source: src/ResolvExpr/Resolver.cc @ 221c542e

//
// 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 : Peter A. Buhr
// Last Modified On : Thu Dec 14 18:44:43 2023
// Update Count     : 251
//

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

#include "Candidate.hpp"
#include "CandidateFinder.hpp"
#include "CurrentObject.h"               // for CurrentObject
#include "RenameVars.h"                  // for RenameVars, global_renamer
#include "Resolver.h"
#include "ResolveTypeof.h"
#include "ResolveMode.hpp"               // for ResolveMode
#include "typeops.h"                     // for extractResultType
#include "Unify.h"                       // for unify
#include "CompilationState.h"
#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/Eval.h"                 // for eval
#include "Common/Iterate.hpp"            // for group_iterate
#include "Common/SemanticError.h"        // for SemanticError
#include "Common/Stats/ResolveTime.h"    // for ResolveTime::start(), ResolveTime::stop()
#include "Common/ToString.hpp"           // for toCString
#include "Common/UniqueName.h"           // for UniqueName
#include "InitTweak/GenInit.h"
#include "InitTweak/InitTweak.h"         // for isIntrinsicSingleArgCallStmt
#include "SymTab/Mangler.h"              // for Mangler
#include "Tuples/Tuples.h"
#include "Validate/FindSpecialDecls.h"   // for SizeType

using namespace std;

namespace ResolvExpr {
        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;
        }

        namespace {
                /// Finds deleted expressions in an expression tree
                struct DeleteFinder final : public ast::WithShortCircuiting, public ast::WithVisitorRef<DeleteFinder> {
                        const ast::DeletedExpr * result = nullptr;

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

                        void previsit( const ast::Expr * expr ) {
                                if ( result ) { visit_children = false; }
                                if (expr->inferred.hasParams()) {
                                        for (auto & imp : expr->inferred.inferParams() ) {
                                                imp.second.expr->accept(*visitor);
                                        }
                                }
                        }
                };

                struct ResolveDesignators final : public ast::WithShortCircuiting {
                        ResolveContext& context;
                        bool result = false;

                        ResolveDesignators( ResolveContext& _context ): context{_context} {};

                        void previsit( const ast::Node * ) {
                                // short circuit if we already know there are designations
                                if ( result ) visit_children = false;
                        }

                        void previsit( const ast::Designation * des ) {
                                if ( result ) visit_children = false;
                                else if ( ! des->designators.empty() ) {
                                        if ( (des->designators.size() == 1) ) {
                                                const ast::Expr * designator = des->designators.at(0);
                                                if ( const ast::NameExpr * designatorName = dynamic_cast<const ast::NameExpr *>(designator) ) {
                                                        auto candidates = context.symtab.lookupId(designatorName->name);
                                                        for ( auto candidate : candidates ) {
                                                                if ( dynamic_cast<const ast::EnumInstType *>(candidate.id->get_type()) ) {
                                                                        result = true;
                                                                        break;
                                                                }
                                                        }
                                                }
                                        }
                                        visit_children = false;
                                }
                        }
                };
        } // anonymous namespace
        /// Check if this expression is or includes a deleted expression
        const ast::DeletedExpr * findDeletedExpr( const ast::Expr * expr ) {
                return ast::Pass<DeleteFinder>::read( expr );
        }

        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 ResolveContext & context, const std::string & kind,
                        std::function<bool(const Candidate &)> pred = anyCandidate, ResolveMode 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( context, env );
                        finder.allowVoid = true;
                        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 final {
                        const ast::Expr * postvisit( const ast::CastExpr * castExpr ) {
                                if (
                                        castExpr->isGenerated == ast::GeneratedCast
                                        && 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 > 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 ) {
                        if ( const ast::CastExpr * castExpr = expr.as< ast::CastExpr >() ) {
                                if ( typesCompatible( castExpr->arg->result, castExpr->result ) ) {
                                        // cast is to the same type as its argument, remove it
                                        swap_and_save_env( expr, castExpr->arg );
                                }
                        }
                }


        } // anonymous namespace
/// 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::strip( expr );
                }

        ast::ptr< ast::Expr > resolveInVoidContext(
                const ast::Expr * expr, const ResolveContext & context,
                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, context, "", anyCandidate, ResolveMode::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;
        }

