gccrs: Add a new visitor that gathers context information

This visitor is intended to be used by other visitors that require
context at some point for a given item.

gcc/rust/ChangeLog:

	* ast/rust-ast-visitor.cc (ContextualASTVisitor::visit): Add multiple
	context saving calls.
	* ast/rust-ast-visitor.h (class DefaultASTVisitor): Make visit
	functions virtual.
	(class ContextualASTVisitor): Add a stack like container for the
	current context chain.

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

diff --git a/gcc/rust/ast/rust-ast-visitor.cc b/gcc/rust/ast/rust-ast-visitor.cc
index b15c8edfed735e8f7c8f50d6e39c6b5d365e07c1..9fb10997e1fdb620d62a5730a769352910c9de79 100644 (file)
--- a/gcc/rust/ast/rust-ast-visitor.cc
+++ b/gcc/rust/ast/rust-ast-visitor.cc
@@ -1447,5 +1447,29 @@ DefaultASTVisitor::visit (AST::BareFunctionType &type)
     visit (type.get_return_type ());
 }
 
+void
+ContextualASTVisitor::visit (AST::Crate &crate)
+{
+  push_context (Context::CRATE);
+  DefaultASTVisitor::visit (crate);
+  pop_context ();
+}
+
+void
+ContextualASTVisitor::visit (AST::InherentImpl &impl)
+{
+  push_context (Context::INHERENT_IMPL);
+  DefaultASTVisitor::visit (impl);
+  pop_context ();
+}
+
+void
+ContextualASTVisitor::visit (AST::TraitImpl &impl)
+{
+  push_context (Context::TRAIT_IMPL);
+  DefaultASTVisitor::visit (impl);
+  pop_context ();
+}
+
 } // namespace AST
 } // namespace Rust

diff --git a/gcc/rust/ast/rust-ast-visitor.h b/gcc/rust/ast/rust-ast-visitor.h
index dbc5d2e806aa543f4e9e3de3d91ee5cbb72d86f9..af86de8f8ea82b68fe34d3c6afaca8494ecf6948 100644 (file)
--- a/gcc/rust/ast/rust-ast-visitor.h
+++ b/gcc/rust/ast/rust-ast-visitor.h
@@ -232,194 +232,196 @@ public:
 
