source: src/ResolvExpr/Resolver.cc @ 1cdfa82

//
// 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.
//
// Resolver.cc --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 12:17:01 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Sat Feb 17 11:19:40 2018
// Update Count     : 213
//

#include <stddef.h>                      // for NULL
#include <cassert>                       // for strict_dynamic_cast, assert
#include <memory>                        // for allocator, allocator_traits<...
#include <tuple>                         // for get
#include <vector>

#include "Alternative.h"                 // for Alternative, AltList
#include "AlternativeFinder.h"           // for AlternativeFinder, resolveIn...
#include "Common/GC.h"                   // for new_generation, collect_young
#include "Common/PassVisitor.h"          // for PassVisitor
#include "Common/SemanticError.h"        // for SemanticError
#include "Common/utility.h"              // for ValueGuard, group_iterate
#include "CurrentObject.h"               // for CurrentObject
#include "InitTweak/GenInit.h"
#include "InitTweak/InitTweak.h"         // for isIntrinsicSingleArgCallStmt
#include "RenameVars.h"                  // for RenameVars, global_renamer
#include "ResolvExpr/TypeEnvironment.h"  // for TypeEnvironment
#include "ResolveTypeof.h"               // for resolveTypeof
#include "Resolver.h"
#include "SymTab/Autogen.h"              // for SizeType
#include "SymTab/Indexer.h"              // for Indexer
#include "SynTree/Declaration.h"         // for ObjectDecl, TypeDecl, Declar...
#include "SynTree/Expression.h"          // for Expression, CastExpr, InitExpr
#include "SynTree/Initializer.h"         // for ConstructorInit, SingleInit
#include "SynTree/Statement.h"           // for ForStmt, Statement, BranchStmt
#include "SynTree/Type.h"                // for Type, BasicType, PointerType
#include "SynTree/TypeSubstitution.h"    // for TypeSubstitution
#include "SynTree/Visitor.h"             // for acceptAll, maybeAccept
#include "Tuples/Tuples.h"
#include "typeops.h"                     // for extractResultType
#include "Unify.h"                       // for unify

using namespace std;

namespace ResolvExpr {
        struct Resolver final : public WithIndexer, public WithGuards, public WithVisitorRef<Resolver>, public WithShortCircuiting, public WithStmtsToAdd {
                Resolver() {}
                Resolver( const SymTab::Indexer & other ) {
                        indexer = other;
                }

                void previsit( FunctionDecl *functionDecl );
                void postvisit( FunctionDecl *functionDecl );
                void previsit( ObjectDecl *objectDecll );
                void previsit( TypeDecl *typeDecl );
                void previsit( EnumDecl * enumDecl );
                void previsit( StaticAssertDecl * assertDecl );

                void previsit( ArrayType * at );
                void previsit( PointerType * at );

                void previsit( ExprStmt *exprStmt );
                void previsit( AsmExpr *asmExpr );
                void previsit( AsmStmt *asmStmt );
                void previsit( IfStmt *ifStmt );
                void previsit( WhileStmt *whileStmt );
                void previsit( ForStmt *forStmt );
                void previsit( SwitchStmt *switchStmt );
                void previsit( CaseStmt *caseStmt );
                void previsit( BranchStmt *branchStmt );
                void previsit( ReturnStmt *returnStmt );
                void previsit( ThrowStmt *throwStmt );
                void previsit( CatchStmt *catchStmt );
                void previsit( WaitForStmt * stmt );
                void previsit( WithStmt * withStmt );

                void previsit( SingleInit *singleInit );
                void previsit( ListInit *listInit );
                void previsit( ConstructorInit *ctorInit );
          private:
                typedef std::list< Initializer * >::iterator InitIterator;

                template< typename PtrType >
                void handlePtrType( PtrType * type );

                void resolveWithExprs( std::list< Expression * > & withExprs, std::list< Statement * > & newStmts );
                void fallbackInit( ConstructorInit * ctorInit );

