source: src/ResolvExpr/Resolver.cc@ 03bf5c8

//
// 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           : Aaron B. Moss
// Created On       : Sun May 17 12:17:01 2015
// Last Modified By : Aaron B. Moss
// Last Modified On : Wed May 29 11:00:00 2019
// Update Count     : 241
//

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

#include "Alternative.h"                 // for Alternative, AltList
#include "AlternativeFinder.h"           // for AlternativeFinder, resolveIn...
#include "Candidate.hpp"
#include "CandidateFinder.hpp"
#include "CurrentObject.h"               // for CurrentObject
#include "RenameVars.h"                  // for RenameVars, global_renamer
#include "Resolver.h"
#include "ResolvMode.h"                  // for ResolvMode
#include "typeops.h"                     // for extractResultType
#include "Unify.h"                       // for unify
#include "AST/Chain.hpp"
#include "AST/Decl.hpp"
#include "AST/Init.hpp"
#include "AST/Pass.hpp"
#include "AST/Print.hpp"
#include "AST/SymbolTable.hpp"
#include "AST/Type.hpp"
#include "Common/PassVisitor.h"          // for PassVisitor
#include "Common/SemanticError.h"        // for SemanticError
#include "Common/utility.h"              // for ValueGuard, group_iterate
#include "InitTweak/GenInit.h"
#include "InitTweak/InitTweak.h"         // for isIntrinsicSingleArgCallStmt
#include "ResolvExpr/TypeEnvironment.h"  // for TypeEnvironment
#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 "Validate/FindSpecialDecls.h"   // for SizeType

using namespace std;

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

                void previsit( FunctionDecl * functionDecl );
                void postvisit( FunctionDecl * functionDecl );
                void previsit( ObjectDecl * objectDecll );
                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( 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 fallbackInit( ConstructorInit * ctorInit );

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

        struct ResolveWithExprs : public WithIndexer, public WithGuards, public WithVisitorRef<ResolveWithExprs>, public WithShortCircuiting, public WithStmtsToAdd {
                void previsit( FunctionDecl * );
                void previsit( WithStmt * );

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

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

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

        namespace {
                struct DeleteFinder_old : 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_old> finder;
                expr->accept( finder );
                return finder.pass.delExpr;
        }

        namespace {
                struct StripCasts_old {
                        Expression * postmutate( CastExpr * castExpr ) {
                                if ( castExpr->isGenerated && ResolvExpr::typesCompatible( castExpr->arg->result, castExpr->result, SymTab::Indexer() ) ) {
                                        // generated cast is to the same type as its argument, so it's unnecessary -- remove it
                                        Expression * expr = castExpr->arg;
                                        castExpr->arg = nullptr;
                                        std::swap( expr->env, castExpr->env );
                                        return expr;
                                }
                                return castExpr;
                        }

                        static void strip( Expression *& expr ) {
                                PassVisitor<StripCasts_old> stripper;
                                expr = expr->acceptMutator( stripper );
                        }
                };

                void finishExpr( Expression *& expr, const TypeEnvironment & env, TypeSubstitution * oldenv = nullptr ) {
                        expr->env = oldenv ? oldenv->clone() : new TypeSubstitution;
                        env.makeSubstitution( *expr->env );
                        StripCasts_old::strip( expr ); // remove unnecessary casts that may be buried in an expression
                }

                void removeExtraneousCast( Expression *& expr, const SymTab::Indexer & indexer ) {
                        if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
                                if ( 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 );
                                        delete castExpr;
                                }
                        }
                }
        } // namespace

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

                        // xxx - this isn't thread-safe, but should work until we parallelize the resolver
                        static unsigned recursion_level = 0;

                        ++recursion_level;
                        TypeEnvironment env;
                        AlternativeFinder finder( indexer, env );
                        finder.find( untyped, recursion_level == 1 ? mode.atTopLevel() : mode );
                        --recursion_level;

                        #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

                        // produce filtered list of alternatives
                        AltList candidates;
                        for ( Alternative & alt : finder.get_alternatives() ) {
                                if ( pred( alt ) ) {
                                        candidates.push_back( std::move( alt ) );
                                }
                        }

                        // produce invalid error if no candidates
                        if ( candidates.empty() ) {
                                SemanticError( untyped, toString( "No reasonable alternatives for ", kindStr, (kindStr != "" ? " " : ""), "expression: ") );
                        }

                        // search for cheapest candidate
                        AltList winners;
                        bool seen_undeleted = false;
                        for ( unsigned i = 0; i < candidates.size(); ++i ) {
                                int c = winners.empty() ? -1 : candidates[i].cost.compare( winners.front().cost );

                                if ( c > 0 ) continue; // skip more expensive than winner

                                if ( c < 0 ) {
                                        // reset on new cheapest
                                        seen_undeleted = ! findDeletedExpr( candidates[i].expr );
                                        winners.clear();
                                } else /* if ( c == 0 ) */ {
                                        if ( findDeletedExpr( candidates[i].expr ) ) {
                                                // skip deleted expression if already seen one equivalent-cost not
                                                if ( seen_undeleted ) continue;
                                        } else if ( ! seen_undeleted ) {
                                                // replace list of equivalent-cost deleted expressions with one non-deleted
                                                winners.clear();
                                                seen_undeleted = true;
                                        }
                                }

                                winners.emplace_back( std::move( candidates[i] ) );
                        }

                        // promote alternative.cvtCost to .cost
                        // xxx - I don't know why this is done, but I'm keeping the behaviour from findMinCost
                        for ( Alternative& winner : winners ) {
                                winner.cost = winner.cvtCost;
                        }

                        // produce ambiguous errors, if applicable
                        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() );
                        }

                        // single selected choice
                        Alternative& choice = winners.front();

