source: src/ResolvExpr/CurrentObject.cc @ 3d5fba21

//
// 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.
//
// CurrentObject.h --
//
// Author           : Rob Schluntz
// Created On       : Tue Jun 13 15:28:32 2017
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Jul  1 09:16:01 2022
// Update Count     : 15
//

#include <stddef.h>                    // for size_t
#include <cassert>                     // for assertf, assert, safe_dynamic_...
#include <deque>
#include <iostream>                    // for ostream, operator<<, basic_ost...
#include <stack>                       // for stack
#include <string>                      // for string, operator<<, allocator

#include "AST/Copy.hpp"                // for shallowCopy
#include "AST/Expr.hpp"                // for InitAlternative
#include "AST/GenericSubstitution.hpp" // for genericSubstitution
#include "AST/Init.hpp"                // for Designation
#include "AST/Node.hpp"                // for readonly
#include "AST/Print.hpp"               // for readonly
#include "AST/Type.hpp"
#include "Common/Eval.h"               // for eval
#include "Common/Indenter.h"           // for Indenter, operator<<
#include "Common/SemanticError.h"      // for SemanticError
#include "Common/utility.h"            // for toString
#include "CurrentObject.h"
#include "SynTree/Constant.h"          // for Constant
#include "SynTree/Declaration.h"       // for ObjectDecl, Declaration, Struc...
#include "SynTree/Expression.h"        // for InitAlternative, VariableExpr
#include "SynTree/Initializer.h"       // for Designation, operator<<
#include "SynTree/Type.h"              // for Type, StructInstType, UnionIns...
#include "SynTree/TypeSubstitution.h"  // for TypeSubstitution

#if 0
#define PRINT(x) x
#else
#define PRINT(x)
#endif

namespace ResolvExpr {
        template< typename AggrInst >
        TypeSubstitution makeGenericSubstitution( AggrInst * inst ) {
                assert( inst );
                assert( inst->get_baseParameters() );
                std::list< TypeDecl * > baseParams = *inst->get_baseParameters();
                std::list< Expression * > typeSubs = inst->get_parameters();
                TypeSubstitution subs( baseParams.begin(), baseParams.end(), typeSubs.begin() );
                return subs;
        }

        TypeSubstitution makeGenericSubstitution( Type * type ) {
                if ( StructInstType * inst = dynamic_cast< StructInstType * >( type ) ) {
                        return makeGenericSubstitution( inst );
                } else if ( UnionInstType * inst = dynamic_cast< UnionInstType * >( type ) ) {
                        return makeGenericSubstitution( inst );
                } else {
                        return TypeSubstitution();
                }
        }

        class MemberIterator {
        public:
                virtual ~MemberIterator() {}

                /// walks the current object using the given designators as a guide
                virtual void setPosition( std::list< Expression * > & designators ) = 0;

                /// retrieve the list of possible Type/Designation pairs for the current position in the currect object
                virtual std::list<InitAlternative> operator*() const = 0;

                /// true if the iterator is not currently at the end
                virtual operator bool() const = 0;

                /// moves the iterator by one member in the current object
                virtual MemberIterator & bigStep() = 0;

                /// moves the iterator by one member in the current subobject
                virtual MemberIterator & smallStep() = 0;

                /// the type of the current object
                virtual Type * getType() = 0;

                /// the type of the current subobject
                virtual Type * getNext() = 0;

                /// printing for debug
                virtual void print( std::ostream & out, Indenter indent ) const = 0;

                /// helper for operator*; aggregates must add designator to each init alternative, but
                /// adding designators in operator* creates duplicates.
                virtual std::list<InitAlternative> first() const = 0; // should be protected
        };

        std::ostream & operator<<(std::ostream & out, const MemberIterator & it) {
                Indenter indenter;
                it.print( out, indenter );
                return out;
        }

        /// create a new MemberIterator that traverses a type correctly
        MemberIterator * createMemberIterator( Type * type );

        /// iterates "other" types, e.g. basic types, pointer types, etc. which do not change at list initializer entry
        class SimpleIterator : public MemberIterator {
        public:
                SimpleIterator( Type * type ) : type( type ) {}

                virtual void setPosition( std::list< Expression * > & designators ) {
                        assertf( designators.empty(), "simple iterator given non-empty designator..." ); // xxx - might be semantic error
                }

                virtual std::list<InitAlternative> operator*() const { return first(); }
                virtual operator bool() const { return type; }

                // big step is the same as small step
                virtual MemberIterator & bigStep() { return smallStep(); }
                virtual MemberIterator & smallStep() {
                        type = nullptr;  // type is nullified on increment since SimpleIterators do not have members
                        return *this;
                }

                virtual void print( std::ostream & out, __attribute__((unused)) Indenter indent ) const {
                        out << "SimpleIterator(" << type << ")";
                }

                virtual Type * getType() { return type; }
                virtual Type * getNext() { return type; }

        protected:
                virtual std::list<InitAlternative> first() const {
                        if ( type ) return std::list<InitAlternative>{ { type->clone(), new Designation( {} ) } };
                        else return std::list<InitAlternative>{};
                }
        private:
                Type * type = nullptr;
        };

        class ArrayIterator : public MemberIterator {
        public:
                ArrayIterator( ArrayType * at ) : array( at ) {
                        PRINT( std::cerr << "Creating array iterator: " << at << std::endl; )
                        base = at->base;
                        memberIter = createMemberIterator( base );
                        if ( at->isVarLen ) SemanticError( at, "VLA initialization does not support @=: " );
                        setSize( at->dimension );
                }

