bounds: ";
   if (!has_type_param_bounds ())
@@ -3167,7 +3169,7 @@ MaybeNamedParam::as_string () const
     case UNNAMED:
       break;
     case IDENTIFIER:
-      str = name + " : ";
+      str = name.as_string () + " : ";
       break;
     case WILDCARD:
       str = "_ : ";
@@ -3216,7 +3218,7 @@ MetaItemSeq::as_string () const
 std::string
 MetaListPaths::as_string () const
 {
-  std::string str = ident + "(";
+  std::string str = ident.as_string () + "(";
 
   auto i = paths.begin ();
   auto e = paths.end ();
@@ -3234,7 +3236,7 @@ MetaListPaths::as_string () const
 std::string
 MetaListNameValueStr::as_string () const
 {
-  std::string str = ident + "(";
+  std::string str = ident.as_string () + "(";
 
   auto i = strs.begin ();
   auto e = strs.end ();
@@ -3313,7 +3315,7 @@ Module::process_file_path ()
   // file that contains the 'mod <file>;' directive
   std::string including_fpath (outer_filename);
 
-  std::string expected_file_path = module_name + ".rs";
+  std::string expected_file_path = module_name.as_string () + ".rs";
   std::string expected_dir_path = "mod.rs";
 
   auto dir_slash_pos = including_fpath.rfind (file_separator);
@@ -3366,8 +3368,8 @@ Module::process_file_path ()
   bool file_mod_found = file_exists (file_mod_path);
 
   // Then, search for <directory>/<module_name>/mod.rs
-  std::string dir_mod_path
-    = current_directory_name + module_name + file_separator + expected_dir_path;
+  std::string dir_mod_path = current_directory_name + module_name.as_string ()
+			     + file_separator + expected_dir_path;
   bool dir_mod_found = file_exists (dir_mod_path);
 
   bool multiple_candidates_found = file_mod_found && dir_mod_found;
@@ -3376,12 +3378,13 @@ Module::process_file_path ()
   if (multiple_candidates_found)
     rust_error_at (locus,
 		   "two candidates found for module %s: %s.rs and %s%smod.rs",
-		   module_name.c_str (), module_name.c_str (),
-		   module_name.c_str (), file_separator);
+		   module_name.as_string ().c_str (),
+		   module_name.as_string ().c_str (),
+		   module_name.as_string ().c_str (), file_separator);
 
   if (no_candidates_found)
     rust_error_at (locus, "no candidate found for module %s",
-		   module_name.c_str ());
+		   module_name.as_string ().c_str ());
 
   if (no_candidates_found || multiple_candidates_found)
     return;
@@ -3878,7 +3881,7 @@ MetaItemLitExpr::check_cfg_predicate (const Session &) const
 bool
 MetaListNameValueStr::check_cfg_predicate (const Session &session) const
 {
-  if (ident == "all")
+  if (ident.as_string () == "all")
     {
       for (const auto &str : strs)
 	{
@@ -3887,7 +3890,7 @@ MetaListNameValueStr::check_cfg_predicate (const Session &session) const
 	}
       return true;
     }
-  else if (ident == "any")
+  else if (ident.as_string () == "any")
     {
       for (const auto &str : strs)
 	{
@@ -3896,7 +3899,7 @@ MetaListNameValueStr::check_cfg_predicate (const Session &session) const
 	}
       return false;
     }
-  else if (ident == "not")
+  else if (ident.as_string () == "not")
     {
       if (strs.size () != 1)
 	{
@@ -3918,7 +3921,7 @@ MetaListNameValueStr::check_cfg_predicate (const Session &session) const
 		     "cfg predicate could not be checked for "
 		     "MetaListNameValueStr with ident of "
 		     "'%s' - ident must be 'all' or 'any'",
-		     ident.c_str ());
+		     ident.as_string ().c_str ());
       return false;
     }
 }
@@ -3926,7 +3929,7 @@ MetaListNameValueStr::check_cfg_predicate (const Session &session) const
 bool
 MetaListPaths::check_cfg_predicate (const Session &session) const
 {
-  if (ident == "all")
+  if (ident.as_string () == "all")
     {
       for (const auto &path : paths)
 	{
@@ -3935,7 +3938,7 @@ MetaListPaths::check_cfg_predicate (const Session &session) const
 	}
       return true;
     }
-  else if (ident == "any")
+  else if (ident.as_string () == "any")
     {
       for (const auto &path : paths)
 	{
@@ -3944,7 +3947,7 @@ MetaListPaths::check_cfg_predicate (const Session &session) const
 	}
       return false;
     }
-  else if (ident == "not")
+  else if (ident.as_string () == "not")
     {
       if (paths.size () != 1)
 	{
@@ -3966,7 +3969,7 @@ MetaListPaths::check_cfg_predicate (const Session &session) const
 		     "cfg predicate could not be checked for "
 		     "MetaListNameValueStr with ident of "
 		     "'%s' - ident must be 'all' or 'any'",
-		     ident.c_str ());
+		     ident.as_string ().c_str ());
       return false;
     }
 }
@@ -4029,7 +4032,7 @@ MetaItemSeq::check_cfg_predicate (const Session &session) const
 bool
 MetaWord::check_cfg_predicate (const Session &session) const
 {
-  return session.options.target_data.has_key (ident);
+  return session.options.target_data.has_key (ident.as_string ());
 }
 
