source: src/SymTab/Validate.cc@ 6ac5223

//
// 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.
//
// Validate.cc --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 21:50:04 2015
// Last Modified By : Andrew Beach
// Last Modified On : Tus Aug  8 13:27:00 2017
// Update Count     : 358
//

// The "validate" phase of translation is used to take a syntax tree and convert it into a standard form that aims to be
// as regular in structure as possible.  Some assumptions can be made regarding the state of the tree after this pass is
// complete, including:
//
// - No nested structure or union definitions; any in the input are "hoisted" to the level of the containing struct or
//   union.
//
// - All enumeration constants have type EnumInstType.
//
// - The type "void" never occurs in lists of function parameter or return types.  A function
//   taking no arguments has no argument types.
//
// - No context instances exist; they are all replaced by the set of declarations signified by the context, instantiated
//   by the particular set of type arguments.
//
// - Every declaration is assigned a unique id.
//
// - No typedef declarations or instances exist; the actual type is substituted for each instance.
//
// - Each type, struct, and union definition is followed by an appropriate assignment operator.
//
// - Each use of a struct or union is connected to a complete definition of that struct or union, even if that
//   definition occurs later in the input.

#include "Validate.h"

#include <cassert>                     // for assertf, assert
#include <cstddef>                     // for size_t
#include <list>                        // for list
#include <string>                      // for string
#include <utility>                     // for pair

#include "CodeGen/CodeGenerator.h"     // for genName
#include "Common/PassVisitor.h"        // for PassVisitor, WithDeclsToAdd
#include "Common/ScopedMap.h"          // for ScopedMap
#include "Common/SemanticError.h"      // for SemanticError
#include "Common/UniqueName.h"         // for UniqueName
#include "Common/utility.h"            // for operator+, cloneAll, deleteAll
#include "Concurrency/Keywords.h"      // for applyKeywords
#include "FixFunction.h"               // for FixFunction
#include "Indexer.h"                   // for Indexer
#include "InitTweak/InitTweak.h"       // for isCtorDtorAssign
#include "Parser/LinkageSpec.h"        // for C
#include "ResolvExpr/typeops.h"        // for typesCompatible
#include "SymTab/AddVisit.h"           // for addVisit
#include "SymTab/Autogen.h"            // for SizeType
#include "SynTree/Attribute.h"         // for noAttributes, Attribute
#include "SynTree/Constant.h"          // for Constant
#include "SynTree/Declaration.h"       // for ObjectDecl, DeclarationWithType
#include "SynTree/Expression.h"        // for CompoundLiteralExpr, Expressio...
#include "SynTree/Initializer.h"       // for ListInit, Initializer
#include "SynTree/Label.h"             // for operator==, Label
#include "SynTree/Mutator.h"           // for Mutator
#include "SynTree/Type.h"              // for Type, TypeInstType, EnumInstType
#include "SynTree/TypeSubstitution.h"  // for TypeSubstitution
#include "SynTree/Visitor.h"           // for Visitor

class CompoundStmt;
class ReturnStmt;
class SwitchStmt;


#define debugPrint( x ) if ( doDebug ) { std::cout << x; }

namespace SymTab {
        class HoistStruct final : public Visitor {
                template< typename Visitor >
                friend void acceptAndAdd( std::list< Declaration * > &translationUnit, Visitor &visitor );
            template< typename Visitor >
            friend void addVisitStatementList( std::list< Statement* > &stmts, Visitor &visitor );
          public:
                /// Flattens nested struct types
                static void hoistStruct( std::list< Declaration * > &translationUnit );

                std::list< Declaration * > &get_declsToAdd() { return declsToAdd; }

                virtual void visit( EnumInstType *enumInstType );
                virtual void visit( StructInstType *structInstType );
                virtual void visit( UnionInstType *unionInstType );
                virtual void visit( StructDecl *aggregateDecl );
                virtual void visit( UnionDecl *aggregateDecl );

                virtual void visit( CompoundStmt *compoundStmt );
                virtual void visit( SwitchStmt *switchStmt );
          private:
                HoistStruct();

                template< typename AggDecl > void handleAggregate( AggDecl *aggregateDecl );

                std::list< Declaration * > declsToAdd, declsToAddAfter;
                bool inStruct;
        };

        /// Fix return types so that every function returns exactly one value
        struct ReturnTypeFixer {
                static void fix( std::list< Declaration * > &translationUnit );

                void postvisit( FunctionDecl * functionDecl );
                void postvisit( FunctionType * ftype );
        };

        /// Replaces enum types by int, and function or array types in function parameter and return lists by appropriate pointers.
        struct EnumAndPointerDecay {
                void previsit( EnumDecl *aggregateDecl );
                void previsit( FunctionType *func );
        };

        /// Associates forward declarations of aggregates with their definitions
        class LinkReferenceToTypes final : public Indexer {
                typedef Indexer Parent;
          public:
                LinkReferenceToTypes( bool doDebug, const Indexer *indexer );
                using Parent::visit;
                void visit( EnumInstType *enumInst ) final;
                void visit( StructInstType *structInst ) final;
                void visit( UnionInstType *unionInst ) final;
                void visit( TraitInstType *contextInst ) final;
                void visit( EnumDecl *enumDecl ) final;
                void visit( StructDecl *structDecl ) final;
                void visit( UnionDecl *unionDecl ) final;
                void visit( TypeInstType *typeInst ) final;
          private:
                const Indexer *indexer;

                typedef std::map< std::string, std::list< EnumInstType * > > ForwardEnumsType;
                typedef std::map< std::string, std::list< StructInstType * > > ForwardStructsType;
                typedef std::map< std::string, std::list< UnionInstType * > > ForwardUnionsType;
                ForwardEnumsType forwardEnums;
                ForwardStructsType forwardStructs;
                ForwardUnionsType forwardUnions;
        };

