source: src/AST/SymbolTable.cpp@ bc48c0d

//
// 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.
//
// SymbolTable.cpp --
//
// Author           : Aaron B. Moss
// Created On       : Wed May 29 11:00:00 2019
// Last Modified By : Aaron B. Moss
// Last Modified On : Wed May 29 11:00:00 2019
// Update Count     : 1
//

#include "SymbolTable.hpp"

#include <cassert>

#include "Copy.hpp"
#include "Decl.hpp"
#include "Expr.hpp"
#include "Inspect.hpp"
#include "Type.hpp"
#include "CodeGen/OperatorTable.hpp"       // for isCtorDtorAssign
#include "Common/SemanticError.hpp"
#include "Common/Stats/Counter.hpp"
#include "GenPoly/GenPoly.hpp"
#include "InitTweak/InitTweak.hpp"
#include "ResolvExpr/Cost.hpp"
#include "ResolvExpr/CandidateFinder.hpp"  // for referenceToRvalueConversion
#include "ResolvExpr/Unify.hpp"
#include "SymTab/Mangler.hpp"

namespace ast {

// Statistics block
namespace {
        static inline auto stats() {
                using namespace Stats::Counters;
                static auto group   = build<CounterGroup>("Symbol Tables");
                static struct {
                        SimpleCounter * count;
                        AverageCounter<double> * size;
                        SimpleCounter * new_scopes;
                        SimpleCounter * lazy_scopes;
                        AverageCounter<double> * avg_scope_depth;
                        MaxCounter<size_t> * max_scope_depth;
                        SimpleCounter * add_calls;
                        SimpleCounter * lookup_calls;
                        SimpleCounter * map_lookups;
                        SimpleCounter * map_mutations;
                } ret = {
                        .count   = build<SimpleCounter>("Count", group),
                        .size    = build<AverageCounter<double>>("Average Size", group),
                        .new_scopes = build<SimpleCounter>("Scopes", group),
                        .lazy_scopes = build<SimpleCounter>("Lazy Scopes", group),
                        .avg_scope_depth = build<AverageCounter<double>>("Average Scope", group),
                        .max_scope_depth = build<MaxCounter<size_t>>("Max Scope", group),
                        .add_calls = build<SimpleCounter>("Add Calls", group),
                        .lookup_calls = build<SimpleCounter>("Lookup Calls", group),
                        .map_lookups = build<SimpleCounter>("Map Lookups", group),
                        .map_mutations = build<SimpleCounter>("Map Mutations", group)
                };
                return ret;
        }
}

Expr * SymbolTable::IdData::combine( const CodeLocation & loc, ResolvExpr::Cost & cost ) const {
        Expr * ret;
        if ( baseExpr ) {
                if (baseExpr->env) {
                        Expr * base = deepCopy(baseExpr);
                        const TypeSubstitution * subs = baseExpr->env;
                        base->env = nullptr;
                        ret = new MemberExpr{loc, id, referenceToRvalueConversion( base, cost )};
                        ret->env = subs;
                } else {
                        ret = new MemberExpr{ loc, id, referenceToRvalueConversion( baseExpr, cost ) };
                }
        } else {
                ret = new VariableExpr{ loc, id };
        }
        if ( deleter ) { ret = new DeletedExpr{ loc, ret, deleter }; }
        return ret;
}

SymbolTable::SymbolTable( ErrorDetection errorMode )
: idTable(), typeTable(), structTable(), enumTable(), unionTable(), traitTable(),
  prevScope(), scope( 0 ), repScope( 0 ), errorMode(errorMode) { ++*stats().count; }

SymbolTable::~SymbolTable() { stats().size->push( idTable ? idTable->size() : 0 ); }

void SymbolTable::OnFindError( CodeLocation location, std::string error ) const {
        assertf( errorMode != AssertClean, "Name collision/redefinition, found during a compilation phase where none should be possible.  Detail: %s", error.c_str() );
        if (errorMode == ValidateOnAdd) {
                SemanticError(location, error);
        }
        assertf( errorMode == IgnoreErrors, "Unrecognized symbol-table error mode %d", errorMode );
}