                Type * functionReturn = nullptr;
                CurrentObject currentObject = nullptr;
                bool inEnumDecl = false;
        };

        void resolve( std::list< Declaration * > translationUnit ) {
                PassVisitor<Resolver> resolver;
                acceptAll( translationUnit, resolver );
        }

        void resolveDecl( Declaration * decl, const SymTab::Indexer &indexer ) {
                PassVisitor<Resolver> resolver( indexer );
                maybeAccept( decl, resolver );
        }

        namespace {
                struct DeleteFinder : public WithShortCircuiting        {
                        DeletedExpr * delExpr = nullptr;
                        void previsit( DeletedExpr * expr ) {
                                if ( delExpr ) visit_children = false;
                                else delExpr = expr;
                        }

                        void previsit( Expression * ) {
                                if ( delExpr ) visit_children = false;
                        }
                };
        }

        DeletedExpr * findDeletedExpr( Expression * expr ) {
                PassVisitor<DeleteFinder> finder;
                expr->accept( finder );
                return finder.pass.delExpr;
        }

        namespace {
                void finishExpr( Expression *expr, const TypeEnvironment &env, TypeSubstitution * oldenv = nullptr ) {
                        expr->env = oldenv ? oldenv->clone() : new TypeSubstitution;
                        env.makeSubstitution( *expr->get_env() );
                }

                void removeExtraneousCast( Expression *& expr, const SymTab::Indexer & indexer ) {
                        if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
                                if ( ResolvExpr::typesCompatible( castExpr->arg->result, castExpr->result, indexer ) ) {
                                        // cast is to the same type as its argument, so it's unnecessary -- remove it
                                        expr = castExpr->arg;
                                        castExpr->arg = nullptr;
                                        std::swap( expr->env, castExpr->env );
                                }
                        }
                }
        } // namespace

        namespace {
                void findUnfinishedKindExpression(Expression * untyped, Alternative & alt, const SymTab::Indexer & indexer, const std::string & kindStr, std::function<bool(const Alternative &)> pred, bool adjust = false, bool prune = true, bool failFast = true) {
                        assertf( untyped, "expected a non-null expression." );

                        auto guard = new_generation();  // set up GC generation for this top-level expression

                        TypeEnvironment env;
                        AlternativeFinder finder( indexer, env );
                        finder.find( untyped, adjust, prune, failFast );

                        #if 0
                        if ( finder.get_alternatives().size() != 1 ) {
                                std::cerr << "untyped expr is ";
                                untyped->print( std::cerr );
                                std::cerr << std::endl << "alternatives are:";
                                for ( const Alternative & alt : finder.get_alternatives() ) {
                                        alt.print( std::cerr );
                                } // for
                        } // if
                        #endif

                        AltList candidates;
                        for ( Alternative & alt : finder.get_alternatives() ) {
                                if ( pred( alt ) ) {
                                        candidates.push_back( std::move( alt ) );
                                }
                        }

                        // xxx - if > 1 alternative with same cost, ignore deleted and pick from remaining
                        // choose the lowest cost expression among the candidates
                        AltList winners;
                        findMinCost( candidates.begin(), candidates.end(), back_inserter( winners ) );
                        if ( winners.size() == 0 ) {
                                SemanticError( untyped, toString( 
                                        "No reasonable alternatives for ", kindStr, (kindStr != "" ? " " : ""), 
                                        "expression: ") );
                        } else if ( winners.size() != 1 ) {
                                std::ostringstream stream;
                                stream << "Cannot choose between " << winners.size() << " alternatives for " 
                                        << kindStr << (kindStr != "" ? " " : "") << "expression\n";
                                untyped->print( stream );
                                stream << " Alternatives are:\n";
                                printAlts( winners, stream, 1 );
                                
                                SemanticError( untyped->location, stream.str() );
                        }

                        // there is one unambiguous interpretation - move the expression into the with statement
                        Alternative & choice = winners.front();
                        if ( findDeletedExpr( choice.expr ) ) {
                                trace( choice.expr );
                                SemanticError( choice.expr, 
                                        "Unique best alternative includes deleted identifier in " );
                        }
                        alt = std::move( choice );
                        trace( alt );
                }

                /// resolve `untyped` to the expression whose alternative satisfies `pred` with the lowest cost; kindStr is used for providing better error messages
                void findKindExpression(Expression *& untyped, const SymTab::Indexer & indexer, const std::string & kindStr, std::function<bool(const Alternative &)> pred, bool adjust = false, bool prune = true, bool failFast = true) {
                        if ( ! untyped ) return;
                        Alternative choice;
                        findUnfinishedKindExpression( untyped, choice, indexer, kindStr, pred, adjust, prune, failFast );
                        finishExpr( choice.expr, choice.env, untyped->env );
                        untyped = choice.expr;
                        choice.expr = nullptr;
                }

                bool standardAlternativeFilter( const Alternative & ) {
                        // currently don't need to filter, under normal circumstances.
                        // in the future, this may be useful for removing deleted expressions
                        return true;
                }
        } // namespace