                ~ArrayIterator() {
                        delete memberIter;
                }

        private:
                void setSize( Expression * expr ) {
                        auto res = eval( expr );
                        if (res.second) {
                                size = res.first;
                        } else {
                                SemanticError( expr->location, toString("Array designator must be a constant expression: ", expr) );
                        }
                }

        public:
                void setPosition( Expression * expr ) {
                        // need to permit integer-constant-expressions, including: integer constants, enumeration constants, character constants, sizeof expressions, _Alignof expressions, cast expressions
                        auto arg = eval( expr );
                        index = arg.first;
                        return;

                        // if ( ConstantExpr * constExpr = dynamic_cast< ConstantExpr * >( expr ) ) {
                        //      try {
                        //              index = constExpr->intValue();
                        //      } catch( SemanticErrorException & ) {
                        //              SemanticError( expr, "Constant expression of non-integral type in array designator: " );
                        //      }
                        // } else if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
                        //      setPosition( castExpr->get_arg() );
                        // } else if ( VariableExpr * varExpr = dynamic_cast< VariableExpr * >( expr ) ) {
                        //      EnumInstType * inst = dynamic_cast<EnumInstType *>( varExpr->get_result() );
                        //      assertf( inst, "ArrayIterator given variable that isn't an enum constant : %s", toString( expr ).c_str() );
                        //      long long int value;
                        //      if ( inst->baseEnum->valueOf( varExpr->var, value ) ) {
                        //              index = value;
                        //      }
                        // } else if ( dynamic_cast< SizeofExpr * >( expr ) || dynamic_cast< AlignofExpr * >( expr ) ) {
                        //      index = 0; // xxx - get actual sizeof/alignof value?
                        // } else {
                        //      assertf( false, "4 bad designator given to ArrayIterator: %s", toString( expr ).c_str() );
                        // }
                }

                virtual void setPosition( std::list< Expression * > & designators ) {
                        if ( ! designators.empty() ) {
                                setPosition( designators.front() );
                                designators.pop_front();
                                memberIter->setPosition( designators );
                        }
                }

                virtual std::list<InitAlternative> operator*() const {
                        return first();
                }

                virtual operator bool() const { return index < size; }

                virtual MemberIterator & bigStep() {
                        PRINT( std::cerr << "bigStep in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        ++index;
                        delete memberIter;
                        if ( index < size ) memberIter = createMemberIterator( base );
                        else memberIter = nullptr;
                        return *this;
                }

                virtual MemberIterator & smallStep() {
                        PRINT( std::cerr << "smallStep in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        if ( memberIter ) {
                                PRINT( std::cerr << "has member iter: " << *memberIter << std::endl; )
                                memberIter->smallStep();
                                if ( *memberIter ) {
                                        PRINT( std::cerr << "has valid member iter" << std::endl; )
                                        return *this;
                                }
                        }
                        return bigStep();
                }

                virtual Type * getType() { return array; }
                virtual Type * getNext() { return base; }

                virtual std::list<InitAlternative> first() const {
                        PRINT( std::cerr << "first in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        if ( memberIter && *memberIter ) {
                                std::list<InitAlternative> ret = memberIter->first();
                                for ( InitAlternative & alt : ret ) {
                                        alt.designation->get_designators().push_front( new ConstantExpr( Constant::from_ulong( index ) ) );
                                }
                                return ret;
                        }
                        return std::list<InitAlternative>();
                }

                virtual void print( std::ostream & out, Indenter indent ) const {
                        out << "ArrayIterator(Array of " << base << ")";
                        if ( memberIter ) {
                                Indenter childIndent = indent+1;
                                out << std::endl << childIndent;
                                memberIter->print( out, childIndent );
                        }
                }

        private:
                ArrayType * array = nullptr;
                Type * base = nullptr;
                size_t index = 0;
                size_t size = 0;
                MemberIterator * memberIter = nullptr;
        };

        class AggregateIterator : public MemberIterator {
        public:
                typedef std::list<Declaration *> MemberList;
                typedef MemberList::const_iterator iterator;
                std::string kind = ""; // for debug
                std::string name;
                Type * inst = nullptr;
                const MemberList & members;
                iterator curMember;
                bool atbegin = true; // false at first {small,big}Step -- this aggr type is only added to the possibilities at the beginning
                Type * curType = nullptr;
                MemberIterator * memberIter = nullptr;
                mutable TypeSubstitution sub;