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

        ++*stats().new_scopes;
        stats().avg_scope_depth->push( scope );
        stats().max_scope_depth->push( scope );
}

void SymbolTable::leaveScope() {
        if ( repScope == scope ) {
                Ptr prev = prevScope;           // make sure prevScope stays live
                *this = std::move(*prevScope);  // replace with previous scope
        }

        --scope;
}

SymbolTable::SpecialFunctionKind SymbolTable::getSpecialFunctionKind(const std::string & name) {
        if (name == "?{}") return CTOR;
        if (name == "^?{}") return DTOR;
        if (name == "?=?") return ASSIGN;
        return NUMBER_OF_KINDS;
}

std::vector<SymbolTable::IdData> SymbolTable::lookupId( const std::string &id ) const {
        static Stats::Counters::CounterGroup * name_lookup_stats = Stats::Counters::build<Stats::Counters::CounterGroup>("Name Lookup Stats");
        static std::map<std::string, Stats::Counters::SimpleCounter *> lookups_by_name;
        static std::map<std::string, Stats::Counters::SimpleCounter *> candidates_by_name;

        SpecialFunctionKind kind = getSpecialFunctionKind(id);
        if (kind != NUMBER_OF_KINDS) return specialLookupId(kind);

        ++*stats().lookup_calls;
        if ( ! idTable ) return {};

        ++*stats().map_lookups;
        auto decls = idTable->find( id );
        if ( decls == idTable->end() ) return {};

        std::vector<IdData> out;
        for ( auto decl : *(decls->second) ) {
                out.push_back( decl.second );
        }

        if (Stats::Counters::enabled) {
                if (! lookups_by_name.count(id)) {
                        // leaks some strings, but it is because Counters do not hold them
                        auto lookupCounterName = new std::string(id + "%count");
                        auto candidatesCounterName = new std::string(id + "%candidate");
                        lookups_by_name.emplace(id, new Stats::Counters::SimpleCounter(lookupCounterName->c_str(), name_lookup_stats));
                        candidates_by_name.emplace(id, new Stats::Counters::SimpleCounter(candidatesCounterName->c_str(), name_lookup_stats));
                }
                (*lookups_by_name[id]) ++;
                *candidates_by_name[id] += out.size();
        }

        return out;
}

std::vector<SymbolTable::IdData> SymbolTable::lookupIdIgnoreHidden( const std::string &id ) const {
        std::vector<IdData> out;
        std::vector<IdData> lookupResult = lookupId(id);
        for ( auto candidate: lookupResult) {
                if ( candidate.id ) {
                        if (candidate.id->isHidden) continue;
                }
                out.push_back(candidate);
        }
        return out;
}

std::vector<SymbolTable::IdData> SymbolTable::specialLookupId( SymbolTable::SpecialFunctionKind kind, const std::string & otypeKey ) const {
        static Stats::Counters::CounterGroup * special_stats = Stats::Counters::build<Stats::Counters::CounterGroup>("Special Lookups");
        static Stats::Counters::SimpleCounter * stat_counts[3] = {
                Stats::Counters::build<Stats::Counters::SimpleCounter>("constructor - count", special_stats),
                Stats::Counters::build<Stats::Counters::SimpleCounter>("destructor - count", special_stats),
                Stats::Counters::build<Stats::Counters::SimpleCounter>("assignment - count", special_stats)
        };

        static Stats::Counters::SimpleCounter * stat_candidates[3] = {
                Stats::Counters::build<Stats::Counters::SimpleCounter>("constructor - candidates", special_stats),
                Stats::Counters::build<Stats::Counters::SimpleCounter>("destructor - candidates", special_stats),
                Stats::Counters::build<Stats::Counters::SimpleCounter>("assignment - candidates", special_stats)
        };