 bool
@@ -4048,10 +4051,13 @@ MetaNameValueStr::check_cfg_predicate (const Session &session) const
   // DEBUG
   rust_debug (
     "checked key-value pair for cfg: '%s', '%s' - is%s in target data",
-    ident.c_str (), str.c_str (),
-    session.options.target_data.has_key_value_pair (ident, str) ? "" : " not");
+    ident.as_string ().c_str (), str.c_str (),
+    session.options.target_data.has_key_value_pair (ident.as_string (), str)
+      ? ""
+      : " not");
 
-  return session.options.target_data.has_key_value_pair (ident, str);
+  return session.options.target_data.has_key_value_pair (ident.as_string (),
+							 str);
 }
 
 bool
@@ -4080,7 +4086,7 @@ MetaNameValueStr::to_attribute () const
   // FIXME: What location do we put here? Is the literal above supposed to have
   // an empty location as well?
   // Should MetaNameValueStr keep a location?
-  return Attribute (SimplePath::from_str (ident, ident_locus),
+  return Attribute (SimplePath::from_str (ident.as_string (), ident_locus),
 		    std::unique_ptr<AttrInputLiteral> (
 		      new AttrInputLiteral (std::move (lit_expr))));
 }
@@ -4107,7 +4113,8 @@ MetaItemSeq::to_attribute () const
 Attribute
 MetaWord::to_attribute () const
 {
-  return Attribute (SimplePath::from_str (ident, ident_locus), nullptr);
+  return Attribute (SimplePath::from_str (ident.as_string (), ident_locus),
+		    nullptr);
 }
 
 Attribute
@@ -4125,7 +4132,7 @@ MetaListPaths::to_attribute () const
 
   std::unique_ptr<AttrInputMetaItemContainer> new_seq_container (
     new AttrInputMetaItemContainer (std::move (new_seq)));
-  return Attribute (SimplePath::from_str (ident, ident_locus),
+  return Attribute (SimplePath::from_str (ident.as_string (), ident_locus),
 		    std::move (new_seq_container));
 }
 
@@ -4140,7 +4147,7 @@ MetaListNameValueStr::to_attribute () const
 
   std::unique_ptr<AttrInputMetaItemContainer> new_seq_container (
     new AttrInputMetaItemContainer (std::move (new_seq)));
-  return Attribute (SimplePath::from_str (ident, ident_locus),
+  return Attribute (SimplePath::from_str (ident.as_string (), ident_locus),
 		    std::move (new_seq_container));
 }
 