        /// 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 ResolveContext & context
                ) {
                        ast::TypeEnvironment env;
                        ast::ptr< ast::Expr > newExpr = resolveInVoidContext( untyped, context, env );
                        finishExpr( newExpr, env, untyped->env );
                        return newExpr;
                }

        namespace {


                /// 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 ResolveContext & context,
                        std::function<bool(const Candidate &)> pred = anyCandidate,
                        const std::string & kind = "", ResolveMode mode = {}
                ) {
                        if ( ! untyped ) return {};
                        CandidateRef choice =
                                findUnfinishedKindExpression( untyped, context, kind, pred, mode );
                        ResolvExpr::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 ResolveContext & context
                ) {
                        Stats::ResolveTime::start( untyped );
                        auto res = findKindExpression( untyped, context );
                        Stats::ResolveTime::stop();
                        return res;
                }
        } // anonymous namespace

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

        namespace {
                bool structOrUnion( const Candidate & i ) {
                        const ast::Type * t = i.expr->result->stripReferences();
                        return dynamic_cast< const ast::StructInstType * >( t ) || dynamic_cast< const ast::UnionInstType * >( t );
                }
                /// 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 ResolveContext & context
                ) {
                        return findKindExpression( untyped, context, 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)->is_mutex() ) { ++it; }
                        return it != end;
                }
        }

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

                ast::ptr< ast::Type > functionReturn = nullptr;
                ast::CurrentObject currentObject;
                // for work previously in GenInit
                static InitTweak::ManagedTypes managedTypes;
                ResolveContext context;

                bool inEnumDecl = false;

        public:
                static size_t traceId;
                Resolver( const ast::TranslationGlobal & global ) :
                        ast::WithSymbolTable(ast::SymbolTable::ErrorDetection::ValidateOnAdd),
                        context{ symtab, global } {}
                Resolver( const ResolveContext & context ) :
                        ast::WithSymbolTable{ context.symtab },
                        context{ symtab, context.global } {}

                const ast::FunctionDecl * previsit( const ast::FunctionDecl * );
                const ast::FunctionDecl * postvisit( const ast::FunctionDecl * );
                const ast::ObjectDecl * previsit( const ast::ObjectDecl * );
                void previsit( const ast::AggregateDecl * );
                void previsit( const ast::StructDecl * );
                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::WhileDoStmt *     previsit( const ast::WhileDoStmt * );
                const ast::ForStmt *         previsit( const ast::ForStmt * );
                const ast::SwitchStmt *      previsit( const ast::SwitchStmt * );
                const ast::CaseClause *      previsit( const ast::CaseClause * );
                const ast::BranchStmt *      previsit( const ast::BranchStmt * );
                const ast::ReturnStmt *      previsit( const ast::ReturnStmt * );
                const ast::ThrowStmt *       previsit( const ast::ThrowStmt * );
                const ast::CatchClause *     previsit( const ast::CatchClause * );
                const ast::CatchClause *     postvisit( const ast::CatchClause * );
                const ast::WaitForStmt *     previsit( const ast::WaitForStmt * );
                const ast::WithStmt *        previsit( const ast::WithStmt * );

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

                const ast::EnumPosExpr *         previsit( const ast::EnumPosExpr * );

                void resolveWithExprs(std::vector<ast::ptr<ast::Expr>> & exprs, std::list<ast::ptr<ast::Stmt>> & stmtsToAdd);

                void beginScope() { managedTypes.beginScope(); }
                void endScope() { managedTypes.endScope(); }
                bool on_error(ast::ptr<ast::Decl> & decl);
        };
        // size_t Resolver::traceId = Stats::Heap::new_stacktrace_id("Resolver");

        InitTweak::ManagedTypes Resolver::managedTypes;

        void resolve( ast::TranslationUnit& translationUnit ) {
                ast::Pass< Resolver >::run( translationUnit, translationUnit.global );
        }

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

        const ast::Expr * resolveStmtExpr(
                const ast::StmtExpr * stmtExpr, const ResolveContext & context
        ) {
                assert( stmtExpr );
                ast::Pass< Resolver > resolver( context );
                auto ret = mutate(stmtExpr->accept(resolver));
                strict_dynamic_cast< ast::StmtExpr * >( ret )->computeResult();
                return ret;
        }

        namespace {
                const ast::Attribute * handleAttribute(const CodeLocation & loc, const ast::Attribute * attr, const ResolveContext & context) {
                        std::string name = attr->normalizedName();
                        if (name == "constructor" || name == "destructor") {
                                if (attr->params.size() == 1) {
                                        auto arg = attr->params.front();
                                        auto resolved = ResolvExpr::findSingleExpression( arg, new ast::BasicType( ast::BasicType::LongLongSignedInt ), context );
                                        auto result = eval(arg);