 class DefaultASTVisitor : public ASTVisitor
 {
-  void visit (AST::Crate &crate);
-
-  void visit (AST::Token &tok) override;
-  void visit (AST::DelimTokenTree &delim_tok_tree) override;
-  void visit (AST::AttrInputMetaItemContainer &input) override;
-  void visit (AST::IdentifierExpr &ident_expr) override;
-  void visit (AST::Lifetime &lifetime) override;
-  void visit (AST::LifetimeParam &lifetime_param) override;
-  void visit (AST::ConstGenericParam &const_param) override;
-  void visit (AST::PathInExpression &path) override;
-  void visit (AST::TypePathSegment &segment) override;
-  void visit (AST::TypePathSegmentGeneric &segment) override;
-  void visit (AST::TypePathSegmentFunction &segment) override;
-  void visit (AST::TypePath &path) override;
-  void visit (AST::QualifiedPathInExpression &path) override;
-  void visit (AST::QualifiedPathInType &path) override;
-  void visit (AST::LiteralExpr &expr) override;
-  void visit (AST::AttrInputLiteral &attr_input) override;
-  void visit (AST::AttrInputMacro &attr_input) override;
-  void visit (AST::MetaItemLitExpr &meta_item) override;
-  void visit (AST::MetaItemPathLit &meta_item) override;
-  void visit (AST::BorrowExpr &expr) override;
-  void visit (AST::DereferenceExpr &expr) override;
-  void visit (AST::ErrorPropagationExpr &expr) override;
-  void visit (AST::NegationExpr &expr) override;
-  void visit (AST::ArithmeticOrLogicalExpr &expr) override;
-  void visit (AST::ComparisonExpr &expr) override;
-  void visit (AST::LazyBooleanExpr &expr) override;
-  void visit (AST::TypeCastExpr &expr) override;
-  void visit (AST::AssignmentExpr &expr) override;
-  void visit (AST::CompoundAssignmentExpr &expr) override;
-  void visit (AST::GroupedExpr &expr) override;
-  void visit (AST::ArrayElemsValues &elems) override;
-  void visit (AST::ArrayElemsCopied &elems) override;
-  void visit (AST::ArrayExpr &expr) override;
-  void visit (AST::ArrayIndexExpr &expr) override;
-  void visit (AST::TupleExpr &expr) override;
-  void visit (AST::TupleIndexExpr &expr) override;
-  void visit (AST::StructExprStruct &expr) override;
-  void visit (AST::StructExprFieldIdentifier &field) override;
-  void visit (AST::StructExprFieldIdentifierValue &field) override;
-  void visit (AST::StructExprFieldIndexValue &field) override;
-  void visit (AST::StructExprStructFields &expr) override;
-  void visit (AST::StructExprStructBase &expr) override;
-  void visit (AST::CallExpr &expr) override;
-  void visit (AST::MethodCallExpr &expr) override;
-  void visit (AST::FieldAccessExpr &expr) override;
-  void visit (AST::ClosureExprInner &expr) override;
-  void visit (AST::BlockExpr &expr) override;
-  void visit (AST::ClosureExprInnerTyped &expr) override;
-  void visit (AST::ContinueExpr &expr) override;
-  void visit (AST::BreakExpr &expr) override;
-  void visit (AST::RangeFromToExpr &expr) override;
-  void visit (AST::RangeFromExpr &expr) override;
-  void visit (AST::RangeToExpr &expr) override;
-  void visit (AST::RangeFullExpr &expr) override;
-  void visit (AST::RangeFromToInclExpr &expr) override;
-  void visit (AST::RangeToInclExpr &expr) override;
-  void visit (AST::ReturnExpr &expr) override;
-  void visit (AST::UnsafeBlockExpr &expr) override;
-  void visit (AST::LoopExpr &expr) override;
-  void visit (AST::WhileLoopExpr &expr) override;
-  void visit (AST::WhileLetLoopExpr &expr) override;
-  void visit (AST::ForLoopExpr &expr) override;
-  void visit (AST::IfExpr &expr) override;
-  void visit (AST::IfExprConseqElse &expr) override;
-  void visit (AST::IfLetExpr &expr) override;
-  void visit (AST::IfLetExprConseqElse &expr) override;
-  void visit (AST::MatchExpr &expr) override;
-  void visit (AST::AwaitExpr &expr) override;
-  void visit (AST::AsyncBlockExpr &expr) override;
-  void visit (AST::TypeParam &param) override;
-  void visit (AST::LifetimeWhereClauseItem &item) override;
-  void visit (AST::TypeBoundWhereClauseItem &item) override;
-  void visit (AST::Method &method) override;
-  void visit (AST::Module &module) override;
-  void visit (AST::ExternCrate &crate) override;
-  void visit (AST::UseTreeGlob &use_tree) override;
-  void visit (AST::UseTreeList &use_tree) override;
-  void visit (AST::UseTreeRebind &use_tree) override;
-  void visit (AST::UseDeclaration &use_decl) override;
-  void visit (AST::Function &function) override;
-  void visit (AST::TypeAlias &type_alias) override;