        /// Replaces array and function types in forall lists by appropriate pointer type and assigns each Object and Function declaration a unique ID.
        class ForallPointerDecay final : public Indexer {
                typedef Indexer Parent;
          public:
                using Parent::visit;
                ForallPointerDecay( const Indexer *indexer );

                virtual void visit( ObjectDecl *object ) override;
                virtual void visit( FunctionDecl *func ) override;

                const Indexer *indexer;
        };

        struct ReturnChecker : public WithGuards {
                /// Checks that return statements return nothing if their return type is void
                /// and return something if the return type is non-void.
                static void checkFunctionReturns( std::list< Declaration * > & translationUnit );

                void previsit( FunctionDecl * functionDecl );
                void previsit( ReturnStmt * returnStmt );

                typedef std::list< DeclarationWithType * > ReturnVals;
                ReturnVals returnVals;
        };

        class EliminateTypedef : public Mutator {
          public:
                EliminateTypedef() : scopeLevel( 0 ) {}
                /// Replaces typedefs by forward declarations
                static void eliminateTypedef( std::list< Declaration * > &translationUnit );
          private:
                virtual Declaration *mutate( TypedefDecl *typeDecl );
                virtual TypeDecl *mutate( TypeDecl *typeDecl );
                virtual DeclarationWithType *mutate( FunctionDecl *funcDecl );
                virtual DeclarationWithType *mutate( ObjectDecl *objDecl );
                virtual CompoundStmt *mutate( CompoundStmt *compoundStmt );
                virtual Type *mutate( TypeInstType *aggregateUseType );
                virtual Expression *mutate( CastExpr *castExpr );

                virtual Declaration *mutate( StructDecl * structDecl );
                virtual Declaration *mutate( UnionDecl * unionDecl );
                virtual Declaration *mutate( EnumDecl * enumDecl );
                virtual Declaration *mutate( TraitDecl * contextDecl );

                template<typename AggDecl>
                AggDecl *handleAggregate( AggDecl * aggDecl );

                template<typename AggDecl>
                void addImplicitTypedef( AggDecl * aggDecl );

                typedef std::unique_ptr<TypedefDecl> TypedefDeclPtr;
                typedef ScopedMap< std::string, std::pair< TypedefDeclPtr, int > > TypedefMap;
                typedef std::map< std::string, TypeDecl * > TypeDeclMap;
                TypedefMap typedefNames;
                TypeDeclMap typedeclNames;
                int scopeLevel;
        };

        struct VerifyCtorDtorAssign {
                /// ensure that constructors, destructors, and assignment have at least one
                /// parameter, the first of which must be a pointer, and that ctor/dtors have no
                /// return values.
                static void verify( std::list< Declaration * > &translationUnit );

                void previsit( FunctionDecl *funcDecl );
        };

        /// ensure that generic types have the correct number of type arguments
        struct ValidateGenericParameters {
                void previsit( StructInstType * inst );
                void previsit( UnionInstType * inst );
        };

        struct ArrayLength {
                /// for array types without an explicit length, compute the length and store it so that it
                /// is known to the rest of the phases. For example,
                ///   int x[] = { 1, 2, 3 };
                ///   int y[][2] = { { 1, 2, 3 }, { 1, 2, 3 } };
                /// here x and y are known at compile-time to have length 3, so change this into
                ///   int x[3] = { 1, 2, 3 };
                ///   int y[3][2] = { { 1, 2, 3 }, { 1, 2, 3 } };
                static void computeLength( std::list< Declaration * > & translationUnit );

                void previsit( ObjectDecl * objDecl );
        };

        struct CompoundLiteral final : public WithDeclsToAdd, public WithVisitorRef<CompoundLiteral> {
                Type::StorageClasses storageClasses;

                void premutate( ObjectDecl *objectDecl );
                Expression * postmutate( CompoundLiteralExpr *compLitExpr );
        };

        void validate( std::list< Declaration * > &translationUnit, bool doDebug ) {
                PassVisitor<EnumAndPointerDecay> epc;
                LinkReferenceToTypes lrt( doDebug, 0 );
                ForallPointerDecay fpd( 0 );
                PassVisitor<CompoundLiteral> compoundliteral;
                PassVisitor<ValidateGenericParameters> genericParams;