                        // fail on only expression deleted
                        if ( ! seen_undeleted ) {
                                SemanticError( untyped->location, choice.expr, "Unique best alternative includes deleted identifier in " );
                        }

                        // xxx - check for ambiguous expressions

                        // output selected choice
                        alt = std::move( choice );
                }

                /// 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, ResolvMode mode = ResolvMode{}) {
                        if ( ! untyped ) return;
                        Alternative choice;
                        findUnfinishedKindExpression( untyped, choice, indexer, kindStr, pred, mode );
                        finishExpr( choice.expr, choice.env, untyped->env );
                        delete untyped;
                        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." );

                CastExpr * untyped = new CastExpr( expr ); // cast to void
                untyped->location = expr->location;

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

                // clean up resolved expression
                Expression * ret = castExpr->arg;
                castExpr->arg = nullptr;

                // unlink the arg so that it isn't deleted twice at the end of the program
                untyped->arg = nullptr;
                return ret;
        }

        void findVoidExpression( Expression *& untyped, const SymTab::Indexer & indexer ) {
                resetTyVarRenaming();
                TypeEnvironment env;
                Expression * newExpr = resolveInVoidContext( untyped, indexer, env );
                finishExpr( newExpr, env, untyped->env );
                delete untyped;
                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 );
                // transfer location to generated cast for error purposes
                CodeLocation location = untyped->location;
                untyped = new CastExpr( untyped, type );
                untyped->location = location;
                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 );
                }
        }


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

        void resolveWithExprs( std::list< Declaration * > & translationUnit ) {
                PassVisitor<ResolveWithExprs> resolver;
                acceptAll( translationUnit, resolver );
        }

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

        void ResolveWithExprs::previsit( FunctionDecl * functionDecl ) {
                {
                        // 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_old::previsit( ObjectDecl * objectDecl ) {
                // 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_old::handlePtrType( PtrType * type ) {
                if ( type->get_dimension() ) {
                        findSingleExpression( type->dimension, Validate::SizeType->clone(), indexer );
                }
        }

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

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

        void Resolver_old::previsit( FunctionDecl * functionDecl ) {
#if 0
                std::cerr << "resolver visiting functiondecl ";
                functionDecl->print( std::cerr );
                std::cerr << std::endl;
#endif
                GuardValue( functionReturn );
                functionReturn = ResolvExpr::extractResultType( functionDecl->type );
        }

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

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

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

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

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

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

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

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

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

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

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

        void Resolver_old::previsit( CaseStmt * caseStmt ) {
                if ( caseStmt->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 );
                        // case condition cannot have a cast in C, so it must be removed, regardless of whether it performs a conversion.
                        // Ideally we would perform the conversion internally here.
                        if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( newExpr ) ) {
                                newExpr = castExpr->arg;
                                castExpr->arg = nullptr;
                                std::swap( newExpr->env, castExpr->env );
                                delete castExpr;
                        }
                        caseStmt->condition = newExpr;
                }
        }

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

        void Resolver_old::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_old::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_old::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() );
                        }

                        if(clause.target.arguments.empty()) {
                                SemanticError( stmt->location, "Waitfor clause must have at least one mutex parameter");
                        }

                        // 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( func.env );
                                                        makeUnifiableVars( function, openVars, resultNeed );
                                                        // add all type variables as open variables now so that those not used in the parameter
                                                        // list are still considered open.
                                                        resultEnv.add( function->forall );

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

                                                        // Make sure we don't widen any existing bindings
                                                        resultEnv.forbidWidening();

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

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

                                                        int n_mutex_param = 0;

                                                        // 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, toString("candidate function not viable: too many mutex arguments, expected ", n_mutex_param, "\n" ));
                                                                }

                                                                n_mutex_param++;

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

                                                                param++;
                                                        }

                                                        // All arguments match !

                                                        // Check if parameters are missing
                                                        if( advance_to_mutex( param, param_end ) ) {
                                                                do {
                                                                        n_mutex_param++;
                                                                        param++;
                                                                } while( advance_to_mutex( param, param_end ) );

                                                                // We ran out of arguments but still have parameters left
                                                                // this function doesn't match
                                                                SemanticError( function, toString("candidate function not viable: too few mutex arguments, expected ", n_mutex_param, "\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 isCharType( Type * 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_old::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 );
                // InitExpr may have inferParams in the case where the expression specializes a function
                // pointer, and newExpr may already have inferParams of its own, so a simple swap is not
                // sufficient.
                newExpr->spliceInferParams( initExpr );
                delete initExpr;

                // 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 );
                                                        delete ce;
                                                }
                                        }
                                }
                        }
                }

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

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

        void Resolver_old::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_old::fallbackInit( ConstructorInit * ctorInit ) {
                // could not find valid constructor, or found an intrinsic constructor
                // fall back on C-style initializer
                delete ctorInit->get_ctor();
                ctorInit->set_ctor( nullptr );
                delete ctorInit->get_dtor();
                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_old> resolver( indexer );
                ctorInit->accept( resolver );
        }

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

        void Resolver_old::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
                delete ctorInit->init;
                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 ) ) {
                        delete ctorInit->ctor;
                        ctorInit->ctor = nullptr;
                }

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

                // xxx - todo -- what about arrays?
                // if ( dtor == nullptr && 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( nullptr );

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

        ///////////////////////////////////////////////////////////////////////////
        //
        // *** NEW RESOLVER ***
        //
        ///////////////////////////////////////////////////////////////////////////

        namespace {
                /// Finds deleted expressions in an expression tree
                struct DeleteFinder_new final : public ast::WithShortCircuiting {
                        const ast::DeletedExpr * delExpr = nullptr;

                        void previsit( const ast::DeletedExpr * expr ) {
                                if ( delExpr ) { visit_children = false; }
                                else { delExpr = expr; }
                        }

                        void previsit( const ast::Expr * ) {
                                if ( delExpr ) { visit_children = false; }
                        }
                };
        } // anonymous namespace

