Changes in src/ResolvExpr/Unify.cc [c6b4432:8f31be6]

File:

• src/ResolvExpr/Unify.cc (modified) (4 diffs)

src/ResolvExpr/Unify.cc

@@ -33 +33 @@
 #include "AST/TypeEnvironment.hpp"
 #include "Common/Eval.h"            // for eval
+#include "Common/PassVisitor.h"     // for PassVisitor
 #include "CommonType.hpp"           // for commonType
 #include "FindOpenVars.h"           // for findOpenVars
 #include "SpecCost.hpp"             // for SpecCost
+#include "SynTree/LinkageSpec.h"    // for C
+#include "SynTree/Constant.h"       // for Constant
+#include "SynTree/Declaration.h"    // for TypeDecl, TypeDecl::Data, Declarati...
+#include "SynTree/Expression.h"     // for TypeExpr, Expression, ConstantExpr
+#include "SynTree/Mutator.h"        // for Mutator
+#include "SynTree/Type.h"           // for Type, TypeInstType, FunctionType
+#include "SynTree/Visitor.h"        // for Visitor
 #include "Tuples/Tuples.h"          // for isTtype
+#include "TypeEnvironment.h"        // for EqvClass, AssertionSet, OpenVarSet
 #include "typeops.h"                // for flatten, occurs
 
@@ -43 +52 @@
 }
 
+namespace SymTab {
+        class Indexer;
+}  // namespace SymTab
+
 // #define DEBUG
 
 namespace ResolvExpr {
+
+// Template Helpers:
+template< typename Iterator1, typename Iterator2 >
+bool unifyList( Iterator1 list1Begin, Iterator1 list1End, Iterator2 list2Begin, Iterator2 list2End, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer, std::list< Type* > &commonTypes ) {
+        for ( ; list1Begin != list1End && list2Begin != list2End; ++list1Begin, ++list2Begin ) {
+                Type *commonType = 0;
+                if ( ! unify( *list1Begin, *list2Begin, env, needAssertions, haveAssertions, openVars, indexer, commonType ) ) {
+                        return false;
+                } // if
+                commonTypes.push_back( commonType );
+        } // for
+        return ( list1Begin == list1End && list2Begin == list2End );
+}
+
+template< typename Iterator1, typename Iterator2 >
+bool unifyList( Iterator1 list1Begin, Iterator1 list1End, Iterator2 list2Begin, Iterator2 list2End, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer ) {
+        std::list< Type* > commonTypes;
+        if ( unifyList( list1Begin, list1End, list2Begin, list2End, env, needAssertions, haveAssertions,  openVars, indexer, commonTypes ) ) {
+                deleteAll( commonTypes );
+                return true;
+        } else {
+                return false;
+        } // if
+}
+
+        struct Unify_old : public WithShortCircuiting {
+                Unify_old( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
+
+                bool get_result() const { return result; }
+
+                void previsit( BaseSyntaxNode * ) { visit_children = false; }
+
+                void postvisit( VoidType * voidType );
+                void postvisit( BasicType * basicType );
+                void postvisit( PointerType * pointerType );
+                void postvisit( ArrayType * arrayType );
+                void postvisit( ReferenceType * refType );
+                void postvisit( FunctionType * functionType );
+                void postvisit( StructInstType * aggregateUseType );
+                void postvisit( UnionInstType * aggregateUseType );
+                void postvisit( EnumInstType * aggregateUseType );
+                void postvisit( TraitInstType * aggregateUseType );
+                void postvisit( TypeInstType * aggregateUseType );
+                void postvisit( TupleType * tupleType );
+                void postvisit( VarArgsType * varArgsType );
+                void postvisit( ZeroType * zeroType );
+                void postvisit( OneType * oneType );
+
+          private:
+                template< typename RefType > void handleRefType( RefType *inst, Type *other );
+                template< typename RefType > void handleGenericRefType( RefType *inst, Type *other );
+
+                bool result;
+                Type *type2;                            // inherited
+                TypeEnvironment &env;
+                AssertionSet &needAssertions;
+                AssertionSet &haveAssertions;
+                const OpenVarSet &openVars;
+                WidenMode widen;
+                const SymTab::Indexer &indexer;
+        };
+
+        /// Attempts an inexact unification of type1 and type2.