                EliminateTypedef::eliminateTypedef( translationUnit );
                HoistStruct::hoistStruct( translationUnit ); // must happen after EliminateTypedef, so that aggregate typedefs occur in the correct order
                ReturnTypeFixer::fix( translationUnit ); // must happen before autogen
                acceptAll( translationUnit, lrt ); // must happen before autogen, because sized flag needs to propagate to generated functions
                acceptAll( translationUnit, genericParams );  // check as early as possible - can't happen before LinkReferenceToTypes
                acceptAll( translationUnit, epc ); // must happen before VerifyCtorDtorAssign, because void return objects should not exist
                VerifyCtorDtorAssign::verify( translationUnit );  // must happen before autogen, because autogen examines existing ctor/dtors
                Concurrency::applyKeywords( translationUnit );
                autogenerateRoutines( translationUnit ); // moved up, used to be below compoundLiteral - currently needs EnumAndPointerDecay
                Concurrency::implementMutexFuncs( translationUnit );
                Concurrency::implementThreadStarter( translationUnit );
                ReturnChecker::checkFunctionReturns( translationUnit );
                mutateAll( translationUnit, compoundliteral );
                acceptAll( translationUnit, fpd );
                ArrayLength::computeLength( translationUnit );
        }

        void validateType( Type *type, const Indexer *indexer ) {
                PassVisitor<EnumAndPointerDecay> epc;
                LinkReferenceToTypes lrt( false, indexer );
                ForallPointerDecay fpd( indexer );
                type->accept( epc );
                type->accept( lrt );
                type->accept( fpd );
        }

        void HoistStruct::hoistStruct( std::list< Declaration * > &translationUnit ) {
                HoistStruct hoister;
                acceptAndAdd( translationUnit, hoister );
        }

        HoistStruct::HoistStruct() : inStruct( false ) {
        }

        void filter( std::list< Declaration * > &declList, bool (*pred)( Declaration * ), bool doDelete ) {
                std::list< Declaration * >::iterator i = declList.begin();
                while ( i != declList.end() ) {
                        std::list< Declaration * >::iterator next = i;
                        ++next;
                        if ( pred( *i ) ) {
                                if ( doDelete ) {
                                        delete *i;
                                } // if
                                declList.erase( i );
                        } // if
                        i = next;
                } // while
        }

        bool isStructOrUnion( Declaration *decl ) {
                return dynamic_cast< StructDecl * >( decl ) || dynamic_cast< UnionDecl * >( decl );
        }

        template< typename AggDecl >
        void HoistStruct::handleAggregate( AggDecl *aggregateDecl ) {
                if ( inStruct ) {
                        // Add elements in stack order corresponding to nesting structure.
                        declsToAdd.push_front( aggregateDecl );
                        Visitor::visit( aggregateDecl );
                } else {
                        inStruct = true;
                        Visitor::visit( aggregateDecl );
                        inStruct = false;
                } // if
                // Always remove the hoisted aggregate from the inner structure.
                filter( aggregateDecl->get_members(), isStructOrUnion, false );
        }

        void HoistStruct::visit( EnumInstType *structInstType ) {
                if ( structInstType->get_baseEnum() ) {
                        declsToAdd.push_front( structInstType->get_baseEnum() );
                }
        }

        void HoistStruct::visit( StructInstType *structInstType ) {
                if ( structInstType->get_baseStruct() ) {
                        declsToAdd.push_front( structInstType->get_baseStruct() );
                }
        }

        void HoistStruct::visit( UnionInstType *structInstType ) {
                if ( structInstType->get_baseUnion() ) {
                        declsToAdd.push_front( structInstType->get_baseUnion() );
                }
        }

        void HoistStruct::visit( StructDecl *aggregateDecl ) {
                handleAggregate( aggregateDecl );
        }

        void HoistStruct::visit( UnionDecl *aggregateDecl ) {
                handleAggregate( aggregateDecl );
        }

        void HoistStruct::visit( CompoundStmt *compoundStmt ) {
                addVisit( compoundStmt, *this );
        }

        void HoistStruct::visit( SwitchStmt *switchStmt ) {
                addVisit( switchStmt, *this );
        }

        void EnumAndPointerDecay::previsit( EnumDecl *enumDecl ) {
                // Set the type of each member of the enumeration to be EnumConstant
                for ( std::list< Declaration * >::iterator i = enumDecl->get_members().begin(); i != enumDecl->get_members().end(); ++i ) {
                        ObjectDecl * obj = dynamic_cast< ObjectDecl * >( *i );
                        assert( obj );
                        obj->set_type( new EnumInstType( Type::Qualifiers( Type::Const ), enumDecl->get_name() ) );
                } // for
        }

        namespace {
                template< typename DWTList >
                void fixFunctionList( DWTList & dwts, FunctionType * func ) {
                        // the only case in which "void" is valid is where it is the only one in the list; then it should be removed
                        // entirely. other fix ups are handled by the FixFunction class
                        typedef typename DWTList::iterator DWTIterator;
                        DWTIterator begin( dwts.begin() ), end( dwts.end() );
                        if ( begin == end ) return;
                        FixFunction fixer;
                        DWTIterator i = begin;
                        *i = (*i)->acceptMutator( fixer );
                        if ( fixer.get_isVoid() ) {
                                DWTIterator j = i;
                                ++i;
                                delete *j;
                                dwts.erase( j );
                                if ( i != end ) {
                                        throw SemanticError( "invalid type void in function type ", func );
                                } // if
                        } else {
                                ++i;
                                for ( ; i != end; ++i ) {
                                        FixFunction fixer;
                                        *i = (*i)->acceptMutator( fixer );
                                        if ( fixer.get_isVoid() ) {
                                                throw SemanticError( "invalid type void in function type ", func );
                                        } // if
                                } // for
                        } // if
                }
        }

        void EnumAndPointerDecay::previsit( FunctionType *func ) {
                // Fix up parameters and return types
                fixFunctionList( func->get_parameters(), func );
                fixFunctionList( func->get_returnVals(), func );
        }