        static Stats::Counters::SimpleCounter * num_lookup_with_key 
                = Stats::Counters::build<Stats::Counters::SimpleCounter>("keyed lookups", special_stats);
        static Stats::Counters::SimpleCounter * num_lookup_without_key 
                = Stats::Counters::build<Stats::Counters::SimpleCounter>("unkeyed lookups", special_stats);

        assert (kind != NUMBER_OF_KINDS);
        ++*stats().lookup_calls;
        if ( ! specialFunctionTable[kind] ) return {};

        std::vector<IdData> out;

        if (otypeKey.empty()) { // returns everything
                ++*num_lookup_without_key;
                for (auto & table : *specialFunctionTable[kind]) {
                        for (auto & decl : *table.second) {
                                out.push_back(decl.second);
                        }
                }
        } else {
                ++*num_lookup_with_key;
                ++*stats().map_lookups;
                auto decls = specialFunctionTable[kind]->find(otypeKey);
                if (decls == specialFunctionTable[kind]->end()) return {};

                for (auto decl : *(decls->second)) {
                        out.push_back(decl.second);
                }
        }

        ++*stat_counts[kind];
        *stat_candidates[kind] += out.size();

        return out;
}

const NamedTypeDecl * SymbolTable::lookupType( const std::string &id ) const {
        ++*stats().lookup_calls;
        if ( ! typeTable ) return nullptr;
        ++*stats().map_lookups;
        auto it = typeTable->find( id );
        return it == typeTable->end() ? nullptr : it->second.decl;
}

const StructDecl * SymbolTable::lookupStruct( const std::string &id ) const {
        ++*stats().lookup_calls;
        if ( ! structTable ) return nullptr;
        ++*stats().map_lookups;
        auto it = structTable->find( id );
        return it == structTable->end() ? nullptr : it->second.decl;
}

const EnumDecl * SymbolTable::lookupEnum( const std::string &id ) const {
        ++*stats().lookup_calls;
        if ( ! enumTable ) return nullptr;
        ++*stats().map_lookups;
        auto it = enumTable->find( id );
        return it == enumTable->end() ? nullptr : it->second.decl;
}

const UnionDecl * SymbolTable::lookupUnion( const std::string &id ) const {
        ++*stats().lookup_calls;
        if ( ! unionTable ) return nullptr;
        ++*stats().map_lookups;
        auto it = unionTable->find( id );
        return it == unionTable->end() ? nullptr : it->second.decl;
}

const TraitDecl * SymbolTable::lookupTrait( const std::string &id ) const {
        ++*stats().lookup_calls;
        if ( ! traitTable ) return nullptr;
        ++*stats().map_lookups;
        auto it = traitTable->find( id );
        return it == traitTable->end() ? nullptr : it->second.decl;
}

const NamedTypeDecl * SymbolTable::globalLookupType( const std::string &id ) const {
        return atScope( 0 )->lookupType( id );
}

const StructDecl * SymbolTable::globalLookupStruct( const std::string &id ) const {
        return atScope( 0 )->lookupStruct( id );
}

const UnionDecl * SymbolTable::globalLookupUnion( const std::string &id ) const {
        return atScope( 0 )->lookupUnion( id );
}

const EnumDecl * SymbolTable::globalLookupEnum( const std::string &id ) const {
        return atScope( 0 )->lookupEnum( id );
}

void SymbolTable::addId( const DeclWithType * decl, const Expr * baseExpr ) {
        // default handling of conflicts is to raise an error
        addIdCommon( decl, OnConflict::error(), baseExpr, decl->isDeleted ? decl : nullptr );
}

void SymbolTable::addDeletedId( const DeclWithType * decl, const Decl * deleter ) {
        // default handling of conflicts is to raise an error
        addIdCommon( decl, OnConflict::error(), nullptr, deleter );
}

bool SymbolTable::addedTypeConflicts(
                const NamedTypeDecl * existing, const NamedTypeDecl * added ) const {
        if ( existing->base == nullptr ) {
                return false;
        } else if ( added->base == nullptr ) {
                return true;
        } else {
                // typedef redeclarations are errors only if types are different
                if ( ! ResolvExpr::typesCompatible( existing->base, added->base ) ) {
                        OnFindError( added->location, "redeclaration of " + added->name );
                }
        }
        // does not need to be added to the table if both existing and added have a base that are
        // the same
        return true;
}