+        /// Returns false if no such unification; if the types can be unified, sets common (unless they unify exactly and have identical type qualifiers)
+        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer, Type *&common );
+        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
+
+        bool unifyExact(
+                const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env,
+                ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open,
+                WidenMode widen );
+
+        bool typesCompatible( const Type * first, const Type * second, const SymTab::Indexer & indexer, const TypeEnvironment & env ) {
+                TypeEnvironment newEnv;
+                OpenVarSet openVars, closedVars; // added closedVars
+                AssertionSet needAssertions, haveAssertions;
+                Type * newFirst = first->clone(), * newSecond = second->clone();
+                env.apply( newFirst );
+                env.apply( newSecond );
+
+                // do we need to do this? Seems like we do, types should be able to be compatible if they
+                // have free variables that can unify
+                findOpenVars( newFirst, openVars, closedVars, needAssertions, haveAssertions, false );
+                findOpenVars( newSecond, openVars, closedVars, needAssertions, haveAssertions, true );
+
+                bool result = unifyExact( newFirst, newSecond, newEnv, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                delete newFirst;
+                delete newSecond;
+                return result;
+        }
 
         bool typesCompatible(
@@ -62 +165 @@
 
                 return unifyExact(newFirst, newSecond, newEnv, need, have, open, noWiden() );
+        }
+
+        bool typesCompatibleIgnoreQualifiers( const Type * first, const Type * second, const SymTab::Indexer &indexer, const TypeEnvironment &env ) {
+                TypeEnvironment newEnv;
+                OpenVarSet openVars;
+                AssertionSet needAssertions, haveAssertions;
+                Type *newFirst = first->clone(), *newSecond = second->clone();
+                env.apply( newFirst );
+                env.apply( newSecond );
+                newFirst->get_qualifiers() = Type::Qualifiers();
+                newSecond->get_qualifiers() = Type::Qualifiers();
+
+                bool result = unifyExact( newFirst, newSecond, newEnv, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                delete newFirst;
+                delete newSecond;
+                return result;
         }
 
@@ -99 +218 @@
                         subSecond,
                         newEnv, need, have, open, noWiden() );
+        }
+
+        bool unify( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer ) {
+                OpenVarSet closedVars;
+                findOpenVars( type1, openVars, closedVars, needAssertions, haveAssertions, false );
+                findOpenVars( type2, openVars, closedVars, needAssertions, haveAssertions, true );
+                Type *commonType = 0;
+                if ( unifyInexact( type1, type2, env, needAssertions, haveAssertions, openVars, WidenMode( true, true ), indexer, commonType ) ) {
+                        if ( commonType ) {
+                                delete commonType;
+                        } // if
+                        return true;
+                } else {
+                        return false;
+                } // if
+        }
+
+        bool unify( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer, Type *&commonType ) {
+                OpenVarSet closedVars;
+                findOpenVars( type1, openVars, closedVars, needAssertions, haveAssertions, false );
+                findOpenVars( type2, openVars, closedVars, needAssertions, haveAssertions, true );
+                return unifyInexact( type1, type2, env, needAssertions, haveAssertions, openVars, WidenMode( true, true ), indexer, commonType );
+        }
+
+        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer ) {
+#ifdef DEBUG
+                TypeEnvironment debugEnv( env );
+#endif
+                if ( type1->get_qualifiers() != type2->get_qualifiers() ) {
+                        return false;
+                }
+
+                bool result;
+                TypeInstType *var1 = dynamic_cast< TypeInstType* >( type1 );
+                TypeInstType *var2 = dynamic_cast< TypeInstType* >( type2 );
+                OpenVarSet::const_iterator entry1, entry2;
+                if ( var1 ) {
+                        entry1 = openVars.find( var1->get_name() );
+                } // if
+                if ( var2 ) {
+                        entry2 = openVars.find( var2->get_name() );
+                } // if
+                bool isopen1 = var1 && ( entry1 != openVars.end() );
+                bool isopen2 = var2 && ( entry2 != openVars.end() );
+
+                if ( isopen1 && isopen2 ) {
+                        if ( entry1->second.kind != entry2->second.kind ) {
+                                result = false;
+                        } else {
+                                result = env.bindVarToVar(
+                                        var1, var2, TypeDecl::Data{ entry1->second, entry2->second }, needAssertions,
+                                        haveAssertions, openVars, widen, indexer );
+                        }
+                } else if ( isopen1 ) {
+                        result = env.bindVar( var1, type2, entry1->second, needAssertions, haveAssertions, openVars, widen, indexer );
+                } else if ( isopen2 ) { // TODO: swap widen values in call, since type positions are flipped?