@@ -4986,4 +4993,11 @@ MetaWord::accept_vis (ASTVisitor &vis)
 }
 
 } // namespace AST
+
+std::ostream &
+operator<< (std::ostream &os, Identifier const &i)
+{
+  return os << i.as_string ();
+}
+
 } // namespace Rust
diff --git a/gcc/rust/ast/rust-ast.h b/gcc/rust/ast/rust-ast.h
index 893b4bb..a4caee7 100644
--- a/gcc/rust/ast/rust-ast.h
+++ b/gcc/rust/ast/rust-ast.h
@@ -28,11 +28,30 @@
 
 namespace Rust {
 // TODO: remove typedefs and make actual types for these
-typedef std::string Identifier;
 typedef int TupleIndex;
 struct Session;
 struct MacroExpander;
 
+class Identifier
+{
+public:
+  Identifier (std::string ident = "")
+    : ident (ident), node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  NodeId get_node_id () const { return node_id; }
+  const std::string &as_string () const { return ident; }
+
+  bool empty () const { return ident.empty (); }
+
+private:
+  std::string ident;
+  NodeId node_id;
+};
+
+std::ostream &
+operator<< (std::ostream &os, Identifier const &i);
+
 namespace AST {
 // foward decl: ast visitor
 class ASTVisitor;
@@ -60,11 +79,11 @@ class Node : public Visitable
 public:
   /**
    * Get the kind of Node this is. This is used to differentiate various AST
-   * elements with very little overhead when extracting the derived type through
-   * static casting is not necessary.
+   * elements with very little overhead when extracting the derived type
+   * through static casting is not necessary.
    */
-  // FIXME: Mark this as `= 0` in the future to make sure every node implements
-  // it
+  // FIXME: Mark this as `= 0` in the future to make sure every node
+  // implements it
   virtual Kind get_ast_kind () const { return Kind::UNKNOWN; }
 };
 
@@ -93,8 +112,8 @@ public:
 
   virtual std::string as_string () const = 0;
 
-  /* Converts token tree to a flat token stream. Tokens must be pointer to avoid
-   * mutual dependency with Token. */
+  /* Converts token tree to a flat token stream. Tokens must be pointer to
+   * avoid mutual dependency with Token. */
   virtual std::vector<std::unique_ptr<Token>> to_token_stream () const = 0;
 
 protected:
@@ -151,9 +170,9 @@ class Token : public TokenTree, public MacroMatch
 
   const_TokenPtr tok_ref;
 
-  /* new idea: wrapper around const_TokenPtr used for heterogeneuous storage in
-   * token trees. rather than convert back and forth when parsing macros, just
-   * wrap it. */
+  /* new idea: wrapper around const_TokenPtr used for heterogeneuous storage
+   * in token trees. rather than convert back and forth when parsing macros,
+   * just wrap it. */
 
 public:
   // Unique pointer custom clone function
@@ -250,15 +269,15 @@ protected:
   // No virtual for now as not polymorphic but can be in future
   /*virtual*/ Token *clone_token_impl () const { return new Token (*this); }
 
-  /* Use covariance to implement clone function as returning this object rather
-   * than base */
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
   Token *clone_token_tree_impl () const final override
   {
     return clone_token_impl ();
   }
 
-  /* Use covariance to implement clone function as returning this object rather
-   * than base */
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
   Token *clone_macro_match_impl () const final override
   {
     return clone_token_impl ();
@@ -282,8 +301,8 @@ public:
   };
 
 private:
-  /* TODO: maybe make subclasses of each type of literal with their typed values
-   * (or generics) */
+  /* TODO: maybe make subclasses of each type of literal with their typed
+   * values (or generics) */
   std::string value_as_string;
   LitType type;
   PrimitiveCoreType type_hint;
@@ -310,8 +329,8 @@ public:
   bool is_error () const { return type == ERROR; }
 };
 
-/* Forward decl - definition moved to rust-expr.h as it requires LiteralExpr to
- * be defined */
+/* Forward decl - definition moved to rust-expr.h as it requires LiteralExpr
+ * to be defined */
 class AttrInputLiteral;
 
 /* TODO: move applicable stuff into here or just don't include it because
@@ -571,8 +590,8 @@ public:
   // Call to parse attribute body to meta item syntax.
   void parse_attr_to_meta_item ();
 