-  void visit (AST::StructStruct &struct_item) override;
-  void visit (AST::TupleStruct &tuple_struct) override;
-  void visit (AST::EnumItem &item) override;
-  void visit (AST::EnumItemTuple &item) override;
-  void visit (AST::EnumItemStruct &item) override;
-  void visit (AST::EnumItemDiscriminant &item) override;
-  void visit (AST::Enum &enum_item) override;
-  void visit (AST::Union &union_item) override;
-  void visit (AST::ConstantItem &const_item) override;
-  void visit (AST::StaticItem &static_item) override;
-  void visit (AST::TraitItemFunc &item) override;
-  void visit (AST::TraitItemMethod &item) override;
-  void visit (AST::TraitItemConst &item) override;
-  void visit (AST::TraitItemType &item) override;
-  void visit (AST::Trait &trait) override;
-  void visit (AST::InherentImpl &impl) override;
-  void visit (AST::TraitImpl &impl) override;
-  void visit (AST::ExternalTypeItem &item) override;
-  void visit (AST::ExternalStaticItem &item) override;
-  void visit (AST::ExternalFunctionItem &item) override;
-  void visit (AST::ExternBlock &block) override;
-  void visit (AST::MacroMatchFragment &match) override;
-  void visit (AST::MacroMatchRepetition &match) override;
-  void visit (AST::MacroMatcher &matcher) override;
-  void visit (AST::MacroRulesDefinition &rules_def) override;
-  void visit (AST::MacroInvocation &macro_invoc) override;
-  void visit (AST::MetaItemPath &meta_item) override;
-  void visit (AST::MetaItemSeq &meta_item) override;
-  void visit (AST::MetaWord &meta_item) override;
-  void visit (AST::MetaNameValueStr &meta_item) override;
-  void visit (AST::MetaListPaths &meta_item) override;
-  void visit (AST::MetaListNameValueStr &meta_item) override;
-  void visit (AST::LiteralPattern &pattern) override;
-  void visit (AST::IdentifierPattern &pattern) override;
-  void visit (AST::WildcardPattern &pattern) override;
-  void visit (AST::RestPattern &pattern) override;
-  void visit (AST::RangePatternBoundLiteral &bound) override;
-  void visit (AST::RangePatternBoundPath &bound) override;
-  void visit (AST::RangePatternBoundQualPath &bound) override;
-  void visit (AST::RangePattern &pattern) override;
-  void visit (AST::ReferencePattern &pattern) override;
-  void visit (AST::StructPatternFieldTuplePat &field) override;
-  void visit (AST::StructPatternFieldIdentPat &field) override;
-  void visit (AST::StructPatternFieldIdent &field) override;
-  void visit (AST::StructPattern &pattern) override;
-  void visit (AST::TupleStructItemsNoRange &tuple_items) override;
-  void visit (AST::TupleStructItemsRange &tuple_items) override;
-  void visit (AST::TupleStructPattern &pattern) override;
-  void visit (AST::TuplePatternItemsMultiple &tuple_items) override;
-  void visit (AST::TuplePatternItemsRanged &tuple_items) override;
-  void visit (AST::TuplePattern &pattern) override;
-  void visit (AST::GroupedPattern &pattern) override;
-  void visit (AST::SlicePattern &pattern) override;
-  void visit (AST::AltPattern &pattern) override;
-  void visit (AST::EmptyStmt &stmt) override;
-  void visit (AST::LetStmt &stmt) override;
-  void visit (AST::ExprStmt &stmt) override;
-  void visit (AST::TraitBound &bound) override;
-  void visit (AST::ImplTraitType &type) override;
-  void visit (AST::TraitObjectType &type) override;
-  void visit (AST::ParenthesisedType &type) override;
-  void visit (AST::ImplTraitTypeOneBound &type) override;
-  void visit (AST::TraitObjectTypeOneBound &type) override;
-  void visit (AST::TupleType &type) override;
-  void visit (AST::NeverType &type) override;
-  void visit (AST::RawPointerType &type) override;
-  void visit (AST::ReferenceType &type) override;
-  void visit (AST::ArrayType &type) override;
-  void visit (AST::SliceType &type) override;
-  void visit (AST::InferredType &type) override;
-  void visit (AST::BareFunctionType &type) override;
+public:
+  virtual void visit (AST::Crate &crate);
+
+protected:
+  virtual void visit (AST::Token &tok) override;
+  virtual void visit (AST::DelimTokenTree &delim_tok_tree) override;
+  virtual void visit (AST::AttrInputMetaItemContainer &input) override;
+  virtual void visit (AST::IdentifierExpr &ident_expr) override;
+  virtual void visit (AST::Lifetime &lifetime) override;
+  virtual void visit (AST::LifetimeParam &lifetime_param) override;
+  virtual void visit (AST::ConstGenericParam &const_param) override;
+  virtual void visit (AST::PathInExpression &path) override;