                                        auto mutAttr = mutate(attr);
                                        mutAttr->params.front() = resolved;
                                        if (! result.hasKnownValue) {
                                                SemanticWarning(loc, Warning::GccAttributes,
                                                        toCString( name, " priorities must be integers from 0 to 65535 inclusive: ", arg ) );
                                        }
                                        else {
                                                auto priority = result.knownValue;
                                                if (priority < 101) {
                                                        SemanticWarning(loc, Warning::GccAttributes,
                                                                toCString( name, " priorities from 0 to 100 are reserved for the implementation" ) );
                                                } else if (priority < 201 && ! buildingLibrary()) {
                                                        SemanticWarning(loc, Warning::GccAttributes,
                                                                toCString( name, " priorities from 101 to 200 are reserved for the implementation" ) );
                                                }
                                        }
                                        return mutAttr;
                                } else if (attr->params.size() > 1) {
                                        SemanticWarning(loc, Warning::GccAttributes, toCString( "too many arguments to ", name, " attribute" ) );
                                } else {
                                        SemanticWarning(loc, Warning::GccAttributes, toCString( "too few arguments to ", name, " attribute" ) );
                                }
                        }
                        return attr;
                }
        }

        const ast::FunctionDecl * Resolver::previsit( const ast::FunctionDecl * functionDecl ) {
                GuardValue( functionReturn );

                assert (functionDecl->unique());
                if (!functionDecl->has_body() && !functionDecl->withExprs.empty()) {
                        SemanticError(functionDecl->location, functionDecl, "Function without body has with declarations");
                }

                if (!functionDecl->isTypeFixed) {
                        auto mutDecl = mutate(functionDecl);
                        auto mutType = mutDecl->type.get_and_mutate();

                        for (auto & attr: mutDecl->attributes) {
                                attr = handleAttribute(mutDecl->location, attr, context );
                        }

                        // handle assertions

                        symtab.enterScope();
                        mutType->forall.clear();
                        mutType->assertions.clear();
                        for (auto & typeParam : mutDecl->type_params) {
                                symtab.addType(typeParam);
                                mutType->forall.emplace_back(new ast::TypeInstType(typeParam));
                        }
                        for (auto & asst : mutDecl->assertions) {
                                asst = fixObjectType(asst.strict_as<ast::ObjectDecl>(), context);
                                symtab.addId(asst);
                                mutType->assertions.emplace_back(new ast::VariableExpr(functionDecl->location, asst));
                        }

                        // temporarily adds params to symbol table.
                        // actual scoping rules for params and withexprs differ - see Pass::visit(FunctionDecl)

                        std::vector<ast::ptr<ast::Type>> paramTypes;
                        std::vector<ast::ptr<ast::Type>> returnTypes;

                        for (auto & param : mutDecl->params) {
                                param = fixObjectType(param.strict_as<ast::ObjectDecl>(), context);
                                symtab.addId(param);
                                paramTypes.emplace_back(param->get_type());
                        }
                        for (auto & ret : mutDecl->returns) {
                                ret = fixObjectType(ret.strict_as<ast::ObjectDecl>(), context);
                                returnTypes.emplace_back(ret->get_type());
                        }
                        // since function type in decl is just a view of param types, need to update that as well
                        mutType->params = std::move(paramTypes);
                        mutType->returns = std::move(returnTypes);

                        auto renamedType = strict_dynamic_cast<const ast::FunctionType *>(renameTyVars(mutType, RenameMode::GEN_EXPR_ID));

                        std::list<ast::ptr<ast::Stmt>> newStmts;
                        resolveWithExprs (mutDecl->withExprs, newStmts);

                        if (mutDecl->stmts) {
                                auto mutStmt = mutDecl->stmts.get_and_mutate();
                                mutStmt->kids.splice(mutStmt->kids.begin(), std::move(newStmts));
                                mutDecl->stmts = mutStmt;
                        }

                        symtab.leaveScope();