        // used in resolveTypeof
        Expression * resolveInVoidContext( Expression *expr, const SymTab::Indexer &indexer ) {
                TypeEnvironment env;
                return resolveInVoidContext( expr, indexer, env );
        }

        Expression * resolveInVoidContext( Expression *expr, const SymTab::Indexer &indexer, TypeEnvironment &env ) {
                // it's a property of the language that a cast expression has either 1 or 0 interpretations; if it has 0
                // interpretations, an exception has already been thrown.
                assertf( expr, "expected a non-null expression." );

                auto untyped = new CastExpr{ expr }; // cast to void

                // set up and resolve expression cast to void
                Alternative choice;
                findUnfinishedKindExpression( untyped, choice, indexer, "", standardAlternativeFilter, true );
                CastExpr * castExpr = strict_dynamic_cast< CastExpr * >( choice.expr );
                env = std::move( choice.env );

                // clean up resolved expression
                return castExpr->arg;
        }

        void findVoidExpression( Expression *& untyped, const SymTab::Indexer &indexer ) {
                resetTyVarRenaming();
                TypeEnvironment env;
                Expression * newExpr = resolveInVoidContext( untyped, indexer, env );
                finishExpr( newExpr, env, untyped->env );
                untyped = newExpr;
        }

        void findSingleExpression( Expression *&untyped, const SymTab::Indexer &indexer ) {
                findKindExpression( untyped, indexer, "", standardAlternativeFilter );
        }

        void findSingleExpression( Expression *& untyped, Type * type, const SymTab::Indexer & indexer ) {
                assert( untyped && type );
                untyped = new CastExpr( untyped, type );
                findSingleExpression( untyped, indexer );
                removeExtraneousCast( untyped, indexer );
        }

        namespace {
                bool isIntegralType( const Alternative & alt ) {
                        Type * type = alt.expr->result;
                        if ( dynamic_cast< EnumInstType * >( type ) ) {
                                return true;
                        } else if ( BasicType *bt = dynamic_cast< BasicType * >( type ) ) {
                                return bt->isInteger();
                        } else if ( dynamic_cast< ZeroType* >( type ) != nullptr || dynamic_cast< OneType* >( type ) != nullptr ) {
                                return true;
                        } else {
                                return false;
                        } // if
                }

                void findIntegralExpression( Expression *& untyped, const SymTab::Indexer &indexer ) {
                        findKindExpression( untyped, indexer, "condition", isIntegralType );
                }
        }

        void Resolver::previsit( ObjectDecl *objectDecl ) {
                Type *new_type = resolveTypeof( objectDecl->get_type(), indexer );
                objectDecl->set_type( new_type );
                // To handle initialization of routine pointers, e.g., int (*fp)(int) = foo(), means that class-variable
                // initContext is changed multiple time because the LHS is analysed twice. The second analysis changes
                // initContext because of a function type can contain object declarations in the return and parameter types. So
                // each value of initContext is retained, so the type on the first analysis is preserved and used for selecting
                // the RHS.
                GuardValue( currentObject );
                currentObject = CurrentObject( objectDecl->get_type() );
                if ( inEnumDecl && dynamic_cast< EnumInstType * >( objectDecl->get_type() ) ) {
                        // enumerator initializers should not use the enum type to initialize, since
                        // the enum type is still incomplete at this point. Use signed int instead.
                        currentObject = CurrentObject( new BasicType( Type::Qualifiers(), BasicType::SignedInt ) );
                }
        }

        template< typename PtrType >
        void Resolver::handlePtrType( PtrType * type ) {
                if ( type->get_dimension() ) {
                        findSingleExpression( type->dimension, SymTab::SizeType->clone(), indexer );
                }
        }

        void Resolver::previsit( ArrayType * at ) {
                handlePtrType( at );
        }

        void Resolver::previsit( PointerType * pt ) {
                handlePtrType( pt );
        }

