source: src/AST/Convert.cpp@ 8fd1b7c

//
// Cforall Version 1.0.0 Copyright (C) 2019 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Convert.cpp -- Convert between the new and old syntax trees.
//
// Author           : Thierry Delisle
// Created On       : Thu May 09 15::37::05 2019
// Last Modified By : Andrew Beach
// Last Modified On : Wed Apr 20 13:58:00 2022
// Update Count     : 43
//

#include "Convert.hpp"

#include <deque>
#include <unordered_map>

#include "AST/Attribute.hpp"
#include "AST/Copy.hpp"
#include "AST/Decl.hpp"
#include "AST/Expr.hpp"
#include "AST/Init.hpp"
#include "AST/Stmt.hpp"
#include "AST/TranslationUnit.hpp"
#include "AST/TypeSubstitution.hpp"

#include "SymTab/Autogen.h"
#include "SynTree/Attribute.h"
#include "SynTree/Declaration.h"
#include "SynTree/TypeSubstitution.h"

#include "Validate/FindSpecialDecls.h"

//================================================================================================
// Utilities
template<template <class...> class C>
struct to {
        template<typename T>
        static auto from( T && v ) -> C< typename T::value_type > {
                C< typename T::value_type > l;
                std::move(std::begin(v), std::end(v), std::back_inserter(l));
                return l;
        }
};

//================================================================================================
namespace ast {
// These are the shared local information used by ConverterNewToOld and
// ConverterOldToNew to update the global information in the two versions.

static ast::ptr<ast::Type> sizeType = nullptr;
static const ast::FunctionDecl * dereferenceOperator = nullptr;
static const ast::StructDecl   * dtorStruct = nullptr;
static const ast::FunctionDecl * dtorStructDestroy = nullptr;

}

//================================================================================================
class ConverterNewToOld : public ast::Visitor {
        BaseSyntaxNode * node = nullptr;
        using Cache = std::unordered_map< const ast::Node *, BaseSyntaxNode * >;
        Cache cache;

        // Statements can no longer be shared.
        // however, since StmtExprResult is now implemented, need to still maintain
        // readonly references.
        Cache readonlyCache;

        template<typename T>
        struct Getter {
                ConverterNewToOld & visitor;

                template<typename U, enum ast::Node::ref_type R>
                T * accept1( const ast::ptr_base<U, R> & ptr ) {
                        if ( ! ptr ) return nullptr;
                        ptr->accept( visitor );
                        T * ret = strict_dynamic_cast< T * >( visitor.node );
                        visitor.node = nullptr;
                        return ret;
                }

                template<typename U>
                std::list< T * > acceptL( const U & container ) {
                        std::list< T * > ret;
                        for ( auto ptr : container ) {
                                ret.emplace_back( accept1( ptr ) );
                        }
                        return ret;
                }
        };

        template<typename T>
        Getter<T> get() {
                return Getter<T>{ *this };
        }

        Label makeLabel(Statement * labelled, const ast::Label& label) {
                // This probably will leak memory, but only until we get rid of the old tree.
                if ( nullptr == labelled && label.location.isSet() ) {
                        labelled = new NullStmt();
                        labelled->location = label.location;
                }
                return Label(
                        label.name,
                        labelled,
                        get<Attribute>().acceptL(label.attributes)
                );
        }

        template<template <class...> class C>
        std::list<Label> makeLabelL(Statement * labelled, const C<ast::Label>& labels) {
                std::list<Label> ret;
                for (auto label : labels) {
                        ret.push_back( makeLabel(labelled, label) );
                }
                return ret;
        }

        /// get new qualifiers from old type
        Type::Qualifiers cv( const ast::Type * ty ) { return { ty->qualifiers.val }; }

        /// returns true and sets `node` if in cache
        bool inCache( const ast::Node * node ) {
                auto it = cache.find( node );
                if ( it == cache.end() ) return false;
                this->node = it->second;
                return true;
        }

public:
        Declaration * decl( const ast::Decl * declNode ) {
                return get<Declaration>().accept1( ast::ptr<ast::Decl>( declNode ) );
        }

private:
        void declPostamble( Declaration * decl, const ast::Decl * node ) {
                decl->location = node->location;
                // name comes from constructor
                // linkage comes from constructor
                decl->extension = node->extension;
                decl->uniqueId = node->uniqueId;
                // storageClasses comes from constructor
                this->node = decl;
        }

        const ast::DeclWithType * declWithTypePostamble (
                        DeclarationWithType * decl, const ast::DeclWithType * node ) {
                cache.emplace( node, decl );
                decl->mangleName = node->mangleName;
                decl->scopeLevel = node->scopeLevel;
                decl->asmName = get<Expression>().accept1( node->asmName );
                // attributes comes from constructor
                decl->isDeleted = node->isDeleted;
                // fs comes from constructor
                declPostamble( decl, node );
                return nullptr;
        }

        const ast::DeclWithType * visit( const ast::ObjectDecl * node ) override final {        
                if ( inCache( node ) ) {
                        return nullptr;
                }
                auto bfwd = get<Expression>().accept1( node->bitfieldWidth );
                auto type = get<Type>().accept1( node->type );
                auto attr = get<Attribute>().acceptL( node->attributes );

                // This field can be unset very early on (Pre-FixReturnTypes).
                auto newType = (type) ? type->clone() : nullptr;

                auto decl = new ObjectDecl(
                        node->name,
                        Type::StorageClasses( node->storage.val ),
                        LinkageSpec::Spec( node->linkage.val ),
                        bfwd,
                        newType,
                        nullptr, // prevent infinite loop
                        attr,
                        Type::FuncSpecifiers( node->funcSpec.val )
                );

                // handles the case where node->init references itself
                // xxx - does it really happen?
                declWithTypePostamble(decl, node);
                auto init = get<Initializer>().accept1( node->init );
                decl->init = init;

                this->node = decl;
                return nullptr;
        }

        const ast::DeclWithType * visit( const ast::FunctionDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;

                // function decl contains real variables that the type must use.
                // the structural change means function type in and out of decl
                // must be handled **differently** on convert back to old.
                auto ftype = new FunctionType(
                        cv(node->type),
                        (bool)node->type->isVarArgs
                );
                ftype->returnVals = get<DeclarationWithType>().acceptL(node->returns);
                ftype->parameters = get<DeclarationWithType>().acceptL(node->params);

                ftype->forall = get<TypeDecl>().acceptL( node->type_params );
                if (!node->assertions.empty()) {
                        assert(!ftype->forall.empty());
                        // find somewhere to place assertions back, for convenience it is the last slot
                        ftype->forall.back()->assertions = get<DeclarationWithType>().acceptL(node->assertions);
                }

                visitType(node->type, ftype);

                auto decl = new FunctionDecl(
                        node->name,
                        Type::StorageClasses( node->storage.val ),
                        LinkageSpec::Spec( node->linkage.val ),
                        ftype,
                        //get<FunctionType>().accept1( node->type ),
                        {},
                        get<Attribute>().acceptL( node->attributes ),
                        Type::FuncSpecifiers( node->funcSpec.val )
                );
                cache.emplace( node, decl );
                decl->statements = get<CompoundStmt>().accept1( node->stmts );
                decl->withExprs = get<Expression>().acceptL( node->withExprs );
                if ( ast::dereferenceOperator == node ) {
                        Validate::dereferenceOperator = decl;
                }
                if ( ast::dtorStructDestroy == node ) {
                        Validate::dtorStructDestroy = decl;
                }
                return declWithTypePostamble( decl, node );
        }

        // InlineMemberDecl vanish after EnumAndPointerDecay pass so no necessary to implement NewToOld
        const ast::DeclWithType * visit( const ast::InlineMemberDecl * node ) override final {  
                assert( false );
                (void) node;
                return nullptr;
        }

        const ast::Decl * namedTypePostamble( NamedTypeDecl * decl, const ast::NamedTypeDecl * node ) {
                // base comes from constructor
                decl->assertions = get<DeclarationWithType>().acceptL( node->assertions );
                declPostamble( decl, node );
                return nullptr;
        }

        const ast::Decl * visit( const ast::TypeDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto decl = new TypeDecl(
                        node->name,
                        Type::StorageClasses( node->storage.val ),
                        get<Type>().accept1( node->base ),
                        (TypeDecl::Kind)(unsigned)node->kind,
                        node->sized,
                        get<Type>().accept1( node->init )
                );
                cache.emplace( node, decl );
                return namedTypePostamble( decl, node );
        }

        const ast::Decl * visit( const ast::TypedefDecl * node ) override final {
                auto decl = new TypedefDecl(
                        node->name,
                        node->location,
                        Type::StorageClasses( node->storage.val ),
            get<Type>().accept1( node->base ),
                        LinkageSpec::Spec( node->linkage.val )
                );
                return namedTypePostamble( decl, node );
        }

        const ast::Decl * aggregatePostamble( AggregateDecl * decl, const ast::AggregateDecl * node ) {
                cache.emplace( node, decl );
                decl->members = get<Declaration>().acceptL( node->members );
                decl->parameters = get<TypeDecl>().acceptL( node->params );
                decl->body = node->body;
                // attributes come from constructor
                decl->parent = get<AggregateDecl>().accept1( node->parent );
                declPostamble( decl, node );
                return nullptr; // ??
        }

        const ast::Decl * visit( const ast::StructDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto decl = new StructDecl(
                        node->name,
                        (AggregateDecl::Aggregate)node->kind,
                        get<Attribute>().acceptL( node->attributes ),
                        LinkageSpec::Spec( node->linkage.val )
                );

                if ( ast::dtorStruct == node ) {
                        Validate::dtorStruct = decl;
                }

                return aggregatePostamble( decl, node );
        }

        const ast::Decl * visit( const ast::UnionDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto decl = new UnionDecl(
                        node->name,
                        get<Attribute>().acceptL( node->attributes ),
                        LinkageSpec::Spec( node->linkage.val )
                );
                return aggregatePostamble( decl, node );
        }

        const ast::Decl * visit( const ast::EnumDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto decl = new EnumDecl(
                        node->name,
                        get<Attribute>().acceptL( node->attributes ),
                        node->isTyped,
                        LinkageSpec::Spec( node->linkage.val ),
                        get<Type>().accept1(node->base)
                );
                return aggregatePostamble( decl, node );
        }

        const ast::Decl * visit( const ast::TraitDecl * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto decl = new TraitDecl(
                        node->name,
                        {},
                        LinkageSpec::Spec( node->linkage.val )
                );
                return aggregatePostamble( decl, node );
        }