+                        result = env.bindVar( var2, type1, entry2->second, needAssertions, haveAssertions, openVars, widen, indexer );
+                } else {
+                        PassVisitor<Unify_old> comparator( type2, env, needAssertions, haveAssertions, openVars, widen, indexer );
+                        type1->accept( comparator );
+                        result = comparator.pass.get_result();
+                } // if
+#ifdef DEBUG
+                std::cerr << "============ unifyExact" << std::endl;
+                std::cerr << "type1 is ";
+                type1->print( std::cerr );
+                std::cerr << std::endl << "type2 is ";
+                type2->print( std::cerr );
+                std::cerr << std::endl << "openVars are ";
+                printOpenVarSet( openVars, std::cerr, 8 );
+                std::cerr << std::endl << "input env is " << std::endl;
+                debugEnv.print( std::cerr, 8 );
+                std::cerr << std::endl << "result env is " << std::endl;
+                env.print( std::cerr, 8 );
+                std::cerr << "result is " << result << std::endl;
+#endif
+                return result;
+        }
+
+        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer ) {
+                return unifyExact( type1, type2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+        }
+
+        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer, Type *&common ) {
+                Type::Qualifiers tq1 = type1->get_qualifiers(), tq2 = type2->get_qualifiers();
+                type1->get_qualifiers() = Type::Qualifiers();
+                type2->get_qualifiers() = Type::Qualifiers();
+                bool result;
+#ifdef DEBUG
+                std::cerr << "unifyInexact type 1 is ";
+                type1->print( std::cerr );
+                std::cerr << " type 2 is ";
+                type2->print( std::cerr );
+                std::cerr << std::endl;
+#endif
+                if ( ! unifyExact( type1, type2, env, needAssertions, haveAssertions, openVars, widen, indexer ) ) {
+#ifdef DEBUG
+                        std::cerr << "unifyInexact: no exact unification found" << std::endl;
+#endif
+                        if ( ( common = commonType( type1, type2, widen.first, widen.second, indexer, env, openVars ) ) ) {
+                                common->tq = tq1.unify( tq2 );
+#ifdef DEBUG
+                                std::cerr << "unifyInexact: common type is ";
+                                common->print( std::cerr );
+                                std::cerr << std::endl;
+#endif
+                                result = true;
+                        } else {
+#ifdef DEBUG
+                                std::cerr << "unifyInexact: no common type found" << std::endl;
+#endif
+                                result = false;
+                        } // if
+                } else {
+                        if ( tq1 != tq2 ) {
+                                if ( ( tq1 > tq2 || widen.first ) && ( tq2 > tq1 || widen.second ) ) {
+                                        common = type1->clone();
+                                        common->tq = tq1.unify( tq2 );
+                                        result = true;
+                                } else {
+                                        result = false;
+                                } // if
+                        } else {
+                                common = type1->clone();
+                                common->tq = tq1.unify( tq2 );
+                                result = true;
+                        } // if
+                } // if
+                type1->get_qualifiers() = tq1;
+                type2->get_qualifiers() = tq2;
+                return result;
+        }
+
+        Unify_old::Unify_old( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer )
+                : result( false ), type2( type2 ), env( env ), needAssertions( needAssertions ), haveAssertions( haveAssertions ), openVars( openVars ), widen( widen ), indexer( indexer ) {
+        }
+
+        void Unify_old::postvisit( __attribute__((unused)) VoidType *voidType) {
+                result = dynamic_cast< VoidType* >( type2 );
+        }
+
+        void Unify_old::postvisit(BasicType *basicType) {