        /// Check if this expression is or includes a deleted expression
        const ast::DeletedExpr * findDeletedExpr( const ast::Expr * expr ) {
                ast::Pass<DeleteFinder_new> finder;
                expr->accept( finder );
                return finder.pass.delExpr;
        }

        namespace {
                /// always-accept candidate filter
                bool anyCandidate( const Candidate & ) { return true; }

                /// Calls the CandidateFinder and finds the single best candidate
                CandidateRef findUnfinishedKindExpression(
                        const ast::Expr * untyped, const ast::SymbolTable & symtab, const std::string & kind, 
                        std::function<bool(const Candidate &)> pred = anyCandidate, ResolvMode mode = {}
                ) {
                        if ( ! untyped ) return nullptr;

                        // xxx - this isn't thread-safe, but should work until we parallelize the resolver
                        static unsigned recursion_level = 0;

                        ++recursion_level;
                        ast::TypeEnvironment env;
                        CandidateFinder finder{ symtab, env };
                        finder.find( untyped, recursion_level == 1 ? mode.atTopLevel() : mode );
                        --recursion_level;

                        // produce a filtered list of candidates
                        CandidateList candidates;
                        for ( auto & cand : finder.candidates ) {
                                if ( pred( *cand ) ) { candidates.emplace_back( cand ); }
                        }

                        // produce invalid error if no candidates
                        if ( candidates.empty() ) {
                                SemanticError( untyped, 
                                        toString( "No reasonable alternatives for ", kind, (kind != "" ? " " : ""), 
                                        "expression: ") );
                        }

                        // search for cheapest candidate
                        CandidateList winners;
                        bool seen_undeleted = false;
                        for ( CandidateRef & cand : candidates ) {
                                int c = winners.empty() ? -1 : cand->cost.compare( winners.front()->cost );

                                if ( c > 0 ) continue;  // skip more expensive than winner

                                if ( c < 0 ) {
                                        // reset on new cheapest
                                        seen_undeleted = ! findDeletedExpr( cand->expr );
                                        winners.clear();
                                } else /* if ( c == 0 ) */ {
                                        if ( findDeletedExpr( cand->expr ) ) {
                                                // skip deleted expression if already seen one equivalent-cost not
                                                if ( seen_undeleted ) continue;
                                        } else if ( ! seen_undeleted ) {
                                                // replace list of equivalent-cost deleted expressions with one non-deleted
                                                winners.clear();
                                                seen_undeleted = true;
                                        }
                                }

                                winners.emplace_back( std::move( cand ) );
                        }

                        // promote candidate.cvtCost to .cost
                        promoteCvtCost( winners );

                        // produce ambiguous errors, if applicable
                        if ( winners.size() != 1 ) {
                                std::ostringstream stream;
                                stream << "Cannot choose between " << winners.size() << " alternatives for " 
                                        << kind << (kind != "" ? " " : "") << "expression\n";
                                ast::print( stream, untyped );
                                stream << " Alternatives are:\n";
                                print( stream, winners, 1 );
                                SemanticError( untyped->location, stream.str() );
                        }

                        // single selected choice
                        CandidateRef & choice = winners.front();

                        // fail on only expression deleted
                        if ( ! seen_undeleted ) {
                                SemanticError( untyped->location, choice->expr.get(), "Unique best alternative "
                                "includes deleted identifier in " );
                        }

                        return std::move( choice );
                }

                /// Strips extraneous casts out of an expression
                struct StripCasts_new final {
                        const ast::Expr * postmutate( const ast::CastExpr * castExpr ) {
                                if ( 
                                        castExpr->isGenerated 
                                        && typesCompatible( castExpr->arg->result, castExpr->result ) 
                                ) {
                                        // generated cast is the same type as its argument, remove it after keeping env
                                        return ast::mutate_field( 
                                                castExpr->arg.get(), &ast::Expr::env, castExpr->env );
                                }
                                return castExpr;
                        }

                        static void strip( ast::ptr< ast::Expr > & expr ) {
                                ast::Pass< StripCasts_new > stripper;
                                expr = expr->accept( stripper );
                        }
                };

                /// Swaps argument into expression pointer, saving original environment
                void swap_and_save_env( ast::ptr< ast::Expr > & expr, const ast::Expr * newExpr ) {
                        ast::ptr< ast::TypeSubstitution > env = expr->env;
                        expr.set_and_mutate( newExpr )->env = env;
                }

                /// Removes cast to type of argument (unlike StripCasts, also handles non-generated casts)
                void removeExtraneousCast( ast::ptr<ast::Expr> & expr, const ast::SymbolTable & symtab ) {
                        if ( const ast::CastExpr * castExpr = expr.as< ast::CastExpr >() ) {
                                if ( typesCompatible( castExpr->arg->result, castExpr->result, symtab ) ) {
                                        // cast is to the same type as its argument, remove it
                                        swap_and_save_env( expr, castExpr->arg );
                                }
                        }
                }

                /// Establish post-resolver invariants for expressions
                void finishExpr( 
                        ast::ptr< ast::Expr > & expr, const ast::TypeEnvironment & env, 
                        const ast::TypeSubstitution * oldenv = nullptr
                ) {
                        // set up new type substitution for expression
                        ast::ptr< ast::TypeSubstitution > newenv = 
                                 oldenv ? oldenv : new ast::TypeSubstitution{};
                        env.writeToSubstitution( *newenv.get_and_mutate() );
                        expr.get_and_mutate()->env = std::move( newenv );
                        // remove unncecessary casts
                        StripCasts_new::strip( expr );
                }
        } // anonymous namespace

                
        ast::ptr< ast::Expr > resolveInVoidContext(
                const ast::Expr * expr, const ast::SymbolTable & symtab, ast::TypeEnvironment & env
        ) {
                assertf( expr, "expected a non-null expression" );
                