        const ast::AsmDecl * visit( const ast::AsmDecl * node ) override final {
                auto decl = new AsmDecl( get<AsmStmt>().accept1( node->stmt ) );
                declPostamble( decl, node );
                return nullptr;
        }

        const ast::DirectiveDecl * visit( const ast::DirectiveDecl * node ) override final {
                auto decl = new DirectiveDecl( get<DirectiveStmt>().accept1( node->stmt ) );
                declPostamble( decl, node );
                return nullptr;
        }

        const ast::StaticAssertDecl * visit( const ast::StaticAssertDecl * node ) override final {
                auto decl = new StaticAssertDecl(
                        get<Expression>().accept1( node->cond ),
                        get<ConstantExpr>().accept1( node->msg )
                );
                declPostamble( decl, node );
                return nullptr;
        }

        const ast::Stmt * stmtPostamble( Statement * stmt, const ast::Stmt * node ) {
                // force statements in old tree to be unique.
                // cache.emplace( node, stmt );
                readonlyCache.emplace( node, stmt );
                stmt->location = node->location;
                stmt->labels = makeLabelL( stmt, node->labels );
                this->node = stmt;
                return nullptr;
        }

        void clausePostamble( Statement * stmt, const ast::StmtClause * node ) {
                stmt->location = node->location;
                this->node = stmt;
        }

        const ast::CompoundStmt * visit( const ast::CompoundStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new CompoundStmt( get<Statement>().acceptL( node->kids ) );
                stmtPostamble( stmt, node );
                return nullptr;
        }

        const ast::Stmt * visit( const ast::ExprStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new ExprStmt( nullptr );
                stmt->expr = get<Expression>().accept1( node->expr );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::AsmStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new AsmStmt(
                        node->isVolatile,
                        get<Expression>().accept1( node->instruction ),
                        get<Expression>().acceptL( node->output ),
                        get<Expression>().acceptL( node->input ),
                        get<ConstantExpr>().acceptL( node->clobber ),
                        makeLabelL( nullptr, node->gotoLabels ) // What are these labelling?
                );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::DirectiveStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new DirectiveStmt( node->directive );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::IfStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new IfStmt(
                        get<Expression>().accept1( node->cond ),
                        get<Statement>().accept1( node->then ),
                        get<Statement>().accept1( node->else_ ),
                        get<Statement>().acceptL( node->inits )
                );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::SwitchStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new SwitchStmt(
                        get<Expression>().accept1( node->cond ),
                        get<Statement>().acceptL( node->cases )
                );
                return stmtPostamble( stmt, node );
        }

        const ast::CaseClause * visit( const ast::CaseClause * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new CaseStmt(
                        get<Expression>().accept1( node->cond ),
                        get<Statement>().acceptL( node->stmts ),
                        node->isDefault()
                );
                clausePostamble( stmt, node );
                return nullptr;
        }

        const ast::Stmt * visit( const ast::WhileDoStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto inits = get<Statement>().acceptL( node->inits );
                auto stmt = new WhileDoStmt(
                        get<Expression>().accept1( node->cond ),
                        get<Statement>().accept1( node->body ),
                        get<Statement>().accept1( node->else_ ),
                        inits,
                        node->isDoWhile
                );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::ForStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new ForStmt(
                        get<Statement>().acceptL( node->inits ),
                        get<Expression>().accept1( node->cond ),
                        get<Expression>().accept1( node->inc ),
                        get<Statement>().accept1( node->body ),
                        get<Statement>().accept1( node->else_ )
                );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::BranchStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                BranchStmt * stmt;
                if (node->computedTarget) {
                        stmt = new BranchStmt( get<Expression>().accept1( node->computedTarget ),
                                BranchStmt::Goto );
                } else {
                        BranchStmt::Type type;
                        switch (node->kind) {
                        #define CASE(n) \
                        case ast::BranchStmt::n: \
                                type = BranchStmt::n; \
                                break
                        CASE(Goto);
                        CASE(Break);
                        CASE(Continue);
                        CASE(FallThrough);
                        CASE(FallThroughDefault);
                        #undef CASE
                        default:
                                assertf(false, "Invalid ast::BranchStmt::Kind: %d\n", node->kind);
                        }

                        // The labels here are also weird.
                        stmt = new BranchStmt( makeLabel( nullptr, node->originalTarget ), type );
                        stmt->target = makeLabel( stmt, node->target );
                }
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::ReturnStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new ReturnStmt( get<Expression>().accept1( node->expr ) );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::ThrowStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                ThrowStmt::Kind kind;
                switch (node->kind) {
                case ast::ExceptionKind::Terminate:
                        kind = ThrowStmt::Terminate;
                        break;
                case ast::ExceptionKind::Resume:
                        kind = ThrowStmt::Resume;
                        break;
                default:
                        assertf(false, "Invalid ast::ThrowStmt::Kind: %d\n", node->kind);
                }
                auto stmt = new ThrowStmt(
                        kind,
                        get<Expression>().accept1( node->expr ),
                        get<Expression>().accept1( node->target )
                );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::TryStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto handlers = get<CatchStmt>().acceptL( node->handlers );
                auto stmt = new TryStmt(
                        get<CompoundStmt>().accept1( node->body ),
                        handlers,
                        get<FinallyStmt>().accept1( node->finally )
                );
                return stmtPostamble( stmt, node );
        }

        const ast::CatchClause * visit( const ast::CatchClause * node ) override final {
                if ( inCache( node ) ) return nullptr;
                CatchStmt::Kind kind;
                switch (node->kind) {
                case ast::ExceptionKind::Terminate:
                        kind = CatchStmt::Terminate;
                        break;
                case ast::ExceptionKind::Resume:
                        kind = CatchStmt::Resume;
                        break;
                default:
                        assertf(false, "Invalid ast::ExceptionKind: %d\n", node->kind);
                }
                auto stmt = new CatchStmt(
                        kind,
                        get<Declaration>().accept1( node->decl ),
                        get<Expression>().accept1( node->cond ),
                        get<Statement>().accept1( node->body )
                );
                return clausePostamble( stmt, node ), nullptr;
        }

        const ast::FinallyClause * visit( const ast::FinallyClause * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new FinallyStmt( get<CompoundStmt>().accept1( node->body ) );
                return clausePostamble( stmt, node ), nullptr;
        }

        const ast::Stmt * visit(const ast::SuspendStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new SuspendStmt();
                stmt->then   = get<CompoundStmt>().accept1( node->then   );
                switch (node->kind) {
                        case ast::SuspendStmt::None     : stmt->type = SuspendStmt::None     ; break;
                        case ast::SuspendStmt::Coroutine: stmt->type = SuspendStmt::Coroutine; break;
                        case ast::SuspendStmt::Generator: stmt->type = SuspendStmt::Generator; break;
                }
                return stmtPostamble( stmt, node );
        }

    const ast::WhenClause * visit( const ast::WhenClause * node ) override final {
                // There is no old-AST WhenClause, so this should never be called.
                assert( !node );
                return nullptr;
        }

        const ast::Stmt * visit( const ast::WaitForStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new WaitForStmt;
                stmt->clauses.reserve( node->clauses.size() );
                for ( auto clause : node->clauses ) {
                        stmt->clauses.push_back({{
                                        get<Expression>().accept1( clause->target ),
                                        get<Expression>().acceptL( clause->target_args ),
                                },
                                get<Statement>().accept1( clause->stmt ),
                                get<Expression>().accept1( clause->when_cond ),
                        });
                }
                stmt->timeout = {
                        get<Expression>().accept1( node->timeout_time ),
                        get<Statement>().accept1( node->timeout_stmt ),
                        get<Expression>().accept1( node->timeout_cond ),
                };
                stmt->orelse = {
                        get<Statement>().accept1( node->else_stmt ),
                        get<Expression>().accept1( node->else_cond ),
                };
                return stmtPostamble( stmt, node );
        }

        const ast::WaitForClause * visit( const ast::WaitForClause * node ) override final {
                // There is no old-AST WaitForClause, so this should never be called.
                assert( !node );
                return nullptr;
        }

    const ast::Stmt * visit( const ast::WaitUntilStmt * node ) override final {
        // There is no old-AST WaitUntilStmt, so this should never be called.
                assert( !node );
                return nullptr;
        }

        const ast::Decl * visit( const ast::WithStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new WithStmt(
                        get<Expression>().acceptL( node->exprs ),
                        get<Statement>().accept1( node->stmt )
                );
                declPostamble( stmt, node );
                return nullptr;
        }

        const ast::NullStmt * visit( const ast::NullStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new NullStmt();
                stmtPostamble( stmt, node );
                return nullptr;
        }

        const ast::Stmt * visit( const ast::DeclStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new DeclStmt( get<Declaration>().accept1( node->decl ) );
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::ImplicitCtorDtorStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                auto stmt = new ImplicitCtorDtorStmt{
                        get<Statement>().accept1( node->callStmt )
                };
                return stmtPostamble( stmt, node );
        }

        const ast::Stmt * visit( const ast::MutexStmt * node ) override final {
                if ( inCache( node ) ) return nullptr;
                 auto stmt = new MutexStmt(
                        get<Statement>().accept1( node->stmt ),
                        get<Expression>().acceptL( node->mutexObjs )
                );
                return stmtPostamble( stmt, node );
        }

        TypeSubstitution * convertTypeSubstitution(const ast::TypeSubstitution * src) {

                if (!src) return nullptr;

                TypeSubstitution *rslt = new TypeSubstitution();

                for (decltype(src->begin()) src_i = src->begin(); src_i != src->end(); src_i++) {
                        rslt->add( src_i->first.typeString(),
                                   get<Type>().accept1(src_i->second) );
                }

                return rslt;
        }

        void convertInferUnion(std::map<UniqueId,ParamEntry> &tgtInferParams,
                                                   std::vector<UniqueId>         &tgtResnSlots,
                                                   const ast::Expr::InferUnion   &srcInferred ) {

                assert( tgtInferParams.empty() );
                assert( tgtResnSlots.empty() );

                if ( srcInferred.data.inferParams ) {
                        const ast::InferredParams &srcParams = srcInferred.inferParams();
                        for (auto & srcParam : srcParams) {
                                auto res = tgtInferParams.emplace(srcParam.first, ParamEntry(
                                        srcParam.second.decl,
                                        get<Declaration>().accept1(srcParam.second.declptr),
                                        get<Type>().accept1(srcParam.second.actualType)->clone(),
                                        get<Type>().accept1(srcParam.second.formalType)->clone(),
                                        get<Expression>().accept1(srcParam.second.expr)->clone()
                                ));
                                assert(res.second);
                        }
                }
                if ( srcInferred.data.resnSlots ) {
                        const ast::ResnSlots &srcSlots = srcInferred.resnSlots();
                        for (auto srcSlot : srcSlots) {
                                tgtResnSlots.push_back(srcSlot);
                        }
                }
        }