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

void SymbolTable::addType( const NamedTypeDecl * decl ) {
        ++*stats().add_calls;
        const std::string &id = decl->name;

        if ( ! typeTable ) {
                typeTable = TypeTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto existing = typeTable->find( id );
                if ( existing != typeTable->end()
                        && existing->second.scope == scope
                        && addedTypeConflicts( existing->second.decl, decl ) ) return;
        }

        lazyInitScope();
        ++*stats().map_mutations;
        typeTable = typeTable->set( id, scoped<NamedTypeDecl>{ decl, scope } );
}

void SymbolTable::addStructId( const std::string &id ) {
        addStruct( new StructDecl( CodeLocation(), id ) );
}

void SymbolTable::addStruct( const StructDecl * decl ) {
        ++*stats().add_calls;
        const std::string &id = decl->name;

        if ( ! structTable ) {
                structTable = StructTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto existing = structTable->find( id );
                if ( existing != structTable->end()
                        && existing->second.scope == scope
                        && addedDeclConflicts( existing->second.decl, decl ) ) return;
        }

        lazyInitScope();
        ++*stats().map_mutations;
        structTable = structTable->set( id, scoped<StructDecl>{ decl, scope } );
}

void SymbolTable::addEnum( const EnumDecl *decl ) {
        ++*stats().add_calls;
        const std::string &id = decl->name;

        if ( ! enumTable ) {
                enumTable = EnumTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto existing = enumTable->find( id );
                if ( existing != enumTable->end()
                        && existing->second.scope == scope
                        && addedDeclConflicts( existing->second.decl, decl ) ) return;
        }

        lazyInitScope();
        ++*stats().map_mutations;
        enumTable = enumTable->set( id, scoped<EnumDecl>{ decl, scope } );
}

void SymbolTable::addUnionId( const std::string &id ) {
        addUnion( new UnionDecl( CodeLocation(), id ) );
}

void SymbolTable::addUnion( const UnionDecl * decl ) {
        ++*stats().add_calls;
        const std::string &id = decl->name;

        if ( ! unionTable ) {
                unionTable = UnionTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto existing = unionTable->find( id );
                if ( existing != unionTable->end()
                        && existing->second.scope == scope
                        && addedDeclConflicts( existing->second.decl, decl ) ) return;
        }

        lazyInitScope();
        ++*stats().map_mutations;
        unionTable = unionTable->set( id, scoped<UnionDecl>{ decl, scope } );
}

void SymbolTable::addTrait( const TraitDecl * decl ) {
        ++*stats().add_calls;
        const std::string &id = decl->name;

        if ( ! traitTable ) {
                traitTable = TraitTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto existing = traitTable->find( id );
                if ( existing != traitTable->end()
                        && existing->second.scope == scope
                        && addedDeclConflicts( existing->second.decl, decl ) ) return;
        }

        lazyInitScope();
        ++*stats().map_mutations;
        traitTable = traitTable->set( id, scoped<TraitDecl>{ decl, scope } );
}


void SymbolTable::addWith( const std::vector< ptr<Expr> > & withExprs, const Decl * withStmt ) {
        for ( const Expr * expr : withExprs ) {
                if ( ! expr->result ) continue;
                const Type * resTy = expr->result->stripReferences();
                auto aggrType = dynamic_cast< const BaseInstType * >( resTy );
                assertf( aggrType, "WithStmt expr has non-aggregate type: %s",
                        toString( expr->result ).c_str() );
                const AggregateDecl * aggr = aggrType->aggr();
                assertf( aggr, "WithStmt has null aggregate from type: %s",
                        toString( expr->result ).c_str() );