                AggregateIterator( const std::string & kind, const std::string & name, Type * inst, const MemberList & members ) : kind( kind ), name( name ), inst( inst ), members( members ), curMember( members.begin() ), sub( makeGenericSubstitution( inst ) ) {
                        PRINT( std::cerr << "Creating " << kind << "(" << name << ")"; )
                        init();
                }

                virtual ~AggregateIterator() {
                        delete memberIter;
                }

                bool init() {
                        PRINT( std::cerr << "--init()--" << members.size() << std::endl; )
                        if ( curMember != members.end() ) {
                                if ( ObjectDecl * field = dynamic_cast< ObjectDecl * >( *curMember ) ) {
                                        PRINT( std::cerr << "incremented to field: " << field << std::endl; )
                                        curType = field->get_type();
                                        memberIter = createMemberIterator( curType );
                                        return true;
                                }
                        }
                        return false;
                }

                virtual std::list<InitAlternative> operator*() const {
                        if (memberIter && *memberIter) {
                                std::list<InitAlternative> ret = memberIter->first();
                                PRINT( std::cerr << "sub: " << sub << std::endl; )
                                for ( InitAlternative & alt : ret ) {
                                        PRINT( std::cerr << "iterating and adding designators" << std::endl; )
                                        alt.designation->get_designators().push_front( new VariableExpr( strict_dynamic_cast< ObjectDecl * >( *curMember ) ) );
                                        // need to substitute for generic types, so that casts are to concrete types
                                        PRINT( std::cerr << "  type is: " << alt.type; )
                                        sub.apply( alt.type ); // also apply to designation??
                                        PRINT( std::cerr << " ==> " << alt.type << std::endl; )
                                }
                                return ret;
                        }
                        return std::list<InitAlternative>();
                }

                virtual void setPosition( std::list< Expression * > & designators ) {
                        if ( ! designators.empty() ) {
                                if ( VariableExpr * varExpr = dynamic_cast< VariableExpr * >( designators.front() ) ) {
                                        for ( curMember = members.begin(); curMember != members.end(); ++curMember ) {
                                                if ( *curMember == varExpr->get_var() ) {
                                                        designators.pop_front();
                                                        delete memberIter;
                                                        memberIter = createMemberIterator( varExpr->get_result() );
                                                        curType = varExpr->get_result();
                                                        atbegin = curMember == members.begin() && designators.empty(); // xxx - is this the right condition for atbegin??
                                                        memberIter->setPosition( designators );
                                                        return;
                                                } // if
                                        } // for
                                        assertf( false, "could not find member in %s: %s", kind.c_str(), toString( varExpr ).c_str() );
                                } else {
                                        assertf( false, "3 bad designator given to %s: %s", kind.c_str(), toString( designators.front() ).c_str() );
                                } // if
                        } // if
                }

                virtual MemberIterator & smallStep() {
                        PRINT( std::cerr << "smallStep in " << kind << std::endl; )
                        atbegin = false;
                        if ( memberIter ) {
                                PRINT( std::cerr << "has member iter, incrementing..." << std::endl; )
                                memberIter->smallStep();
                                if ( *memberIter ) {
                                        PRINT( std::cerr << "success!" << std::endl; )
                                        return *this;
                                }
                        }
                        return bigStep();
                }

                virtual Type * getType() { return inst; }
                virtual Type * getNext() {
                        if ( memberIter && *memberIter ) return memberIter->getType(); // xxx - ??? recursive call???
                        return nullptr;
                }

                virtual std::list<InitAlternative> first() const {
                        std::list<InitAlternative> ret;
                        PRINT( std::cerr << "first " << kind << std::endl; )
                        if ( memberIter && *memberIter ) { // might not need *memberIter??
                                PRINT( std::cerr << "adding children" << std::endl; )
                                ret = memberIter->first();
                                for ( InitAlternative & alt : ret ) {
                                        PRINT( std::cerr << "iterating and adding designators" << std::endl; )
                                        alt.designation->get_designators().push_front( new VariableExpr( strict_dynamic_cast< ObjectDecl * >( *curMember ) ) );
                                }
                        }
                        if ( atbegin ) {
                                // xxx - what about case of empty struct??
                                // only add self if at the very beginning of the structure
                                PRINT( std::cerr << "adding self" << std::endl; )
                                ret.push_front( { inst->clone(), new Designation( {} ) } );
                        }
                        return ret;
                }

                virtual void print( std::ostream & out, Indenter indent ) const {
                        out << kind << "(" << name << ")";
                        if ( memberIter ) {
                                Indenter childIndent = indent+1;
                                out << std::endl << childIndent;
                                memberIter->print( out, childIndent );
                        }
                }
        };

        class UnionIterator : public AggregateIterator {
        public:
                UnionIterator( UnionInstType * inst ) : AggregateIterator( "UnionIterator", inst->get_name(), inst, inst->get_baseUnion()->get_members() ) {}

                virtual operator bool() const { return (memberIter && *memberIter); }
                virtual MemberIterator & bigStep() {
                        // unions only initialize one member
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        delete memberIter;
                        memberIter = nullptr;
                        curType = nullptr;
                        curMember = members.end();
                        return *this;
                }
        };