        LinkReferenceToTypes::LinkReferenceToTypes( bool doDebug, const Indexer *other_indexer ) : Indexer( doDebug ) {
                if ( other_indexer ) {
                        indexer = other_indexer;
                } else {
                        indexer = this;
                } // if
        }

        void LinkReferenceToTypes::visit( EnumInstType *enumInst ) {
                Parent::visit( enumInst );
                EnumDecl *st = indexer->lookupEnum( enumInst->get_name() );
                // it's not a semantic error if the enum is not found, just an implicit forward declaration
                if ( st ) {
                        //assert( ! enumInst->get_baseEnum() || enumInst->get_baseEnum()->get_members().empty() || ! st->get_members().empty() );
                        enumInst->set_baseEnum( st );
                } // if
                if ( ! st || st->get_members().empty() ) {
                        // use of forward declaration
                        forwardEnums[ enumInst->get_name() ].push_back( enumInst );
                } // if
        }

        void LinkReferenceToTypes::visit( StructInstType *structInst ) {
                Parent::visit( structInst );
                StructDecl *st = indexer->lookupStruct( structInst->get_name() );
                // it's not a semantic error if the struct is not found, just an implicit forward declaration
                if ( st ) {
                        //assert( ! structInst->get_baseStruct() || structInst->get_baseStruct()->get_members().empty() || ! st->get_members().empty() );
                        structInst->set_baseStruct( st );
                } // if
                if ( ! st || st->get_members().empty() ) {
                        // use of forward declaration
                        forwardStructs[ structInst->get_name() ].push_back( structInst );
                } // if
        }

        void LinkReferenceToTypes::visit( UnionInstType *unionInst ) {
                Parent::visit( unionInst );
                UnionDecl *un = indexer->lookupUnion( unionInst->get_name() );
                // it's not a semantic error if the union is not found, just an implicit forward declaration
                if ( un ) {
                        unionInst->set_baseUnion( un );
                } // if
                if ( ! un || un->get_members().empty() ) {
                        // use of forward declaration
                        forwardUnions[ unionInst->get_name() ].push_back( unionInst );
                } // if
        }

        void LinkReferenceToTypes::visit( TraitInstType *traitInst ) {
                Parent::visit( traitInst );
                if ( traitInst->get_name() == "sized" ) {
                        // "sized" is a special trait with no members - just flick the sized status on for the type variable
                        if ( traitInst->get_parameters().size() != 1 ) {
                                throw SemanticError( "incorrect number of trait parameters: ", traitInst );
                        }
                        TypeExpr * param = safe_dynamic_cast< TypeExpr * > ( traitInst->get_parameters().front() );
                        TypeInstType * inst = safe_dynamic_cast< TypeInstType * > ( param->get_type() );
                        TypeDecl * decl = inst->get_baseType();
                        decl->set_sized( true );
                        // since "sized" is special, the next few steps don't apply
                        return;
                }
                TraitDecl *traitDecl = indexer->lookupTrait( traitInst->get_name() );
                if ( ! traitDecl ) {
                        throw SemanticError( "use of undeclared trait " + traitInst->get_name() );
                } // if
                if ( traitDecl->get_parameters().size() != traitInst->get_parameters().size() ) {
                        throw SemanticError( "incorrect number of trait parameters: ", traitInst );
                } // if

                for ( TypeDecl * td : traitDecl->get_parameters() ) {
                        for ( DeclarationWithType * assert : td->get_assertions() ) {
                                traitInst->get_members().push_back( assert->clone() );
                        } // for
                } // for

                // need to clone members of the trait for ownership purposes
                std::list< Declaration * > members;
                std::transform( traitDecl->get_members().begin(), traitDecl->get_members().end(), back_inserter( members ), [](Declaration * dwt) { return dwt->clone(); } );

                applySubstitution( traitDecl->get_parameters().begin(), traitDecl->get_parameters().end(), traitInst->get_parameters().begin(), members.begin(), members.end(), back_inserter( traitInst->get_members() ) );

                // need to carry over the 'sized' status of each decl in the instance
                for ( auto p : group_iterate( traitDecl->get_parameters(), traitInst->get_parameters() ) ) {
                        TypeExpr * expr = safe_dynamic_cast< TypeExpr * >( std::get<1>(p) );
                        if ( TypeInstType * inst = dynamic_cast< TypeInstType * >( expr->get_type() ) ) {
                                TypeDecl * formalDecl = std::get<0>(p);
                                TypeDecl * instDecl = inst->get_baseType();
                                if ( formalDecl->get_sized() ) instDecl->set_sized( true );
                        }
                }
        }

        void LinkReferenceToTypes::visit( EnumDecl *enumDecl ) {
                // visit enum members first so that the types of self-referencing members are updated properly
                Parent::visit( enumDecl );
                if ( ! enumDecl->get_members().empty() ) {
                        ForwardEnumsType::iterator fwds = forwardEnums.find( enumDecl->get_name() );
                        if ( fwds != forwardEnums.end() ) {
                                for ( std::list< EnumInstType * >::iterator inst = fwds->second.begin(); inst != fwds->second.end(); ++inst ) {
                                        (*inst )->set_baseEnum( enumDecl );
                                } // for
                                forwardEnums.erase( fwds );
                        } // if
                } // if
        }

