source: src/SymTab/Indexer.cc @ 1f133dc

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Indexer.cc --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 21:37:33 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Thu Aug 17 16:08:40 2017
// Update Count     : 20
//

#include "Indexer.h"

#include <cassert>                 // for assert, strict_dynamic_cast
#include <iostream>                // for operator<<, basic_ostream, ostream
#include <string>                  // for string, operator<<, operator!=
#include <unordered_map>           // for operator!=, unordered_map<>::const...
#include <unordered_set>           // for unordered_set
#include <utility>                 // for pair, make_pair, move

#include "CodeGen/OperatorTable.h" // for isCtorDtor, isCtorDtorAssign
#include "Common/SemanticError.h"  // for SemanticError
#include "Common/utility.h"        // for cloneAll
#include "GenPoly/GenPoly.h"
#include "InitTweak/InitTweak.h"   // for isConstructor, isCopyFunction, isC...
#include "Mangler.h"               // for Mangler
#include "Parser/LinkageSpec.h"    // for isMangled, isOverridable, Spec
#include "ResolvExpr/typeops.h"    // for typesCompatible
#include "SynTree/Constant.h"      // for Constant
#include "SynTree/Declaration.h"   // for DeclarationWithType, FunctionDecl
#include "SynTree/Expression.h"    // for Expression, ImplicitCopyCtorExpr
#include "SynTree/Initializer.h"   // for Initializer
#include "SynTree/Statement.h"     // for CompoundStmt, Statement, ForStmt (...
#include "SynTree/Type.h"          // for Type, StructInstType, UnionInstType

#define debugPrint(x) if ( doDebug ) { std::cerr << x; }

namespace SymTab {
        std::ostream & operator<<( std::ostream & out, const Indexer::IdData & data ) {
                return out << "(" << data.id << "," << data.baseExpr << ")";
        }

        typedef std::unordered_map< std::string, Indexer::IdData > MangleTable;
        typedef std::unordered_map< std::string, MangleTable > IdTable;
        typedef std::unordered_map< std::string, NamedTypeDecl* > TypeTable;
        typedef std::unordered_map< std::string, StructDecl* > StructTable;
        typedef std::unordered_map< std::string, EnumDecl* > EnumTable;
        typedef std::unordered_map< std::string, UnionDecl* > UnionTable;
        typedef std::unordered_map< std::string, TraitDecl* > TraitTable;

        void dump( const IdTable &table, std::ostream &os ) {
                for ( IdTable::const_iterator id = table.begin(); id != table.end(); ++id ) {
                        for ( MangleTable::const_iterator mangle = id->second.begin(); mangle != id->second.end(); ++mangle ) {
                                os << mangle->second << std::endl;
                        }
                }
        }

        template< typename Decl >
        void dump( const std::unordered_map< std::string, Decl* > &table, std::ostream &os ) {
                for ( typename std::unordered_map< std::string, Decl* >::const_iterator it = table.begin(); it != table.end(); ++it ) {
                        os << it->second << std::endl;
                } // for
        }

        struct Indexer::Impl {
                Impl( unsigned long _scope ) : refCount(1), scope( _scope ), size( 0 ), base(),
                                idTable(), typeTable(), structTable(), enumTable(), unionTable(), traitTable() {}
                Impl( unsigned long _scope, Indexer &&_base ) : refCount(1), scope( _scope ), size( 0 ), base( _base ),
                                idTable(), typeTable(), structTable(), enumTable(), unionTable(), traitTable() {}
                unsigned long refCount;   ///< Number of references to these tables
                unsigned long scope;      ///< Scope these tables are associated with
                unsigned long size;       ///< Number of elements stored in this table
                const Indexer base;       ///< Base indexer this extends

                IdTable idTable;          ///< Identifier namespace
                TypeTable typeTable;      ///< Type namespace
                StructTable structTable;  ///< Struct namespace
                EnumTable enumTable;      ///< Enum namespace
                UnionTable unionTable;    ///< Union namespace
                TraitTable traitTable;    ///< Trait namespace
        };