        void Resolver::previsit( TypeDecl *typeDecl ) {
                if ( typeDecl->get_base() ) {
                        Type *new_type = resolveTypeof( typeDecl->get_base(), indexer );
                        typeDecl->set_base( new_type );
                } // if
        }

        void Resolver::previsit( FunctionDecl *functionDecl ) {
#if 0
                std::cerr << "resolver visiting functiondecl ";
                functionDecl->print( std::cerr );
                std::cerr << std::endl;
#endif
                Type *new_type = resolveTypeof( functionDecl->type, indexer );
                functionDecl->set_type( new_type );
                GuardValue( functionReturn );
                functionReturn = ResolvExpr::extractResultType( functionDecl->type );

                {
                        // resolve with-exprs with parameters in scope and add any newly generated declarations to the
                        // front of the function body.
                        auto guard = makeFuncGuard( [this]() { indexer.enterScope(); }, [this](){ indexer.leaveScope(); } );
                        indexer.addFunctionType( functionDecl->type );
                        std::list< Statement * > newStmts;
                        resolveWithExprs( functionDecl->withExprs, newStmts );
                        if ( functionDecl->statements ) {
                                functionDecl->statements->kids.splice( functionDecl->statements->kids.begin(), newStmts );
                        } else {
                                assertf( functionDecl->withExprs.empty() && newStmts.empty(), "Function %s without a body has with-clause and/or generated with declarations.", functionDecl->name.c_str() );
                        }
                }
        }

        void Resolver::postvisit( FunctionDecl *functionDecl ) {
                // default value expressions have an environment which shouldn't be there and trips up later passes.
                // xxx - it might be necessary to somehow keep the information from this environment, but I can't currently
                // see how it's useful.
                for ( Declaration * d : functionDecl->type->parameters ) {
                        if ( ObjectDecl * obj = dynamic_cast< ObjectDecl * >( d ) ) {
                                if ( SingleInit * init = dynamic_cast< SingleInit * >( obj->init ) ) {
                                        delete init->value->env;
                                        init->value->env = nullptr;
                                }
                        }
                }
        }

        void Resolver::previsit( EnumDecl * ) {
                // in case we decide to allow nested enums
                GuardValue( inEnumDecl );
                inEnumDecl = true;
        }

        void Resolver::previsit( StaticAssertDecl * assertDecl ) {
                findIntegralExpression( assertDecl->condition, indexer );
        }

        void Resolver::previsit( ExprStmt *exprStmt ) {
                visit_children = false;
                assertf( exprStmt->expr, "ExprStmt has null Expression in resolver" );
                findVoidExpression( exprStmt->expr, indexer );
        }

        void Resolver::previsit( AsmExpr *asmExpr ) {
                visit_children = false;
                findVoidExpression( asmExpr->operand, indexer );
                if ( asmExpr->get_inout() ) {
                        findVoidExpression( asmExpr->inout, indexer );
                } // if
        }

        void Resolver::previsit( AsmStmt *asmStmt ) {
                visit_children = false;
                acceptAll( asmStmt->get_input(), *visitor );
                acceptAll( asmStmt->get_output(), *visitor );
        }

        void Resolver::previsit( IfStmt *ifStmt ) {
                findIntegralExpression( ifStmt->condition, indexer );
        }

        void Resolver::previsit( WhileStmt *whileStmt ) {
                findIntegralExpression( whileStmt->condition, indexer );
        }

        void Resolver::previsit( ForStmt *forStmt ) {
                if ( forStmt->condition ) {
                        findIntegralExpression( forStmt->condition, indexer );
                } // if

                if ( forStmt->increment ) {
                        findVoidExpression( forStmt->increment, indexer );
                } // if
        }

        void Resolver::previsit( SwitchStmt *switchStmt ) {
                GuardValue( currentObject );
                findIntegralExpression( switchStmt->condition, indexer );

                currentObject = CurrentObject( switchStmt->condition->result );
        }

        void Resolver::previsit( CaseStmt *caseStmt ) {
                if ( caseStmt->get_condition() ) {
                        std::list< InitAlternative > initAlts = currentObject.getOptions();
                        assertf( initAlts.size() == 1, "SwitchStmt did not correctly resolve an integral expression." );
                        // must remove cast from case statement because RangeExpr cannot be cast.
                        Expression * newExpr = new CastExpr( caseStmt->condition, initAlts.front().type->clone() );
                        findSingleExpression( newExpr, indexer );
                        CastExpr * castExpr = strict_dynamic_cast< CastExpr * >( newExpr );
                        caseStmt->condition = castExpr->arg;
                        castExpr->arg = nullptr;
                }
        }