                // set up and resolve expression cast to void
                ast::ptr< ast::CastExpr > untyped = new ast::CastExpr{ expr };
                CandidateRef choice = findUnfinishedKindExpression( 
                        untyped, symtab, "", anyCandidate, ResolvMode::withAdjustment() );
                
                // a cast expression has either 0 or 1 interpretations (by language rules);
                // if 0, an exception has already been thrown, and this code will not run
                const ast::CastExpr * castExpr = choice->expr.strict_as< ast::CastExpr >();
                env = std::move( choice->env );

                return castExpr->arg;
        }

        namespace {
                /// Resolve `untyped` to the expression whose candidate is the best match for a `void` 
                /// context.
                ast::ptr< ast::Expr > findVoidExpression( 
                        const ast::Expr * untyped, const ast::SymbolTable & symtab
                ) {
                        resetTyVarRenaming();
                        ast::TypeEnvironment env;
                        ast::ptr< ast::Expr > newExpr = resolveInVoidContext( untyped, symtab, env );
                        finishExpr( newExpr, env, untyped->env );
                        return newExpr;
                }

                /// resolve `untyped` to the expression whose candidate satisfies `pred` with the 
                /// lowest cost, returning the resolved version
                ast::ptr< ast::Expr > findKindExpression(
                        const ast::Expr * untyped, const ast::SymbolTable & symtab, 
                        std::function<bool(const Candidate &)> pred = anyCandidate, 
                        const std::string & kind = "", ResolvMode mode = {}
                ) {
                        if ( ! untyped ) return {};
                        CandidateRef choice = 
                                findUnfinishedKindExpression( untyped, symtab, kind, pred, mode );
                        finishExpr( choice->expr, choice->env, untyped->env );
                        return std::move( choice->expr );
                }

                /// Resolve `untyped` to the single expression whose candidate is the best match
                ast::ptr< ast::Expr > findSingleExpression( 
                        const ast::Expr * untyped, const ast::SymbolTable & symtab 
                ) {
                        return findKindExpression( untyped, symtab );
                }
        } // anonymous namespace

                ast::ptr< ast::Expr > findSingleExpression(
                        const ast::Expr * untyped, const ast::Type * type, const ast::SymbolTable & symtab
                ) {
                        assert( untyped && type );
                        ast::ptr< ast::Expr > castExpr = new ast::CastExpr{ untyped, type };
                        ast::ptr< ast::Expr > newExpr = findSingleExpression( castExpr, symtab );
                        removeExtraneousCast( newExpr, symtab );
                        return newExpr;
                }

        namespace {
                /// Predicate for "Candidate has integral type"
                bool hasIntegralType( const Candidate & i ) {
                        const ast::Type * type = i.expr->result;
                        
                        if ( auto bt = dynamic_cast< const ast::BasicType * >( type ) ) {
                                return bt->isInteger();
                        } else if ( 
                                dynamic_cast< const ast::EnumInstType * >( type ) 
                                || dynamic_cast< const ast::ZeroType * >( type )
                                || dynamic_cast< const ast::OneType * >( type )
                        ) {
                                return true;
                        } else return false;
                }

                /// Resolve `untyped` as an integral expression, returning the resolved version
                ast::ptr< ast::Expr > findIntegralExpression( 
                        const ast::Expr * untyped, const ast::SymbolTable & symtab 
                ) {
                        return findKindExpression( untyped, symtab, hasIntegralType, "condition" );
                }

                /// check if a type is a character type
                bool isCharType( const ast::Type * t ) {
                        if ( auto bt = dynamic_cast< const ast::BasicType * >( t ) ) {
                                return bt->kind == ast::BasicType::Char 
                                        || bt->kind == ast::BasicType::SignedChar 
                                        || bt->kind == ast::BasicType::UnsignedChar;
                        }
                        return false;
                }

                /// Advance a type itertor to the next mutex parameter
                template<typename Iter>
                inline bool nextMutex( Iter & it, const Iter & end ) {
                        while ( it != end && ! (*it)->get_type()->is_mutex() ) { ++it; }
                        return it != end;
                }
        }

        class Resolver_new final
        : public ast::WithSymbolTable, public ast::WithGuards,
          public ast::WithVisitorRef<Resolver_new>, public ast::WithShortCircuiting,
          public ast::WithStmtsToAdd<> {

                ast::ptr< ast::Type > functionReturn = nullptr;
                ast::CurrentObject currentObject;
                bool inEnumDecl = false;

        public:
                Resolver_new() = default;
                Resolver_new( const ast::SymbolTable & syms ) { symtab = syms; }

                void previsit( const ast::FunctionDecl * );
                const ast::FunctionDecl * postvisit( const ast::FunctionDecl * );
                void previsit( const ast::ObjectDecl * );
                void previsit( const ast::EnumDecl * );
                const ast::StaticAssertDecl * previsit( const ast::StaticAssertDecl * );

                const ast::ArrayType * previsit( const ast::ArrayType * );
                const ast::PointerType * previsit( const ast::PointerType * );

                const ast::ExprStmt *        previsit( const ast::ExprStmt * );
                const ast::AsmExpr *         previsit( const ast::AsmExpr * );
                const ast::AsmStmt *         previsit( const ast::AsmStmt * );
                const ast::IfStmt *          previsit( const ast::IfStmt * );
                const ast::WhileStmt *       previsit( const ast::WhileStmt * );
                const ast::ForStmt *         previsit( const ast::ForStmt * );
                const ast::SwitchStmt *      previsit( const ast::SwitchStmt * );
                const ast::CaseStmt *        previsit( const ast::CaseStmt * );
                const ast::BranchStmt *      previsit( const ast::BranchStmt * );
                const ast::ReturnStmt *      previsit( const ast::ReturnStmt * );
                const ast::ThrowStmt *       previsit( const ast::ThrowStmt * );
                const ast::CatchStmt *       previsit( const ast::CatchStmt * );
                const ast::WaitForStmt *     previsit( const ast::WaitForStmt * );