        class StructIterator : public AggregateIterator {
        public:
                StructIterator( StructInstType * inst ) : AggregateIterator( "StructIterator", inst->get_name(), inst, inst->get_baseStruct()->get_members() ) {}

                virtual operator bool() const { return curMember != members.end() || (memberIter && *memberIter); }

                virtual MemberIterator & bigStep() {
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        delete memberIter;
                        memberIter = nullptr;
                        curType = nullptr;
                        for ( ; curMember != members.end(); ) {
                                ++curMember;
                                if ( init() ) {
                                        return *this;
                                }
                        }
                        return *this;
                }
        };

        class TupleIterator : public AggregateIterator {
        public:
                TupleIterator( TupleType * inst ) : AggregateIterator( "TupleIterator", toString("Tuple", inst->size()), inst, inst->get_members() ) {}

                virtual operator bool() const { return curMember != members.end() || (memberIter && *memberIter); }

                virtual MemberIterator & bigStep() {
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        delete memberIter;
                        memberIter = nullptr;
                        curType = nullptr;
                        for ( ; curMember != members.end(); ) {
                                ++curMember;
                                if ( init() ) {
                                        return *this;
                                }
                        }
                        return *this;
                }
        };

        MemberIterator * createMemberIterator( Type * type ) {
                if ( ReferenceToType * aggr = dynamic_cast< ReferenceToType * >( type ) ) {
                        if ( StructInstType * sit = dynamic_cast< StructInstType * >( aggr ) ) {
                                return new StructIterator( sit );
                        } else if ( UnionInstType * uit = dynamic_cast< UnionInstType * >( aggr ) ) {
                                return new UnionIterator( uit );
                        } else {
                                assertf( dynamic_cast< EnumInstType * >( type ) || dynamic_cast< TypeInstType * >( type ), "Encountered unhandled ReferenceToType in createMemberIterator: %s", toString( type ).c_str() );
                                return new SimpleIterator( type );
                        }
                } else if ( ArrayType * at = dynamic_cast< ArrayType * >( type ) ) {
                        return new ArrayIterator( at );
                } else if ( TupleType * tt = dynamic_cast< TupleType * >( type ) ) {
                        return new TupleIterator( tt );
                } else {
                        return new SimpleIterator( type );
                }
        }

        CurrentObject::CurrentObject() {}
        CurrentObject::CurrentObject( Type * type ) {
                objStack.push( new SimpleIterator( type ) );
        }


        void CurrentObject::setNext( Designation * designation ) {
                assertf( ! objStack.empty(), "obj stack empty in setNext" );
                PRINT( std::cerr << "____setNext" << designation << std::endl; )
                objStack.top()->setPosition( designation->get_designators() );
        }

        Designation * CurrentObject::findNext( Designation * designation ) {
                typedef std::list< Expression * > DesignatorChain;
                PRINT( std::cerr << "___findNext" << std::endl; )
                // find all the d's
                std::list<DesignatorChain> desigAlts{ { } }, newDesigAlts;
                std::list<Type *> curTypes { (objStack.top())->getType() }, newTypes;
                for ( Expression * expr : designation->get_designators() ) {
                        PRINT( std::cerr << "____untyped: " << expr << std::endl; )
                        std::list<DesignatorChain>::iterator dit = desigAlts.begin();
                        if ( NameExpr * nexpr = dynamic_cast<NameExpr *>(expr) ) {
                                for ( Type * t : curTypes ) {
                                        assert( dit != desigAlts.end() );
                                        DesignatorChain & d = *dit;
                                        PRINT( std::cerr << "____actual: " << t << std::endl; )
                                        ReferenceToType * refType = dynamic_cast<ReferenceToType *>(t);
                                        std::list<Declaration *> members;
                                        if ( refType ) {
                                                refType->lookup( nexpr->get_name(), members ); // concatenate identical field name
                                                // xxx - need to also include anonymous members in this somehow...
                                                for ( Declaration * mem: members ) {
                                                        if ( ObjectDecl * field = dynamic_cast<ObjectDecl *>(mem) ) {
                                                                PRINT( std::cerr << "____alt: " << field->get_type() << std::endl; )
                                                                DesignatorChain newD = d;
                                                                newD.push_back( new VariableExpr( field ) );
                                                                newDesigAlts.push_back( newD );
                                                                newTypes.push_back( field->get_type() );
                                                        } // if
                                                } // for
                                        } // if
                                        ++dit;
                                } // for
                        } else {
                                for ( Type * t : curTypes ) {
                                        assert( dit != desigAlts.end() );
                                        DesignatorChain & d = *dit;
                                        if ( ArrayType * at = dynamic_cast< ArrayType * > ( t ) ) {
                                                PRINT( std::cerr << "____alt: " << at->get_base() << std::endl; )
                                                d.push_back( expr );
                                                newDesigAlts.push_back( d );
                                                newTypes.push_back( at->get_base() );
                                        }
                                        ++dit;
                                } // for
                        } // if
                        desigAlts = newDesigAlts;
                        newDesigAlts.clear();
                        curTypes = newTypes;
                        newTypes.clear();
                        assertf( desigAlts.size() == curTypes.size(), "Designator alternatives (%zu) and current types (%zu) out of sync", desigAlts.size(), curTypes.size() );
                } // for
                if ( desigAlts.size() > 1 ) {
                        SemanticError( designation, toString("Too many alternatives (", desigAlts.size(), ") for designation: ") );
                } else if ( desigAlts.size() == 0 ) {
                        SemanticError( designation, "No reasonable alternatives for designation: " );
                }
                DesignatorChain & d = desigAlts.back();
                PRINT( for ( Expression * expr : d ) {
                        std::cerr << "____desig: " << expr << std::endl;
                } ) // for
                assertf( ! curTypes.empty(), "empty designator chosen");