        Indexer::Impl *Indexer::newRef( Indexer::Impl *toClone ) {
                if ( ! toClone ) return 0;

                // shorten the search chain by skipping empty links
                Indexer::Impl *ret = toClone->size == 0 ? toClone->base.tables : toClone;
                if ( ret ) { ++ret->refCount; }

                return ret;
        }

        void Indexer::deleteRef( Indexer::Impl *toFree ) {
                if ( ! toFree ) return;

                if ( --toFree->refCount == 0 ) delete toFree;
        }

        void Indexer::removeSpecialOverrides( const std::string &id, std::list< IdData > & out ) const {
                // only need to perform this step for constructors, destructors, and assignment functions
                if ( ! CodeGen::isCtorDtorAssign( id ) ) return;

                // helpful data structure to organize properties for a type
                struct ValueType {
                        struct DeclBall { // properties for this particular decl
                                IdData decl;
                                bool isUserDefinedFunc;
                                bool isCopyFunc;
                        };
                        // properties for this type
                        bool existsUserDefinedCopyFunc = false;    // user-defined copy ctor found
                        BaseSyntaxNode * deleteStmt = nullptr;     // non-null if a user-defined function is found
                        std::list< DeclBall > decls;

                        // another FunctionDecl for the current type was found - determine
                        // if it has special properties and update data structure accordingly
                        ValueType & operator+=( IdData data ) {
                                DeclarationWithType * function = data.id;
                                bool isUserDefinedFunc = ! LinkageSpec::isOverridable( function->linkage );
                                bool isCopyFunc = InitTweak::isCopyFunction( function, function->name );
                                decls.push_back( DeclBall{ data, isUserDefinedFunc, isCopyFunc } );
                                existsUserDefinedCopyFunc = existsUserDefinedCopyFunc || (isUserDefinedFunc && isCopyFunc);
                                if ( isUserDefinedFunc && ! deleteStmt ) {
                                        // any user-defined function can act as an implicit delete statement for generated constructors.
                                        // a delete stmt should not act as an implicit delete statement.
                                        deleteStmt = data.id;
                                }
                                return *this;
                        }
                }; // ValueType

                std::list< IdData > copy;
                copy.splice( copy.end(), out );

                // organize discovered declarations by type
                std::unordered_map< std::string, ValueType > funcMap;
                for ( auto decl : copy ) {
                        if ( FunctionDecl * function = dynamic_cast< FunctionDecl * >( decl.id ) ) {
                                std::list< DeclarationWithType * > & params = function->type->parameters;
                                assert( ! params.empty() );
                                // use base type of pointer, so that qualifiers on the pointer type aren't considered.
                                Type * base = InitTweak::getPointerBase( params.front()->get_type() );
                                assert( base );
                                funcMap[ Mangler::mangle( base ) ] += decl;
                        } else {
                                out.push_back( decl );
                        }
                }

                // if a type contains user defined ctor/dtor/assign, then special rules trigger, which determine
                // the set of ctor/dtor/assign that can be used  by the requester. In particular, if the user defines
                // a default ctor, then the generated default ctor is unavailable, likewise for copy ctor
                // and dtor. If the user defines any ctor/dtor, then no generated field ctors are available.
                // If the user defines any ctor then the generated default ctor is unavailable (intrinsic default
                // ctor must be overridden exactly). If the user defines anything that looks like a copy constructor,
                // then the generated copy constructor is unavailable, and likewise for the assignment operator.
                for ( std::pair< const std::string, ValueType > & pair : funcMap ) {
                        ValueType & val = pair.second;
                        for ( ValueType::DeclBall ball : val.decls ) {
                                bool isNotUserDefinedFunc = ! ball.isUserDefinedFunc && ball.decl.id->linkage != LinkageSpec::Intrinsic;
                                bool isCopyFunc = ball.isCopyFunc;
                                bool existsUserDefinedCopyFunc = val.existsUserDefinedCopyFunc;