                        mutDecl->type = renamedType;
                        mutDecl->mangleName = Mangle::mangle(mutDecl);
                        mutDecl->isTypeFixed = true;
                        functionDecl = mutDecl;
                }
                managedTypes.handleDWT(functionDecl);

                functionReturn = extractResultType( functionDecl->type );
                return functionDecl;
        }

        const ast::FunctionDecl * Resolver::postvisit( const ast::FunctionDecl * functionDecl ) {
                // default value expressions have an environment which shouldn't be there and trips up
                // later passes.
                assert( functionDecl->unique() );
                ast::FunctionType * mutType = mutate( functionDecl->type.get() );

                for ( unsigned i = 0 ; i < mutType->params.size() ; ++i ) {
                        if ( const ast::ObjectDecl * obj = mutType->params[i].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
                                        auto mutParam = mutate( mutType->params[i].strict_as< ast::ObjectDecl >() );
                                        auto mutInit = mutate( mutParam->init.strict_as< ast::SingleInit >() );
                                        auto mutValue = mutate( mutInit->value.get() );

                                        mutValue->env = nullptr;
                                        mutInit->value = mutValue;
                                        mutParam->init = mutInit;
                                        mutType->params[i] = mutParam;

                                        assert( ! mutType->params[i].strict_as< ast::ObjectDecl >()->init.strict_as< ast::SingleInit >()->value->env);
                                }
                        }
                }
                mutate_field(functionDecl, &ast::FunctionDecl::type, mutType);
                return functionDecl;
        }

        const ast::ObjectDecl * Resolver::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 );

                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.

                        if ( auto enumBase = dynamic_cast< const ast::EnumInstType * >
                                ( objectDecl->get_type() )->base->base ) {
                                objectDecl = fixObjectType( objectDecl, context );
                                currentObject = ast::CurrentObject{
                                        objectDecl->location,
                                        enumBase
                                };
                        } else {
                                objectDecl = fixObjectType( objectDecl, context );
                                currentObject = ast::CurrentObject{
                                        objectDecl->location, new ast::BasicType{ ast::BasicType::SignedInt } };
                        }

                }
                else {
                        if ( !objectDecl->isTypeFixed ) {
                                auto newDecl = fixObjectType(objectDecl, context);
                                auto mutDecl = mutate(newDecl);

                                // generate CtorInit wrapper when necessary.
                                // in certain cases, fixObjectType is called before reaching
                                // this object in visitor pass, thus disabling CtorInit codegen.
                                // this happens on aggregate members and function parameters.
                                if ( InitTweak::tryConstruct( mutDecl ) && ( managedTypes.isManaged( mutDecl ) || ((! isInFunction() || mutDecl->storage.is_static ) && ! InitTweak::isConstExpr( mutDecl->init ) ) ) ) {
                                        // constructed objects cannot be designated
                                        if ( InitTweak::isDesignated( mutDecl->init ) ) {
                                                ast::Pass<ResolveDesignators> res( context );
                                                maybe_accept( mutDecl->init.get(), res );
                                                if ( !res.core.result ) {
                                                        SemanticError( mutDecl, "Cannot include designations in the initializer for a managed Object.\n"
                                                                                   "If this is really what you want, initialize with @=." );
                                                }
                                        }
                                        // constructed objects should not have initializers nested too deeply
                                        if ( ! InitTweak::checkInitDepth( mutDecl ) ) SemanticError( mutDecl, "Managed object's initializer is too deep " );

                                        mutDecl->init = InitTweak::genCtorInit( mutDecl->location, mutDecl );
                                }

                                objectDecl = mutDecl;
                        }
                        currentObject = ast::CurrentObject{ objectDecl->location, objectDecl->get_type() };
                }

                return objectDecl;
        }

        void Resolver::previsit( const ast::AggregateDecl * _aggDecl ) {
                auto aggDecl = mutate(_aggDecl);
                assertf(aggDecl == _aggDecl, "type declarations must be unique");

                for (auto & member: aggDecl->members) {
                        // nested type decls are hoisted already. no need to do anything
                        if (auto obj = member.as<ast::ObjectDecl>()) {
                                member = fixObjectType(obj, context);
                        }
                }
        }

        void Resolver::previsit( const ast::StructDecl * structDecl ) {
                previsit(static_cast<const ast::AggregateDecl *>(structDecl));
                managedTypes.handleStruct(structDecl);
        }

        void Resolver::previsit( const ast::EnumDecl * ) {
                // in case we decide to allow nested enums
                GuardValue( inEnumDecl );
                inEnumDecl = true;
                // don't need to fix types for enum fields
        }