+  virtual void visit (AST::TypePathSegment &segment) override;
+  virtual void visit (AST::TypePathSegmentGeneric &segment) override;
+  virtual void visit (AST::TypePathSegmentFunction &segment) override;
+  virtual void visit (AST::TypePath &path) override;
+  virtual void visit (AST::QualifiedPathInExpression &path) override;
+  virtual void visit (AST::QualifiedPathInType &path) override;
+  virtual void visit (AST::LiteralExpr &expr) override;
+  virtual void visit (AST::AttrInputLiteral &attr_input) override;
+  virtual void visit (AST::AttrInputMacro &attr_input) override;
+  virtual void visit (AST::MetaItemLitExpr &meta_item) override;
+  virtual void visit (AST::MetaItemPathLit &meta_item) override;
+  virtual void visit (AST::BorrowExpr &expr) override;
+  virtual void visit (AST::DereferenceExpr &expr) override;
+  virtual void visit (AST::ErrorPropagationExpr &expr) override;
+  virtual void visit (AST::NegationExpr &expr) override;
+  virtual void visit (AST::ArithmeticOrLogicalExpr &expr) override;
+  virtual void visit (AST::ComparisonExpr &expr) override;
+  virtual void visit (AST::LazyBooleanExpr &expr) override;
+  virtual void visit (AST::TypeCastExpr &expr) override;
+  virtual void visit (AST::AssignmentExpr &expr) override;
+  virtual void visit (AST::CompoundAssignmentExpr &expr) override;
+  virtual void visit (AST::GroupedExpr &expr) override;
+  virtual void visit (AST::ArrayElemsValues &elems) override;
+  virtual void visit (AST::ArrayElemsCopied &elems) override;
+  virtual void visit (AST::ArrayExpr &expr) override;
+  virtual void visit (AST::ArrayIndexExpr &expr) override;
+  virtual void visit (AST::TupleExpr &expr) override;
+  virtual void visit (AST::TupleIndexExpr &expr) override;
+  virtual void visit (AST::StructExprStruct &expr) override;
+  virtual void visit (AST::StructExprFieldIdentifier &field) override;
+  virtual void visit (AST::StructExprFieldIdentifierValue &field) override;
+  virtual void visit (AST::StructExprFieldIndexValue &field) override;
+  virtual void visit (AST::StructExprStructFields &expr) override;
+  virtual void visit (AST::StructExprStructBase &expr) override;
+  virtual void visit (AST::CallExpr &expr) override;
+  virtual void visit (AST::MethodCallExpr &expr) override;
+  virtual void visit (AST::FieldAccessExpr &expr) override;
+  virtual void visit (AST::ClosureExprInner &expr) override;
+  virtual void visit (AST::BlockExpr &expr) override;
+  virtual void visit (AST::ClosureExprInnerTyped &expr) override;
+  virtual void visit (AST::ContinueExpr &expr) override;
+  virtual void visit (AST::BreakExpr &expr) override;
+  virtual void visit (AST::RangeFromToExpr &expr) override;
+  virtual void visit (AST::RangeFromExpr &expr) override;
+  virtual void visit (AST::RangeToExpr &expr) override;
+  virtual void visit (AST::RangeFullExpr &expr) override;
+  virtual void visit (AST::RangeFromToInclExpr &expr) override;
+  virtual void visit (AST::RangeToInclExpr &expr) override;
+  virtual void visit (AST::ReturnExpr &expr) override;
+  virtual void visit (AST::UnsafeBlockExpr &expr) override;
+  virtual void visit (AST::LoopExpr &expr) override;
+  virtual void visit (AST::WhileLoopExpr &expr) override;
+  virtual void visit (AST::WhileLetLoopExpr &expr) override;
+  virtual void visit (AST::ForLoopExpr &expr) override;
+  virtual void visit (AST::IfExpr &expr) override;
+  virtual void visit (AST::IfExprConseqElse &expr) override;
+  virtual void visit (AST::IfLetExpr &expr) override;
+  virtual void visit (AST::IfLetExprConseqElse &expr) override;
+  virtual void visit (AST::MatchExpr &expr) override;
+  virtual void visit (AST::AwaitExpr &expr) override;
+  virtual void visit (AST::AsyncBlockExpr &expr) override;
+  virtual void visit (AST::TypeParam &param) override;
+  virtual void visit (AST::LifetimeWhereClauseItem &item) override;
+  virtual void visit (AST::TypeBoundWhereClauseItem &item) override;
+  virtual void visit (AST::Method &method) override;
+  virtual void visit (AST::Module &module) override;
+  virtual void visit (AST::ExternCrate &crate) override;
+  virtual void visit (AST::UseTreeGlob &use_tree) override;
+  virtual void visit (AST::UseTreeList &use_tree) override;
+  virtual void visit (AST::UseTreeRebind &use_tree) override;
+  virtual void visit (AST::UseDeclaration &use_decl) override;
+  virtual void visit (AST::Function &function) override;
+  virtual void visit (AST::TypeAlias &type_alias) override;