                                // only implicitly delete non-user defined functions that are not intrinsic, and are
                                // not copy functions (assignment or copy constructor). If a  user-defined copy function exists,
                                // do not pass along the non-user-defined copy functions since signatures do not have to match,
                                // and the generated functions will often be cheaper.
                                if ( isNotUserDefinedFunc ) {
                                        if ( isCopyFunc ) {
                                                // Skip over non-user-defined copy functions when there is a user-defined copy function.
                                                // Since their signatures do not have to be exact, deleting them is the wrong choice.
                                                if ( existsUserDefinedCopyFunc ) continue;
                                        } else {
                                                // delete non-user-defined non-copy functions if applicable.
                                                // deleteStmt will be non-null only if a user-defined function is found.
                                                ball.decl.deleteStmt = val.deleteStmt;
                                        }
                                }
                                out.push_back( ball.decl );
                        }
                }
        }

        void Indexer::makeWritable() {
                if ( ! tables ) {
                        // create indexer if not yet set
                        tables = new Indexer::Impl( scope );
                } else if ( tables->refCount > 1 || tables->scope != scope ) {
                        // make this indexer the base of a fresh indexer at the current scope
                        tables = new Indexer::Impl( scope, std::move( *this ) );
                }
        }

        Indexer::Indexer() : tables( 0 ), scope( 0 ) {}

        Indexer::Indexer( const Indexer &that ) : doDebug( that.doDebug ), tables( newRef( that.tables ) ), scope( that.scope ) {}

        Indexer::Indexer( Indexer &&that ) : doDebug( that.doDebug ), tables( that.tables ), scope( that.scope ) {
                that.tables = 0;
        }

        Indexer::~Indexer() {
                deleteRef( tables );
        }

        Indexer& Indexer::operator= ( const Indexer &that ) {
                deleteRef( tables );

                tables = newRef( that.tables );
                scope = that.scope;
                doDebug = that.doDebug;

                return *this;
        }

        Indexer& Indexer::operator= ( Indexer &&that ) {
                deleteRef( tables );

                tables = that.tables;
                scope = that.scope;
                doDebug = that.doDebug;

                that.tables = 0;

                return *this;
        }

        void Indexer::lookupId( const std::string &id, std::list< IdData > &out ) const {
                std::unordered_set< std::string > foundMangleNames;

                Indexer::Impl *searchTables = tables;
                while ( searchTables ) {

                        IdTable::const_iterator decls = searchTables->idTable.find( id );
                        if ( decls != searchTables->idTable.end() ) {
                                const MangleTable &mangleTable = decls->second;
                                for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                        // mark the mangled name as found, skipping this insertion if a declaration for that name has already been found
                                        if ( foundMangleNames.insert( decl->first ).second == false ) continue;

                                        out.push_back( decl->second );
                                }
                        }

                        // get declarations from base indexers
                        searchTables = searchTables->base.tables;
                }

                // some special functions, e.g. constructors and destructors
                // remove autogenerated functions when they are defined so that
                // they can never be matched
                removeSpecialOverrides( id, out );
        }

        NamedTypeDecl *Indexer::lookupType( const std::string &id ) const {
                if ( ! tables ) return 0;

                TypeTable::const_iterator ret = tables->typeTable.find( id );
                return ret != tables->typeTable.end() ? ret->second : tables->base.lookupType( id );
        }

        StructDecl *Indexer::lookupStruct( const std::string &id ) const {
                if ( ! tables ) return 0;

                StructTable::const_iterator ret = tables->structTable.find( id );
                return ret != tables->structTable.end() ? ret->second : tables->base.lookupStruct( id );
        }

        EnumDecl *Indexer::lookupEnum( const std::string &id ) const {
                if ( ! tables ) return 0;

                EnumTable::const_iterator ret = tables->enumTable.find( id );
                return ret != tables->enumTable.end() ? ret->second : tables->base.lookupEnum( id );
        }

        UnionDecl *Indexer::lookupUnion( const std::string &id ) const {
                if ( ! tables ) return 0;