                // set new designators
                assertf( ! objStack.empty(), "empty object stack when setting designation" );
                Designation * actualDesignation = new Designation( d );
                objStack.top()->setPosition( d ); // destroys d
                return actualDesignation;
        }

        void CurrentObject::increment() {
                PRINT( std::cerr << "____increment" << std::endl; )
                if ( ! objStack.empty() ) {
                        PRINT( std::cerr << *objStack.top() << std::endl; )
                        objStack.top()->smallStep();
                }
        }

        void CurrentObject::enterListInit() {
                PRINT( std::cerr << "____entering list init" << std::endl; )
                assertf( ! objStack.empty(), "empty obj stack entering list init" );
                Type * type = objStack.top()->getNext();
                if ( type ) {
                        objStack.push( createMemberIterator( type ) );
                } else {
                        assertf( false, "not sure about this case..." );
                }
        }

        void CurrentObject::exitListInit() {
                PRINT( std::cerr << "____exiting list init" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty" );
                delete objStack.top();
                objStack.pop();
                if ( ! objStack.empty() ) {
                        PRINT( std::cerr << *objStack.top() << std::endl; )
                        objStack.top()->bigStep();
                }
        }

        std::list< InitAlternative > CurrentObject::getOptions() {
                PRINT( std::cerr << "____getting current options" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty in getOptions" );
                return **objStack.top();
        }

        Type * CurrentObject::getCurrentType() {
                PRINT( std::cerr << "____getting current type" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty in getCurrentType" );
                return objStack.top()->getNext();
        }
} // namespace ResolvExpr

namespace ast {
        /// create a new MemberIterator that traverses a type correctly
        MemberIterator * createMemberIterator( const CodeLocation & loc, const Type * type );

        /// Iterates "other" types (e.g. basic, pointer) which do not change at list initializer entry
        class SimpleIterator final : public MemberIterator {
                CodeLocation location;
                const Type * type = nullptr;
        public:
                SimpleIterator( const CodeLocation & loc, const Type * t ) : location( loc ), type( t ) {}

                void setPosition(
                        std::deque< ptr< Expr > >::const_iterator begin,
                        std::deque< ptr< Expr > >::const_iterator end
                ) override {
                        if ( begin != end ) {
                                SemanticError( location, "Un-designated initializer given non-empty designator" );
                        }
                }

                std::deque< InitAlternative > operator* () const override { return first(); }

                operator bool() const override { return type; }

                SimpleIterator & bigStep() override { return smallStep(); }
                SimpleIterator & smallStep() override {
                        type = nullptr;  // empty on increment because no members
                        return *this;
                }

                const Type * getType() override { return type; }

                const Type * getNext() override { return type; }

                std::deque< InitAlternative > first() const override {
                        if ( type ) return { InitAlternative{ type, new Designation{ location } } };
                        return {};
                }
        };

        /// Iterates array types
        class ArrayIterator final : public MemberIterator {
                CodeLocation location;
                const ArrayType * array = nullptr;
                const Type * base = nullptr;
                size_t index = 0;
                size_t size = 0;
                std::unique_ptr< MemberIterator > memberIter;

                void setSize( const Expr * expr ) {
                        auto res = eval( expr );
                        if ( ! res.second ) {
                                SemanticError( location, toString( "Array designator must be a constant expression: ", expr ) );
                        }
                        size = res.first;
                }

        public:
                ArrayIterator( const CodeLocation & loc, const ArrayType * at ) : location( loc ), array( at ), base( at->base ) {
                        PRINT( std::cerr << "Creating array iterator: " << at << std::endl; )
                        memberIter.reset( createMemberIterator( loc, base ) );
                        if ( at->isVarLen ) {
                                SemanticError( location, at, "VLA initialization does not support @=: " );
                        }
                        setSize( at->dimension );
                }

                void setPosition( const Expr * expr ) {
                        // need to permit integer-constant-expressions, including: integer constants,
                        // enumeration constants, character constants, sizeof expressions, alignof expressions,
                        // cast expressions

                        auto arg = eval( expr );
                        index = arg.first;
                        return;