                const ast::SingleInit *      previsit( const ast::SingleInit * );
                const ast::ListInit *        previsit( const ast::ListInit * );
                const ast::ConstructorInit * previsit( const ast::ConstructorInit * );
        };

        void resolve( std::list< ast::ptr< ast::Decl > >& translationUnit ) {
                ast::Pass< Resolver_new > resolver;
                accept_all( translationUnit, resolver );
        }

        ast::ptr< ast::Init > resolveCtorInit( 
                const ast::ConstructorInit * ctorInit, const ast::SymbolTable & symtab 
        ) {
                assert( ctorInit );
                ast::Pass< Resolver_new > resolver{ symtab };
                return ctorInit->accept( resolver );
        }

        ast::ptr< ast::Expr > resolveStmtExpr( 
                const ast::StmtExpr * stmtExpr, const ast::SymbolTable & symtab 
        ) {
                assert( stmtExpr );
                ast::Pass< Resolver_new > resolver{ symtab };
                ast::ptr< ast::Expr > ret = stmtExpr;
                ret = ret->accept( resolver );
                strict_dynamic_cast< ast::StmtExpr * >( ret.get_and_mutate() )->computeResult();
                return ret;
        }

        void Resolver_new::previsit( const ast::FunctionDecl * functionDecl ) {
                GuardValue( functionReturn );
                functionReturn = extractResultType( functionDecl->type );
        }

        const ast::FunctionDecl * Resolver_new::postvisit( const ast::FunctionDecl * functionDecl ) {
                // default value expressions have an environment which shouldn't be there and trips up
                // later passes.
                ast::ptr< ast::FunctionDecl > ret = functionDecl;
                for ( unsigned i = 0; i < functionDecl->type->params.size(); ++i ) {
                        const ast::ptr< ast::DeclWithType > & d = functionDecl->type->params[i];

                        if ( const ast::ObjectDecl * obj = d.as< ast::ObjectDecl >() ) {
                                if ( const ast::SingleInit * init = obj->init.as< ast::SingleInit >() ) {
                                        if ( init->value->env == nullptr ) continue;
                                        // clone initializer minus the initializer environment
                                        ast::chain_mutate( ret )
                                                ( &ast::FunctionDecl::type )
                                                        ( &ast::FunctionType::params )[i]
                                                                ( &ast::ObjectDecl::init )
                                                                        ( &ast::SingleInit::value )->env = nullptr;

                                        assert( functionDecl != ret.get() || functionDecl->unique() );
                                        assert( ! ret->type->params[i].strict_as< ast::ObjectDecl >()->init.strict_as< ast::SingleInit >()->value->env );
                                }
                        }
                }
                return ret.release();
        }

        void Resolver_new::previsit( const ast::ObjectDecl * objectDecl ) {
                // To handle initialization of routine pointers [e.g. int (*fp)(int) = foo()], 
                // class-variable `initContext` is changed multiple times because the LHS is analyzed 
                // twice. The second analysis changes `initContext` because a function type can contain 
                // object declarations in the return and parameter types. Therefore each value of 
                // `initContext` is retained so the type on the first analysis is preserved and used for 
                // selecting the RHS.
                GuardValue( currentObject );
                currentObject = ast::CurrentObject{ objectDecl->location, objectDecl->get_type() };
                if ( inEnumDecl && dynamic_cast< const ast::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 `int` instead.
                        currentObject = ast::CurrentObject{ 
                                objectDecl->location, new ast::BasicType{ ast::BasicType::SignedInt } };
                }
        }

        void Resolver_new::previsit( const ast::EnumDecl * ) {
                // in case we decide to allow nested enums
                GuardValue( inEnumDecl );
                inEnumDecl = false;
        }

        const ast::StaticAssertDecl * Resolver_new::previsit( 
                const ast::StaticAssertDecl * assertDecl 
        ) {
                return ast::mutate_field( 
                        assertDecl, &ast::StaticAssertDecl::cond, 
                        findIntegralExpression( assertDecl->cond, symtab ) );
        }

        template< typename PtrType >
        const PtrType * handlePtrType( const PtrType * type, const ast::SymbolTable & symtab ) {
                if ( type->dimension ) {
                        #warning should use new equivalent to Validate::SizeType rather than sizeType here
                        ast::ptr< ast::Type > sizeType = new ast::BasicType{ ast::BasicType::LongUnsignedInt };
                        ast::mutate_field( 
                                type, &PtrType::dimension, 
                                findSingleExpression( type->dimension, sizeType, symtab ) );
                }
                return type;
        }

        const ast::ArrayType * Resolver_new::previsit( const ast::ArrayType * at ) {
                return handlePtrType( at, symtab );
        }

        const ast::PointerType * Resolver_new::previsit( const ast::PointerType * pt ) {
                return handlePtrType( pt, symtab );
        }

        const ast::ExprStmt * Resolver_new::previsit( const ast::ExprStmt * exprStmt ) {
                visit_children = false;
                assertf( exprStmt->expr, "ExprStmt has null expression in resolver" );
                
                return ast::mutate_field( 
                        exprStmt, &ast::ExprStmt::expr, findVoidExpression( exprStmt->expr, symtab ) );
        }

        const ast::AsmExpr * Resolver_new::previsit( const ast::AsmExpr * asmExpr ) {
                visit_children = false;

                asmExpr = ast::mutate_field( 
                        asmExpr, &ast::AsmExpr::operand, findVoidExpression( asmExpr->operand, symtab ) );
                
                if ( asmExpr->inout ) {
                        asmExpr = ast::mutate_field(
                                asmExpr, &ast::AsmExpr::inout, findVoidExpression( asmExpr->inout, symtab ) );
                }
                