-  /* Determines whether cfg predicate is true and item with attribute should not
-   * be stripped. Attribute body must already be parsed to meta item. */
+  /* Determines whether cfg predicate is true and item with attribute should
+   * not be stripped. Attribute body must already be parsed to meta item. */
   bool check_cfg_predicate (const Session &session) const;
 
   // Returns whether body has been parsed to meta item form or not.
@@ -583,7 +602,8 @@ public:
   std::vector<Attribute> separate_cfg_attrs () const;
 
 protected:
-  // not virtual as currently no subclasses of Attribute, but could be in future
+  // not virtual as currently no subclasses of Attribute, but could be in
+  // future
   /*virtual*/ Attribute *clone_attribute_impl () const
   {
     return new Attribute (*this);
@@ -849,8 +869,8 @@ public:
   DelimType get_delim_type () const { return delim_type; }
 };
 
-/* Forward decl - definition moved to rust-expr.h as it requires LiteralExpr to
- * be defined */
+/* Forward decl - definition moved to rust-expr.h as it requires LiteralExpr
+ * to be defined */
 class AttrInputLiteral;
 
 // abstract base meta item class
@@ -879,8 +899,9 @@ class MetaListPaths;
 // Forward decl - defined in rust-macro.h
 class MetaListNameValueStr;
 
-/* Base statement abstract class. Note that most "statements" are not allowed in
- * top-level module scope - only a subclass of statements called "items" are. */
+/* Base statement abstract class. Note that most "statements" are not allowed
+ * in top-level module scope - only a subclass of statements called "items"
+ * are. */
 class Stmt : public Node
 {
 public:
@@ -1022,9 +1043,9 @@ protected:
   // pure virtual clone implementation
   virtual ExprWithoutBlock *clone_expr_without_block_impl () const = 0;
 
-  /* Save having to specify two clone methods in derived classes by making expr
-   * clone return exprwithoutblock clone. Hopefully won't affect performance too
-   * much. */
+  /* Save having to specify two clone methods in derived classes by making
+   * expr clone return exprwithoutblock clone. Hopefully won't affect
+   * performance too much. */
   ExprWithoutBlock *clone_expr_impl () const final override
   {
     return clone_expr_without_block_impl ();
@@ -1042,7 +1063,8 @@ public:
 
 /* HACK: IdentifierExpr, delete when figure out identifier vs expr problem in
  * Pratt parser */
-/* Alternatively, identifiers could just be represented as single-segment paths
+/* Alternatively, identifiers could just be represented as single-segment
+ * paths
  */
 class IdentifierExpr : public ExprWithoutBlock
 {
@@ -1057,7 +1079,7 @@ public:
       locus (locus)
   {}
 
-  std::string as_string () const override { return ident; }
+  std::string as_string () const override { return ident.as_string (); }
 
   Location get_locus () const override final { return locus; }
 
@@ -1181,9 +1203,9 @@ protected:
   // Clone function implementation as pure virtual method
   virtual TypeNoBounds *clone_type_no_bounds_impl () const = 0;
 
-  /* Save having to specify two clone methods in derived classes by making type
-   * clone return typenobounds clone. Hopefully won't affect performance too
-   * much. */
+  /* Save having to specify two clone methods in derived classes by making
+   * type clone return typenobounds clone. Hopefully won't affect performance
+   * too much. */
   TypeNoBounds *clone_type_impl () const final override
   {
     return clone_type_no_bounds_impl ();
@@ -1192,8 +1214,8 @@ protected:
   TypeNoBounds () : Type () {}
 };
 
-/* Abstract base class representing a type param bound - Lifetime and TraitBound
- * extends it */
+/* Abstract base class representing a type param bound - Lifetime and
+ * TraitBound extends it */
 class TypeParamBound : public Visitable
 {
 public:
@@ -1271,16 +1293,16 @@ public:
   std::string get_lifetime_name () const { return lifetime_name; }
 
 protected:
-  /* Use covariance to implement clone function as returning this object rather
-   * than base */
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
   Lifetime *clone_type_param_bound_impl () const override
   {
     return new Lifetime (node_id, lifetime_type, lifetime_name, locus);
   }
 };
 