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

        template< typename PtrType >
        const PtrType * handlePtrType( const PtrType * type, const ResolveContext & context ) {
                if ( type->dimension ) {
                        const ast::Type * sizeType = context.global.sizeType.get();
                        ast::ptr< ast::Expr > dimension = findSingleExpression( type->dimension, sizeType, context );
                        assertf(dimension->env->empty(), "array dimension expr has nonempty env");
                        dimension.get_and_mutate()->env = nullptr;
                        ast::mutate_field( type, &PtrType::dimension, dimension );
                }
                return type;
        }

        const ast::ArrayType * Resolver::previsit( const ast::ArrayType * at ) {
                return handlePtrType( at, context );
        }

        const ast::PointerType * Resolver::previsit( const ast::PointerType * pt ) {
                return handlePtrType( pt, context );
        }

        const ast::ExprStmt * Resolver::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, context ) );
        }

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

                asmExpr = ast::mutate_field(
                        asmExpr, &ast::AsmExpr::operand, findVoidExpression( asmExpr->operand, context ) );

                return asmExpr;
        }

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

        const ast::WhileDoStmt * Resolver::previsit( const ast::WhileDoStmt * whileDoStmt ) {
                return ast::mutate_field(
                        whileDoStmt, &ast::WhileDoStmt::cond, findIntegralExpression( whileDoStmt->cond, context ) );
        }

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

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

                return forStmt;
        }

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

        const ast::CaseClause * Resolver::previsit( const ast::CaseClause * 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, context );

                        // 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::CaseClause::cond, newExpr );
                }
                return caseStmt;
        }

        const ast::BranchStmt * Resolver::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, context ) );
                }
                return branchStmt;
        }

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

        const ast::ThrowStmt * Resolver::previsit( const ast::ThrowStmt * throwStmt ) {
                visit_children = false;
                if ( throwStmt->expr ) {
                        const ast::StructDecl * exceptionDecl =
                                symtab.lookupStruct( "__cfaehm_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, context ) );
                }
                return throwStmt;
        }

        const ast::CatchClause * Resolver::previsit( const ast::CatchClause * catchClause ) {
                // Until we are very sure this invarent (ifs that move between passes have then)
                // holds, check it. This allows a check for when to decode the mangling.
                if ( auto ifStmt = catchClause->body.as<ast::IfStmt>() ) {
                        assert( ifStmt->then );
                }
                // Encode the catchStmt so the condition can see the declaration.
                if ( catchClause->cond ) {
                        ast::CatchClause * clause = mutate( catchClause );
                        clause->body = new ast::IfStmt( clause->location, clause->cond, nullptr, clause->body );
                        clause->cond = nullptr;
                        return clause;
                }
                return catchClause;
        }

        const ast::CatchClause * Resolver::postvisit( const ast::CatchClause * catchClause ) {
                // Decode the catchStmt so everything is stored properly.
                const ast::IfStmt * ifStmt = catchClause->body.as<ast::IfStmt>();
                if ( nullptr != ifStmt && nullptr == ifStmt->then ) {
                        assert( ifStmt->cond );
                        assert( ifStmt->else_ );
                        ast::CatchClause * clause = ast::mutate( catchClause );
                        clause->cond = ifStmt->cond;
                        clause->body = ifStmt->else_;
                        // ifStmt should be implicately deleted here.
                        return clause;
                }
                return catchClause;
        }

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

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

                        ast::TypeEnvironment env;
                        CandidateFinder funcFinder( context, env );

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

                        if ( funcFinder.candidates.empty() ) {
                                stringstream ss;
                                ss << "Use of undeclared indentifier '";
                                ss << clause.target.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, *param, resultEnv, need, have, open )
                                                                ) {
                                                                        // Type doesn't match
                                                                        stringstream ss;
                                                                        ss << "candidate function not viable: no known conversion "
                                                                                "from '";
                                                                        ast::print( ss, *param );
                                                                        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
                        auto clause2 = new ast::WaitForClause( clause.location );

                        clause2->target = funcCandidates.front()->expr;