        Expression * visitBaseExpr_skipResultType(const ast::Expr * src, Expression * tgt) {

                tgt->location  = src->location;
                tgt->env       = convertTypeSubstitution(src->env);
                tgt->extension = src->extension;

                convertInferUnion(tgt->inferParams, tgt->resnSlots, src->inferred);
                return tgt;
        }

        Expression * visitBaseExpr(const ast::Expr * src, Expression * tgt) {

                tgt->result = get<Type>().accept1(src->result);
                // Unconditionally use a clone of the result type.
                // We know this will leak some objects: much of the immediate conversion result.
                // In some cases, using the conversion result directly gives unintended object sharing.
                // A parameter (ObjectDecl, a child of a FunctionType) is shared by the weak-ref cache.
                // But tgt->result must be fully owned privately by tgt.
                // Applying these conservative copies here means
                // - weak references point at the declaration's copy, not these expr.result copies (good)
                // - we copy more objects than really needed (bad, tolerated)
                if (tgt->result) {
                        tgt->result = tgt->result->clone();
                }
                return visitBaseExpr_skipResultType(src, tgt);
        }

        const ast::Expr * visit( const ast::ApplicationExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new ApplicationExpr(
                                get<Expression>().accept1(node->func),
                                get<Expression>().acceptL(node->args)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::UntypedExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new UntypedExpr(
                                get<Expression>().accept1(node->func),
                                get<Expression>().acceptL(node->args)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::NameExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new NameExpr(
                                node->name
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::QualifiedNameExpr * node ) override final {
                auto temp = new QualifiedNameExpr(
                                get<Declaration>().accept1(node->type_decl),
                                node->name
                );
                auto expr = visitBaseExpr( node,
                        temp
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::AddressExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new AddressExpr(
                                get<Expression>().accept1(node->arg)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::LabelAddressExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new LabelAddressExpr(
                                makeLabel(nullptr, node->arg)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::CastExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new CastExpr(
                                get<Expression>().accept1(node->arg),
                                (node->isGenerated == ast::GeneratedCast)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::KeywordCastExpr * node ) override final {
                AggregateDecl::Aggregate castTarget = (AggregateDecl::Aggregate)node->target;
                assert( AggregateDecl::Generator <= castTarget && castTarget <= AggregateDecl::Thread );
                auto expr = visitBaseExpr( node,
                        new KeywordCastExpr(
                                get<Expression>().accept1(node->arg),
                                castTarget,
                                {node->concrete_target.field, node->concrete_target.getter}
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::VirtualCastExpr * node ) override final {
                auto expr = visitBaseExpr_skipResultType( node,
                        new VirtualCastExpr(
                                get<Expression>().accept1(node->arg),
                                get<Type>().accept1(node->result)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::UntypedMemberExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new UntypedMemberExpr(
                                get<Expression>().accept1(node->member),
                                get<Expression>().accept1(node->aggregate)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::MemberExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new MemberExpr(
                                get<DeclarationWithType>().accept1(node->member),
                                get<Expression>().accept1(node->aggregate)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::VariableExpr * node ) override final {
                auto expr = new VariableExpr();
                expr->var = get<DeclarationWithType>().accept1(node->var);
                visitBaseExpr( node, expr );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::ConstantExpr * node ) override final {
                // Old world:   two types: rslt->constant.type, rslt->result
                // New workd:   one public type: node->result, plus node->underlyer only to support roundtrip conversion
                //              preserving underlyer because the correct type for string literals is complicated to construct,
            //              and distinguishing a string from other literals using the type is hard to do accurately
                // Both worlds: the outer, expression-level type can change during resolution
                //              for a string, that's char[k] before-resolve and char * after
                // Old world:   the inner Constant type stays what it was built with
                //              for a string, that's char[k] always
                // Both worlds: the "rep" field of a constant is the C source file fragment that compiles to the desired value
        //              for a string, that includes outer quotes, backslashes, et al cases from the Literals test
                ConstantExpr *rslt = new ConstantExpr(Constant(
                        get<Type>().accept1(node->underlyer),
                        node->rep,
                        node->ival));
                auto expr = visitBaseExpr( node, rslt );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::SizeofExpr * node ) override final {
                assert (node->expr || node->type);
                assert (! (node->expr && node->type));
                SizeofExpr *rslt;
                if (node->expr) {
                        rslt = new SizeofExpr(
                                get<Expression>().accept1(node->expr)
                        );
                        assert (!rslt->isType);
                }
                else {
                        assert(node->type);
                        rslt = new SizeofExpr(
                                get<Type>().accept1(node->type)
                        );
                        assert (rslt->isType);
                }
                auto expr = visitBaseExpr( node, rslt );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::AlignofExpr * node ) override final {
                assert (node->expr || node->type);
                assert (! (node->expr && node->type));
                AlignofExpr *rslt;
                if (node->expr) {
                        rslt = new AlignofExpr(
                                get<Expression>().accept1(node->expr)
                        );
                        assert (!rslt->isType);
                }
                else {
                        assert(node->type);
                        rslt = new AlignofExpr(
                                get<Type>().accept1(node->type)
                        );
                        assert (rslt->isType);
                }
                auto expr = visitBaseExpr( node, rslt );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::UntypedOffsetofExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new UntypedOffsetofExpr(
                                get<Type>().accept1(node->type),
                                node->member
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::OffsetofExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new OffsetofExpr(
                                get<Type>().accept1(node->type),
                                get<DeclarationWithType>().accept1(node->member)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::OffsetPackExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new OffsetPackExpr(
                                get<StructInstType>().accept1(node->type)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::LogicalExpr * node ) override final {
                assert (node->isAnd == ast::LogicalFlag::AndExpr ||
                                node->isAnd == ast::LogicalFlag::OrExpr );
                auto expr = visitBaseExpr( node,
                        new LogicalExpr(
                                get<Expression>().accept1(node->arg1),
                                get<Expression>().accept1(node->arg2),
                                (node->isAnd == ast::LogicalFlag::AndExpr)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::ConditionalExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new ConditionalExpr(
                                get<Expression>().accept1(node->arg1),
                                get<Expression>().accept1(node->arg2),
                                get<Expression>().accept1(node->arg3)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::CommaExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new CommaExpr(
                                get<Expression>().accept1(node->arg1),
                                get<Expression>().accept1(node->arg2)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::TypeExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new TypeExpr(
                                get<Type>().accept1(node->type)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::DimensionExpr * node ) override final {
                auto expr = visitBaseExpr( node, new DimensionExpr( node->name ) );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::AsmExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new AsmExpr(
                                new std::string(node->inout),
                                get<Expression>().accept1(node->constraint),
                                get<Expression>().accept1(node->operand)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::ImplicitCopyCtorExpr * node ) override final {
                auto rslt = new ImplicitCopyCtorExpr(
                        get<ApplicationExpr>().accept1(node->callExpr)
                );

                auto expr = visitBaseExpr( node, rslt );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::ConstructorExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new ConstructorExpr(
                                get<Expression>().accept1(node->callExpr)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::CompoundLiteralExpr * node ) override final {
                auto expr = visitBaseExpr_skipResultType( node,
                        new CompoundLiteralExpr(
                                get<Type>().accept1(node->result),
                                get<Initializer>().accept1(node->init)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::RangeExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new RangeExpr(
                                get<Expression>().accept1(node->low),
                                get<Expression>().accept1(node->high)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::UntypedTupleExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new UntypedTupleExpr(
                                get<Expression>().acceptL(node->exprs)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::TupleExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new TupleExpr(
                                get<Expression>().acceptL(node->exprs)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::TupleIndexExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new TupleIndexExpr(
                                get<Expression>().accept1(node->tuple),
                                node->index
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::TupleAssignExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new TupleAssignExpr(
                                get<StmtExpr>().accept1(node->stmtExpr)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::StmtExpr * node ) override final {
                auto rslt = new StmtExpr(
                        get<CompoundStmt>().accept1(node->stmts)
                );

                rslt->returnDecls = get<ObjectDecl>().acceptL(node->returnDecls);
                rslt->dtors       = get<Expression>().acceptL(node->dtors);

                // is this even used after convert?
                //if (tmp->resultExpr) {
                //      // this MUST be found by children visit
                //      rslt->resultExpr  = strict_dynamic_cast<ExprStmt *>(readonlyCache.at(tmp->resultExpr));
                //}

                auto expr = visitBaseExpr( node, rslt );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::UniqueExpr * node ) override final {
                auto rslt = new UniqueExpr(
                        get<Expression>().accept1(node->expr),
                        node->id
                );

                rslt->object = get<ObjectDecl>  ().accept1(node->object);
                rslt->var    = get<VariableExpr>().accept1(node->var);

                auto expr = visitBaseExpr( node, rslt );
                this->node = expr->clone();
                return nullptr;
        }

        const ast::Expr * visit( const ast::UntypedInitExpr * node ) override final {
                std::list<InitAlternative> initAlts;
                for (auto ia : node->initAlts) {
                        initAlts.push_back(InitAlternative(
                                get<Type>       ().accept1(ia.type),
                                get<Designation>().accept1(ia.designation)
                        ));
                }
                auto expr = visitBaseExpr( node,
                        new UntypedInitExpr(
                                get<Expression>().accept1(node->expr),
                                initAlts
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::InitExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new InitExpr(
                                get<Expression>().accept1(node->expr),
                                get<Designation>().accept1(node->designation)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::DeletedExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new DeletedExpr(
                                get<Expression>().accept1(node->expr),
                                inCache(node->deleteStmt) ?
                                        strict_dynamic_cast<Declaration*>(this->node) :
                                        get<Declaration>().accept1(node->deleteStmt)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::DefaultArgExpr * node ) override final {
                auto expr = visitBaseExpr( node,
                        new DefaultArgExpr(
                                get<Expression>().accept1(node->expr)
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Expr * visit( const ast::GenericExpr * node ) override final {
                std::list<GenericExpr::Association> associations;
                for (auto association : node->associations) {
                        associations.push_back(GenericExpr::Association(
                                get<Type>      ().accept1(association.type),
                                get<Expression>().accept1(association.expr)
                        ));
                }
                auto expr = visitBaseExpr( node,
                        new GenericExpr(
                                get<Expression>().accept1(node->control),
                                associations
                        )
                );
                this->node = expr;
                return nullptr;
        }