+                if ( BasicType *otherBasic = dynamic_cast< BasicType* >( type2 ) ) {
+                        result = basicType->get_kind() == otherBasic->get_kind();
+                } // if
+        }
+
+        void markAssertionSet( AssertionSet &assertions, DeclarationWithType *assert ) {
+                AssertionSet::iterator i = assertions.find( assert );
+                if ( i != assertions.end() ) {
+                        i->second.isUsed = true;
+                } // if
+        }
+
+        void markAssertions( AssertionSet &assertion1, AssertionSet &assertion2, Type *type ) {
+                for ( std::list< TypeDecl* >::const_iterator tyvar = type->get_forall().begin(); tyvar != type->get_forall().end(); ++tyvar ) {
+                        for ( std::list< DeclarationWithType* >::const_iterator assert = (*tyvar)->get_assertions().begin(); assert != (*tyvar)->get_assertions().end(); ++assert ) {
+                                markAssertionSet( assertion1, *assert );
+                                markAssertionSet( assertion2, *assert );
+                        } // for
+                } // for
+        }
+
+        void Unify_old::postvisit(PointerType *pointerType) {
+                if ( PointerType *otherPointer = dynamic_cast< PointerType* >( type2 ) ) {
+                        result = unifyExact( pointerType->get_base(), otherPointer->get_base(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        markAssertions( haveAssertions, needAssertions, pointerType );
+                        markAssertions( haveAssertions, needAssertions, otherPointer );
+                } // if
+        }
+
+        void Unify_old::postvisit(ReferenceType *refType) {
+                if ( ReferenceType *otherRef = dynamic_cast< ReferenceType* >( type2 ) ) {
+                        result = unifyExact( refType->get_base(), otherRef->get_base(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        markAssertions( haveAssertions, needAssertions, refType );
+                        markAssertions( haveAssertions, needAssertions, otherRef );
+                } // if
+        }
+
+        void Unify_old::postvisit(ArrayType *arrayType) {
+                ArrayType *otherArray = dynamic_cast< ArrayType* >( type2 );
+                // to unify, array types must both be VLA or both not VLA
+                // and must both have a dimension expression or not have a dimension
+                if ( otherArray && arrayType->get_isVarLen() == otherArray->get_isVarLen() ) {
+
+                        if ( ! arrayType->get_isVarLen() && ! otherArray->get_isVarLen() &&
+                                arrayType->get_dimension() != 0 && otherArray->get_dimension() != 0 ) {
+                                ConstantExpr * ce1 = dynamic_cast< ConstantExpr * >( arrayType->get_dimension() );
+                                ConstantExpr * ce2 = dynamic_cast< ConstantExpr * >( otherArray->get_dimension() );
+                                // see C11 Reference Manual 6.7.6.2.6
+                                // two array types with size specifiers that are integer constant expressions are
+                                // compatible if both size specifiers have the same constant value
+                                if ( ce1 && ce2 ) {
+                                        Constant * c1 = ce1->get_constant();
+                                        Constant * c2 = ce2->get_constant();
+
+                                        if ( c1->get_value() != c2->get_value() ) {
+                                                // does not unify if the dimension is different
+                                                return;
+                                        }
+                                }
+                        }
+
+                        result = unifyExact( arrayType->get_base(), otherArray->get_base(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                } // if
+        }
+
+        template< typename Iterator, typename Func >
+        std::unique_ptr<Type> combineTypes( Iterator begin, Iterator end, Func & toType ) {
+                std::list< Type * > types;
+                for ( ; begin != end; ++begin ) {
+                        // it's guaranteed that a ttype variable will be bound to a flat tuple, so ensure that this results in a flat tuple