                return asmExpr;
        }

        const ast::AsmStmt * Resolver_new::previsit( const ast::AsmStmt * asmStmt ) {
                visitor->maybe_accept( asmStmt, &ast::AsmStmt::input );
                visitor->maybe_accept( asmStmt, &ast::AsmStmt::output );
                visit_children = false;
                return asmStmt;
        }

        const ast::IfStmt * Resolver_new::previsit( const ast::IfStmt * ifStmt ) {
                return ast::mutate_field(
                        ifStmt, &ast::IfStmt::cond, findIntegralExpression( ifStmt->cond, symtab ) );
        }

        const ast::WhileStmt * Resolver_new::previsit( const ast::WhileStmt * whileStmt ) {
                return ast::mutate_field( 
                        whileStmt, &ast::WhileStmt::cond, findIntegralExpression( whileStmt->cond, symtab ) );
        }

        const ast::ForStmt * Resolver_new::previsit( const ast::ForStmt * forStmt ) {
                if ( forStmt->cond ) {
                        forStmt = ast::mutate_field(
                                forStmt, &ast::ForStmt::cond, findIntegralExpression( forStmt->cond, symtab ) );
                }

                if ( forStmt->inc ) {
                        forStmt = ast::mutate_field(
                                forStmt, &ast::ForStmt::inc, findVoidExpression( forStmt->inc, symtab ) );
                }

                return forStmt;
        }

        const ast::SwitchStmt * Resolver_new::previsit( const ast::SwitchStmt * switchStmt ) {
                GuardValue( currentObject );
                switchStmt = ast::mutate_field(
                        switchStmt, &ast::SwitchStmt::cond, 
                        findIntegralExpression( switchStmt->cond, symtab ) );
                currentObject = ast::CurrentObject{ switchStmt->location, switchStmt->cond->result };
                return switchStmt;
        }

        const ast::CaseStmt * Resolver_new::previsit( const ast::CaseStmt * caseStmt ) {
                if ( caseStmt->cond ) {
                        std::deque< ast::InitAlternative > initAlts = currentObject.getOptions();
                        assertf( initAlts.size() == 1, "SwitchStmt did not correctly resolve an integral "
                                "expression." );
                        
                        ast::ptr< ast::Expr > untyped = 
                                new ast::CastExpr{ caseStmt->location, caseStmt->cond, initAlts.front().type };
                        ast::ptr< ast::Expr > newExpr = findSingleExpression( untyped, symtab );
                        
                        // case condition cannot have a cast in C, so it must be removed here, regardless of 
                        // whether it would perform a conversion.
                        if ( const ast::CastExpr * castExpr = newExpr.as< ast::CastExpr >() ) {
                                swap_and_save_env( newExpr, castExpr->arg );
                        }
                        
                        caseStmt = ast::mutate_field( caseStmt, &ast::CaseStmt::cond, newExpr );
                }
                return caseStmt;
        }

        const ast::BranchStmt * Resolver_new::previsit( const ast::BranchStmt * branchStmt ) {
                visit_children = false;
                // must resolve the argument of a computed goto
                if ( branchStmt->kind == ast::BranchStmt::Goto && branchStmt->computedTarget ) {
                        // computed goto argument is void*
                        ast::ptr< ast::Type > target = new ast::PointerType{ new ast::VoidType{} };
                        branchStmt = ast::mutate_field(
                                branchStmt, &ast::BranchStmt::computedTarget, 
                                findSingleExpression( branchStmt->computedTarget, target, symtab ) );
                }
                return branchStmt;
        }

        const ast::ReturnStmt * Resolver_new::previsit( const ast::ReturnStmt * returnStmt ) {
                visit_children = false;
                if ( returnStmt->expr ) {
                        returnStmt = ast::mutate_field(
                                returnStmt, &ast::ReturnStmt::expr, 
                                findSingleExpression( returnStmt->expr, functionReturn, symtab ) );
                }
                return returnStmt;
        }

        const ast::ThrowStmt * Resolver_new::previsit( const ast::ThrowStmt * throwStmt ) {
                visit_children = false;
                if ( throwStmt->expr ) {
                        const ast::StructDecl * exceptionDecl = 
                                symtab.lookupStruct( "__cfaabi_ehm__base_exception_t" );
                        assert( exceptionDecl );
                        ast::ptr< ast::Type > exceptType = 
                                new ast::PointerType{ new ast::StructInstType{ exceptionDecl } };
                        throwStmt = ast::mutate_field(
                                throwStmt, &ast::ThrowStmt::expr, 
                                findSingleExpression( throwStmt->expr, exceptType, symtab ) );
                }
                return throwStmt;
        }

        const ast::CatchStmt * Resolver_new::previsit( const ast::CatchStmt * catchStmt ) {
                if ( catchStmt->cond ) {
                        ast::ptr< ast::Type > boolType = new ast::BasicType{ ast::BasicType::Bool };
                        catchStmt = ast::mutate_field( 
                                catchStmt, &ast::CatchStmt::cond, 
                                findSingleExpression( catchStmt->cond, boolType, symtab ) );
                }
                return catchStmt;
        }

        const ast::WaitForStmt * Resolver_new::previsit( const ast::WaitForStmt * stmt ) {
                visit_children = false;

                // Resolve all clauses first
                for ( unsigned i = 0; i < stmt->clauses.size(); ++i ) {
                        const ast::WaitForStmt::Clause & clause = stmt->clauses[i];

                        ast::TypeEnvironment env;
                        CandidateFinder funcFinder{ symtab, env };

                        // Find all candidates for a function in canonical form
                        funcFinder.find( clause.target.func, ResolvMode::withAdjustment() );