                addMembers( aggr, expr, OnConflict::deleteWith( withStmt ) );
        }
}

void SymbolTable::addIds( const std::vector< ptr<DeclWithType> > & decls ) {
        for ( const DeclWithType * decl : decls ) { addId( decl ); }
}

void SymbolTable::addTypes( const std::vector< ptr<TypeDecl> > & tds ) {
        for ( const TypeDecl * td : tds ) {
                addType( td );
                addIds( td->assertions );
        }
}


void SymbolTable::addFunction( const FunctionDecl * func ) {
        for (auto & td : func->type_params) {
                addType(td);
        }
        for (auto & asst : func->assertions) {
                addId(asst);
        }
        // addTypes( func->type->forall );
        addIds( func->returns );
        addIds( func->params );
}


void SymbolTable::lazyInitScope() {
        // do nothing if already in represented scope
        if ( repScope == scope ) return;

        ++*stats().lazy_scopes;
        // create rollback
        prevScope = std::make_shared<SymbolTable>( *this );
        // update repScope
        repScope = scope;
}

const ast::SymbolTable * SymbolTable::atScope( unsigned long target ) const {
        // by lazy construction, final symtab in list has repScope 0, cannot be > target
        // otherwise, will find first scope representing the target
        const SymbolTable * symtab = this;
        while ( symtab->repScope > target ) {
                symtab = symtab->prevScope.get();
        }
        return symtab;
}

namespace {
        /// gets the base type of the first parameter; decl must be a ctor/dtor/assignment function
        std::string getOtypeKey( const FunctionType * ftype, bool stripParams = true ) {
                const auto & params = ftype->params;
                assert( ! params.empty() );
                // use base type of pointer, so that qualifiers on the pointer type aren't considered.
                const Type * base = ast::getPointerBase( params.front() );
                assert( base );
                if (stripParams) {
                        if (dynamic_cast<const PointerType *>(base)) return Mangle::Encoding::pointer;
                        return Mangle::mangle( base, Mangle::Type | Mangle::NoGenericParams );
                } else {
                        return Mangle::mangle( base );
                }
        }

        /// gets the declaration for the function acting on a type specified by otype key,
        /// nullptr if none such
        const FunctionDecl * getFunctionForOtype(
                        const DeclWithType * decl, const std::string & otypeKey ) {
                auto func = dynamic_cast< const FunctionDecl * >( decl );
                if ( ! func || otypeKey != getOtypeKey( func->type, false ) ) return nullptr;
                return func;
        }
}

bool SymbolTable::removeSpecialOverrides(
                SymbolTable::IdData & data, SymbolTable::MangleTable::Ptr & mangleTable ) {
        // if a type contains user defined ctor/dtor/assign, then special rules trigger, which
        // determine the set of ctor/dtor/assign that can be used  by the requester. In particular,
        // if the user defines a default ctor, then the generated default ctor is unavailable,
        // likewise for copy ctor and dtor. If the user defines any ctor/dtor, then no generated
        // field ctors are available. If the user defines any ctor then the generated default ctor
        // is unavailable (intrinsic default ctor must be overridden exactly). If the user defines
        // anything that looks like a copy constructor, then the generated copy constructor is
        // unavailable, and likewise for the assignment operator.

        // only relevant on function declarations
        const FunctionDecl * function = data.id.as< FunctionDecl >();
        if ( ! function ) return true;
        // only need to perform this check for constructors, destructors, and assignment functions
        if ( ! CodeGen::isCtorDtorAssign( data.id->name ) ) return true;