                UnionTable::const_iterator ret = tables->unionTable.find( id );
                return ret != tables->unionTable.end() ? ret->second : tables->base.lookupUnion( id );
        }

        TraitDecl *Indexer::lookupTrait( const std::string &id ) const {
                if ( ! tables ) return 0;

                TraitTable::const_iterator ret = tables->traitTable.find( id );
                return ret != tables->traitTable.end() ? ret->second : tables->base.lookupTrait( id );
        }

        const Indexer::IdData * Indexer::lookupIdAtScope( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return nullptr;
                if ( tables->scope < scope ) return nullptr;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        MangleTable::const_iterator decl = mangleTable.find( mangleName );
                        if ( decl != mangleTable.end() ) return &decl->second;
                }

                return tables->base.lookupIdAtScope( id, mangleName, scope );
        }

        Indexer::IdData * Indexer::lookupIdAtScope( const std::string &id, const std::string &mangleName, unsigned long scope ) {
                return const_cast<IdData *>(const_cast<const Indexer *>(this)->lookupIdAtScope( id, mangleName, scope ));
        }

        bool Indexer::hasIncompatibleCDecl( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return false;
                if ( tables->scope < scope ) return false;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                // check for C decls with the same name, skipping those with a compatible type (by mangleName)
                                if ( ! LinkageSpec::isMangled( decl->second.id->get_linkage() ) && decl->first != mangleName ) return true;
                        }
                }

                return tables->base.hasIncompatibleCDecl( id, mangleName, scope );
        }

        bool Indexer::hasCompatibleCDecl( const std::string &id, const std::string &mangleName, unsigned long scope ) const {
                if ( ! tables ) return false;
                if ( tables->scope < scope ) return false;

                IdTable::const_iterator decls = tables->idTable.find( id );
                if ( decls != tables->idTable.end() ) {
                        const MangleTable &mangleTable = decls->second;
                        for ( MangleTable::const_iterator decl = mangleTable.begin(); decl != mangleTable.end(); ++decl ) {
                                // check for C decls with the same name, skipping
                                // those with an incompatible type (by mangleName)
                                if ( ! LinkageSpec::isMangled( decl->second.id->get_linkage() ) && decl->first == mangleName ) return true;
                        }
                }

                return tables->base.hasCompatibleCDecl( id, mangleName, scope );
        }

        NamedTypeDecl *Indexer::lookupTypeAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                TypeTable::const_iterator ret = tables->typeTable.find( id );
                return ret != tables->typeTable.end() ? ret->second : tables->base.lookupTypeAtScope( id, scope );
        }

        StructDecl *Indexer::lookupStructAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                StructTable::const_iterator ret = tables->structTable.find( id );
                return ret != tables->structTable.end() ? ret->second : tables->base.lookupStructAtScope( id, scope );
        }

        EnumDecl *Indexer::lookupEnumAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                EnumTable::const_iterator ret = tables->enumTable.find( id );
                return ret != tables->enumTable.end() ? ret->second : tables->base.lookupEnumAtScope( id, scope );
        }

        UnionDecl *Indexer::lookupUnionAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                UnionTable::const_iterator ret = tables->unionTable.find( id );
                return ret != tables->unionTable.end() ? ret->second : tables->base.lookupUnionAtScope( id, scope );
        }

        TraitDecl *Indexer::lookupTraitAtScope( const std::string &id, unsigned long scope ) const {
                if ( ! tables ) return 0;
                if ( tables->scope < scope ) return 0;

                TraitTable::const_iterator ret = tables->traitTable.find( id );
                return ret != tables->traitTable.end() ? ret->second : tables->base.lookupTraitAtScope( id, scope );
        }

        bool isFunction( DeclarationWithType * decl ) {
                return GenPoly::getFunctionType( decl->get_type() );
        }

        bool isObject( DeclarationWithType * decl ) {
                return ! isFunction( decl );
        }

        bool isDefinition( DeclarationWithType * decl ) {
                if ( FunctionDecl * func = dynamic_cast< FunctionDecl * >( decl ) ) {
                        // a function is a definition if it has a body
                        return func->statements;
                } else {
                        // an object is a definition if it is not marked extern.
                        // both objects must be marked extern
                        return ! decl->get_storageClasses().is_extern;
                }
        }