        const ast::Type * visitType( const ast::Type * node, Type * type ) {
                // Some types do this in their constructor so add a check.
                if ( !node->attributes.empty() && type->attributes.empty() ) {
                        type->attributes = get<Attribute>().acceptL( node->attributes );
                }
                this->node = type;
                return nullptr;
        }

        const ast::Type * visit( const ast::VoidType * node ) override final {
                return visitType( node, new VoidType{ cv( node ) } );
        }

        const ast::Type * visit( const ast::BasicType * node ) override final {
                auto type = new BasicType{ cv( node ), (BasicType::Kind)(unsigned)node->kind };
                // I believe this should always be a BasicType.
                if ( ast::sizeType == node ) {
                        Validate::SizeType = type;
                }
                return visitType( node, type );
        }

        const ast::Type * visit( const ast::PointerType * node ) override final {
                return visitType( node, new PointerType{
                        cv( node ),
                        get<Type>().accept1( node->base ),
                        get<Expression>().accept1( node->dimension ),
                        (bool)node->isVarLen,
                        (bool)node->isStatic
                } );
        }

        const ast::Type * visit( const ast::ArrayType * node ) override final {
                return visitType( node, new ArrayType{
                        cv( node ),
                        get<Type>().accept1( node->base ),
                        get<Expression>().accept1( node->dimension ),
                        (bool)node->isVarLen,
                        (bool)node->isStatic
                } );
        }

        const ast::Type * visit( const ast::ReferenceType * node ) override final {
                return visitType( node, new ReferenceType{
                        cv( node ),
                        get<Type>().accept1( node->base )
                } );
        }

        const ast::Type * visit( const ast::QualifiedType * node ) override final {
                return visitType( node, new QualifiedType{
                        cv( node ),
                        get<Type>().accept1( node->parent ),
                        get<Type>().accept1( node->child )
                } );
        }

        const ast::Type * visit( const ast::FunctionType * node ) override final {
                static std::string dummy_paramvar_prefix = "__param_";
                static std::string dummy_returnvar_prefix = "__retval_";

                auto ty = new FunctionType {
                        cv( node ),
                        (bool)node->isVarArgs
                };
                auto returns = get<Type>().acceptL(node->returns);
                auto params = get<Type>().acceptL(node->params);

                int ret_index = 0;
                for (auto t: returns) {
                        // xxx - LinkageSpec shouldn't matter but needs to be something
                        ObjectDecl * dummy = new ObjectDecl(dummy_returnvar_prefix + std::to_string(ret_index++), {}, LinkageSpec::C, nullptr, t, nullptr);
                        ty->returnVals.push_back(dummy);
                }
                int param_index = 0;
                for (auto t: params) {
                        ObjectDecl * dummy = new ObjectDecl(dummy_paramvar_prefix + std::to_string(param_index++), {}, LinkageSpec::C, nullptr, t, nullptr);
                        ty->parameters.push_back(dummy);
                }

                // ty->returnVals = get<DeclarationWithType>().acceptL( node->returns );
                // ty->parameters = get<DeclarationWithType>().acceptL( node->params );

                auto types = get<TypeInstType>().acceptL( node->forall );
                for (auto t : types) {
                        auto newT = new TypeDecl(*t->baseType);
                        newT->name = t->name; // converted by typeString()
                        for (auto asst : newT->assertions) delete asst;
                        newT->assertions.clear();
                        ty->forall.push_back(newT);
                }
                auto assts = get<VariableExpr>().acceptL( node->assertions );
                if (!assts.empty()) {
                        assert(!types.empty());
                        for (auto asst : assts) {
                                auto newDecl = new ObjectDecl(*strict_dynamic_cast<ObjectDecl*>(asst->var));
                                delete newDecl->type;
                                newDecl->type = asst->result->clone();
                                newDecl->storageClasses.is_extern = true; // hack
                                ty->forall.back()->assertions.push_back(newDecl);
                        }
                }

                return visitType( node, ty );
        }

        const ast::Type * postvisit( const ast::BaseInstType * old, ReferenceToType * ty ) {
                ty->parameters = get<Expression>().acceptL( old->params );
                ty->hoistType = old->hoistType;
                return visitType( old, ty );
        }

        const ast::Type * visit( const ast::StructInstType * node ) override final {
                StructInstType * ty;
                if ( node->base ) {
                        ty = new StructInstType{
                                cv( node ),
                                get<StructDecl>().accept1( node->base ),
                                get<Attribute>().acceptL( node->attributes )
                        };
                } else {
                        ty = new StructInstType{
                                cv( node ),
                                node->name,
                                get<Attribute>().acceptL( node->attributes )
                        };
                }
                return postvisit( node, ty );
        }

        const ast::Type * visit( const ast::UnionInstType * node ) override final {
                UnionInstType * ty;
                if ( node->base ) {
                        ty = new UnionInstType{
                                cv( node ),
                                get<UnionDecl>().accept1( node->base ),
                                get<Attribute>().acceptL( node->attributes )
                        };
                } else {
                        ty = new UnionInstType{
                                cv( node ),
                                node->name,
                                get<Attribute>().acceptL( node->attributes )
                        };
                }
                return postvisit( node, ty );
        }

        const ast::Type * visit( const ast::EnumInstType * node ) override final {
                EnumInstType * ty;
                if ( node->base ) {
                        ty = new EnumInstType{
                                cv( node ),
                                get<EnumDecl>().accept1( node->base ),
                                get<Attribute>().acceptL( node->attributes )
                        };
                } else {
                        ty = new EnumInstType{
                                cv( node ),
                                node->name,
                                get<Attribute>().acceptL( node->attributes )
                        };
                }
                return postvisit( node, ty );
        }

        const ast::Type * visit( const ast::TraitInstType * node ) override final {
                TraitInstType * ty;
                if ( node->base ) {
                        ty = new TraitInstType{
                                cv( node ),
                                get<TraitDecl>().accept1( node->base ),
                                get<Attribute>().acceptL( node->attributes )
                        };
                } else {
                        ty = new TraitInstType{
                                cv( node ),
                                node->name,
                                get<Attribute>().acceptL( node->attributes )
                        };
                }
                return postvisit( node, ty );
        }

        const ast::Type * visit( const ast::TypeInstType * node ) override final {
                TypeInstType * ty;
                if ( node->base ) {
                        ty = new TypeInstType{
                                cv( node ),
                                node->typeString(),
                                get<TypeDecl>().accept1( node->base ),
                                get<Attribute>().acceptL( node->attributes )
                        };
                } else {
                        ty = new TypeInstType{
                                cv( node ),
                                node->typeString(),
                                node->kind == ast::TypeDecl::Ftype,
                                get<Attribute>().acceptL( node->attributes )
                        };
                }
                return postvisit( node, ty );
        }

        const ast::Type * visit( const ast::TupleType * node ) override final {
                return visitType( node, new TupleType{
                        cv( node ),
                        get<Type>().acceptL( node->types )
                        // members generated by TupleType c'tor
                } );
        }

        const ast::Type * visit( const ast::TypeofType * node ) override final {
                return visitType( node, new TypeofType{
                        cv( node ),
                        get<Expression>().accept1( node->expr ),
                        (bool)node->kind
                } );
        }

        const ast::Type * visit( const ast::VTableType * node ) override final {
                return visitType( node, new VTableType{
                        cv( node ),
                        get<Type>().accept1( node->base )
                } );
        }

        const ast::Type * visit( const ast::VarArgsType * node ) override final {
                return visitType( node, new VarArgsType{ cv( node ) } );
        }

        const ast::Type * visit( const ast::ZeroType * node ) override final {
                return visitType( node, new ZeroType{ cv( node ) } );
        }

        const ast::Type * visit( const ast::OneType * node ) override final {
                return visitType( node, new OneType{ cv( node ) } );
        }

        const ast::Type * visit( const ast::GlobalScopeType * node ) override final {
                return visitType( node, new GlobalScopeType{} );
        }

        const ast::Designation * visit( const ast::Designation * node ) override final {
                auto designation = new Designation( get<Expression>().acceptL( node->designators ) );
                designation->location = node->location;
                this->node = designation;
                return nullptr;
        }

        const ast::Init * visit( const ast::SingleInit * node ) override final {
                auto init = new SingleInit(
                        get<Expression>().accept1( node->value ),
                        ast::MaybeConstruct == node->maybeConstructed
                );
                init->location = node->location;
                this->node = init;
                return nullptr;
        }

        const ast::Init * visit( const ast::ListInit * node ) override final {
                auto init = new ListInit(
                        get<Initializer>().acceptL( node->initializers ),
                        get<Designation>().acceptL( node->designations ),
                        ast::MaybeConstruct == node->maybeConstructed
                );
                init->location = node->location;
                this->node = init;
                return nullptr;
        }

        const ast::Init * visit( const ast::ConstructorInit * node ) override final {
                auto init = new ConstructorInit(
                        get<Statement>().accept1( node->ctor ),
                        get<Statement>().accept1( node->dtor ),
                        get<Initializer>().accept1( node->init )
                );
                init->location = node->location;
                this->node = init;
                return nullptr;
        }

        const ast::Attribute * visit( const ast::Attribute * node ) override final {
                auto attr = new Attribute(
                        node->name,
                        get<Expression>().acceptL(node->params)
                );
                this->node = attr;
                return nullptr;
        }

        const ast::TypeSubstitution * visit( const ast::TypeSubstitution * node ) override final {
                // Handled by convertTypeSubstitution helper instead.
                // TypeSubstitution is not a node in the old model, so the conversion result wouldn't fit in this->node.
                assert( 0 );
                (void)node;
                return nullptr;
        }
};

std::list< Declaration * > convert( const ast::TranslationUnit && translationUnit ) {
        // Copy values from the global store to the local static variables.
        ast::sizeType = translationUnit.global.sizeType;
        ast::dereferenceOperator = translationUnit.global.dereference;
        ast::dtorStruct = translationUnit.global.dtorStruct;
        ast::dtorStructDestroy = translationUnit.global.dtorDestroy;

        ConverterNewToOld c;
        std::list< Declaration * > decls;
        for(auto d : translationUnit.decls) {
                decls.emplace_back( c.decl( d ) );
        }
        return decls;
}

//================================================================================================

class ConverterOldToNew : public Visitor {
public:
        ast::Decl * decl() {
                return strict_dynamic_cast< ast::Decl * >( node );
        }
        