-/* Base generic parameter in AST. Abstract - can be represented by a Lifetime or
- * Type param */
+/* Base generic parameter in AST. Abstract - can be represented by a Lifetime
+ * or Type param */
 class GenericParam : public Visitable
 {
 public:
@@ -1363,8 +1385,8 @@ public:
   Kind get_kind () const override final { return Kind::Lifetime; }
 
 protected:
-  /* Use covariance to implement clone function as returning this object rather
-   * than base */
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
   LifetimeParam *clone_generic_param_impl () const override
   {
     return new LifetimeParam (*this);
@@ -1957,4 +1979,15 @@ class PathExpr : public ExprWithoutBlock
 } // namespace AST
 } // namespace Rust
 
+namespace std {
+template <> struct less<Rust::Identifier>
+{
+  bool operator() (const Rust::Identifier &lhs,
+		   const Rust::Identifier &rhs) const
+  {
+    return lhs.as_string () < rhs.as_string ();
+  }
+};
+} // namespace std
+
 #endif
diff --git a/gcc/rust/ast/rust-expr.h b/gcc/rust/ast/rust-expr.h
index 8ea2c8c..9a1da7a 100644
--- a/gcc/rust/ast/rust-expr.h
+++ b/gcc/rust/ast/rust-expr.h
@@ -1667,7 +1667,7 @@ public:
       locus (locus)
   {}
 
-  std::string as_string () const override { return field_name; }
+  std::string as_string () const override { return field_name.as_string (); }
 
   Location get_locus () const override final { return locus; }
 
@@ -1741,7 +1741,7 @@ public:
 
   void accept_vis (ASTVisitor &vis) override;
 
-  std::string get_field_name () const { return field_name; }
+  std::string get_field_name () const { return field_name.as_string (); }
 
   Location get_locus () const override final { return locus; }
 
diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index 4563f61..5b3529b 100644
--- a/gcc/rust/ast/rust-item.h
+++ b/gcc/rust/ast/rust-item.h
@@ -752,7 +752,7 @@ public:
   // Creates an error state method.
   static Method create_error ()
   {
-    return Method ("", FunctionQualifiers (Location (), NONE, true),
+    return Method ({""}, FunctionQualifiers (Location (), NONE, true),
 		   std::vector<std::unique_ptr<GenericParam>> (),
 		   SelfParam::create_error (), std::vector<FunctionParam> (),
 		   nullptr, WhereClause::create_empty (), nullptr,
@@ -1136,7 +1136,7 @@ public:
   Location get_locus () const override final { return locus; }
 
   // Invalid if name is empty, so base stripping on that.
-  void mark_for_strip () override { module_name = ""; }
+  void mark_for_strip () override { module_name = {""}; }
   bool is_marked_for_strip () const override { return module_name.empty (); }
 
 protected:
@@ -1865,7 +1865,7 @@ public:
   Location get_locus () const override final { return locus; }
 
   // Invalid if name is empty, so base stripping on that.
-  void mark_for_strip () override { struct_name = ""; }
+  void mark_for_strip () override { struct_name = {""}; }
   bool is_marked_for_strip () const override { return struct_name.empty (); }
 
   Identifier get_struct_name () const { return struct_name; }
@@ -2240,7 +2240,7 @@ public:
   Identifier get_identifier () const { return variant_name; }
 
   // Based on idea that name is never empty.
-  void mark_for_strip () override { variant_name = ""; }
+  void mark_for_strip () override { variant_name = {""}; }
   bool is_marked_for_strip () const override { return variant_name.empty (); }
 
 protected:
@@ -2461,7 +2461,7 @@ public:
   Identifier get_identifier () const { return enum_name; }
 
   // Invalid if name is empty, so base stripping on that.
-  void mark_for_strip () override { enum_name = ""; }
+  void mark_for_strip () override { enum_name = {""}; }
   bool is_marked_for_strip () const override { return enum_name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -2561,7 +2561,7 @@ public:
   void accept_vis (ASTVisitor &vis) override;
 