        bool addedIdConflicts( Indexer::IdData & existing, DeclarationWithType *added, BaseSyntaxNode * deleteStmt, Indexer::ConflictFunction handleConflicts ) {
                // if we're giving the same name mangling to things of different types then there is something wrong
                assert( (isObject( added ) && isObject( existing.id ) )
                        || ( isFunction( added ) && isFunction( existing.id ) ) );

                if ( LinkageSpec::isOverridable( existing.id->get_linkage() ) ) {
                        // new definition shadows the autogenerated one, even at the same scope
                        return false;
                } else if ( LinkageSpec::isMangled( added->get_linkage() ) || ResolvExpr::typesCompatible( added->get_type(), existing.id->get_type(), Indexer() ) ) {

                        // it is a conflict if one declaration is deleted and the other is not
                        if ( deleteStmt && ! existing.deleteStmt ) {
                                return handleConflicts( existing, "deletion of defined identifier " );
                        } else if ( ! deleteStmt && existing.deleteStmt ) {
                                return handleConflicts( existing, "definition of deleted identifier " );
                        }

                        if ( isDefinition( added ) && isDefinition( existing.id ) ) {
                                if ( isFunction( added ) ) {
                                        return handleConflicts( existing, "duplicate function definition for " );
                                } else {
                                        return handleConflicts( existing, "duplicate object definition for " );
                                } // if
                        } // if
                } else {
                        return handleConflicts( existing, "duplicate definition for " );
                } // if

                return true;
        }

        void Indexer::addId( DeclarationWithType *decl, ConflictFunction handleConflicts, Expression * baseExpr, BaseSyntaxNode * deleteStmt ) {
                if ( decl->name == "" ) return;
                debugPrint( "Adding Id " << decl->name << std::endl );
                makeWritable();

                const std::string &name = decl->name;
                std::string mangleName;
                if ( LinkageSpec::isOverridable( decl->linkage ) ) {
                        // mangle the name without including the appropriate suffix, so overridable routines are placed into the
                        // same "bucket" as their user defined versions.
                        mangleName = Mangler::mangle( decl, false );
                } else {
                        mangleName = Mangler::mangle( decl );
                } // if

                // this ensures that no two declarations with the same unmangled name at the same scope both have C linkage
                if ( ! LinkageSpec::isMangled( decl->linkage ) ) {
                        // NOTE this is broken in Richard's original code in such a way that it never triggers (it
                        // doesn't check decls that have the same manglename, and all C-linkage decls are defined to
                        // have their name as their manglename, hence the error can never trigger).
                        // The code here is closer to correct, but name mangling would have to be completely
                        // isomorphic to C type-compatibility, which it may not be.
                        if ( hasIncompatibleCDecl( name, mangleName, scope ) ) {
                                SemanticError( decl, "conflicting overload of C function " );
                        }
                } else {
                        // Check that a Cforall declaration doesn't override any C declaration
                        if ( hasCompatibleCDecl( name, mangleName, scope ) ) {
                                SemanticError( decl, "Cforall declaration hides C function " );
                        }
                }

                // Skip repeat declarations of the same identifier
                IdData * existing = lookupIdAtScope( name, mangleName, scope );
                if ( existing && existing->id && addedIdConflicts( *existing, decl, deleteStmt, handleConflicts ) ) return;