        ConverterOldToNew() = default;
        ConverterOldToNew(const ConverterOldToNew &) = delete;
        ConverterOldToNew(ConverterOldToNew &&) = delete;
private:
        /// conversion output
        ast::Node * node = nullptr;
        /// cache of nodes that might be referenced by readonly<> for de-duplication
        /// in case that some nodes are dropped by conversion (due to possible structural change)
        /// use smart pointers in cache value to prevent accidental invalidation.
        /// at conversion stage, all created nodes are guaranteed to be unique, therefore
        /// const_casting out of smart pointers is permitted.
        std::unordered_map< const BaseSyntaxNode *, ast::readonly<ast::Node> > cache = {};

        // Local Utilities:

        template<typename NewT, typename OldT>
        NewT * getAccept1( OldT old ) {
                if ( ! old ) return nullptr;
                old->accept(*this);
                ast::Node * ret = node;
                node = nullptr;
                return strict_dynamic_cast< NewT * >( ret );
        }

#       define GET_ACCEPT_1(child, type) \
                getAccept1< ast::type, decltype( old->child ) >( old->child )


        template<typename NewT, typename OldC>
        std::vector< ast::ptr<NewT> > getAcceptV( const OldC& old ) {
                std::vector< ast::ptr<NewT> > ret;
                ret.reserve( old.size() );
                for ( auto a : old ) {
                        a->accept( *this );
                        ret.emplace_back( strict_dynamic_cast< NewT * >(node) );
                        node = nullptr;
                }
                return ret;
        }

#       define GET_ACCEPT_V(child, type) \
                getAcceptV< ast::type, decltype( old->child ) >( old->child )

#       define GET_ACCEPT_E(child, type) \
                getAccept1< ast::type, decltype( old->base ) >( old->base )

        template<typename NewT, typename OldC>
        std::deque< ast::ptr<NewT> > getAcceptD( const OldC& old ) {
                std::deque< ast::ptr<NewT> > ret;
                for ( auto a : old ) {
                        a->accept( *this );
                        ret.emplace_back( strict_dynamic_cast< NewT * >(node) );
                        node = nullptr;
                }
                return ret;
        }

#       define GET_ACCEPT_D(child, type) \
                getAcceptD< ast::type, decltype( old->child ) >( old->child )

        ast::Label make_label(const Label* old) {
                CodeLocation const & location =
                    ( old->labelled ) ? old->labelled->location : CodeLocation();
                return ast::Label(
                        location,
                        old->name,
                        GET_ACCEPT_V(attributes, Attribute)
                );
        }

        template<template <class...> class C>
        C<ast::Label> make_labels(C<Label> olds) {
                C<ast::Label> ret;
                for (auto oldn : olds) {
                        ret.push_back( make_label( &oldn ) );
                }
                return ret;
        }

#       define GET_LABELS_V(labels) \
                to<std::vector>::from( make_labels( std::move( labels ) ) )

        static ast::CV::Qualifiers cv( const Type * ty ) { return { ty->tq.val }; }

        /// returns true and sets `node` if in cache
        bool inCache( const BaseSyntaxNode * old ) {
                auto it = cache.find( old );
                if ( it == cache.end() ) return false;
                node = const_cast<ast::Node *>(it->second.get());
                return true;
        }

        // Now all the visit functions:

        virtual void visit( const ObjectDecl * old ) override final {
                if ( inCache( old ) ) {
                        return;
                }
                auto&& type = GET_ACCEPT_1(type, Type);
                auto&& init = GET_ACCEPT_1(init, Init);
                auto&& bfwd = GET_ACCEPT_1(bitfieldWidth, Expr);
                auto&& attr = GET_ACCEPT_V(attributes, Attribute);

                auto decl = new ast::ObjectDecl(
                        old->location,
                        old->name,
                        type,
                        init,
                        { old->get_storageClasses().val },
                        { old->linkage.val },
                        bfwd,
                        std::move(attr),
                        { old->get_funcSpec().val }
                );
                cache.emplace(old, decl);
                assert(cache.find( old ) != cache.end());
                decl->scopeLevel = old->scopeLevel;
                decl->mangleName = old->mangleName;
                decl->isDeleted  = old->isDeleted;
                decl->asmName    = GET_ACCEPT_1(asmName, Expr);
                decl->uniqueId   = old->uniqueId;
                decl->extension  = old->extension;

                this->node = decl;
        }

        virtual void visit( const FunctionDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto paramVars = GET_ACCEPT_V(type->parameters, DeclWithType);
                auto returnVars = GET_ACCEPT_V(type->returnVals, DeclWithType);
                auto forall = GET_ACCEPT_V(type->forall, TypeDecl);

                // function type is now derived from parameter decls instead of storing them

                /*
                auto ftype = new ast::FunctionType((ast::ArgumentFlag)old->type->isVarArgs, cv(old->type));
                ftype->params.reserve(paramVars.size());
                ftype->returns.reserve(returnVars.size());

                for (auto & v: paramVars) {
                        ftype->params.emplace_back(v->get_type());
                }
                for (auto & v: returnVars) {
                        ftype->returns.emplace_back(v->get_type());
                }
                ftype->forall = std::move(forall);
                */

                // can function type have attributes? seems not to be the case.
                // visitType(old->type, ftype);

                // collect assertions and put directly in FunctionDecl
                std::vector<ast::ptr<ast::DeclWithType>> assertions;
                for (auto & param: forall) {
                        for (auto & asst: param->assertions) {
                                assertf(asst->unique(), "newly converted decl must be unique");
                                assertions.emplace_back(asst);
                        }
                        auto mut = param.get_and_mutate();
                        assertf(mut == param, "newly converted decl must be unique");
                        mut->assertions.clear();
                }

                auto decl = new ast::FunctionDecl{
                        old->location,
                        old->name,
                        // GET_ACCEPT_1(type, FunctionType),
                        std::move(forall),
                        std::move(assertions),
                        std::move(paramVars),
                        std::move(returnVars),
                        {},
                        { old->storageClasses.val },
                        { old->linkage.val },
                        GET_ACCEPT_V(attributes, Attribute),
                        { old->get_funcSpec().val },
                        (old->type->isVarArgs) ? ast::VariableArgs : ast::FixedArgs
                };

                // decl->type = ftype;
                cache.emplace( old, decl );

                decl->withExprs = GET_ACCEPT_V(withExprs, Expr);
                decl->stmts = GET_ACCEPT_1(statements, CompoundStmt);
                decl->scopeLevel = old->scopeLevel;
                decl->mangleName = old->mangleName;
                decl->isDeleted  = old->isDeleted;
                decl->asmName    = GET_ACCEPT_1(asmName, Expr);
                decl->uniqueId   = old->uniqueId;
                decl->extension  = old->extension;

                this->node = decl;

                if ( Validate::dereferenceOperator == old ) {
                        ast::dereferenceOperator = decl;
                }

                if ( Validate::dtorStructDestroy == old ) {
                        ast::dtorStructDestroy = decl;
                }
        }

        virtual void visit( const StructDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto decl = new ast::StructDecl(
                        old->location,
                        old->name,
                        (ast::AggregateDecl::Aggregate)old->kind,
                        GET_ACCEPT_V(attributes, Attribute),
                        { old->linkage.val }
                );
                cache.emplace( old, decl );
                decl->parent = GET_ACCEPT_1(parent, AggregateDecl);
                decl->body   = old->body;
                decl->params = GET_ACCEPT_V(parameters, TypeDecl);
                decl->members    = GET_ACCEPT_V(members, Decl);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;

                if ( Validate::dtorStruct == old ) {
                        ast::dtorStruct = decl;
                }
        }

        virtual void visit( const UnionDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto decl = new ast::UnionDecl(
                        old->location,
                        old->name,
                        GET_ACCEPT_V(attributes, Attribute),
                        { old->linkage.val }
                );
                cache.emplace( old, decl );
                decl->parent = GET_ACCEPT_1(parent, AggregateDecl);
                decl->body   = old->body;
                decl->params = GET_ACCEPT_V(parameters, TypeDecl);
                decl->members    = GET_ACCEPT_V(members, Decl);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }


        virtual void visit( const EnumDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto decl = new ast::EnumDecl(
                        old->location,
                        old->name,
                        old->isTyped,
                        GET_ACCEPT_V(attributes, Attribute),
                        { old->linkage.val },
                        GET_ACCEPT_1(base, Type),
                        old->hide == EnumDecl::EnumHiding::Hide ? ast::EnumDecl::EnumHiding::Hide : ast::EnumDecl::EnumHiding::Visible,
                        old->enumValues
                );
                cache.emplace( old, decl );
                decl->parent = GET_ACCEPT_1(parent, AggregateDecl);
                decl->body   = old->body;
                decl->params = GET_ACCEPT_V(parameters, TypeDecl);
                decl->members    = GET_ACCEPT_V(members, Decl);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };
                this->node = decl;
        }

        virtual void visit( const TraitDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto decl = new ast::TraitDecl(
                        old->location,
                        old->name,
                        GET_ACCEPT_V(attributes, Attribute),
                        { old->linkage.val }
                );
                cache.emplace( old, decl );
                decl->parent = GET_ACCEPT_1(parent, AggregateDecl);
                decl->body   = old->body;
                decl->params = GET_ACCEPT_V(parameters, TypeDecl);
                decl->members    = GET_ACCEPT_V(members, Decl);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }

        virtual void visit( const TypeDecl * old ) override final {
                if ( inCache( old ) ) return;
                auto decl = new ast::TypeDecl{
                        old->location,
                        old->name,
                        { old->storageClasses.val },
                        GET_ACCEPT_1(base, Type),
                        (ast::TypeDecl::Kind)(unsigned)old->kind,
                        old->sized,
                        GET_ACCEPT_1(init, Type)
                };
                cache.emplace( old, decl );
                decl->assertions = GET_ACCEPT_V(assertions, DeclWithType);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;

                this->node = decl;
        }

        virtual void visit( const TypedefDecl * old ) override final {
                auto decl = new ast::TypedefDecl(
                        old->location,
                        old->name,
                        { old->storageClasses.val },
                        GET_ACCEPT_1(base, Type),
                        { old->linkage.val }
                );
                decl->assertions = GET_ACCEPT_V(assertions, DeclWithType);
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }

        virtual void visit( const AsmDecl * old ) override final {
                auto decl = new ast::AsmDecl{
                        old->location,
                        GET_ACCEPT_1(stmt, AsmStmt)
                };
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }

        virtual void visit( const DirectiveDecl * old ) override final {
                auto decl = new ast::DirectiveDecl{
                        old->location,
                        GET_ACCEPT_1(stmt, DirectiveStmt)
                };
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }

        virtual void visit( const StaticAssertDecl * old ) override final {
                auto decl = new ast::StaticAssertDecl{
                        old->location,
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_1(message, ConstantExpr)
                };
                decl->extension  = old->extension;
                decl->uniqueId   = old->uniqueId;
                decl->storage    = { old->storageClasses.val };

                this->node = decl;
        }

        virtual void visit( const InlineMemberDecl * old ) override final {
                if ( inCache( old ) ) {
                        return;
                }
                auto&& type = GET_ACCEPT_1(type, Type);
                auto&& attr = GET_ACCEPT_V(attributes, Attribute);

                auto decl = new ast::InlineMemberDecl(
                        old->location,
                        old->name,
                        type,
                        { old->get_storageClasses().val },
                        { old->linkage.val },
                        std::move(attr),
                        { old->get_funcSpec().val }
                );
                cache.emplace(old, decl);
                assert(cache.find( old ) != cache.end());
                decl->scopeLevel = old->scopeLevel;
                decl->mangleName = old->mangleName;
                decl->isDeleted  = old->isDeleted;
                decl->asmName    = GET_ACCEPT_1(asmName, Expr);
                decl->uniqueId   = old->uniqueId;
                decl->extension  = old->extension;

                this->node = decl;
        }

        virtual void visit( const CompoundStmt * old ) override final {
                if ( inCache( old ) ) return;
                auto stmt = new ast::CompoundStmt(
                        old->location,
                        to<std::list>::from( GET_ACCEPT_V(kids, Stmt) ),
                        GET_LABELS_V(old->labels)
                );

                this->node = stmt;
                cache.emplace( old, this->node );
        }

        virtual void visit( const ExprStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::ExprStmt(
                        old->location,
                        GET_ACCEPT_1(expr, Expr),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const AsmStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::AsmStmt(
                        old->location,
                        old->voltile,
                        GET_ACCEPT_1(instruction, Expr),
                        GET_ACCEPT_V(output, Expr),
                        GET_ACCEPT_V(input, Expr),
                        GET_ACCEPT_V(clobber, ConstantExpr),
                        GET_LABELS_V(old->gotolabels),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const DirectiveStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::DirectiveStmt(
                        old->location,
                        old->directive,
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const IfStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::IfStmt(
                        old->location,
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_1(then, Stmt),
                        GET_ACCEPT_1(else_, Stmt),
                        GET_ACCEPT_V(initialization, Stmt),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const SwitchStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::SwitchStmt(
                        old->location,
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_V(statements, CaseClause),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const CaseStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::CaseClause(
                        old->location,
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_V(stmts, Stmt)
                );
                auto labels = GET_LABELS_V(old->labels);
                assertf(labels.empty(), "Labels found on CaseStmt.");
                cache.emplace( old, this->node );
        }

        virtual void visit( const WhileDoStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::WhileDoStmt(
                        old->location,
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_1(body, Stmt),
                        GET_ACCEPT_1(else_, Stmt),
                        GET_ACCEPT_V(initialization, Stmt),
                        (old->isDoWhile) ? ast::DoWhile : ast::While,
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const ForStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::ForStmt(
                        old->location,
                        GET_ACCEPT_V(initialization, Stmt),
                        GET_ACCEPT_1(condition, Expr),
                        GET_ACCEPT_1(increment, Expr),
                        GET_ACCEPT_1(body, Stmt),
                        GET_ACCEPT_1(else_, Stmt),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const BranchStmt * old ) override final {
                if ( inCache( old ) ) return;
                if (old->computedTarget) {
                        this->node = new ast::BranchStmt(
                                old->location,
                                GET_ACCEPT_1(computedTarget, Expr),
                                GET_LABELS_V(old->labels)
                        );
                } else {
                        ast::BranchStmt::Kind kind;
                        switch (old->type) {
                        #define CASE(n) \
                        case BranchStmt::n: \
                                kind = ast::BranchStmt::n; \
                                break
                        CASE(Goto);
                        CASE(Break);
                        CASE(Continue);
                        CASE(FallThrough);
                        CASE(FallThroughDefault);
                        #undef CASE
                        default:
                                assertf(false, "Invalid BranchStmt::Type %d\n", old->type);
                        }

                        auto stmt = new ast::BranchStmt(
                                old->location,
                                kind,
                                make_label(&old->originalTarget),
                                GET_LABELS_V(old->labels)
                        );
                        stmt->target = make_label(&old->target);
                        this->node = stmt;
                }
                cache.emplace( old, this->node );
        }

        virtual void visit( const ReturnStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::ReturnStmt(
                        old->location,
                        GET_ACCEPT_1(expr, Expr),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const ThrowStmt * old ) override final {
                if ( inCache( old ) ) return;
                ast::ExceptionKind kind;
                switch (old->kind) {
                case ThrowStmt::Terminate:
                        kind = ast::ExceptionKind::Terminate;
                        break;
                case ThrowStmt::Resume:
                        kind = ast::ExceptionKind::Resume;
                        break;
                default:
                        assertf(false, "Invalid ThrowStmt::Kind %d\n", old->kind);
                }

                this->node = new ast::ThrowStmt(
                        old->location,
                        kind,
                        GET_ACCEPT_1(expr, Expr),
                        GET_ACCEPT_1(target, Expr),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const TryStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::TryStmt(
                        old->location,
                        GET_ACCEPT_1(block, CompoundStmt),
                        GET_ACCEPT_V(handlers, CatchClause),
                        GET_ACCEPT_1(finallyBlock, FinallyClause),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const CatchStmt * old ) override final {
                if ( inCache( old ) ) return;
                ast::ExceptionKind kind;
                switch (old->kind) {
                case CatchStmt::Terminate:
                        kind = ast::ExceptionKind::Terminate;
                        break;
                case CatchStmt::Resume:
                        kind = ast::ExceptionKind::Resume;
                        break;
                default:
                        assertf(false, "Invalid CatchStmt::Kind %d\n", old->kind);
                }

                this->node = new ast::CatchClause(
                        old->location,
                        kind,
                        GET_ACCEPT_1(decl, Decl),
                        GET_ACCEPT_1(cond, Expr),
                        GET_ACCEPT_1(body, Stmt)
                );
                auto labels = GET_LABELS_V(old->labels);
                assertf(labels.empty(), "Labels found on CatchStmt.");
                cache.emplace( old, this->node );
        }

        virtual void visit( const FinallyStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::FinallyClause(
                        old->location,
                        GET_ACCEPT_1(block, CompoundStmt)
                );
                auto labels = GET_LABELS_V(old->labels);
                assertf(labels.empty(), "Labels found on FinallyStmt.");
                cache.emplace( old, this->node );
        }

        virtual void visit( const SuspendStmt * old ) override final {
                if ( inCache( old ) ) return;
                ast::SuspendStmt::Kind type;
                switch (old->type) {
                        case SuspendStmt::Coroutine: type = ast::SuspendStmt::Coroutine; break;
                        case SuspendStmt::Generator: type = ast::SuspendStmt::Generator; break;
                        case SuspendStmt::None     : type = ast::SuspendStmt::None     ; break;
                        default: abort();
                }
                this->node = new ast::SuspendStmt(
                        old->location,
                        GET_ACCEPT_1(then  , CompoundStmt),
                        type,
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const WaitForStmt * old ) override final {
                if ( inCache( old ) ) return;
                ast::WaitForStmt * stmt = new ast::WaitForStmt(
                        old->location,
                        GET_LABELS_V(old->labels)
                );

                stmt->clauses.reserve( old->clauses.size() );
                for (size_t i = 0 ; i < old->clauses.size() ; ++i) {
                        auto clause = new ast::WaitForClause( old->location );

                        clause->target = GET_ACCEPT_1(clauses[i].target.function, Expr);
                        clause->target_args = GET_ACCEPT_V(clauses[i].target.arguments, Expr);
                        clause->stmt = GET_ACCEPT_1(clauses[i].statement, Stmt);
                        clause->when_cond = GET_ACCEPT_1(clauses[i].condition, Expr);

                        stmt->clauses.push_back( clause );
                }
                stmt->timeout_time = GET_ACCEPT_1(timeout.time, Expr);
                stmt->timeout_stmt = GET_ACCEPT_1(timeout.statement, Stmt);
                stmt->timeout_cond = GET_ACCEPT_1(timeout.condition, Expr);
                stmt->else_stmt = GET_ACCEPT_1(orelse.statement, Stmt);
                stmt->else_cond = GET_ACCEPT_1(orelse.condition, Expr);

                this->node = stmt;
                cache.emplace( old, this->node );
        }

        virtual void visit( const WithStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::WithStmt(
                        old->location,
                        GET_ACCEPT_V(exprs, Expr),
                        GET_ACCEPT_1(stmt, Stmt)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const NullStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::NullStmt(
                        old->location,
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const DeclStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::DeclStmt(
                        old->location,
                        GET_ACCEPT_1(decl, Decl),
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, this->node );
        }

        virtual void visit( const ImplicitCtorDtorStmt * old ) override final {
                if ( inCache( old ) ) return;
                auto stmt = new ast::ImplicitCtorDtorStmt(
                        old->location,
                        nullptr,
                        GET_LABELS_V(old->labels)
                );
                cache.emplace( old, stmt );
                stmt->callStmt = GET_ACCEPT_1(callStmt, Stmt);
                this->node = stmt;
        }

        virtual void visit( const MutexStmt * old ) override final {
                if ( inCache( old ) ) return;
                this->node = new ast::MutexStmt(
                        old->location,
                        GET_ACCEPT_1(stmt, Stmt),
                        GET_ACCEPT_V(mutexObjs, Expr)
                );
                cache.emplace( old, this->node );
        }

        // TypeSubstitution shouldn't exist yet in old.
        ast::TypeSubstitution * convertTypeSubstitution(const TypeSubstitution * old) {
                
                if (!old) return nullptr;
                if (old->empty()) return nullptr;
                assert(false);