   // Invalid if name is empty, so base stripping on that.
-  void mark_for_strip () override { union_name = ""; }
+  void mark_for_strip () override { union_name = {""}; }
   bool is_marked_for_strip () const override { return union_name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -2907,7 +2907,7 @@ public:
   std::string as_string () const;
 
   // Invalid if function name is empty, so base stripping on that.
-  void mark_for_strip () { function_name = ""; }
+  void mark_for_strip () { function_name = {""}; }
   bool is_marked_for_strip () const { return function_name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -3120,7 +3120,7 @@ public:
   std::string as_string () const;
 
   // Invalid if method name is empty, so base stripping on that.
-  void mark_for_strip () { function_name = ""; }
+  void mark_for_strip () { function_name = {""}; }
   bool is_marked_for_strip () const { return function_name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -3399,7 +3399,7 @@ public:
   void accept_vis (ASTVisitor &vis) override;
 
   // Invalid if name is empty, so base stripping on that.
-  void mark_for_strip () override { name = ""; }
+  void mark_for_strip () override { name = {""}; }
   bool is_marked_for_strip () const override { return name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -3534,7 +3534,7 @@ public:
   void accept_vis (ASTVisitor &vis) override;
 
   // Invalid if trait name is empty, so base stripping on that.
-  void mark_for_strip () override { name = ""; }
+  void mark_for_strip () override { name = {""}; }
   bool is_marked_for_strip () const override { return name.empty (); }
 
   // TODO: think of better way to do this
@@ -4346,7 +4346,7 @@ public:
   void accept_vis (ASTVisitor &vis) override;
 
   // Based on idea that nane should never be empty.
-  void mark_for_strip () override { item_name = ""; };
+  void mark_for_strip () override { item_name = {""}; };
   bool is_marked_for_strip () const override { return item_name.empty (); };
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
diff --git a/gcc/rust/ast/rust-macro.h b/gcc/rust/ast/rust-macro.h
index 77c9b84..877df2a 100644
--- a/gcc/rust/ast/rust-macro.h
+++ b/gcc/rust/ast/rust-macro.h
@@ -537,7 +537,7 @@ public:
   void accept_vis (ASTVisitor &vis) override;
 
   // Invalid if rule name is empty, so base stripping on that.
-  void mark_for_strip () override { rule_name = ""; }
+  void mark_for_strip () override { rule_name = {""}; }
   bool is_marked_for_strip () const override { return rule_name.empty (); }
 
   // TODO: this mutable getter seems really dodgy. Think up better way.
@@ -921,7 +921,7 @@ public:
     : ident (std::move (ident)), ident_locus (ident_locus)
   {}
 
-  std::string as_string () const override { return ident; }
+  std::string as_string () const override { return ident.as_string (); }
 
   void accept_vis (ASTVisitor &vis) override;
 
@@ -960,7 +960,7 @@ public:
 
   std::string as_string () const override
   {
-    return ident + " = \"" + str + "\"";
+    return ident.as_string () + " = \"" + str + "\"";
   }
 
   void accept_vis (ASTVisitor &vis) override;
diff --git a/gcc/rust/ast/rust-path.cc b/gcc/rust/ast/rust-path.cc
index 9a3489b..ee6a6fb 100644
--- a/gcc/rust/ast/rust-path.cc
+++ b/gcc/rust/ast/rust-path.cc
@@ -96,7 +96,7 @@ GenericArg::disambiguate_to_type () const
   rust_assert (get_kind () == Kind::Either);
 
   auto segment = std::unique_ptr<TypePathSegment> (
-    new TypePathSegment (path, false, locus));
+    new TypePathSegment (path.as_string (), false, locus));
   auto segments = std::vector<std::unique_ptr<TypePathSegment>> ();
   segments.emplace_back (std::move (segment));
 