        void LinkReferenceToTypes::visit( StructDecl *structDecl ) {
                // visit struct members first so that the types of self-referencing members are updated properly
                // xxx - need to ensure that type parameters match up between forward declarations and definition (most importantly, number of type parameters and and their defaults)
                Parent::visit( structDecl );
                if ( ! structDecl->get_members().empty() ) {
                        ForwardStructsType::iterator fwds = forwardStructs.find( structDecl->get_name() );
                        if ( fwds != forwardStructs.end() ) {
                                for ( std::list< StructInstType * >::iterator inst = fwds->second.begin(); inst != fwds->second.end(); ++inst ) {
                                        (*inst )->set_baseStruct( structDecl );
                                } // for
                                forwardStructs.erase( fwds );
                        } // if
                } // if
        }

        void LinkReferenceToTypes::visit( UnionDecl *unionDecl ) {
                Parent::visit( unionDecl );
                if ( ! unionDecl->get_members().empty() ) {
                        ForwardUnionsType::iterator fwds = forwardUnions.find( unionDecl->get_name() );
                        if ( fwds != forwardUnions.end() ) {
                                for ( std::list< UnionInstType * >::iterator inst = fwds->second.begin(); inst != fwds->second.end(); ++inst ) {
                                        (*inst )->set_baseUnion( unionDecl );
                                } // for
                                forwardUnions.erase( fwds );
                        } // if
                } // if
        }

        void LinkReferenceToTypes::visit( TypeInstType *typeInst ) {
                if ( NamedTypeDecl *namedTypeDecl = lookupType( typeInst->get_name() ) ) {
                        if ( TypeDecl *typeDecl = dynamic_cast< TypeDecl * >( namedTypeDecl ) ) {
                                typeInst->set_isFtype( typeDecl->get_kind() == TypeDecl::Ftype );
                        } // if
                } // if
        }

        ForallPointerDecay::ForallPointerDecay( const Indexer *other_indexer ) :  Indexer( false ) {
                if ( other_indexer ) {
                        indexer = other_indexer;
                } else {
                        indexer = this;
                } // if
        }

        /// Fix up assertions - flattens assertion lists, removing all trait instances
        void forallFixer( Type * func ) {
                for ( TypeDecl * type : func->get_forall() ) {
                        std::list< DeclarationWithType * > toBeDone, nextRound;
                        toBeDone.splice( toBeDone.end(), type->get_assertions() );
                        while ( ! toBeDone.empty() ) {
                                for ( DeclarationWithType * assertion : toBeDone ) {
                                        if ( TraitInstType *traitInst = dynamic_cast< TraitInstType * >( assertion->get_type() ) ) {
                                                // expand trait instance into all of its members
                                                for ( Declaration * member : traitInst->get_members() ) {
                                                        DeclarationWithType *dwt = safe_dynamic_cast< DeclarationWithType * >( member );
                                                        nextRound.push_back( dwt->clone() );
                                                }
                                                delete traitInst;
                                        } else {
                                                // pass assertion through
                                                FixFunction fixer;
                                                assertion = assertion->acceptMutator( fixer );
                                                if ( fixer.get_isVoid() ) {
                                                        throw SemanticError( "invalid type void in assertion of function ", func );
                                                }
                                                type->get_assertions().push_back( assertion );
                                        } // if
                                } // for
                                toBeDone.clear();
                                toBeDone.splice( toBeDone.end(), nextRound );
                        } // while
                } // for
        }

        void ForallPointerDecay::visit( ObjectDecl *object ) {
                forallFixer( object->get_type() );
                if ( PointerType *pointer = dynamic_cast< PointerType * >( object->get_type() ) ) {
                        forallFixer( pointer->get_base() );
                } // if
                Parent::visit( object );
                object->fixUniqueId();
        }

        void ForallPointerDecay::visit( FunctionDecl *func ) {
                forallFixer( func->get_type() );
                Parent::visit( func );
                func->fixUniqueId();
        }

        void ReturnChecker::checkFunctionReturns( std::list< Declaration * > & translationUnit ) {
                PassVisitor<ReturnChecker> checker;
                acceptAll( translationUnit, checker );
        }

        void ReturnChecker::previsit( FunctionDecl * functionDecl ) {
                GuardValue( returnVals );
                returnVals = functionDecl->get_functionType()->get_returnVals();
        }

        void ReturnChecker::previsit( ReturnStmt * returnStmt ) {
                // Previously this also checked for the existence of an expr paired with no return values on
                // the  function return type. This is incorrect, since you can have an expression attached to
                // a return statement in a void-returning function in C. The expression is treated as if it
                // were cast to void.
                if ( ! returnStmt->get_expr() && returnVals.size() != 0 ) {
                        throw SemanticError( "Non-void function returns no values: " , returnStmt );
                }
        }


        bool isTypedef( Declaration *decl ) {
                return dynamic_cast< TypedefDecl * >( decl );
        }

        void EliminateTypedef::eliminateTypedef( std::list< Declaration * > &translationUnit ) {
                EliminateTypedef eliminator;
                mutateAll( translationUnit, eliminator );
                if ( eliminator.typedefNames.count( "size_t" ) ) {
                        // grab and remember declaration of size_t
                        SizeType = eliminator.typedefNames["size_t"].first->get_base()->clone();
                } else {
                        // xxx - missing global typedef for size_t - default to long unsigned int, even though that may be wrong
                        // eventually should have a warning for this case.
                        SizeType = new BasicType( Type::Qualifiers(), BasicType::LongUnsignedInt );
                }
                filter( translationUnit, isTypedef, true );