                /*
                ast::TypeSubstitution *rslt = new ast::TypeSubstitution();

                for (decltype(old->begin()) old_i = old->begin(); old_i != old->end(); old_i++) {
                        rslt->add( old_i->first,
                                   getAccept1<ast::Type>(old_i->second) );
                }

                return rslt;
                */
        }

        void convertInferUnion(ast::Expr::InferUnion               &newInferred,
                                                   const std::map<UniqueId,ParamEntry> &oldInferParams,
                                                   const std::vector<UniqueId>         &oldResnSlots) {

                assert( oldInferParams.empty() || oldResnSlots.empty() );
                // assert( newInferred.mode == ast::Expr::InferUnion::Empty );

                if ( !oldInferParams.empty() ) {
                        ast::InferredParams &tgt = newInferred.inferParams();
                        for (auto & old : oldInferParams) {
                                tgt[old.first] = ast::ParamEntry(
                                        old.second.decl,
                                        getAccept1<ast::Decl>(old.second.declptr),
                                        getAccept1<ast::Type>(old.second.actualType),
                                        getAccept1<ast::Type>(old.second.formalType),
                                        getAccept1<ast::Expr>(old.second.expr)
                                );
                        }
                } else if ( !oldResnSlots.empty() ) {
                        ast::ResnSlots &tgt = newInferred.resnSlots();
                        for (auto old : oldResnSlots) {
                                tgt.push_back(old);
                        }
                }
        }

        ast::Expr * visitBaseExpr_SkipResultType( const Expression * old, ast::Expr * nw) {

                nw->env    = convertTypeSubstitution(old->env);

                nw->extension = old->extension;
                convertInferUnion(nw->inferred, old->inferParams, old->resnSlots);

                return nw;
        }

        ast::Expr * visitBaseExpr( const Expression * old, ast::Expr * nw) {

                nw->result = GET_ACCEPT_1(result, Type);
                return visitBaseExpr_SkipResultType(old, nw);;
        }

        virtual void visit( const ApplicationExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::ApplicationExpr(
                                old->location,
                                GET_ACCEPT_1(function, Expr),
                                GET_ACCEPT_V(args, Expr)
                        )
                );
        }

        virtual void visit( const UntypedExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::UntypedExpr(
                                old->location,
                                GET_ACCEPT_1(function, Expr),
                                GET_ACCEPT_V(args, Expr)
                        )
                );
        }

        virtual void visit( const NameExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::NameExpr(
                                old->location,
                                old->get_name()
                        )
                );
        }

        virtual void visit( const QualifiedNameExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::QualifiedNameExpr (
                                old->location,
                                GET_ACCEPT_1(type_decl, Decl),
                                old->name
                        )
                );
        }

        virtual void visit( const CastExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::CastExpr(
                                old->location,
                                GET_ACCEPT_1(arg, Expr),
                                old->isGenerated ? ast::GeneratedCast : ast::ExplicitCast
                        )
                );
        }

        virtual void visit( const KeywordCastExpr * old ) override final {
                ast::AggregateDecl::Aggregate castTarget = (ast::AggregateDecl::Aggregate)old->target;
                assert( ast::AggregateDecl::Generator <= castTarget && castTarget <= ast::AggregateDecl::Thread );
                this->node = visitBaseExpr( old,
                        new ast::KeywordCastExpr(
                                old->location,
                                GET_ACCEPT_1(arg, Expr),
                                castTarget,
                                {old->concrete_target.field, old->concrete_target.getter}
                        )
                );
        }

        virtual void visit( const VirtualCastExpr * old ) override final {
                this->node = visitBaseExpr_SkipResultType( old,
                        new ast::VirtualCastExpr(
                                old->location,
                                GET_ACCEPT_1(arg, Expr),
                                GET_ACCEPT_1(result, Type)
                        )
                );
        }

        virtual void visit( const AddressExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::AddressExpr(
                                old->location,
                                GET_ACCEPT_1(arg, Expr)
                        )
                );
        }

        virtual void visit( const LabelAddressExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::LabelAddressExpr(
                                old->location,
                                make_label(&old->arg)
                        )
                );
        }

        virtual void visit( const UntypedMemberExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::UntypedMemberExpr(
                                old->location,
                                GET_ACCEPT_1(member, Expr),
                                GET_ACCEPT_1(aggregate, Expr)
                        )
                );
        }

        virtual void visit( const MemberExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::MemberExpr(
                                old->location,
                                GET_ACCEPT_1(member, DeclWithType),
                                GET_ACCEPT_1(aggregate, Expr),
                                ast::MemberExpr::NoOpConstructionChosen
                        )
                );
        }

        virtual void visit( const VariableExpr * old ) override final {
                auto expr = new ast::VariableExpr(
                        old->location
                );

                expr->var = GET_ACCEPT_1(var, DeclWithType);
                visitBaseExpr( old, expr );

                this->node = expr;
        }

        virtual void visit( const ConstantExpr * old ) override final {
                ast::ConstantExpr *rslt = new ast::ConstantExpr(
                        old->location,
                        GET_ACCEPT_1(result, Type),
                        old->constant.rep,
                        old->constant.ival
                );
                rslt->underlyer = getAccept1< ast::Type, Type* >( old->constant.type );
                this->node = visitBaseExpr( old, rslt );
        }

        virtual void visit( const SizeofExpr * old ) override final {
                assert (old->expr || old->type);
                assert (! (old->expr && old->type));
                ast::SizeofExpr *rslt;
                if (old->expr) {
                        assert(!old->isType);
                        rslt = new ast::SizeofExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr)
                        );
                }
                if (old->type) {
                        assert(old->isType);
                        rslt = new ast::SizeofExpr(
                                old->location,
                                GET_ACCEPT_1(type, Type)
                        );
                }
                this->node = visitBaseExpr( old, rslt );
        }

        virtual void visit( const AlignofExpr * old ) override final {
                assert (old->expr || old->type);
                assert (! (old->expr && old->type));
                ast::AlignofExpr *rslt;
                if (old->expr) {
                        assert(!old->isType);
                        rslt = new ast::AlignofExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr)
                        );
                }
                if (old->type) {
                        assert(old->isType);
                        rslt = new ast::AlignofExpr(
                                old->location,
                                GET_ACCEPT_1(type, Type)
                        );
                }
                this->node = visitBaseExpr( old, rslt );
        }

        virtual void visit( const UntypedOffsetofExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::UntypedOffsetofExpr(
                                old->location,
                                GET_ACCEPT_1(type, Type),
                                old->member
                        )
                );
        }

        virtual void visit( const OffsetofExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::OffsetofExpr(
                                old->location,
                                GET_ACCEPT_1(type, Type),
                                GET_ACCEPT_1(member, DeclWithType)
                        )
                );
        }

        virtual void visit( const OffsetPackExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::OffsetPackExpr(
                                old->location,
                                GET_ACCEPT_1(type, StructInstType)
                        )
                );
        }

        virtual void visit( const LogicalExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::LogicalExpr(
                                old->location,
                                GET_ACCEPT_1(arg1, Expr),
                                GET_ACCEPT_1(arg2, Expr),
                                old->get_isAnd() ?
                                        ast::LogicalFlag::AndExpr :
                                        ast::LogicalFlag::OrExpr
                        )
                );
        }

        virtual void visit( const ConditionalExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::ConditionalExpr(
                                old->location,
                                GET_ACCEPT_1(arg1, Expr),
                                GET_ACCEPT_1(arg2, Expr),
                                GET_ACCEPT_1(arg3, Expr)
                        )
                );
        }

        virtual void visit( const CommaExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::CommaExpr(
                                old->location,
                                GET_ACCEPT_1(arg1, Expr),
                                GET_ACCEPT_1(arg2, Expr)
                        )
                );
        }

        virtual void visit( const TypeExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::TypeExpr(
                                old->location,
                                GET_ACCEPT_1(type, Type)
                        )
                );
        }

        virtual void visit( const DimensionExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::DimensionExpr( old->location, old->name )
                );
        }

        virtual void visit( const AsmExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::AsmExpr(
                                old->location,
                                old->inout,
                                GET_ACCEPT_1(constraint, Expr),
                                GET_ACCEPT_1(operand, Expr)
                        )
                );
        }

        virtual void visit( const ImplicitCopyCtorExpr * old ) override final {
                auto rslt = new ast::ImplicitCopyCtorExpr(
                        old->location,
                        GET_ACCEPT_1(callExpr, ApplicationExpr)
                );

                this->node = visitBaseExpr( old, rslt );
        }

        virtual void visit( const ConstructorExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::ConstructorExpr(
                                old->location,
                                GET_ACCEPT_1(callExpr, Expr)
                        )
                );
        }

        virtual void visit( const CompoundLiteralExpr * old ) override final {
                this->node = visitBaseExpr_SkipResultType( old,
                        new ast::CompoundLiteralExpr(
                                old->location,
                                GET_ACCEPT_1(result, Type),
                                GET_ACCEPT_1(initializer, Init)
                        )
                );
        }

        virtual void visit( const RangeExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::RangeExpr(
                                old->location,
                                GET_ACCEPT_1(low, Expr),
                                GET_ACCEPT_1(high, Expr)
                        )
                );
        }

        virtual void visit( const UntypedTupleExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::UntypedTupleExpr(
                                old->location,
                                GET_ACCEPT_V(exprs, Expr)
                        )
                );
        }

        virtual void visit( const TupleExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::TupleExpr(
                                old->location,
                                GET_ACCEPT_V(exprs, Expr)
                        )
                );
        }

        virtual void visit( const TupleIndexExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::TupleIndexExpr(
                                old->location,
                                GET_ACCEPT_1(tuple, Expr),
                                old->index
                        )
                );
        }

        virtual void visit( const TupleAssignExpr * old ) override final {
                this->node = visitBaseExpr_SkipResultType( old,
                        new ast::TupleAssignExpr(
                                old->location,
                                GET_ACCEPT_1(result, Type),
                                GET_ACCEPT_1(stmtExpr, StmtExpr)
                        )
                );
        }

        virtual void visit( const StmtExpr * old ) override final {
                auto rslt = new ast::StmtExpr(
                        old->location,
                        GET_ACCEPT_1(statements, CompoundStmt)
                );
                rslt->returnDecls = GET_ACCEPT_V(returnDecls, ObjectDecl);
                rslt->dtors       = GET_ACCEPT_V(dtors      , Expr);

                this->node = visitBaseExpr_SkipResultType( old, rslt );
        }

        virtual void visit( const UniqueExpr * old ) override final {
                auto rslt = new ast::UniqueExpr(
                        old->location,
                        GET_ACCEPT_1(expr, Expr),
                        old->get_id()
                );
                rslt->object = GET_ACCEPT_1(object, ObjectDecl);
                rslt->var    = GET_ACCEPT_1(var   , VariableExpr);