+                        flatten( toType( *begin ), back_inserter( types ) );
+                }
+                return std::unique_ptr<Type>( new TupleType( Type::Qualifiers(), types ) );
+        }
+
+        template< typename Iterator1, typename Iterator2 >
+        bool unifyTypeList( Iterator1 list1Begin, Iterator1 list1End, Iterator2 list2Begin, Iterator2 list2End, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, const SymTab::Indexer &indexer ) {
+                auto get_type = [](DeclarationWithType * dwt){ return dwt->get_type(); };
+                for ( ; list1Begin != list1End && list2Begin != list2End; ++list1Begin, ++list2Begin ) {
+                        Type * t1 = (*list1Begin)->get_type();
+                        Type * t2 = (*list2Begin)->get_type();
+                        bool isTtype1 = Tuples::isTtype( t1 );
+                        bool isTtype2 = Tuples::isTtype( t2 );
+                        // xxx - assumes ttype must be last parameter
+                        // xxx - there may be a nice way to refactor this, but be careful because the argument positioning might matter in some cases.
+                        if ( isTtype1 && ! isTtype2 ) {
+                                // combine all of the things in list2, then unify
+                                return unifyExact( t1, combineTypes( list2Begin, list2End, get_type ).get(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else if ( isTtype2 && ! isTtype1 ) {
+                                // combine all of the things in list1, then unify
+                                return unifyExact( combineTypes( list1Begin, list1End, get_type ).get(), t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else if ( ! unifyExact( t1, t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer ) ) {
+                                return false;
+                        } // if
+                } // for
+                // may get to the end of one argument list before the end of the other. This is only okay when the other is a ttype
+                if ( list1Begin != list1End ) {
+                        // try unifying empty tuple type with ttype
+                        Type * t1 = (*list1Begin)->get_type();
+                        if ( Tuples::isTtype( t1 ) ) {
+                                return unifyExact( t1, combineTypes( list2Begin, list2End, get_type ).get(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else return false;
+                } else if ( list2Begin != list2End ) {
+                        // try unifying empty tuple type with ttype
+                        Type * t2 = (*list2Begin)->get_type();
+                        if ( Tuples::isTtype( t2 ) ) {
+                                return unifyExact( combineTypes( list1Begin, list1End, get_type ).get(), t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else return false;
+                } else {
+                        return true;
+                } // if
+        }
+
+        /// Finds ttypes and replaces them with their expansion, if known.
+        /// This needs to be done so that satisfying ttype assertions is easier.
+        /// If this isn't done then argument lists can have wildly different
+        /// size and structure, when they should be compatible.
+        struct TtypeExpander_old : public WithShortCircuiting {
+                TypeEnvironment & tenv;
+                TtypeExpander_old( TypeEnvironment & tenv ) : tenv( tenv ) {}
+                void premutate( TypeInstType * ) { visit_children = false; }
+                Type * postmutate( TypeInstType * typeInst ) {
+                        if ( const EqvClass *eqvClass = tenv.lookup( typeInst->get_name() ) ) {
+                                // expand ttype parameter into its actual type
+                                if ( eqvClass->data.kind == TypeDecl::Ttype && eqvClass->type ) {
+                                        delete typeInst;
+                                        return eqvClass->type->clone();
+                                }
+                        }
+                        return typeInst;
+                }
+        };
+
+        /// flattens a list of declarations, so that each tuple type has a single declaration.