        }

        Type *EliminateTypedef::mutate( TypeInstType * typeInst ) {
                // instances of typedef types will come here. If it is an instance
                // of a typdef type, link the instance to its actual type.
                TypedefMap::const_iterator def = typedefNames.find( typeInst->get_name() );
                if ( def != typedefNames.end() ) {
                        Type *ret = def->second.first->get_base()->clone();
                        ret->get_qualifiers() |= typeInst->get_qualifiers();
                        // place instance parameters on the typedef'd type
                        if ( ! typeInst->get_parameters().empty() ) {
                                ReferenceToType *rtt = dynamic_cast<ReferenceToType*>(ret);
                                if ( ! rtt ) {
                                        throw SemanticError("cannot apply type parameters to base type of " + typeInst->get_name());
                                }
                                rtt->get_parameters().clear();
                                cloneAll( typeInst->get_parameters(), rtt->get_parameters() );
                                mutateAll( rtt->get_parameters(), *this );  // recursively fix typedefs on parameters
                        } // if
                        delete typeInst;
                        return ret;
                } else {
                        TypeDeclMap::const_iterator base = typedeclNames.find( typeInst->get_name() );
                        assertf( base != typedeclNames.end(), "Can't find typedecl name %s", typeInst->get_name().c_str() );
                        typeInst->set_baseType( base->second );
                } // if
                return typeInst;
        }

        Declaration *EliminateTypedef::mutate( TypedefDecl * tyDecl ) {
                Declaration *ret = Mutator::mutate( tyDecl );

                if ( typedefNames.count( tyDecl->get_name() ) == 1 && typedefNames[ tyDecl->get_name() ].second == scopeLevel ) {
                        // typedef to the same name from the same scope
                        // must be from the same type

                        Type * t1 = tyDecl->get_base();
                        Type * t2 = typedefNames[ tyDecl->get_name() ].first->get_base();
                        if ( ! ResolvExpr::typesCompatible( t1, t2, Indexer() ) ) {
                                throw SemanticError( "cannot redefine typedef: " + tyDecl->get_name() );
                        }
                } else {
                        typedefNames[ tyDecl->get_name() ] = std::make_pair( TypedefDeclPtr( tyDecl ), scopeLevel );
                } // if

                // When a typedef is a forward declaration:
                //    typedef struct screen SCREEN;
                // the declaration portion must be retained:
                //    struct screen;
                // because the expansion of the typedef is:
                //    void rtn( SCREEN *p ) => void rtn( struct screen *p )
                // hence the type-name "screen" must be defined.
                // Note, qualifiers on the typedef are superfluous for the forward declaration.

                Type *designatorType = tyDecl->get_base()->stripDeclarator();
                if ( StructInstType *aggDecl = dynamic_cast< StructInstType * >( designatorType ) ) {
                        return new StructDecl( aggDecl->get_name(), DeclarationNode::Struct, noAttributes, tyDecl->get_linkage() );
                } else if ( UnionInstType *aggDecl = dynamic_cast< UnionInstType * >( designatorType ) ) {
                        return new UnionDecl( aggDecl->get_name(), noAttributes, tyDecl->get_linkage() );
                } else if ( EnumInstType *enumDecl = dynamic_cast< EnumInstType * >( designatorType ) ) {
                        return new EnumDecl( enumDecl->get_name(), noAttributes, tyDecl->get_linkage() );
                } else {
                        return ret->clone();
                } // if
        }

        TypeDecl *EliminateTypedef::mutate( TypeDecl * typeDecl ) {
                TypedefMap::iterator i = typedefNames.find( typeDecl->get_name() );
                if ( i != typedefNames.end() ) {
                        typedefNames.erase( i ) ;
                } // if

                typedeclNames[ typeDecl->get_name() ] = typeDecl;
                return Mutator::mutate( typeDecl );
        }

        DeclarationWithType *EliminateTypedef::mutate( FunctionDecl * funcDecl ) {
                typedefNames.beginScope();
                DeclarationWithType *ret = Mutator::mutate( funcDecl );
                typedefNames.endScope();
                return ret;
        }

        DeclarationWithType *EliminateTypedef::mutate( ObjectDecl * objDecl ) {
                typedefNames.beginScope();
                DeclarationWithType *ret = Mutator::mutate( objDecl );
                typedefNames.endScope();

                if ( FunctionType *funtype = dynamic_cast<FunctionType *>( ret->get_type() ) ) { // function type?
                        // replace the current object declaration with a function declaration
                        FunctionDecl * newDecl = new FunctionDecl( ret->get_name(), ret->get_storageClasses(), ret->get_linkage(), funtype, 0, objDecl->get_attributes(), ret->get_funcSpec() );
                        objDecl->get_attributes().clear();
                        objDecl->set_type( nullptr );
                        delete objDecl;
                        return newDecl;
                } // if
                return ret;
        }