        void Resolver::previsit( BranchStmt *branchStmt ) {
                visit_children = false;
                // must resolve the argument for a computed goto
                if ( branchStmt->get_type() == BranchStmt::Goto ) { // check for computed goto statement
                        if ( branchStmt->computedTarget ) {
                                // computed goto argument is void *
                                findSingleExpression( branchStmt->computedTarget, new PointerType( Type::Qualifiers(), new VoidType( Type::Qualifiers() ) ), indexer );
                        } // if
                } // if
        }

        void Resolver::previsit( ReturnStmt *returnStmt ) {
                visit_children = false;
                if ( returnStmt->expr ) {
                        findSingleExpression( returnStmt->expr, functionReturn->clone(), indexer );
                } // if
        }

        void Resolver::previsit( ThrowStmt *throwStmt ) {
                visit_children = false;
                // TODO: Replace *exception type with &exception type.
                if ( throwStmt->get_expr() ) {
                        StructDecl * exception_decl =
                                indexer.lookupStruct( "__cfaabi_ehm__base_exception_t" );
                        assert( exception_decl );
                        Type * exceptType = new PointerType( noQualifiers, new StructInstType( noQualifiers, exception_decl ) );
                        findSingleExpression( throwStmt->expr, exceptType, indexer );
                }
        }

        void Resolver::previsit( CatchStmt *catchStmt ) {
                if ( catchStmt->cond ) {
                        findSingleExpression( catchStmt->cond, new BasicType( noQualifiers, BasicType::Bool ), indexer );
                }
        }

        template< typename iterator_t >
        inline bool advance_to_mutex( iterator_t & it, const iterator_t & end ) {
                while( it != end && !(*it)->get_type()->get_mutex() ) {
                        it++;
                }

                return it != end;
        }

        void Resolver::previsit( WaitForStmt * stmt ) {
                visit_children = false;

                // Resolve all clauses first
                for( auto& clause : stmt->clauses ) {

                        TypeEnvironment env;
                        AlternativeFinder funcFinder( indexer, env );

                        // Find all alternatives for a function in canonical form
                        funcFinder.findWithAdjustment( clause.target.function );

                        if ( funcFinder.get_alternatives().empty() ) {
                                stringstream ss;
                                ss << "Use of undeclared indentifier '";
                                ss << strict_dynamic_cast<NameExpr*>( clause.target.function )->name;
                                ss << "' in call to waitfor";
                                SemanticError( stmt->location, ss.str() );
                        }

                        // Find all alternatives for all arguments in canonical form
                        std::vector< AlternativeFinder > argAlternatives;
                        funcFinder.findSubExprs( clause.target.arguments.begin(), clause.target.arguments.end(), back_inserter( argAlternatives ) );

                        // List all combinations of arguments
                        std::vector< AltList > possibilities;
                        combos( argAlternatives.begin(), argAlternatives.end(), back_inserter( possibilities ) );

                        AltList                func_candidates;
                        std::vector< AltList > args_candidates;

                        // For every possible function :
                        //      try matching the arguments to the parameters
                        //      not the other way around because we have more arguments than parameters
                        SemanticErrorException errors;
                        for ( Alternative & func : funcFinder.get_alternatives() ) {
                                try {
                                        PointerType * pointer = dynamic_cast< PointerType* >( func.expr->get_result()->stripReferences() );
                                        if( !pointer ) {
                                                SemanticError( func.expr->get_result(), "candidate not viable: not a pointer type\n" );
                                        }

                                        FunctionType * function = dynamic_cast< FunctionType* >( pointer->get_base() );
                                        if( !function ) {
                                                SemanticError( pointer->get_base(), "candidate not viable: not a function type\n" );
                                        }


                                        {
                                                auto param     = function->parameters.begin();
                                                auto param_end = function->parameters.end();

                                                if( !advance_to_mutex( param, param_end ) ) {
                                                        SemanticError(function, "candidate function not viable: no mutex parameters\n");
                                                }
                                        }