                        if ( funcFinder.candidates.empty() ) {
                                stringstream ss;
                                ss << "Use of undeclared indentifier '";
                                ss << clause.target.func.strict_as< ast::NameExpr >()->name;
                                ss << "' in call to waitfor";
                                SemanticError( stmt->location, ss.str() );
                        }

                        if ( clause.target.args.empty() ) {
                                SemanticError( stmt->location, 
                                        "Waitfor clause must have at least one mutex parameter");
                        }

                        // Find all alternatives for all arguments in canonical form
                        std::vector< CandidateFinder > argFinders = 
                                funcFinder.findSubExprs( clause.target.args );
                        
                        // List all combinations of arguments
                        std::vector< CandidateList > possibilities;
                        combos( argFinders.begin(), argFinders.end(), back_inserter( possibilities ) );

                        // For every possible function:
                        // * try matching the arguments to the parameters, not the other way around because 
                        //   more arguments than parameters
                        CandidateList funcCandidates;
                        std::vector< CandidateList > argsCandidates;
                        SemanticErrorException errors;
                        for ( CandidateRef & func : funcFinder.candidates ) {
                                try {
                                        auto pointerType = dynamic_cast< const ast::PointerType * >( 
                                                func->expr->result->stripReferences() );
                                        if ( ! pointerType ) {
                                                SemanticError( stmt->location, func->expr->result.get(), 
                                                        "candidate not viable: not a pointer type\n" );
                                        }

                                        auto funcType = pointerType->base.as< ast::FunctionType >();
                                        if ( ! funcType ) {
                                                SemanticError( stmt->location, func->expr->result.get(), 
                                                        "candidate not viable: not a function type\n" );
                                        }

                                        {
                                                auto param    = funcType->params.begin();
                                                auto paramEnd = funcType->params.end();

                                                if( ! nextMutex( param, paramEnd ) ) {
                                                        SemanticError( stmt->location, funcType, 
                                                                "candidate function not viable: no mutex parameters\n");
                                                }
                                        }

                                        CandidateRef func2{ new Candidate{ *func } };
                                        // strip reference from function
                                        func2->expr = referenceToRvalueConversion( func->expr, func2->cost );

                                        // Each argument must be matched with a parameter of the current candidate
                                        for ( auto & argsList : possibilities ) {
                                                try {
                                                        // Declare data structures needed for resolution
                                                        ast::OpenVarSet open;
                                                        ast::AssertionSet need, have;
                                                        ast::TypeEnvironment resultEnv{ func->env };
                                                        // Add all type variables as open so that those not used in the 
                                                        // parameter list are still considered open
                                                        resultEnv.add( funcType->forall );

                                                        // load type variables from arguments into one shared space
                                                        for ( auto & arg : argsList ) {
                                                                resultEnv.simpleCombine( arg->env );
                                                        }

                                                        // Make sure we don't widen any existing bindings
                                                        resultEnv.forbidWidening();

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

                                                        auto param = funcType->params.begin();
                                                        auto paramEnd = funcType->params.end();

                                                        unsigned n_mutex_param = 0;

                                                        // For every argument of its set, check if it matches one of the 
                                                        // parameters. The order is important
                                                        for ( auto & arg : argsList ) {
                                                                // Ignore non-mutex arguments
                                                                if ( ! nextMutex( param, paramEnd ) ) {
                                                                        // We ran out of parameters but still have arguments.
                                                                        // This function doesn't match
                                                                        SemanticError( stmt->location, funcType, 
                                                                                toString("candidate function not viable: too many mutex "
                                                                                "arguments, expected ", n_mutex_param, "\n" ) );
                                                                }

                                                                ++n_mutex_param;

                                                                // Check if the argument matches the parameter type in the current 
                                                                // scope
                                                                ast::ptr< ast::Type > paramType = (*param)->get_type();
                                                                if ( 
                                                                        ! unify( 
                                                                                arg->expr->result, paramType, resultEnv, need, have, open, 
                                                                                symtab ) 
                                                                ) {
                                                                        // Type doesn't match
                                                                        stringstream ss;
                                                                        ss << "candidate function not viable: no known conversion "
                                                                                "from '";
                                                                        ast::print( ss, (*param)->get_type() );
                                                                        ss << "' to '";
                                                                        ast::print( ss, arg->expr->result );
                                                                        ss << "' with env '";
                                                                        ast::print( ss, resultEnv );
                                                                        ss << "'\n";
                                                                        SemanticError( stmt->location, funcType, ss.str() );
                                                                }

                                                                ++param;
                                                        }

                                                        // All arguments match!

                                                        // Check if parameters are missing
                                                        if ( nextMutex( param, paramEnd ) ) {
                                                                do {
                                                                        ++n_mutex_param;
                                                                        ++param;
                                                                } while ( nextMutex( param, paramEnd ) );

                                                                // We ran out of arguments but still have parameters left; this 
                                                                // function doesn't match
                                                                SemanticError( stmt->location, funcType, 
                                                                        toString( "candidate function not viable: too few mutex "
                                                                        "arguments, expected ", n_mutex_param, "\n" ) );
                                                        }

                                                        // All parameters match!

                                                        // Finish the expressions to tie in proper environments
                                                        finishExpr( func2->expr, resultEnv );
                                                        for ( CandidateRef & arg : argsList ) {
                                                                finishExpr( arg->expr, resultEnv );
                                                        }

                                                        // This is a match, store it and save it for later
                                                        funcCandidates.emplace_back( std::move( func2 ) );
                                                        argsCandidates.emplace_back( std::move( argsList ) );

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

                        // Make sure correct number of arguments
                        if( funcCandidates.empty() ) {
                                SemanticErrorException top( stmt->location, 
                                        "No alternatives for function in call to waitfor" );
                                top.append( errors );
                                throw top;
                        }

                        if( argsCandidates.empty() ) {
                                SemanticErrorException top( stmt->location, 
                                        "No alternatives for arguments in call to waitfor" ); 
                                top.append( errors );
                                throw top;
                        }

                        if( funcCandidates.size() > 1 ) {
                                SemanticErrorException top( stmt->location, 
                                        "Ambiguous function in call to waitfor" );
                                top.append( errors );
                                throw top;
                        }
                        if( argsCandidates.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.