        // set up information for this type
        bool dataIsUserDefinedFunc = ! function->linkage.is_overrideable;
        bool dataIsCopyFunc = InitTweak::isCopyFunction( function );
        std::string dataOtypeKey = getOtypeKey( function->type, false ); // requires exact match to override autogen

        if ( dataIsUserDefinedFunc && dataIsCopyFunc ) {
                // this is a user-defined copy function
                // if this is the first such, delete/remove non-user-defined overloads as needed
                std::vector< std::string > removed;
                std::vector< MangleTable::value_type > deleted;
                bool alreadyUserDefinedFunc = false;

                for ( const auto& entry : *mangleTable ) {
                        // skip decls that aren't functions or are for the wrong type
                        const FunctionDecl * decl = getFunctionForOtype( entry.second.id, dataOtypeKey );
                        if ( ! decl ) continue;

                        bool isCopyFunc = InitTweak::isCopyFunction( decl );
                        if ( ! decl->linkage.is_overrideable ) {
                                // matching user-defined function
                                if ( isCopyFunc ) {
                                        // mutation already performed, return early
                                        return true;
                                } else {
                                        // note that non-copy deletions already performed
                                        alreadyUserDefinedFunc = true;
                                }
                        } else {
                                // non-user-defined function; mark for deletion/removal as appropriate
                                if ( isCopyFunc ) {
                                        removed.push_back( entry.first );
                                } else if ( ! alreadyUserDefinedFunc ) {
                                        deleted.push_back( entry );
                                }
                        }
                }

                // perform removals from mangle table, and deletions if necessary
                for ( const auto& key : removed ) {
                        ++*stats().map_mutations;
                        mangleTable = mangleTable->erase( key );
                }
                if ( ! alreadyUserDefinedFunc ) for ( const auto& entry : deleted ) {
                        ++*stats().map_mutations;
                        mangleTable = mangleTable->set( entry.first, entry.second.withDeleter( function ) );
                }
        } else if ( dataIsUserDefinedFunc ) {
                // this is a user-defined non-copy function
                // if this is the first user-defined function, delete non-user-defined overloads
                std::vector< MangleTable::value_type > deleted;

                for ( const auto& entry : *mangleTable ) {
                        // skip decls that aren't functions or are for the wrong type
                        const FunctionDecl * decl = getFunctionForOtype( entry.second.id, dataOtypeKey );
                        if ( ! decl ) continue;

                        // exit early if already a matching user-defined function;
                        // earlier function will have mutated table
                        if ( ! decl->linkage.is_overrideable ) return true;

                        // skip mutating intrinsic functions
                        if ( decl->linkage == Linkage::Intrinsic ) continue;

                        // user-defined non-copy functions do not override copy functions
                        if ( InitTweak::isCopyFunction( decl ) ) continue;

                        // this function to be deleted after mangleTable iteration is complete
                        deleted.push_back( entry );
                }

                // mark deletions to update mangle table
                // this needs to be a separate loop because of iterator invalidation
                for ( const auto& entry : deleted ) {
                        ++*stats().map_mutations;
                        mangleTable = mangleTable->set( entry.first, entry.second.withDeleter( function ) );
                }
        } else if ( function->linkage != Linkage::Intrinsic ) {
                // this is an overridable generated function
                // if there already exists a matching user-defined function, delete this appropriately
                for ( const auto& entry : *mangleTable ) {
                        // skip decls that aren't functions or are for the wrong type
                        const FunctionDecl * decl = getFunctionForOtype( entry.second.id, dataOtypeKey );
                        if ( ! decl ) continue;

                        // skip non-user-defined functions
                        if ( decl->linkage.is_overrideable ) continue;

                        if ( dataIsCopyFunc ) {
                                // remove current function if exists a user-defined copy function
                                // since the signatures for copy functions don't need to match exactly, using
                                // a delete statement is the wrong approach
                                if ( InitTweak::isCopyFunction( decl ) ) return false;
                        } else {
                                // mark current function deleted by first user-defined function found
                                data.deleter = decl;
                                return true;
                        }
                }
        }

        // nothing (more) to fix, return true
        return true;
}

namespace {
        /// true iff the declaration represents a function
        bool isFunction( const DeclWithType * decl ) {
                return GenPoly::getFunctionType( decl->get_type() );
        }