                        // if ( auto constExpr = dynamic_cast< const ConstantExpr * >( expr ) ) {
                        //      try {
                        //              index = constExpr->intValue();
                        //      } catch ( SemanticErrorException & ) {
                        //              SemanticError( expr, "Constant expression of non-integral type in array designator: " );
                        //      }
                        // } else if ( auto castExpr = dynamic_cast< const CastExpr * >( expr ) ) {
                        //      setPosition( castExpr->arg );
                        // } else if ( dynamic_cast< const SizeofExpr * >( expr ) || dynamic_cast< const AlignofExpr * >( expr ) ) {
                        //      index = 0;
                        // } else {
                        //      assertf( false, "2 bad designator given to ArrayIterator: %s", toString( expr ).c_str() );
                        // }
                }

                void setPosition(
                        std::deque< ptr< Expr > >::const_iterator begin,
                        std::deque< ptr< Expr > >::const_iterator end
                ) override {
                        if ( begin == end ) return;

                        setPosition( *begin );
                        memberIter->setPosition( ++begin, end );
                }

                std::deque< InitAlternative > operator* () const override { return first(); }

                operator bool() const override { return index < size; }

                ArrayIterator & bigStep() override {
                        PRINT( std::cerr << "bigStep in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        ++index;
                        memberIter.reset( index < size ? createMemberIterator( location, base ) : nullptr );
                        return *this;
                }

                ArrayIterator & smallStep() override {
                        PRINT( std::cerr << "smallStep in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        if ( memberIter ) {
                                PRINT( std::cerr << "has member iter: " << *memberIter << std::endl; )
                                memberIter->smallStep();
                                if ( *memberIter ) {
                                        PRINT( std::cerr << "has valid member iter" << std::endl; )
                                        return *this;
                                }
                        }
                        return bigStep();
                }

                const Type * getType() override { return array; }

                const Type * getNext() override { return base; }

                std::deque< InitAlternative > first() const override {
                        PRINT( std::cerr << "first in ArrayIterator (" << index << "/" << size << ")" << std::endl; )
                        if ( memberIter && *memberIter ) {
                                std::deque< InitAlternative > ret = memberIter->first();
                                for ( InitAlternative & alt : ret ) {
                                        alt.designation.get_and_mutate()->designators.emplace_front( ConstantExpr::from_ulong( location, index ) );
                                }
                                return ret;
                        }
                        return {};
                }
        };

        class AggregateIterator : public MemberIterator {
        protected:
                using MemberList = std::vector< ptr< Decl > >;

                CodeLocation location;
                std::string kind;  // for debug
                std::string name;
                const Type * inst;
                const MemberList & members;
                MemberList::const_iterator curMember;
                bool atbegin = true;  // false at first {small,big}Step
                const Type * curType = nullptr;
                std::unique_ptr< MemberIterator > memberIter = nullptr;
                TypeSubstitution sub;

                bool init() {
                        PRINT( std::cerr << "--init()--" << members.size() << std::endl; )
                        if ( curMember != members.end() ) {
                                if ( auto field = curMember->as< ObjectDecl >() ) {
                                        PRINT( std::cerr << "incremented to field: " << field << std::endl; )
                                        curType = field->get_type();
                                        memberIter.reset( createMemberIterator( location, curType ) );
                                        return true;
                                }
                        }
                        return false;
                }

                AggregateIterator(
                        const CodeLocation & loc, const std::string k, const std::string & n, const Type * i,
                        const MemberList & ms )
                : location( loc ), kind( k ), name( n ), inst( i ), members( ms ), curMember( ms.begin() ),
                  sub( genericSubstitution( i ) ) {
                        PRINT( std::cerr << "Creating " << kind << "(" << name << ")"; )
                        init();
                }

        public:
                void setPosition(
                        std::deque< ptr< Expr > >::const_iterator begin,
                        std::deque< ptr< Expr > >::const_iterator end
                ) final {
                        if ( begin == end ) return;

                        if ( auto varExpr = begin->as< VariableExpr >() ) {
                                for ( curMember = members.begin(); curMember != members.end(); ++curMember ) {
                                        if ( *curMember != varExpr->var ) continue;

                                        ++begin;

                                        memberIter.reset( createMemberIterator( location, varExpr->result ) );
                                        curType = varExpr->result;
                                        atbegin = curMember == members.begin() && begin == end;
                                        memberIter->setPosition( begin, end );
                                        return;
                                }
                                assertf( false, "could not find member in %s: %s", kind.c_str(), toString( varExpr ).c_str() );
                        } else {
                                assertf( false, "1 bad designator given to %s: %s", kind.c_str(), toString( *begin ).c_str() );
                        }
                }

                std::deque< InitAlternative > operator* () const final {
                        if ( memberIter && *memberIter ) {
                                std::deque< InitAlternative > ret = memberIter->first();
                                PRINT( std::cerr << "sub: " << sub << std::endl; )
                                for ( InitAlternative & alt : ret ) {
                                        PRINT( std::cerr << "iterating and adding designators" << std::endl; )
                                        alt.designation.get_and_mutate()->designators.emplace_front(
                                                new VariableExpr{ location, curMember->strict_as< ObjectDecl >() } );
                                        // need to substitute for generic types so that casts are to concrete types
                                        alt.type = shallowCopy(alt.type.get());
                                        PRINT( std::cerr << "  type is: " << alt.type; )
                                        sub.apply( alt.type ); // also apply to designation??
                                        PRINT( std::cerr << " ==> " << alt.type << std::endl; )
                                }
                                return ret;
                        }
                        return {};
                }