                        clause2->target_args.reserve( clause.target_args.size() );
                        const ast::StructDecl * decl_monitor = symtab.lookupStruct( "monitor$" );
                        for ( auto arg : argsCandidates.front() ) {
                                const auto & loc = stmt->location;

                                ast::Expr * init = new ast::CastExpr( loc,
                                        new ast::UntypedExpr( loc,
                                                new ast::NameExpr( loc, "get_monitor" ),
                                                { arg->expr }
                                        ),
                                        new ast::PointerType(
                                                new ast::StructInstType(
                                                        decl_monitor
                                                )
                                        )
                                );

                                clause2->target_args.emplace_back( findSingleExpression( init, context ) );
                        }

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

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

                if ( stmt->timeout_stmt ) {
                        // resolve the timeout as a size_t, the conditions like IfStmt, and stmts normally
                        ast::ptr< ast::Type > target =
                                new ast::BasicType{ ast::BasicType::LongLongUnsignedInt };
                        auto timeout_time = findSingleExpression( stmt->timeout_time, target, context );
                        auto timeout_cond = findSingleExpression( stmt->timeout_cond, context );
                        auto timeout_stmt = stmt->timeout_stmt->accept( *visitor );

                        // set results into stmt
                        auto n = mutate( stmt );
                        n->timeout_time = std::move( timeout_time );
                        n->timeout_cond = std::move( timeout_cond );
                        n->timeout_stmt = std::move( timeout_stmt );
                        stmt = n;
                }

                if ( stmt->else_stmt ) {
                        // resolve the condition like IfStmt, stmts normally
                        auto else_cond = findSingleExpression( stmt->else_cond, context );
                        auto else_stmt = stmt->else_stmt->accept( *visitor );

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

                return stmt;
        }

        const ast::WithStmt * Resolver::previsit( const ast::WithStmt * withStmt ) {
                auto mutStmt = mutate(withStmt);
                resolveWithExprs(mutStmt->exprs, stmtsToAddBefore);
                return mutStmt;
        }

        void Resolver::resolveWithExprs(std::vector<ast::ptr<ast::Expr>> & exprs, std::list<ast::ptr<ast::Stmt>> & stmtsToAdd) {
                for (auto & expr : exprs) {
                        // only struct- and union-typed expressions are viable candidates
                        expr = findKindExpression( expr, context, structOrUnion, "with expression" );

                        // if with expression might be impure, create a temporary so that it is evaluated once
                        if ( Tuples::maybeImpure( expr ) ) {
                                static UniqueName tmpNamer( "_with_tmp_" );
                                const CodeLocation loc = expr->location;
                                auto tmp = new ast::ObjectDecl(loc, tmpNamer.newName(), expr->result, new ast::SingleInit(loc, expr ) );
                                expr = new ast::VariableExpr( loc, tmp );
                                stmtsToAdd.push_back( new ast::DeclStmt(loc, tmp ) );
                                if ( InitTweak::isConstructable( tmp->type ) ) {
                                        // generate ctor/dtor and resolve them
                                        tmp->init = InitTweak::genCtorInit( loc, tmp );
                                }
                                // since tmp is freshly created, this should modify tmp in-place
                                tmp->accept( *visitor );
                        }
                        else if (expr->env && expr->env->empty()) {
                                expr = ast::mutate_field(expr.get(), &ast::Expr::env, nullptr);
                        }
                }
        }


        const ast::SingleInit * Resolver::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, context );
                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 );

                // 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::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::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;
        }

        const ast::EnumPosExpr * Resolver::previsit( const ast::EnumPosExpr * enumPos ) {
                visitor->maybe_accept( enumPos, &ast::EnumPosExpr::expr );
                return enumPos;
        }

        // suppress error on autogen functions and mark invalid autogen as deleted.
        bool Resolver::on_error(ast::ptr<ast::Decl> & decl) {
                if (auto functionDecl = decl.as<ast::FunctionDecl>()) {
                        // xxx - can intrinsic gen ever fail?
                        if (functionDecl->linkage == ast::Linkage::AutoGen) {
                                auto mutDecl = mutate(functionDecl);
                                mutDecl->isDeleted = true;
                                mutDecl->stmts = nullptr;
                                decl = mutDecl;
                                return false;
                        }
                }
                return true;
        }

} // namespace ResolvExpr

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