        Expression *EliminateTypedef::mutate( CastExpr * castExpr ) {
                typedefNames.beginScope();
                Expression *ret = Mutator::mutate( castExpr );
                typedefNames.endScope();
                return ret;
        }

        CompoundStmt *EliminateTypedef::mutate( CompoundStmt * compoundStmt ) {
                typedefNames.beginScope();
                scopeLevel += 1;
                CompoundStmt *ret = Mutator::mutate( compoundStmt );
                scopeLevel -= 1;
                std::list< Statement * >::iterator i = compoundStmt->get_kids().begin();
                while ( i != compoundStmt->get_kids().end() ) {
                        std::list< Statement * >::iterator next = i+1;
                        if ( DeclStmt *declStmt = dynamic_cast< DeclStmt * >( *i ) ) {
                                if ( dynamic_cast< TypedefDecl * >( declStmt->get_decl() ) ) {
                                        delete *i;
                                        compoundStmt->get_kids().erase( i );
                                } // if
                        } // if
                        i = next;
                } // while
                typedefNames.endScope();
                return ret;
        }

        // there may be typedefs nested within aggregates. in order for everything to work properly, these should be removed
        // as well
        template<typename AggDecl>
        AggDecl *EliminateTypedef::handleAggregate( AggDecl * aggDecl ) {
                std::list<Declaration *>::iterator it = aggDecl->get_members().begin();
                for ( ; it != aggDecl->get_members().end(); ) {
                        std::list< Declaration * >::iterator next = it+1;
                        if ( dynamic_cast< TypedefDecl * >( *it ) ) {
                                delete *it;
                                aggDecl->get_members().erase( it );
                        } // if
                        it = next;
                }
                return aggDecl;
        }

        template<typename AggDecl>
        void EliminateTypedef::addImplicitTypedef( AggDecl * aggDecl ) {
                if ( typedefNames.count( aggDecl->get_name() ) == 0 ) {
                        Type *type = nullptr;
                        if ( StructDecl * newDeclStructDecl = dynamic_cast< StructDecl * >( aggDecl ) ) {
                                type = new StructInstType( Type::Qualifiers(), newDeclStructDecl->get_name() );
                        } else if ( UnionDecl * newDeclUnionDecl = dynamic_cast< UnionDecl * >( aggDecl ) ) {
                                type = new UnionInstType( Type::Qualifiers(), newDeclUnionDecl->get_name() );
                        } else if ( EnumDecl * newDeclEnumDecl = dynamic_cast< EnumDecl * >( aggDecl )  ) {
                                type = new EnumInstType( Type::Qualifiers(), newDeclEnumDecl->get_name() );
                        } // if
                        TypedefDeclPtr tyDecl( new TypedefDecl( aggDecl->get_name(), Type::StorageClasses(), type, aggDecl->get_linkage() ) );
                        typedefNames[ aggDecl->get_name() ] = std::make_pair( std::move( tyDecl ), scopeLevel );
                } // if
        }

        Declaration *EliminateTypedef::mutate( StructDecl * structDecl ) {
                addImplicitTypedef( structDecl );
                Mutator::mutate( structDecl );
                return handleAggregate( structDecl );
        }

        Declaration *EliminateTypedef::mutate( UnionDecl * unionDecl ) {
                addImplicitTypedef( unionDecl );
                Mutator::mutate( unionDecl );
                return handleAggregate( unionDecl );
        }

        Declaration *EliminateTypedef::mutate( EnumDecl * enumDecl ) {
                addImplicitTypedef( enumDecl );
                Mutator::mutate( enumDecl );
                return handleAggregate( enumDecl );
        }

        Declaration *EliminateTypedef::mutate( TraitDecl * contextDecl ) {
                Mutator::mutate( contextDecl );
                return handleAggregate( contextDecl );
        }

        void VerifyCtorDtorAssign::verify( std::list< Declaration * > & translationUnit ) {
                PassVisitor<VerifyCtorDtorAssign> verifier;
                acceptAll( translationUnit, verifier );
        }

        void VerifyCtorDtorAssign::previsit( FunctionDecl * funcDecl ) {
                FunctionType * funcType = funcDecl->get_functionType();
                std::list< DeclarationWithType * > &returnVals = funcType->get_returnVals();
                std::list< DeclarationWithType * > &params = funcType->get_parameters();

                if ( InitTweak::isCtorDtorAssign( funcDecl->get_name() ) ) {
                        if ( params.size() == 0 ) {
                                throw SemanticError( "Constructors, destructors, and assignment functions require at least one parameter ", funcDecl );
                        }
                        PointerType * ptrType = dynamic_cast< PointerType * >( params.front()->get_type() );
                        if ( ! ptrType || ptrType->is_array() ) {
                                throw SemanticError( "First parameter of a constructor, destructor, or assignment function must be a pointer ", funcDecl );
                        }
                        if ( InitTweak::isCtorDtor( funcDecl->get_name() ) && returnVals.size() != 0 ) {
                                throw SemanticError( "Constructors and destructors cannot have explicit return values ", funcDecl );
                        }
                }
        }

        template< typename Aggr >
        void validateGeneric( Aggr * inst ) {
                std::list< TypeDecl * > * params = inst->get_baseParameters();
                if ( params ) {
                        std::list< Expression * > & args = inst->get_parameters();