                AggregateIterator & smallStep() final {
                        PRINT( std::cerr << "smallStep in " << kind << std::endl; )
                        atbegin = false;
                        if ( memberIter ) {
                                PRINT( std::cerr << "has member iter, incrementing..." << std::endl; )
                                memberIter->smallStep();
                                if ( *memberIter ) {
                                        PRINT( std::cerr << "success!" << std::endl; )
                                        return *this;
                                }
                        }
                        return bigStep();
                }

                AggregateIterator & bigStep() override = 0;

                const Type * getType() final { return inst; }

                const Type * getNext() final {
                        return ( memberIter && *memberIter ) ? memberIter->getType() : nullptr;
                }

                std::deque< InitAlternative > first() const final {
                        std::deque< InitAlternative > ret;
                        PRINT( std::cerr << "first " << kind << std::endl; )
                        if ( memberIter && *memberIter ) {
                                PRINT( std::cerr << "adding children" << std::endl; )
                                ret = memberIter->first();
                                for ( InitAlternative & alt : ret ) {
                                        PRINT( std::cerr << "iterating and adding designators" << std::endl; )
                                        alt.designation.get_and_mutate()->designators.emplace_front(
                                                new VariableExpr{ location, curMember->strict_as< ObjectDecl >() } );
                                }
                        }
                        if ( atbegin ) {
                                // only add self if at the very beginning of the structure
                                PRINT( std::cerr << "adding self" << std::endl; )
                                ret.emplace_front( inst, new Designation{ location } );
                        }
                        return ret;
                }
        };

        class StructIterator final : public AggregateIterator {
        public:
                StructIterator( const CodeLocation & loc, const StructInstType * inst )
                : AggregateIterator( loc, "StructIterator", inst->name, inst, inst->base->members ) {}

                operator bool() const override {
                        return curMember != members.end() || (memberIter && *memberIter);
                }

                StructIterator & bigStep() override {
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        memberIter = nullptr;
                        curType = nullptr;
                        while ( curMember != members.end() ) {
                                ++curMember;
                                if ( init() ) return *this;
                        }
                        return *this;
                }
        };

        class UnionIterator final : public AggregateIterator {
        public:
                UnionIterator( const CodeLocation & loc, const UnionInstType * inst )
                : AggregateIterator( loc, "UnionIterator", inst->name, inst, inst->base->members ) {}

                operator bool() const override { return memberIter && *memberIter; }

                UnionIterator & bigStep() override {
                        // unions only initialize one member
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        memberIter = nullptr;
                        curType = nullptr;
                        curMember = members.end();
                        return *this;
                }
        };

        class TupleIterator final : public AggregateIterator {
        public:
                TupleIterator( const CodeLocation & loc, const TupleType * inst )
                : AggregateIterator(
                        loc, "TupleIterator", toString("Tuple", inst->size()), inst, inst->members
                ) {}

                operator bool() const override {
                        return curMember != members.end() || (memberIter && *memberIter);
                }

                TupleIterator & bigStep() override {
                        PRINT( std::cerr << "bigStep in " << kind << std::endl; )
                        atbegin = false;
                        memberIter = nullptr;
                        curType = nullptr;
                        while ( curMember != members.end() ) {
                                ++curMember;
                                if ( init() ) return *this;
                        }
                        return *this;
                }
        };

        MemberIterator * createMemberIterator( const CodeLocation & loc, const Type * type ) {
                if ( auto aggr = dynamic_cast< const BaseInstType * >( type ) ) {
                        if ( auto sit = dynamic_cast< const StructInstType * >( aggr ) ) {
                                assert( sit->base );
                                return new StructIterator{ loc, sit };
                        } else if ( auto uit = dynamic_cast< const UnionInstType * >( aggr ) ) {
                                assert( uit->base );
                                return new UnionIterator{ loc, uit };
                        } else {
                                assertf(
                                        dynamic_cast< const EnumInstType * >( type )
                                                || dynamic_cast< const TypeInstType * >( type ),
                                        "Encountered unhandled BaseInstType in createMemberIterator: %s",
                                                toString( type ).c_str() );
                                return new SimpleIterator{ loc, type };
                        }
                } else if ( auto at = dynamic_cast< const ArrayType * >( type ) ) {
                        return new ArrayIterator{ loc, at };
                } else if ( auto tt = dynamic_cast< const TupleType * >( type ) ) {
                        return new TupleIterator{ loc, tt };
                } else {
                        return new SimpleIterator{ loc, type };
                }
        }