+  virtual void visit (AST::StructStruct &struct_item) override;
+  virtual void visit (AST::TupleStruct &tuple_struct) override;
+  virtual void visit (AST::EnumItem &item) override;
+  virtual void visit (AST::EnumItemTuple &item) override;
+  virtual void visit (AST::EnumItemStruct &item) override;
+  virtual void visit (AST::EnumItemDiscriminant &item) override;
+  virtual void visit (AST::Enum &enum_item) override;
+  virtual void visit (AST::Union &union_item) override;
+  virtual void visit (AST::ConstantItem &const_item) override;
+  virtual void visit (AST::StaticItem &static_item) override;
+  virtual void visit (AST::TraitItemFunc &item) override;
+  virtual void visit (AST::TraitItemMethod &item) override;
+  virtual void visit (AST::TraitItemConst &item) override;
+  virtual void visit (AST::TraitItemType &item) override;
+  virtual void visit (AST::Trait &trait) override;
+  virtual void visit (AST::InherentImpl &impl) override;
+  virtual void visit (AST::TraitImpl &impl) override;
+  virtual void visit (AST::ExternalTypeItem &item) override;
+  virtual void visit (AST::ExternalStaticItem &item) override;
+  virtual void visit (AST::ExternalFunctionItem &item) override;
+  virtual void visit (AST::ExternBlock &block) override;
+  virtual void visit (AST::MacroMatchFragment &match) override;
+  virtual void visit (AST::MacroMatchRepetition &match) override;
+  virtual void visit (AST::MacroMatcher &matcher) override;
+  virtual void visit (AST::MacroRulesDefinition &rules_def) override;
+  virtual void visit (AST::MacroInvocation &macro_invoc) override;
+  virtual void visit (AST::MetaItemPath &meta_item) override;
+  virtual void visit (AST::MetaItemSeq &meta_item) override;
+  virtual void visit (AST::MetaWord &meta_item) override;
+  virtual void visit (AST::MetaNameValueStr &meta_item) override;
+  virtual void visit (AST::MetaListPaths &meta_item) override;
+  virtual void visit (AST::MetaListNameValueStr &meta_item) override;
+  virtual void visit (AST::LiteralPattern &pattern) override;
+  virtual void visit (AST::IdentifierPattern &pattern) override;
+  virtual void visit (AST::WildcardPattern &pattern) override;
+  virtual void visit (AST::RestPattern &pattern) override;
+  virtual void visit (AST::RangePatternBoundLiteral &bound) override;
+  virtual void visit (AST::RangePatternBoundPath &bound) override;
+  virtual void visit (AST::RangePatternBoundQualPath &bound) override;
+  virtual void visit (AST::RangePattern &pattern) override;
+  virtual void visit (AST::ReferencePattern &pattern) override;
+  virtual void visit (AST::StructPatternFieldTuplePat &field) override;
+  virtual void visit (AST::StructPatternFieldIdentPat &field) override;
+  virtual void visit (AST::StructPatternFieldIdent &field) override;
+  virtual void visit (AST::StructPattern &pattern) override;
+  virtual void visit (AST::TupleStructItemsNoRange &tuple_items) override;
+  virtual void visit (AST::TupleStructItemsRange &tuple_items) override;
+  virtual void visit (AST::TupleStructPattern &pattern) override;
+  virtual void visit (AST::TuplePatternItemsMultiple &tuple_items) override;
+  virtual void visit (AST::TuplePatternItemsRanged &tuple_items) override;
+  virtual void visit (AST::TuplePattern &pattern) override;
+  virtual void visit (AST::GroupedPattern &pattern) override;
+  virtual void visit (AST::SlicePattern &pattern) override;
+  virtual void visit (AST::AltPattern &pattern) override;
+  virtual void visit (AST::EmptyStmt &stmt) override;
+  virtual void visit (AST::LetStmt &stmt) override;
+  virtual void visit (AST::ExprStmt &stmt) override;
+  virtual void visit (AST::TraitBound &bound) override;
+  virtual void visit (AST::ImplTraitType &type) override;
+  virtual void visit (AST::TraitObjectType &type) override;
+  virtual void visit (AST::ParenthesisedType &type) override;
+  virtual void visit (AST::ImplTraitTypeOneBound &type) override;
+  virtual void visit (AST::TraitObjectTypeOneBound &type) override;
+  virtual void visit (AST::TupleType &type) override;
+  virtual void visit (AST::NeverType &type) override;
+  virtual void visit (AST::RawPointerType &type) override;
+  virtual void visit (AST::ReferenceType &type) override;
+  virtual void visit (AST::ArrayType &type) override;
+  virtual void visit (AST::SliceType &type) override;
+  virtual void visit (AST::InferredType &type) override;
+  virtual void visit (AST::BareFunctionType &type) override;
 