                        // insert defaults arguments when a type argument is missing (currently only supports missing arguments at the end of the list).
                        // A substitution is used to ensure that defaults are replaced correctly, e.g.,
                        //   forall(otype T, otype alloc = heap_allocator(T)) struct vector;
                        //   vector(int) v;
                        // after insertion of default values becomes
                        //   vector(int, heap_allocator(T))
                        // and the substitution is built with T=int so that after substitution, the result is
                        //   vector(int, heap_allocator(int))
                        TypeSubstitution sub;
                        auto paramIter = params->begin();
                        for ( size_t i = 0; paramIter != params->end(); ++paramIter, ++i ) {
                                if ( i < args.size() ) {
                                        TypeExpr * expr = safe_dynamic_cast< TypeExpr * >( *std::next( args.begin(), i ) );
                                        sub.add( (*paramIter)->get_name(), expr->get_type()->clone() );
                                } else if ( i == args.size() ) {
                                        Type * defaultType = (*paramIter)->get_init();
                                        if ( defaultType ) {
                                                args.push_back( new TypeExpr( defaultType->clone() ) );
                                                sub.add( (*paramIter)->get_name(), defaultType->clone() );
                                        }
                                }
                        }

                        sub.apply( inst );
                        if ( args.size() < params->size() ) throw SemanticError( "Too few type arguments in generic type ", inst );
                        if ( args.size() > params->size() ) throw SemanticError( "Too many type arguments in generic type ", inst );
                }
        }

        void ValidateGenericParameters::previsit( StructInstType * inst ) {
                validateGeneric( inst );
        }

        void ValidateGenericParameters::previsit( UnionInstType * inst ) {
                validateGeneric( inst );
        }

        void CompoundLiteral::premutate( ObjectDecl *objectDecl ) {
                storageClasses = objectDecl->get_storageClasses();
        }

        Expression *CompoundLiteral::postmutate( CompoundLiteralExpr *compLitExpr ) {
                // transform [storage_class] ... (struct S){ 3, ... };
                // into [storage_class] struct S temp =  { 3, ... };
                static UniqueName indexName( "_compLit" );

                ObjectDecl *tempvar = new ObjectDecl( indexName.newName(), storageClasses, LinkageSpec::C, nullptr, compLitExpr->get_result(), compLitExpr->get_initializer() );
                compLitExpr->set_result( nullptr );
                compLitExpr->set_initializer( nullptr );
                delete compLitExpr;
                declsToAddBefore.push_back( tempvar );                                  // add modified temporary to current block
                return new VariableExpr( tempvar );
        }

        void ReturnTypeFixer::fix( std::list< Declaration * > &translationUnit ) {
                PassVisitor<ReturnTypeFixer> fixer;
                acceptAll( translationUnit, fixer );
        }

        void ReturnTypeFixer::postvisit( FunctionDecl * functionDecl ) {
                FunctionType * ftype = functionDecl->get_functionType();
                std::list< DeclarationWithType * > & retVals = ftype->get_returnVals();
                assertf( retVals.size() == 0 || retVals.size() == 1, "Function %s has too many return values: %zu", functionDecl->get_name().c_str(), retVals.size() );
                if ( retVals.size() == 1 ) {
                        // ensure all function return values have a name - use the name of the function to disambiguate (this also provides a nice bit of help for debugging).
                        // ensure other return values have a name.
                        DeclarationWithType * ret = retVals.front();
                        if ( ret->get_name() == "" ) {
                                ret->set_name( toString( "_retval_", CodeGen::genName( functionDecl ) ) );
                        }
                        ret->get_attributes().push_back( new Attribute( "unused" ) );
                }
        }

        void ReturnTypeFixer::postvisit( FunctionType * ftype ) {
                // xxx - need to handle named return values - this information needs to be saved somehow
                // so that resolution has access to the names.
                // Note that this pass needs to happen early so that other passes which look for tuple types
                // find them in all of the right places, including function return types.
                std::list< DeclarationWithType * > & retVals = ftype->get_returnVals();
                if ( retVals.size() > 1 ) {
                        // generate a single return parameter which is the tuple of all of the return values
                        TupleType * tupleType = safe_dynamic_cast< TupleType * >( ResolvExpr::extractResultType( ftype ) );
                        // ensure return value is not destructed by explicitly creating an empty ListInit node wherein maybeConstruct is false.
                        ObjectDecl * newRet = new ObjectDecl( "", Type::StorageClasses(), LinkageSpec::Cforall, 0, tupleType, new ListInit( std::list<Initializer*>(), noDesignators, false ) );
                        deleteAll( retVals );
                        retVals.clear();
                        retVals.push_back( newRet );
                }
        }

        void ArrayLength::computeLength( std::list< Declaration * > & translationUnit ) {
                PassVisitor<ArrayLength> len;
                acceptAll( translationUnit, len );
        }

        void ArrayLength::previsit( ObjectDecl * objDecl ) {
                if ( ArrayType * at = dynamic_cast< ArrayType * >( objDecl->get_type() ) ) {
                        if ( at->get_dimension() ) return;
                        if ( ListInit * init = dynamic_cast< ListInit * >( objDecl->get_init() ) ) {
                                at->set_dimension( new ConstantExpr( Constant::from_ulong( init->get_initializers().size() ) ) );
                        }
                }
        }
} // namespace SymTab

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