@@ -108,14 +108,14 @@ std::string
 GenericArgsBinding::as_string () const
 {
   // TODO: rewrite to work with non-literalisable types
-  return identifier + " = " + type->as_string ();
+  return identifier.as_string () + " = " + type->as_string ();
 }
 
 std::string
 ConstGenericParam::as_string () const
 {
   std::string str ("ConstGenericParam: ");
-  str += "const " + name + ": " + type->as_string ();
+  str += "const " + name.as_string () + ": " + type->as_string ();
 
   if (has_default_value ())
     str += " = " + get_default_value ().as_string ();
diff --git a/gcc/rust/ast/rust-path.h b/gcc/rust/ast/rust-path.h
index 8e4eb19..cad9d5d 100644
--- a/gcc/rust/ast/rust-path.h
+++ b/gcc/rust/ast/rust-path.h
@@ -77,7 +77,7 @@ public:
   // Creates an error state generic args binding.
   static GenericArgsBinding create_error ()
   {
-    return GenericArgsBinding ("", nullptr);
+    return GenericArgsBinding ({""}, nullptr);
   }
 
   // Pointer type for type in constructor to enable polymorphism
@@ -159,19 +159,20 @@ public:
 
   static GenericArg create_error ()
   {
-    return GenericArg (nullptr, nullptr, "", Kind::Error, Location ());
+    return GenericArg (nullptr, nullptr, {""}, Kind::Error, Location ());
   }
 
   static GenericArg create_const (std::unique_ptr<Expr> expression)
   {
     auto locus = expression->get_locus ();
-    return GenericArg (std::move (expression), nullptr, "", Kind::Const, locus);
+    return GenericArg (std::move (expression), nullptr, {""}, Kind::Const,
+		       locus);
   }
 
   static GenericArg create_type (std::unique_ptr<Type> type)
   {
     auto locus = type->get_locus ();
-    return GenericArg (nullptr, std::move (type), "", Kind::Type, locus);
+    return GenericArg (nullptr, std::move (type), {""}, Kind::Type, locus);
   }
 
   static GenericArg create_ambiguous (Identifier path, Location locus)
@@ -245,7 +246,7 @@ public:
   {
     rust_assert (kind == Kind::Either);
 
-    return path;
+    return path.as_string ();
   }
 
   std::string as_string () const
@@ -255,7 +256,7 @@ public:
       case Kind::Error:
 	gcc_unreachable ();
       case Kind::Either:
-	return "Ambiguous: " + path;
+	return "Ambiguous: " + path.as_string ();
       case Kind::Const:
 	return "Const: { " + expression->as_string () + " }";
       case Kind::Type:
diff --git a/gcc/rust/ast/rust-pattern.cc b/gcc/rust/ast/rust-pattern.cc
index 14179ca..e4712c3 100644
--- a/gcc/rust/ast/rust-pattern.cc
+++ b/gcc/rust/ast/rust-pattern.cc
@@ -48,7 +48,7 @@ IdentifierPattern::as_string () const
   if (is_mut)
     str += "mut ";
 
-  str += variable_ident;
+  str += variable_ident.as_string ();
 
   if (has_pattern_to_bind ())
     str += " @ " + to_bind->as_string ();
@@ -126,7 +126,7 @@ StructPatternFieldIdentPat::as_string () const
 
   str += "\n";
 
-  str += ident + " : " + ident_pattern->as_string ();
+  str += ident.as_string () + " : " + ident_pattern->as_string ();
 
   return str;
 }
@@ -144,7 +144,7 @@ StructPatternFieldIdent::as_string () const
   if (has_mut)
     str += "mut ";
 
-  str += ident;
+  str += ident.as_string ();
 
   return str;
 }
diff --git a/gcc/rust/ast/rust-type.h b/gcc/rust/ast/rust-type.h
index 7fa1bc6..7b679d5 100644
--- a/gcc/rust/ast/rust-type.h
+++ b/gcc/rust/ast/rust-type.h
@@ -813,7 +813,7 @@ public:
   // Creates an error state param.
   static MaybeNamedParam create_error ()
   {
-    return MaybeNamedParam ("", UNNAMED, nullptr, {}, Location ());
+    return MaybeNamedParam ({""}, UNNAMED, nullptr, {}, Location ());
   }
 
   Location get_locus () const { return locus; }