   template <typename T> void visit (T &node);
 
   template <typename T> void visit (std::unique_ptr<T> &node);
 
-private:
-  void visit (AST::GenericArgsBinding &binding);
-  void visit (AST::PathExprSegment &segment);
-  void visit (AST::GenericArgs &args);
-  void visit (AST::QualifiedPathType &path);
-  void visit (AST::TypePathFunction &tpf);
-  void visit (AST::PathIdentSegment &segment);
-  void visit (AST::SimplePath &path);
-  void visit (AST::SimplePathSegment &segment);
-  void visit (AST::StructBase &base);
-  void visit (AST::ClosureParam &param);
-  void visit (AST::LoopLabel &label);
-  void visit (AST::MatchCase &arm);
-  void visit (AST::MatchArm &arm);
-  void visit (AST::Visibility &vis);
-  void visit (AST::FunctionQualifiers &qualifiers);
-  void visit (AST::SelfParam &self);
-  void visit (AST::WhereClause &where);
-  void visit (AST::FunctionParam &param);
-  void visit (AST::StructField &field);
-  void visit (AST::TupleField &field);
-  void visit (AST::TraitFunctionDecl &decl);
-  void visit (AST::TraitMethodDecl &decl);
-  void visit (AST::NamedFunctionParam &param);
-  void visit (AST::MacroRule &rule);
-  void visit (AST::MacroInvocData &data);
-  void visit (AST::MacroTranscriber &transcriber);
-  void visit (AST::StructPatternElements &spe);
-  void visit (AST::MaybeNamedParam &param);
+  virtual void visit (AST::GenericArgsBinding &binding);
+  virtual void visit (AST::PathExprSegment &segment);
+  virtual void visit (AST::GenericArgs &args);
+  virtual void visit (AST::QualifiedPathType &path);
+  virtual void visit (AST::TypePathFunction &tpf);
+  virtual void visit (AST::PathIdentSegment &segment);
+  virtual void visit (AST::SimplePath &path);
+  virtual void visit (AST::SimplePathSegment &segment);
+  virtual void visit (AST::StructBase &base);
+  virtual void visit (AST::ClosureParam &param);
+  virtual void visit (AST::LoopLabel &label);
+  virtual void visit (AST::MatchCase &arm);
+  virtual void visit (AST::MatchArm &arm);
+  virtual void visit (AST::Visibility &vis);
+  virtual void visit (AST::FunctionQualifiers &qualifiers);
+  virtual void visit (AST::SelfParam &self);
+  virtual void visit (AST::WhereClause &where);
+  virtual void visit (AST::FunctionParam &param);
+  virtual void visit (AST::StructField &field);
+  virtual void visit (AST::TupleField &field);
+  virtual void visit (AST::TraitFunctionDecl &decl);
+  virtual void visit (AST::TraitMethodDecl &decl);
+  virtual void visit (AST::NamedFunctionParam &param);
+  virtual void visit (AST::MacroRule &rule);
+  virtual void visit (AST::MacroInvocData &data);
+  virtual void visit (AST::MacroTranscriber &transcriber);
+  virtual void visit (AST::StructPatternElements &spe);
+  virtual void visit (AST::MaybeNamedParam &param);
+  void visit (AST::Attribute &attribute) {}
 
   template <typename T> void visit_outer_attrs (T &node)
   {
@@ -432,8 +434,37 @@ private:
     for (auto &attr : node.get_inner_attrs ())
       visit (attr);
   }
+};
 
-  void visit (AST::Attribute &attribute) {}
+class ContextualASTVisitor : public DefaultASTVisitor
+{
+protected:
+  enum class Context
+  {
+    FUNCTION,
+    INHERENT_IMPL,
+    TRAIT_IMPL,
+    MODULE,
+    CRATE,
+  };
+  using DefaultASTVisitor::visit;
+
+  virtual void visit (AST::Crate &crate) override;
+
+  virtual void visit (AST::InherentImpl &impl) override;
+
+  virtual void visit (AST::TraitImpl &impl) override;
+
+  template <typename T> void visit (T &item)
+  {
+    DefaultASTVisitor::visit (item);
+  }
+
+  std::vector<Context> context;
+
+  void push_context (Context ctx) { context.push_back (ctx); }
+
+  void pop_context () { context.pop_back (); }
 };
 
 } // namespace AST