                        // build new clause
                        ast::WaitForStmt::Clause clause2;
                        
                        clause2.target.func = funcCandidates.front()->expr;
                        
                        clause2.target.args.reserve( clause.target.args.size() );
                        for ( auto arg : argsCandidates.front() ) {
                                clause2.target.args.emplace_back( std::move( arg->expr ) );
                        }

                        // Resolve the conditions as if it were an IfStmt, statements normally
                        clause2.cond = findSingleExpression( clause.cond, symtab );
                        clause2.stmt = clause.stmt->accept( *visitor );

                        // set results into stmt
                        auto n = mutate( stmt );
                        n->clauses[i] = std::move( clause2 );
                        stmt = n;
                }

                if ( stmt->timeout.stmt ) {
                        // resolve the timeout as a size_t, the conditions like IfStmt, and stmts normally
                        ast::WaitForStmt::Timeout timeout2;

                        ast::ptr< ast::Type > target = 
                                new ast::BasicType{ ast::BasicType::LongLongUnsignedInt };
                        timeout2.time = findSingleExpression( stmt->timeout.time, target, symtab );
                        timeout2.cond = findSingleExpression( stmt->timeout.cond, symtab );
                        timeout2.stmt = stmt->timeout.stmt->accept( *visitor );

                        // set results into stmt
                        auto n = mutate( stmt );
                        n->timeout = std::move( timeout2 );
                        stmt = n;
                }

                if ( stmt->orElse.stmt ) {
                        // resolve the condition like IfStmt, stmts normally
                        ast::WaitForStmt::OrElse orElse2;

                        orElse2.cond = findSingleExpression( stmt->orElse.cond, symtab );
                        orElse2.stmt = stmt->orElse.stmt->accept( *visitor );

                        // set results into stmt
                        auto n = mutate( stmt );
                        n->orElse = std::move( orElse2 );
                        stmt = n;
                }

                return stmt;
        }



        const ast::SingleInit * Resolver_new::previsit( const ast::SingleInit * singleInit ) {
                visit_children = false;
                // resolve initialization using the possibilities as determined by the `currentObject` 
                // cursor.
                ast::ptr< ast::Expr > untyped = new ast::UntypedInitExpr{ 
                        singleInit->location, singleInit->value, currentObject.getOptions() };
                ast::ptr<ast::Expr> newExpr = findSingleExpression( untyped, symtab );
                const ast::InitExpr * initExpr = newExpr.strict_as< ast::InitExpr >();

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

                // discard InitExpr wrapper and retain relevant pieces.
                // `initExpr` may have inferred params in the case where the expression specialized a 
                // function pointer, and newExpr may already have inferParams of its own, so a simple 
                // swap is not sufficient
                ast::Expr::InferUnion inferred = initExpr->inferred;
                swap_and_save_env( newExpr, initExpr->expr );
                newExpr.get_and_mutate()->inferred.splice( std::move(inferred) );

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

                removeExtraneousCast( newExpr, symtab );

                // check if actual object's type is char[]
                if ( auto at = dynamic_cast< const ast::ArrayType * >( initContext ) ) {
                        if ( isCharType( at->base ) ) {
                                // check if the resolved type is char*
                                if ( auto pt = newExpr->result.as< ast::PointerType >() ) {
                                        if ( isCharType( pt->base ) ) {
                                                // strip cast if we're initializing a char[] with a char* 
                                                // e.g. char x[] = "hello"
                                                if ( auto ce = newExpr.as< ast::CastExpr >() ) {
                                                        swap_and_save_env( newExpr, ce->arg );
                                                }
                                        }
                                }
                        }
                }

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

                // set initializer expression to resolved expression
                return ast::mutate_field( singleInit, &ast::SingleInit::value, std::move(newExpr) );
        }

        const ast::ListInit * Resolver_new::previsit( const ast::ListInit * listInit ) {
                // move cursor into brace-enclosed initializer-list
                currentObject.enterListInit( listInit->location );

                assert( listInit->designations.size() == listInit->initializers.size() );
                for ( unsigned i = 0; i < listInit->designations.size(); ++i ) {
                        // iterate designations and initializers in pairs, moving the cursor to the current 
                        // designated object and resolving the initializer against that object
                        listInit = ast::mutate_field_index(
                                listInit, &ast::ListInit::designations, i, 
                                currentObject.findNext( listInit->designations[i] ) );
                        listInit = ast::mutate_field_index(
                                listInit, &ast::ListInit::initializers, i,
                                listInit->initializers[i]->accept( *visitor ) );
                }

                // move cursor out of brace-enclosed initializer-list
                currentObject.exitListInit();

                visit_children = false;
                return listInit;
        }

        const ast::ConstructorInit * Resolver_new::previsit( const ast::ConstructorInit * ctorInit ) {
                visitor->maybe_accept( ctorInit, &ast::ConstructorInit::ctor );
                visitor->maybe_accept( ctorInit, &ast::ConstructorInit::dtor );

                // found a constructor - can get rid of C-style initializer
                // xxx - Rob suggests this field is dead code
                ctorInit = ast::mutate_field( ctorInit, &ast::ConstructorInit::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 = ast::mutate_field( ctorInit, &ast::ConstructorInit::ctor, nullptr );
                }
                if ( InitTweak::isIntrinsicSingleArgCallStmt( ctorInit->dtor ) ) {
                        ctorInit = ast::mutate_field( ctorInit, &ast::ConstructorInit::dtor, nullptr );
                }

                return ctorInit;
        }

} // namespace ResolvExpr

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