+        /// makes use of TtypeExpander to ensure ttypes are flat as well.
+        void flattenList( std::list< DeclarationWithType * > src, std::list< DeclarationWithType * > & dst, TypeEnvironment & env ) {
+                dst.clear();
+                for ( DeclarationWithType * dcl : src ) {
+                        PassVisitor<TtypeExpander_old> expander( env );
+                        dcl->acceptMutator( expander );
+                        std::list< Type * > types;
+                        flatten( dcl->get_type(), back_inserter( types ) );
+                        for ( Type * t : types ) {
+                                // outermost const, volatile, _Atomic qualifiers in parameters should not play a role in the unification of function types, since they do not determine whether a function is callable.
+                                // Note: MUST consider at least mutex qualifier, since functions can be overloaded on outermost mutex and a mutex function has different requirements than a non-mutex function.
+                                t->get_qualifiers() -= Type::Qualifiers(Type::Const | Type::Volatile | Type::Atomic);
+
+                                dst.push_back( new ObjectDecl( "", Type::StorageClasses(), LinkageSpec::C, nullptr, t, nullptr ) );
+                        }
+                        delete dcl;
+                }
+        }
+
+        void Unify_old::postvisit(FunctionType *functionType) {
+                FunctionType *otherFunction = dynamic_cast< FunctionType* >( type2 );
+                if ( otherFunction && functionType->get_isVarArgs() == otherFunction->get_isVarArgs() ) {
+                        // flatten the parameter lists for both functions so that tuple structure
+                        // doesn't affect unification. Must be a clone so that the types don't change.
+                        std::unique_ptr<FunctionType> flatFunc( functionType->clone() );
+                        std::unique_ptr<FunctionType> flatOther( otherFunction->clone() );
+                        flattenList( flatFunc->get_parameters(), flatFunc->get_parameters(), env );
+                        flattenList( flatOther->get_parameters(), flatOther->get_parameters(), env );
+
+                        // sizes don't have to match if ttypes are involved; need to be more precise wrt where the ttype is to prevent errors
+                        if (
+                                        (flatFunc->parameters.size() == flatOther->parameters.size() &&
+                                                flatFunc->returnVals.size() == flatOther->returnVals.size())
+                                        || flatFunc->isTtype()
+                                        || flatOther->isTtype()
+                        ) {
+                                if ( unifyTypeList( flatFunc->parameters.begin(), flatFunc->parameters.end(), flatOther->parameters.begin(), flatOther->parameters.end(), env, needAssertions, haveAssertions, openVars, indexer ) ) {
+                                        if ( unifyTypeList( flatFunc->returnVals.begin(), flatFunc->returnVals.end(), flatOther->returnVals.begin(), flatOther->returnVals.end(), env, needAssertions, haveAssertions, openVars, indexer ) ) {
+
+                                                // the original types must be used in mark assertions, since pointer comparisons are used
+                                                markAssertions( haveAssertions, needAssertions, functionType );
+                                                markAssertions( haveAssertions, needAssertions, otherFunction );
+
+                                                result = true;
+                                        } // if
+                                } // if
+                        } // if
+                } // if
+        }
+
+        template< typename RefType >
+        void Unify_old::handleRefType( RefType *inst, Type *other ) {
+                // check that other type is compatible and named the same
+                RefType *otherStruct = dynamic_cast< RefType* >( other );
+                result = otherStruct && inst->name == otherStruct->name;
+        }
+
+        template< typename RefType >
+        void Unify_old::handleGenericRefType( RefType *inst, Type *other ) {
+                // Check that other type is compatible and named the same
+                handleRefType( inst, other );
+                if ( ! result ) return;
+                // Check that parameters of types unify, if any
+                std::list< Expression* > params = inst->parameters;
+                std::list< Expression* > otherParams = ((RefType*)other)->parameters;
+
+                std::list< Expression* >::const_iterator it = params.begin(), jt = otherParams.begin();
+                for ( ; it != params.end() && jt != otherParams.end(); ++it, ++jt ) {
+                        TypeExpr *param = dynamic_cast< TypeExpr* >(*it);
+                        assertf(param, "Aggregate parameters should be type expressions");