                // add to indexer
                tables->idTable[ name ][ mangleName ] = IdData{ decl, baseExpr, deleteStmt };
                ++tables->size;
        }

        void Indexer::addId( DeclarationWithType * decl, Expression * baseExpr ) {
                // default handling of conflicts is to raise an error
                addId( decl, [decl](IdData &, const std::string & msg) { SemanticError( decl, msg ); return true; }, baseExpr, decl->isDeleted ? decl : nullptr );
        }

        void Indexer::addDeletedId( DeclarationWithType * decl, BaseSyntaxNode * deleteStmt ) {
                // default handling of conflicts is to raise an error
                addId( decl, [decl](IdData &, const std::string & msg) { SemanticError( decl, msg ); return true; }, nullptr, deleteStmt );
        }

        bool addedTypeConflicts( NamedTypeDecl *existing, NamedTypeDecl *added ) {
                if ( existing->get_base() == 0 ) {
                        return false;
                } else if ( added->get_base() == 0 ) {
                        return true;
                } else {
                        SemanticError( added, "redeclaration of " );
                }
        }

        void Indexer::addType( NamedTypeDecl *decl ) {
                debugPrint( "Adding type " << decl->name << std::endl );
                makeWritable();

                const std::string &id = decl->get_name();
                TypeTable::iterator existing = tables->typeTable.find( id );
                if ( existing == tables->typeTable.end() ) {
                        NamedTypeDecl *parent = tables->base.lookupTypeAtScope( id, scope );
                        if ( ! parent || ! addedTypeConflicts( parent, decl ) ) {
                                tables->typeTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedTypeConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        bool addedDeclConflicts( AggregateDecl *existing, AggregateDecl *added ) {
                if ( ! existing->body ) {
                        return false;
                } else if ( added->body ) {
                        SemanticError( added, "redeclaration of " );
                } // if
                return true;
        }

        void Indexer::addStruct( const std::string &id ) {
                debugPrint( "Adding fwd decl for struct " << id << std::endl );
                addStruct( new StructDecl( id ) );
        }

        void Indexer::addStruct( StructDecl *decl ) {
                debugPrint( "Adding struct " << decl->name << std::endl );
                makeWritable();

                const std::string &id = decl->get_name();
                StructTable::iterator existing = tables->structTable.find( id );
                if ( existing == tables->structTable.end() ) {
                        StructDecl *parent = tables->base.lookupStructAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->structTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addEnum( EnumDecl *decl ) {
                debugPrint( "Adding enum " << decl->name << std::endl );
                makeWritable();

                const std::string &id = decl->get_name();
                EnumTable::iterator existing = tables->enumTable.find( id );
                if ( existing == tables->enumTable.end() ) {
                        EnumDecl *parent = tables->base.lookupEnumAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->enumTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addUnion( const std::string &id ) {
                debugPrint( "Adding fwd decl for union " << id << std::endl );
                addUnion( new UnionDecl( id ) );
        }

        void Indexer::addUnion( UnionDecl *decl ) {
                debugPrint( "Adding union " << decl->name << std::endl );
                makeWritable();

                const std::string &id = decl->get_name();
                UnionTable::iterator existing = tables->unionTable.find( id );
                if ( existing == tables->unionTable.end() ) {
                        UnionDecl *parent = tables->base.lookupUnionAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->unionTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addTrait( TraitDecl *decl ) {
                debugPrint( "Adding trait " << decl->name << std::endl );
                makeWritable();

                const std::string &id = decl->get_name();
                TraitTable::iterator existing = tables->traitTable.find( id );
                if ( existing == tables->traitTable.end() ) {
                        TraitDecl *parent = tables->base.lookupTraitAtScope( id, scope );
                        if ( ! parent || ! addedDeclConflicts( parent, decl ) ) {
                                tables->traitTable.insert( existing, std::make_pair( id, decl ) );
                                ++tables->size;
                        }
                } else {
                        if ( ! addedDeclConflicts( existing->second, decl ) ) {
                                existing->second = decl;
                        }
                }
        }

        void Indexer::addMembers( AggregateDecl * aggr, Expression * expr, ConflictFunction handleConflicts ) {
                for ( Declaration * decl : aggr->members ) {
                        if ( DeclarationWithType * dwt = dynamic_cast< DeclarationWithType * >( decl ) ) {
                                addId( dwt, handleConflicts, expr );
                                if ( dwt->name == "" ) {
                                        Type * t = dwt->get_type()->stripReferences();
                                        if ( dynamic_cast< StructInstType * >( t ) || dynamic_cast< UnionInstType * >( t ) ) {
                                                Expression * base = expr->clone();
                                                ResolvExpr::Cost cost = ResolvExpr::Cost::zero; // xxx - carry this cost into the indexer as a base cost?
                                                ResolvExpr::referenceToRvalueConversion( base, cost );
                                                addMembers( t->getAggr(), new MemberExpr( dwt, base ), handleConflicts );
                                        }
                                }
                        }
                }
        }