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

        /// true if the declaration represents a definition instead of a forward decl
        bool isDefinition( const DeclWithType * decl ) {
                if ( auto func = dynamic_cast< const FunctionDecl * >( decl ) ) {
                        // a function is a definition if it has a body
                        return func->stmts;
                } else {
                        // an object is a definition if it is not marked extern
                        return ! decl->storage.is_extern;
                }
        }
}

bool SymbolTable::addedIdConflicts(
                const SymbolTable::IdData & existing, const DeclWithType * added,
                SymbolTable::OnConflict handleConflicts, const Decl * deleter ) {
        // if we're giving the same name mangling to things of different types then there is something
        // wrong
        assert( (isObject( added ) && isObject( existing.id ) )
                || ( isFunction( added ) && isFunction( existing.id ) ) );

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

                // it is a conflict if one declaration is deleted and the other is not
                if ( deleter && ! existing.deleter ) {
                        if ( handleConflicts.mode == OnConflict::Error ) {
                                OnFindError( added, "deletion of defined identifier " );
                        }
                        return true;
                } else if ( ! deleter && existing.deleter ) {
                        if ( handleConflicts.mode == OnConflict::Error ) {
                                OnFindError( added, "definition of deleted identifier " );
                        }
                        return true;
                }

                // it is a conflict if both declarations are definitions
                if ( isDefinition( added ) && isDefinition( existing.id ) ) {
                        if ( handleConflicts.mode == OnConflict::Error ) {
                                OnFindError( added,
                                        isFunction( added ) ?
                                                "duplicate function definition for " :
                                                "duplicate object definition for " );
                        }
                        return true;
                }
        } else {
                if ( handleConflicts.mode == OnConflict::Error ) {
                        OnFindError( added, "duplicate definition for " );
                }
                return true;
        }

        return true;
}

void SymbolTable::addIdCommon(
                const DeclWithType * decl, SymbolTable::OnConflict handleConflicts,
                const Expr * baseExpr, const Decl * deleter ) {
        SpecialFunctionKind kind = getSpecialFunctionKind(decl->name);
        if (kind == NUMBER_OF_KINDS) { // not a special decl
                addIdToTable(decl, decl->name, idTable, handleConflicts, baseExpr, deleter);
        } else {
                std::string key;
                if (auto func = dynamic_cast<const FunctionDecl *>(decl)) {
                        key = getOtypeKey(func->type);
                } else if (auto obj = dynamic_cast<const ObjectDecl *>(decl)) {
                        key = getOtypeKey(obj->type.strict_as<PointerType>()->base.strict_as<FunctionType>());
                } else {
                        assertf(false, "special decl with non-function type");
                }
                addIdToTable(decl, key, specialFunctionTable[kind], handleConflicts, baseExpr, deleter);
        }
}

void SymbolTable::addIdToTable(
                const DeclWithType * decl, const std::string & lookupKey,
                IdTable::Ptr & table, SymbolTable::OnConflict handleConflicts,
                const Expr * baseExpr, const Decl * deleter ) {
        ++*stats().add_calls;
        const std::string &name = decl->name;
        if ( name == "" ) return;

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

        // this ensures that no two declarations with the same unmangled name at the same scope
        // both have C linkage
        if ( decl->linkage.is_overloadable ) {
                // Check that a Cforall declaration doesn't override any C declaration
                if ( hasCompatibleCDecl( name, mangleName ) ) {
                        OnFindError( decl, "Cforall declaration hides C function " );
                }
        } else {
                // NOTE: only correct if name mangling is completely isomorphic to C
                // type-compatibility, which it may not be.
                if ( hasIncompatibleCDecl( name, mangleName ) ) {
                        OnFindError( decl, "conflicting overload of C function " );
                }
        }