                                        Alternative newFunc( func );
                                        // Strip reference from function
                                        referenceToRvalueConversion( newFunc.expr, newFunc.cost );

                                        // For all the set of arguments we have try to match it with the parameter of the current function alternative
                                        for ( auto & argsList : possibilities ) {

                                                try {
                                                        // Declare data structures need for resolution
                                                        OpenVarSet openVars;
                                                        AssertionSet resultNeed, resultHave;
                                                        TypeEnvironment resultEnv;

                                                        // Load type variables from arguemnts into one shared space
                                                        simpleCombineEnvironments( argsList.begin(), argsList.end(), resultEnv );

                                                        // Make sure we don't widen any existing bindings
                                                        for ( auto & i : resultEnv ) {
                                                                i.allowWidening = false;
                                                        }

                                                        // Find any unbound type variables
                                                        resultEnv.extractOpenVars( openVars );

                                                        auto param     = function->parameters.begin();
                                                        auto param_end = function->parameters.end();

                                                        // For every arguments of its set, check if it matches one of the parameter
                                                        // The order is important
                                                        for( auto & arg : argsList ) {

                                                                // Ignore non-mutex arguments
                                                                if( !advance_to_mutex( param, param_end ) ) {
                                                                        // We ran out of parameters but still have arguments
                                                                        // this function doesn't match
                                                                        SemanticError( function, "candidate function not viable: too many mutex arguments\n" );
                                                                }

                                                                // Check if the argument matches the parameter type in the current scope
                                                                if( ! unify( (*param)->get_type(), arg.expr->get_result(), resultEnv, resultNeed, resultHave, openVars, this->indexer ) ) {
                                                                        // Type doesn't match
                                                                        stringstream ss;
                                                                        ss << "candidate function not viable: no known convertion from '";
                                                                        arg.expr->get_result()->print( ss );
                                                                        ss << "' to '";
                                                                        (*param)->get_type()->print( ss );
                                                                        ss << "'\n";
                                                                        SemanticError( function, ss.str() );
                                                                }

                                                                param++;
                                                        }

                                                        // All arguments match !

                                                        // Check if parameters are missing
                                                        if( advance_to_mutex( param, param_end ) ) {
                                                                // We ran out of arguments but still have parameters left
                                                                // this function doesn't match
                                                                SemanticError( function, "candidate function not viable: too few mutex arguments\n" );
                                                        }

                                                        // All parameters match !

                                                        // Finish the expressions to tie in the proper environments
                                                        finishExpr( newFunc.expr, resultEnv );
                                                        for( Alternative & alt : argsList ) {
                                                                finishExpr( alt.expr, resultEnv );
                                                        }

                                                        // This is a match store it and save it for later
                                                        func_candidates.push_back( newFunc );
                                                        args_candidates.push_back( argsList );

                                                }
                                                catch( SemanticErrorException &e ) {
                                                        errors.append( e );
                                                }
                                        }
                                }
                                catch( SemanticErrorException &e ) {
                                        errors.append( e );
                                }
                        }

                        // Make sure we got the right number of arguments
                        if( func_candidates.empty() )    { SemanticErrorException top( stmt->location, "No alternatives for function in call to waitfor"  ); top.append( errors ); throw top; }
                        if( args_candidates.empty() )    { SemanticErrorException top( stmt->location, "No alternatives for arguments in call to waitfor" ); top.append( errors ); throw top; }
                        if( func_candidates.size() > 1 ) { SemanticErrorException top( stmt->location, "Ambiguous function in call to waitfor"            ); top.append( errors ); throw top; }
                        if( args_candidates.size() > 1 ) { SemanticErrorException top( stmt->location, "Ambiguous arguments in call to waitfor"           ); top.append( errors ); throw top; }
                        // TODO: need to use findDeletedExpr to ensure no deleted identifiers are used.