        CurrentObject::CurrentObject( const CodeLocation & loc, const Type * type ) : objStack() {
                objStack.emplace_back( new SimpleIterator{ loc, type } );
        }

        const Designation * CurrentObject::findNext( const Designation * designation ) {
                using DesignatorChain = std::deque< ptr< Expr > >;
                PRINT( std::cerr << "___findNext" << std::endl; )

                // find all the d's
                std::vector< DesignatorChain > desigAlts{ {} }, newDesigAlts;
                std::deque< const Type * > curTypes{ objStack.back()->getType() }, newTypes;
                for ( const Expr * expr : designation->designators ) {
                        PRINT( std::cerr << "____untyped: " << expr << std::endl; )
                        auto dit = desigAlts.begin();
                        if ( auto nexpr = dynamic_cast< const NameExpr * >( expr ) ) {
                                for ( const Type * t : curTypes ) {
                                        assert( dit != desigAlts.end() );

                                        DesignatorChain & d = *dit;
                                        PRINT( std::cerr << "____actual: " << t << std::endl; )
                                        if ( auto refType = dynamic_cast< const BaseInstType * >( t ) ) {
                                                // concatenate identical field names
                                                for ( const Decl * mem : refType->lookup( nexpr->name ) ) {
                                                        if ( auto field = dynamic_cast< const ObjectDecl * >( mem ) ) {
                                                                PRINT( std::cerr << "____alt: " << field->type << std::endl; )
                                                                DesignatorChain d2 = d;
                                                                d2.emplace_back( new VariableExpr{ expr->location, field } );
                                                                newDesigAlts.emplace_back( std::move( d2 ) );
                                                                newTypes.emplace_back( field->type );
                                                        }
                                                }
                                        }

                                        ++dit;
                                }
                        } else {
                                for ( const Type * t : curTypes ) {
                                        assert( dit != desigAlts.end() );

                                        DesignatorChain & d = *dit;
                                        if ( auto at = dynamic_cast< const ArrayType * >( t ) ) {
                                                PRINT( std::cerr << "____alt: " << at->get_base() << std::endl; )
                                                d.emplace_back( expr );
                                                newDesigAlts.emplace_back( d );
                                                newTypes.emplace_back( at->base );
                                        }
                                }
                        }

                        // reset queue
                        desigAlts = std::move( newDesigAlts );
                        newDesigAlts.clear();
                        curTypes = std::move( newTypes );
                        newTypes.clear();
                        assertf( desigAlts.size() == curTypes.size(), "Designator alternatives (%zu) and current types (%zu) out of sync", desigAlts.size(), curTypes.size() );
                }

                if ( desigAlts.size() > 1 ) {
                        SemanticError( designation, toString("Too many alternatives (", desigAlts.size(), ") for designation: ") );
                } else if ( desigAlts.empty() ) {
                        SemanticError( designation, "No reasonable alternatives for designation: " );
                }

                DesignatorChain & d = desigAlts.back();
                PRINT( for ( Expression * expr : d ) {
                        std::cerr << "____desig: " << expr << std::endl;
                } ) // for
                assertf( ! curTypes.empty(), "empty designator chosen");

                // set new designators
                assertf( ! objStack.empty(), "empty object stack when setting designation" );
                Designation * actualDesignation =
                        new Designation{ designation->location, DesignatorChain{d} };
                objStack.back()->setPosition( d ); // destroys d
                return actualDesignation;
        }

        void CurrentObject::setNext( const Designation * designation ) {
                PRINT( std::cerr << "____setNext" << designation << std::endl; )
                assertf( ! objStack.empty(), "obj stack empty in setNext" );
                objStack.back()->setPosition( designation->designators );
        }

        void CurrentObject::increment() {
                PRINT( std::cerr << "____increment" << std::endl; )
                if ( objStack.empty() ) return;
                PRINT( std::cerr << *objStack.back() << std::endl; )
                objStack.back()->smallStep();
        }

        void CurrentObject::enterListInit( const CodeLocation & loc ) {
                PRINT( std::cerr << "____entering list init" << std::endl; )
                assertf( ! objStack.empty(), "empty obj stack entering list init" );
                const ast::Type * type = objStack.back()->getNext();
                assert( type );
                objStack.emplace_back( createMemberIterator( loc, type ) );
        }

        void CurrentObject::exitListInit() {
                PRINT( std::cerr << "____exiting list init" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty" );
                objStack.pop_back();
                if ( ! objStack.empty() ) {
                        PRINT( std::cerr << *objStack.back() << std::endl; )
                        objStack.back()->bigStep();
                }
        }

        std::deque< InitAlternative > CurrentObject::getOptions() {
                PRINT( std::cerr << "____getting current options" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty in getOptions" );
                return **objStack.back();
        }

        const Type * CurrentObject::getCurrentType() {
                PRINT( std::cerr << "____getting current type" << std::endl; )
                assertf( ! objStack.empty(), "objstack empty in getCurrentType" );
                return objStack.back()->getNext();
        }
}

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