        // ensure tables exist and add identifier
        MangleTable::Ptr mangleTable;
        if ( ! table ) {
                table = IdTable::new_ptr();
                mangleTable = MangleTable::new_ptr();
        } else {
                ++*stats().map_lookups;
                auto decls = table->find( lookupKey );
                if ( decls == table->end() ) {
                        mangleTable = MangleTable::new_ptr();
                } else {
                        mangleTable = decls->second;
                        // skip in-scope repeat declarations of same identifier
                        ++*stats().map_lookups;
                        auto existing = mangleTable->find( mangleName );
                        if ( existing != mangleTable->end()
                                        && existing->second.scope == scope
                                        && existing->second.id
                                        && addedIdConflicts( existing->second, decl, handleConflicts, deleter ) ) {
                                if ( handleConflicts.mode == OnConflict::Delete ) {
                                        // set delete expression for conflicting identifier
                                        lazyInitScope();
                                        *stats().map_mutations += 2;
                                        table = table->set(
                                                lookupKey,
                                                mangleTable->set(
                                                        mangleName,
                                                        existing->second.withDeleter( handleConflicts.deleter ) ) );
                                }
                                return;
                        }
                }
        }

        // add/overwrite with new identifier
        lazyInitScope();
        IdData data{ decl, baseExpr, deleter, scope };
        // Ensure that auto-generated ctor/dtor/assignment are deleted if necessary
        if (table != idTable) { // adding to special table
                if ( ! removeSpecialOverrides( data, mangleTable ) ) return;
        }
        *stats().map_mutations += 2;
        table = table->set( lookupKey, mangleTable->set( mangleName, std::move(data) ) );
}

void SymbolTable::addMembers(
                const AggregateDecl * aggr, const Expr * expr, SymbolTable::OnConflict handleConflicts ) {
        for ( const ptr<Decl> & decl : aggr->members ) {
                auto dwt = decl.as<DeclWithType>();
                if ( nullptr == dwt ) continue;
                addIdCommon( dwt, handleConflicts, expr );
                // Inline through unnamed struct/union members.
                if ( "" != dwt->name ) continue;
                const Type * t = dwt->get_type()->stripReferences();
                if ( auto rty = dynamic_cast<const BaseInstType *>( t ) ) {
                        if ( ! dynamic_cast<const StructInstType *>(rty)
                                && ! dynamic_cast<const UnionInstType *>(rty) ) continue;
                        ResolvExpr::Cost cost = ResolvExpr::Cost::zero;
                        ast::ptr<ast::TypeSubstitution> tmp = expr->env;
                        expr = mutate_field(expr, &Expr::env, nullptr);
                        const Expr * base = ResolvExpr::referenceToRvalueConversion( expr, cost );
                        base = mutate_field(base, &Expr::env, tmp);

                        addMembers(
                                rty->aggr(), new MemberExpr{ base->location, dwt, base }, handleConflicts );
                }
        }
}

bool SymbolTable::hasCompatibleCDecl( const std::string &id, const std::string &mangleName ) const {
        if ( ! idTable ) return false;

        ++*stats().map_lookups;
        auto decls = idTable->find( id );
        if ( decls == idTable->end() ) return false;

        for ( auto decl : *(decls->second) ) {
                // skip other scopes (hidden by this decl)
                if ( decl.second.scope != scope ) continue;
                // check for C decl with compatible type (by mangleName)
                if ( !decl.second.id->linkage.is_overloadable && decl.first == mangleName ) return true;
        }

        return false;
}

bool SymbolTable::hasIncompatibleCDecl( const std::string &id, const std::string &mangleName ) const {
        if ( ! idTable ) return false;

        ++*stats().map_lookups;
        auto decls = idTable->find( id );
        if ( decls == idTable->end() ) return false;

        for ( auto decl : *(decls->second) ) {
                // skip other scopes (hidden by this decl)
                if ( decl.second.scope != scope ) continue;
                // check for C decl with incompatible type (by manglename)
                if ( !decl.second.id->linkage.is_overloadable && decl.first != mangleName ) return true;
        }

        return false;
}

}

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