                        // Swap the results from the alternative with the unresolved values.
                        // Alternatives will handle deletion on destruction
                        std::swap( clause.target.function, func_candidates.front().expr );
                        for( auto arg_pair : group_iterate( clause.target.arguments, args_candidates.front() ) ) {
                                std::swap ( std::get<0>( arg_pair), std::get<1>( arg_pair).expr );
                        }

                        // Resolve the conditions as if it were an IfStmt
                        // Resolve the statments normally
                        findSingleExpression( clause.condition, this->indexer );
                        clause.statement->accept( *visitor );
                }


                if( stmt->timeout.statement ) {
                        // Resolve the timeout as an size_t for now
                        // Resolve the conditions as if it were an IfStmt
                        // Resolve the statments normally
                        findSingleExpression( stmt->timeout.time, new BasicType( noQualifiers, BasicType::LongLongUnsignedInt ), this->indexer );
                        findSingleExpression( stmt->timeout.condition, this->indexer );
                        stmt->timeout.statement->accept( *visitor );
                }

                if( stmt->orelse.statement ) {
                        // Resolve the conditions as if it were an IfStmt
                        // Resolve the statments normally
                        findSingleExpression( stmt->orelse.condition, this->indexer );
                        stmt->orelse.statement->accept( *visitor );
                }
        }

        bool isStructOrUnion( const Alternative & alt ) {
                Type * t = alt.expr->result->stripReferences();
                return dynamic_cast< StructInstType * >( t ) || dynamic_cast< UnionInstType * >( t );
        }

        void Resolver::resolveWithExprs( std::list< Expression * > & withExprs, std::list< Statement * > & newStmts ) {
                for ( Expression *& expr : withExprs )  {
                        // only struct- and union-typed expressions are viable candidates
                        findKindExpression( expr, indexer, "with statement", isStructOrUnion );

                        // if with expression might be impure, create a temporary so that it is evaluated once
                        if ( Tuples::maybeImpure( expr ) ) {
                                static UniqueName tmpNamer( "_with_tmp_" );
                                ObjectDecl * tmp = ObjectDecl::newObject( tmpNamer.newName(), expr->result->clone(), new SingleInit( expr ) );
                                expr = new VariableExpr( tmp );
                                newStmts.push_back( new DeclStmt( tmp ) );
                                if ( InitTweak::isConstructable( tmp->type ) ) {
                                        // generate ctor/dtor and resolve them
                                        tmp->init = InitTweak::genCtorInit( tmp );
                                        tmp->accept( *visitor );
                                }
                        }
                }
        }

        void Resolver::previsit( WithStmt * withStmt ) {
                resolveWithExprs( withStmt->exprs, stmtsToAddBefore );
        }

        template< typename T >
        bool isCharType( T t ) {
                if ( BasicType * bt = dynamic_cast< BasicType * >( t ) ) {
                        return bt->get_kind() == BasicType::Char || bt->get_kind() == BasicType::SignedChar ||
                                bt->get_kind() == BasicType::UnsignedChar;
                }
                return false;
        }

        void Resolver::previsit( SingleInit *singleInit ) {
                visit_children = false;
                // resolve initialization using the possibilities as determined by the currentObject cursor
                Expression * newExpr = new UntypedInitExpr( singleInit->value, currentObject.getOptions() );
                findSingleExpression( newExpr, indexer );
                InitExpr * initExpr = strict_dynamic_cast< InitExpr * >( newExpr );

                // move cursor to the object that is actually initialized
                currentObject.setNext( initExpr->get_designation() );

                // discard InitExpr wrapper and retain relevant pieces
                newExpr = initExpr->expr;
                initExpr->expr = nullptr;
                std::swap( initExpr->env, newExpr->env );
                std::swap( initExpr->inferParams, newExpr->inferParams ) ;

                // get the actual object's type (may not exactly match what comes back from the resolver due to conversions)
                Type * initContext = currentObject.getCurrentType();

                removeExtraneousCast( newExpr, indexer );

                // check if actual object's type is char[]
                if ( ArrayType * at = dynamic_cast< ArrayType * >( initContext ) ) {
                        if ( isCharType( at->get_base() ) ) {
                                // check if the resolved type is char *
                                if ( PointerType * pt = dynamic_cast< PointerType *>( newExpr->get_result() ) ) {
                                        if ( isCharType( pt->get_base() ) ) {
                                                if ( CastExpr *ce = dynamic_cast< CastExpr * >( newExpr ) ) {
                                                        // strip cast if we're initializing a char[] with a char *, e.g.  char x[] = "hello";
                                                        newExpr = ce->get_arg();
                                                        ce->set_arg( nullptr );
                                                        std::swap( ce->env, newExpr->env );
                                                }
                                        }
                                }
                        }
                }