+                        TypeExpr *otherParam = dynamic_cast< TypeExpr* >(*jt);
+                        assertf(otherParam, "Aggregate parameters should be type expressions");
+
+                        Type* paramTy = param->get_type();
+                        Type* otherParamTy = otherParam->get_type();
+
+                        bool tupleParam = Tuples::isTtype( paramTy );
+                        bool otherTupleParam = Tuples::isTtype( otherParamTy );
+
+                        if ( tupleParam && otherTupleParam ) {
+                                ++it; ++jt;  // skip ttype parameters for break
+                        } else if ( tupleParam ) {
+                                // bundle other parameters into tuple to match
+                                std::list< Type * > binderTypes;
+
+                                do {
+                                        binderTypes.push_back( otherParam->get_type()->clone() );
+                                        ++jt;
+
+                                        if ( jt == otherParams.end() ) break;
+
+                                        otherParam = dynamic_cast< TypeExpr* >(*jt);
+                                        assertf(otherParam, "Aggregate parameters should be type expressions");
+                                } while (true);
+
+                                otherParamTy = new TupleType{ paramTy->get_qualifiers(), binderTypes };
+                                ++it;  // skip ttype parameter for break
+                        } else if ( otherTupleParam ) {
+                                // bundle parameters into tuple to match other
+                                std::list< Type * > binderTypes;
+
+                                do {
+                                        binderTypes.push_back( param->get_type()->clone() );
+                                        ++it;
+
+                                        if ( it == params.end() ) break;
+
+                                        param = dynamic_cast< TypeExpr* >(*it);
+                                        assertf(param, "Aggregate parameters should be type expressions");
+                                } while (true);
+
+                                paramTy = new TupleType{ otherParamTy->get_qualifiers(), binderTypes };
+                                ++jt;  // skip ttype parameter for break
+                        }
+
+                        if ( ! unifyExact( paramTy, otherParamTy, env, needAssertions, haveAssertions, openVars, WidenMode(false, false), indexer ) ) {
+                                result = false;
+                                return;
+                        }
+
+                        // ttype parameter should be last
+                        if ( tupleParam || otherTupleParam ) break;
+                }
+                result = ( it == params.end() && jt == otherParams.end() );
+        }
+
+        void Unify_old::postvisit(StructInstType *structInst) {
+                handleGenericRefType( structInst, type2 );
+        }
+
+        void Unify_old::postvisit(UnionInstType *unionInst) {
+                handleGenericRefType( unionInst, type2 );
+        }
+
+        void Unify_old::postvisit(EnumInstType *enumInst) {
+                handleRefType( enumInst, type2 );
+        }
+
+        void Unify_old::postvisit(TraitInstType *contextInst) {
+                handleRefType( contextInst, type2 );
+        }
+
+        void Unify_old::postvisit(TypeInstType *typeInst) {
+                assert( openVars.find( typeInst->get_name() ) == openVars.end() );
+                TypeInstType *otherInst = dynamic_cast< TypeInstType* >( type2 );
+                if ( otherInst && typeInst->get_name() == otherInst->get_name() ) {
+                        result = true;
+///   } else {
+///     NamedTypeDecl *nt = indexer.lookupType( typeInst->get_name() );
+///     if ( nt ) {
+///       TypeDecl *type = dynamic_cast< TypeDecl* >( nt );
+///       assert( type );
+///       if ( type->get_base() ) {
+///         result = unifyExact( type->get_base(), typeInst, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+///       }
+///     }
+                } // if
+        }
+
+        template< typename Iterator1, typename Iterator2 >
+        bool unifyList( Iterator1 list1Begin, Iterator1 list1End, Iterator2 list2Begin, Iterator2 list2End, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, const SymTab::Indexer &indexer ) {
+                auto get_type = [](Type * t) { return t; };
+                for ( ; list1Begin != list1End && list2Begin != list2End; ++list1Begin, ++list2Begin ) {
+                        Type * t1 = *list1Begin;
+                        Type * t2 = *list2Begin;
+                        bool isTtype1 = Tuples::isTtype( t1 );
+                        bool isTtype2 = Tuples::isTtype( t2 );
+                        // xxx - assumes ttype must be last parameter
+                        // xxx - there may be a nice way to refactor this, but be careful because the argument positioning might matter in some cases.
+                        if ( isTtype1 && ! isTtype2 ) {
+                                // combine all of the things in list2, then unify
+                                return unifyExact( t1, combineTypes( list2Begin, list2End, get_type ).get(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else if ( isTtype2 && ! isTtype1 ) {
+                                // combine all of the things in list1, then unify
+                                return unifyExact( combineTypes( list1Begin, list1End, get_type ).get(), t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else if ( ! unifyExact( t1, t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer ) ) {
+                                return false;
+                        } // if
+
+                } // for
+                if ( list1Begin != list1End ) {
+                        // try unifying empty tuple type with ttype
+                        Type * t1 = *list1Begin;
+                        if ( Tuples::isTtype( t1 ) ) {
+                                return unifyExact( t1, combineTypes( list2Begin, list2End, get_type ).get(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else return false;
+                } else if ( list2Begin != list2End ) {
+                        // try unifying empty tuple type with ttype
+                        Type * t2 = *list2Begin;
+                        if ( Tuples::isTtype( t2 ) ) {
+                                return unifyExact( combineTypes( list1Begin, list1End, get_type ).get(), t2, env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
+                        } else return false;
+                } else {
+                        return true;
+                } // if
+        }
+
+        void Unify_old::postvisit(TupleType *tupleType) {
+                if ( TupleType *otherTuple = dynamic_cast< TupleType* >( type2 ) ) {
+                        std::unique_ptr<TupleType> flat1( tupleType->clone() );
+                        std::unique_ptr<TupleType> flat2( otherTuple->clone() );
+                        std::list<Type *> types1, types2;
+
+                        PassVisitor<TtypeExpander_old> expander( env );
+                        flat1->acceptMutator( expander );
+                        flat2->acceptMutator( expander );
+
+                        flatten( flat1.get(), back_inserter( types1 ) );
+                        flatten( flat2.get(), back_inserter( types2 ) );
+
+                        result = unifyList( types1.begin(), types1.end(), types2.begin(), types2.end(), env, needAssertions, haveAssertions, openVars, indexer );
+                } // if
+        }
+
+        void Unify_old::postvisit( __attribute__((unused)) VarArgsType *varArgsType ) {
+                result = dynamic_cast< VarArgsType* >( type2 );
+        }
+
+        void Unify_old::postvisit( __attribute__((unused)) ZeroType *zeroType ) {
+                result = dynamic_cast< ZeroType* >( type2 );
+        }
+
+        void Unify_old::postvisit( __attribute__((unused)) OneType *oneType ) {
+                result = dynamic_cast< OneType* >( type2 );
+        }
+
+        Type * extractResultType( FunctionType * function ) {
+                if ( function->get_returnVals().size() == 0 ) {
+                        return new VoidType( Type::Qualifiers() );
+                } else if ( function->get_returnVals().size() == 1 ) {
+                        return function->get_returnVals().front()->get_type()->clone();
+                } else {
+                        std::list< Type * > types;
+                        for ( DeclarationWithType * decl : function->get_returnVals() ) {
+                                types.push_back( decl->get_type()->clone() );
+                        } // for
+                        return new TupleType( Type::Qualifiers(), types );
+                }
         }