                this->node = visitBaseExpr( old, rslt );
        }

        virtual void visit( const UntypedInitExpr * old ) override final {
                std::deque<ast::InitAlternative> initAlts;
                for (auto ia : old->initAlts) {
                        initAlts.push_back(ast::InitAlternative(
                                getAccept1< ast::Type, Type * >( ia.type ),
                                getAccept1< ast::Designation, Designation * >( ia.designation )
                        ));
                }
                this->node = visitBaseExpr( old,
                        new ast::UntypedInitExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr),
                                std::move(initAlts)
                        )
                );
        }

        virtual void visit( const InitExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::InitExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr),
                                GET_ACCEPT_1(designation, Designation)
                        )
                );
        }

        virtual void visit( const DeletedExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::DeletedExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr),
                                inCache(old->deleteStmt) ?
                                        strict_dynamic_cast<ast::Decl*>(this->node) :
                                        GET_ACCEPT_1(deleteStmt, Decl)
                        )
                );
        }

        virtual void visit( const DefaultArgExpr * old ) override final {
                this->node = visitBaseExpr( old,
                        new ast::DefaultArgExpr(
                                old->location,
                                GET_ACCEPT_1(expr, Expr)
                        )
                );
        }

        virtual void visit( const GenericExpr * old ) override final {
                std::vector<ast::GenericExpr::Association> associations;
                for (auto association : old->associations) {
                        associations.push_back(ast::GenericExpr::Association(
                                getAccept1< ast::Type, Type * >( association.type ),
                                getAccept1< ast::Expr, Expression * >( association.expr )
                        ));
                }
                this->node = visitBaseExpr( old,
                        new ast::GenericExpr(
                                old->location,
                                GET_ACCEPT_1(control, Expr),
                                std::move(associations)
                        )
                );
        }

        void visitType( const Type * old, ast::Type * type ) {
                // Some types do this in their constructor so add a check.
                if ( !old->attributes.empty() && type->attributes.empty() ) {
                        type->attributes = GET_ACCEPT_V(attributes, Attribute);
                }
                this->node = type;
        }

        virtual void visit( const VoidType * old ) override final {
                visitType( old, new ast::VoidType{ cv( old ) } );
        }

        virtual void visit( const BasicType * old ) override final {
                auto type = new ast::BasicType{ (ast::BasicType::Kind)(unsigned)old->kind, cv( old ) };
                // I believe this should always be a BasicType.
                if ( Validate::SizeType == old ) {
                        ast::sizeType = type;
                }
                visitType( old, type );
        }

        virtual void visit( const PointerType * old ) override final {
                visitType( old, new ast::PointerType{
                        GET_ACCEPT_1( base, Type ),
                        GET_ACCEPT_1( dimension, Expr ),
                        (ast::LengthFlag)old->isVarLen,
                        (ast::DimensionFlag)old->isStatic,
                        cv( old )
                } );
        }

        virtual void visit( const ArrayType * old ) override final {
                visitType( old, new ast::ArrayType{
                        GET_ACCEPT_1( base, Type ),
                        GET_ACCEPT_1( dimension, Expr ),
                        (ast::LengthFlag)old->isVarLen,
                        (ast::DimensionFlag)old->isStatic,
                        cv( old )
                } );
        }

        virtual void visit( const ReferenceType * old ) override final {
                visitType( old, new ast::ReferenceType{
                        GET_ACCEPT_1( base, Type ),
                        cv( old )
                } );
        }

        virtual void visit( const QualifiedType * old ) override final {
                visitType( old, new ast::QualifiedType{
                        GET_ACCEPT_1( parent, Type ),
                        GET_ACCEPT_1( child, Type ),
                        cv( old )
                } );
        }

        virtual void visit( const FunctionType * old ) override final {
                auto ty = new ast::FunctionType {
                        (ast::ArgumentFlag)old->isVarArgs,
                        cv( old )
                };
                auto returnVars = GET_ACCEPT_V(returnVals, DeclWithType);
                auto paramVars = GET_ACCEPT_V(parameters, DeclWithType);
                // ty->returns = GET_ACCEPT_V( returnVals, DeclWithType );
                // ty->params = GET_ACCEPT_V( parameters, DeclWithType );
                for (auto & v: returnVars) {
                        ty->returns.emplace_back(v->get_type());
                }
                for (auto & v: paramVars) {
                        ty->params.emplace_back(v->get_type());
                }
                // xxx - when will this be non-null?
                // will have to create dangling (no-owner) decls to be pointed to
                auto foralls = GET_ACCEPT_V( forall, TypeDecl );

                for (auto & param : foralls) {
                        ty->forall.emplace_back(new ast::TypeInstType(param));
                        for (auto asst : param->assertions) {
                                ty->assertions.emplace_back(
                                        new ast::VariableExpr(param->location, asst));
                        }
                }
                visitType( old, ty );
        }

        void postvisit( const ReferenceToType * old, ast::BaseInstType * ty ) {
                ty->params = GET_ACCEPT_V( parameters, Expr );
                ty->hoistType = old->hoistType;
                visitType( old, ty );
        }

        virtual void visit( const StructInstType * old ) override final {
                ast::StructInstType * ty;
                if ( old->baseStruct ) {
                        ty = new ast::StructInstType{
                                GET_ACCEPT_1( baseStruct, StructDecl ),
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                } else {
                        ty = new ast::StructInstType{
                                old->name,
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                }
                postvisit( old, ty );
        }

        virtual void visit( const UnionInstType * old ) override final {
                ast::UnionInstType * ty;
                if ( old->baseUnion ) {
                        ty = new ast::UnionInstType{
                                GET_ACCEPT_1( baseUnion, UnionDecl ),
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                } else {
                        ty = new ast::UnionInstType{
                                old->name,
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                }
                postvisit( old, ty );
        }

        virtual void visit( const EnumInstType * old ) override final {
                ast::EnumInstType * ty; 
                if ( old->baseEnum ) {
                        ty = new ast::EnumInstType{
                                GET_ACCEPT_1( baseEnum, EnumDecl ),
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                } else {
                        ty = new ast::EnumInstType{
                                old->name,
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                }
                postvisit( old, ty );
        }

        virtual void visit( const TraitInstType * old ) override final {
                ast::TraitInstType * ty;
                if ( old->baseTrait ) {
                        ty = new ast::TraitInstType{
                                GET_ACCEPT_1( baseTrait, TraitDecl ),
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                } else {
                        ty = new ast::TraitInstType{
                                old->name,
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                }
                postvisit( old, ty );
        }

        virtual void visit( const TypeInstType * old ) override final {
                ast::TypeInstType * ty;
                if ( old->baseType ) {
                        ty = new ast::TypeInstType{
                                old->name,
                                GET_ACCEPT_1( baseType, TypeDecl ),
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                } else {
                        ty = new ast::TypeInstType{
                                old->name,
                                old->isFtype ? ast::TypeDecl::Ftype : ast::TypeDecl::Dtype,
                                cv( old ),
                                GET_ACCEPT_V( attributes, Attribute )
                        };
                }
                postvisit( old, ty );
        }

        virtual void visit( const TupleType * old ) override final {
                visitType( old, new ast::TupleType{
                        GET_ACCEPT_V( types, Type ),
                        // members generated by TupleType c'tor
                        cv( old )
                } );
        }

        virtual void visit( const TypeofType * old ) override final {
                visitType( old, new ast::TypeofType{
                        GET_ACCEPT_1( expr, Expr ),
                        (ast::TypeofType::Kind)old->is_basetypeof,
                        cv( old )
                } );
        }

        virtual void visit( const VTableType * old ) override final {
                visitType( old, new ast::VTableType{
                        GET_ACCEPT_1( base, Type ),
                        cv( old )
                } );
        }

        virtual void visit( const AttrType * ) override final {
                assertf( false, "AttrType deprecated in new AST." );
        }

        virtual void visit( const VarArgsType * old ) override final {
                visitType( old, new ast::VarArgsType{ cv( old ) } );
        }

        virtual void visit( const ZeroType * old ) override final {
                visitType( old, new ast::ZeroType{ cv( old ) } );
        }

        virtual void visit( const OneType * old ) override final {
                visitType( old, new ast::OneType{ cv( old ) } );
        }

        virtual void visit( const GlobalScopeType * old ) override final {
                visitType( old, new ast::GlobalScopeType{} );
        }

        virtual void visit( const Designation * old ) override final {
                this->node = new ast::Designation(
                        old->location,
                        GET_ACCEPT_D(designators, Expr)
                );
        }

        virtual void visit( const SingleInit * old ) override final {
                this->node = new ast::SingleInit(
                        old->location,
                        GET_ACCEPT_1(value, Expr),
                        (old->get_maybeConstructed()) ? ast::MaybeConstruct : ast::NoConstruct
                );
        }

        virtual void visit( const ListInit * old ) override final {
                this->node = new ast::ListInit(
                        old->location,
                        GET_ACCEPT_V(initializers, Init),
                        GET_ACCEPT_V(designations, Designation),
                        (old->get_maybeConstructed()) ? ast::MaybeConstruct : ast::NoConstruct
                );
        }

        virtual void visit( const ConstructorInit * old ) override final {
                this->node = new ast::ConstructorInit(
                        old->location,
                        GET_ACCEPT_1(ctor, Stmt),
                        GET_ACCEPT_1(dtor, Stmt),
                        GET_ACCEPT_1(init, Init)
                );
        }

        virtual void visit( const Constant * ) override final {
                // Handled in visit( ConstantEpxr * ).
                // In the new tree, Constant fields are inlined into containing ConstantExpression.
                assert( 0 );
        }

        virtual void visit( const Attribute * old ) override final {
                this->node = new ast::Attribute(
                        old->name,
                        GET_ACCEPT_V( parameters, Expr )
                );
        }
};

#undef GET_LABELS_V
#undef GET_ACCEPT_V
#undef GET_ACCEPT_1

ast::TranslationUnit convert( const std::list< Declaration * > && translationUnit ) {
        ConverterOldToNew c;
        ast::TranslationUnit unit;
        if (Validate::SizeType) {
                // this should be a BasicType.
                auto old = strict_dynamic_cast<BasicType *>(Validate::SizeType);
                ast::sizeType = new ast::BasicType{ (ast::BasicType::Kind)(unsigned)old->kind };
        }

        for(auto d : translationUnit) {
                d->accept( c );
                unit.decls.emplace_back( c.decl() );
        }
        deleteAll(translationUnit);

        // Load the local static varables into the global store.
        unit.global.sizeType = ast::sizeType;
        unit.global.dereference = ast::dereferenceOperator;
        unit.global.dtorStruct = ast::dtorStruct;
        unit.global.dtorDestroy = ast::dtorStructDestroy;

        return unit;
}