                // set initializer expr to resolved express
                singleInit->value = newExpr;

                // move cursor to next object in preparation for next initializer
                currentObject.increment();
        }

        void Resolver::previsit( ListInit * listInit ) {
                visit_children = false;
                // move cursor into brace-enclosed initializer-list
                currentObject.enterListInit();
                // xxx - fix this so that the list isn't copied, iterator should be used to change current element
                std::list<Designation *> newDesignations;
                for ( auto p : group_iterate(listInit->get_designations(), listInit->get_initializers()) ) {
                        // iterate designations and initializers in pairs, moving the cursor to the current designated object and resolving
                        // the initializer against that object.
                        Designation * des = std::get<0>(p);
                        Initializer * init = std::get<1>(p);
                        newDesignations.push_back( currentObject.findNext( des ) );
                        init->accept( *visitor );
                }
                // set the set of 'resolved' designations and leave the brace-enclosed initializer-list
                listInit->get_designations() = newDesignations; // xxx - memory management
                currentObject.exitListInit();

                // xxx - this part has not be folded into CurrentObject yet
                // } else if ( TypeInstType * tt = dynamic_cast< TypeInstType * >( initContext ) ) {
                //      Type * base = tt->get_baseType()->get_base();
                //      if ( base ) {
                //              // know the implementation type, so try using that as the initContext
                //              ObjectDecl tmpObj( "", Type::StorageClasses(), LinkageSpec::Cforall, nullptr, base->clone(), nullptr );
                //              currentObject = &tmpObj;
                //              visit( listInit );
                //      } else {
                //              // missing implementation type -- might be an unknown type variable, so try proceeding with the current init context
                //              Parent::visit( listInit );
                //      }
                // } else {
        }

        // ConstructorInit - fall back on C-style initializer
        void Resolver::fallbackInit( ConstructorInit * ctorInit ) {
                // could not find valid constructor, or found an intrinsic constructor
                // fall back on C-style initializer
                ctorInit->set_ctor( nullptr );
                ctorInit->set_dtor( nullptr );
                maybeAccept( ctorInit->get_init(), *visitor );
        }

        // needs to be callable from outside the resolver, so this is a standalone function
        void resolveCtorInit( ConstructorInit * ctorInit, const SymTab::Indexer & indexer ) {
                assert( ctorInit );
                PassVisitor<Resolver> resolver( indexer );
                ctorInit->accept( resolver );
        }

        void resolveStmtExpr( StmtExpr * stmtExpr, const SymTab::Indexer & indexer ) {
                assert( stmtExpr );
                PassVisitor<Resolver> resolver( indexer );
                stmtExpr->accept( resolver );
                stmtExpr->computeResult();
                // xxx - aggregate the environments from all statements? Possibly in AlternativeFinder instead?
        }

        void Resolver::previsit( ConstructorInit *ctorInit ) {
                visit_children = false;
                // xxx - fallback init has been removed => remove fallbackInit function and remove complexity from FixInit and remove C-init from ConstructorInit
                maybeAccept( ctorInit->ctor, *visitor );
                maybeAccept( ctorInit->dtor, *visitor );

                // found a constructor - can get rid of C-style initializer
                ctorInit->init = nullptr;

                // intrinsic single parameter constructors and destructors do nothing. Since this was
                // implicitly generated, there's no way for it to have side effects, so get rid of it
                // to clean up generated code.
                if ( InitTweak::isIntrinsicSingleArgCallStmt( ctorInit->ctor ) ) {
                        ctorInit->ctor = nullptr;
                }

                if ( InitTweak::isIntrinsicSingleArgCallStmt( ctorInit->dtor ) ) {
                        ctorInit->dtor = nullptr;
                }

                // xxx - todo -- what about arrays?
                // if ( dtor == NULL && InitTweak::isIntrinsicCallStmt( ctorInit->get_ctor() ) ) {
                //      // can reduce the constructor down to a SingleInit using the
                //      // second argument from the ctor call, since
                //      delete ctorInit->get_ctor();
                //      ctorInit->set_ctor( NULL );

                //      Expression * arg =
                //      ctorInit->set_init( new SingleInit( arg ) );
                // }
        }
} // namespace ResolvExpr

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