        void Indexer::addWith( std::list< Expression * > & withExprs, BaseSyntaxNode * withStmt ) {
                for ( Expression * expr : withExprs ) {
                        if ( expr->result ) {
                                AggregateDecl * aggr = expr->result->stripReferences()->getAggr();
                                assertf( aggr, "WithStmt expr has non-aggregate type: %s", toString( expr->result ).c_str() );

                                addMembers( aggr, expr, [withStmt](IdData & existing, const std::string &) {
                                        // on conflict, delete the identifier
                                        existing.deleteStmt = withStmt;
                                        return true;
                                });
                        }
                }
        }

        void Indexer::addIds( const std::list< DeclarationWithType * > & decls ) {
                for ( auto d : decls ) {
                        addId( d );
                }
        }

        void Indexer::addTypes( const std::list< TypeDecl * > & tds ) {
                for ( auto td : tds ) {
                        addType( td );
                        addIds( td->assertions );
                }
        }

        void Indexer::addFunctionType( FunctionType * ftype ) {
                addTypes( ftype->forall );
                addIds( ftype->returnVals );
                addIds( ftype->parameters );
        }

        void Indexer::enterScope() {
                ++scope;

                if ( doDebug ) {
                        std::cerr << "--- Entering scope " << scope << std::endl;
                }
        }

        void Indexer::leaveScope() {
                using std::cerr;

                assert( scope > 0 && "cannot leave initial scope" );
                if ( doDebug ) {
                        cerr << "--- Leaving scope " << scope << " containing" << std::endl;
                }
                --scope;

                while ( tables && tables->scope > scope ) {
                        if ( doDebug ) {
                                dump( tables->idTable, cerr );
                                dump( tables->typeTable, cerr );
                                dump( tables->structTable, cerr );
                                dump( tables->enumTable, cerr );
                                dump( tables->unionTable, cerr );
                                dump( tables->traitTable, cerr );
                        }

                        // swap tables for base table until we find one at an appropriate scope
                        Indexer::Impl *base = newRef( tables->base.tables );
                        deleteRef( tables );
                        tables = base;
                }
        }

        void Indexer::print( std::ostream &os, int indent ) const {
                using std::cerr;

                if ( tables ) {
                        os << "--- scope " << tables->scope << " ---" << std::endl;

                        os << "===idTable===" << std::endl;
                        dump( tables->idTable, os );
                        os << "===typeTable===" << std::endl;
                        dump( tables->typeTable, os );
                        os << "===structTable===" << std::endl;
                        dump( tables->structTable, os );
                        os << "===enumTable===" << std::endl;
                        dump( tables->enumTable, os );
                        os << "===unionTable===" << std::endl;
                        dump( tables->unionTable, os );
                        os << "===contextTable===" << std::endl;
                        dump( tables->traitTable, os );

                        tables->base.print( os, indent );
                } else {
                        os << "--- end ---" << std::endl;
                }

        }

        Expression * Indexer::IdData::combine( ResolvExpr::Cost & cost ) const {
                Expression * ret = nullptr;
                if ( baseExpr ) {
                        Expression * base = baseExpr->clone();
                        ResolvExpr::referenceToRvalueConversion( base, cost );
                        ret = new MemberExpr( id, base );
                        // xxx - this introduces hidden environments, for now remove them.
                        // std::swap( base->env, ret->env );
                        delete base->env;
                        base->env = nullptr;
                } else {
                        ret = new VariableExpr( id );
                }
                if ( deleteStmt ) ret = new DeletedExpr( ret, deleteStmt );
                return ret;
        }
} // namespace SymTab

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //