Changeset 954908d

Timestamp:

Nov 8, 2017, 6:03:52 PM (6 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, aaron-thesis, arm-eh, ast-experimental, cleanup-dtors, deferred_resn, demangler, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, pthread-emulation, qualifiedEnum, resolv-new, with_gc

Children:

3351cc0

Parents:

bd41764 (diff), 3f7e12cb (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

Location:

src

Files:

• ResolvExpr/AlternativeFinder.cc (modified) (7 diffs)
• ResolvExpr/AlternativeFinder.h (modified) (2 diffs)
• ResolvExpr/TypeEnvironment.cc (modified) (1 diff)
• ResolvExpr/TypeEnvironment.h (modified) (1 diff)
• Tuples/TupleAssignment.cc (modified) (11 diffs)
• Tuples/Tuples.h (modified) (2 diffs)
• prelude/builtins.c (modified) (1 diff)

src/ResolvExpr/AlternativeFinder.cc

@@ -22 +22 @@
 #include <memory>                  // for allocator_traits<>::value_type
 #include <utility>                 // for pair
+#include <vector>                  // for vector
 
 #include "Alternative.h"           // for AltList, Alternative
@@ -333 +334 @@
                 tmpCost.incPoly( -tmpCost.get_polyCost() );
                 if ( tmpCost != Cost::zero ) {
-                // if ( convCost != Cost::zero ) {
                         Type *newType = formalType->clone();
                         env.apply( newType );
@@ -405 +405 @@
 ///     needAssertions.insert( needAssertions.end(), (*tyvar)->get_assertions().begin(), (*tyvar)->get_assertions().end() );
                 }
-        }
-
-        /// instantiate a single argument by matching actuals from [actualIt, actualEnd) against formalType,
-        /// producing expression(s) in out and their total cost in cost.
-        template< typename AltIterator, typename OutputIterator >
-        bool instantiateArgument( Type * formalType, Initializer * defaultValue, AltIterator & actualIt, AltIterator actualEnd, OpenVarSet & openVars, TypeEnvironment & resultEnv, AssertionSet & resultNeed, AssertionSet & resultHave, const SymTab::Indexer & indexer, Cost & cost, OutputIterator out ) {
-                if ( TupleType * tupleType = dynamic_cast< TupleType * >( formalType ) ) {
-                        // formalType is a TupleType - group actuals into a TupleExpr whose type unifies with the TupleType
-                        std::list< Expression * > exprs;
-                        for ( Type * type : *tupleType ) {
-                                if ( ! instantiateArgument( type, defaultValue, actualIt, actualEnd, openVars, resultEnv, resultNeed, resultHave, indexer, cost, back_inserter( exprs ) ) ) {
-                                        deleteAll( exprs );
-                                        return false;
-                                }
-                        }
-                        *out++ = new TupleExpr( exprs );
-                } else if ( TypeInstType * ttype = Tuples::isTtype( formalType ) ) {
-                        // xxx - mixing default arguments with variadic??
-                        std::list< Expression * > exprs;
-                        for ( ; actualIt != actualEnd; ++actualIt ) {
-                                exprs.push_back( actualIt->expr->clone() );
-                                cost += actualIt->cost;
-                        }
-                        Expression * arg = nullptr;
-                        if ( exprs.size() == 1 && Tuples::isTtype( exprs.front()->get_result() ) ) {
-                                // the case where a ttype value is passed directly is special, e.g. for argument forwarding purposes
-                                // xxx - what if passing multiple arguments, last of which is ttype?
-                                // xxx - what would happen if unify was changed so that unifying tuple types flattened both before unifying lists? then pass in TupleType(ttype) below.
-                                arg = exprs.front();
-                        } else {
-                                arg = new TupleExpr( exprs );
-                        }
-                        assert( arg && arg->get_result() );
-                        if ( ! unify( ttype, arg->get_result(), resultEnv, resultNeed, resultHave, openVars, indexer ) ) {
-                                return false;
-                        }
-                        *out++ = arg;
-                } else if ( actualIt != actualEnd ) {
-                        // both actualType and formalType are atomic (non-tuple) types - if they unify
-                        // then accept actual as an argument, otherwise return false (fail to instantiate argument)
-                        Expression * actual = actualIt->expr;
-                        Type * actualType = actual->get_result();
-
-                        PRINT(
-                                std::cerr << "formal type is ";
-                                formalType->print( std::cerr );
-                                std::cerr << std::endl << "actual type is ";
-                                actualType->print( std::cerr );
-                                std::cerr << std::endl;
-                        )
-                        if ( ! unify( formalType, actualType, resultEnv, resultNeed, resultHave, openVars, indexer ) ) {
-                                // std::cerr << "unify failed" << std::endl;
-                                return false;
-                        }
-                        // move the expression from the alternative to the output iterator
-                        *out++ = actual;
-                        actualIt->expr = nullptr;
-                        cost += actualIt->cost;
-                        ++actualIt;
-                } else {
-                        // End of actuals - Handle default values
-                        if ( SingleInit *si = dynamic_cast<SingleInit *>( defaultValue )) {
-                                if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( si->get_value() ) ) {
-                                        // so far, only constant expressions are accepted as default values
-                                        if ( ConstantExpr *cnstexpr = dynamic_cast<ConstantExpr *>( castExpr->get_arg() ) ) {
-                                                if ( Constant *cnst = dynamic_cast<Constant *>( cnstexpr->get_constant() ) ) {
-                                                        if ( unify( formalType, cnst->get_type(), resultEnv, resultNeed, resultHave, openVars, indexer ) ) {
-                                                                *out++ = cnstexpr->clone();
-                                                                return true;
-                                                        } // if
-                                                } // if
-                                        } // if
-                                }
-                        } // if
-                        return false;
-                } // if
-                return true;
-        }
-
-        bool AlternativeFinder::instantiateFunction( std::list< DeclarationWithType* >& formals, const AltList &actuals, bool isVarArgs, OpenVarSet& openVars, TypeEnvironment &resultEnv, AssertionSet &resultNeed, AssertionSet &resultHave, AltList & out ) {
-                simpleCombineEnvironments( actuals.begin(), actuals.end(), resultEnv );
-                // make sure we don't widen any existing bindings
-                for ( TypeEnvironment::iterator i = resultEnv.begin(); i != resultEnv.end(); ++i ) {
-                        i->allowWidening = false;
-                }
-                resultEnv.extractOpenVars( openVars );
-
-                // flatten actuals so that each actual has an atomic (non-tuple) type
-                AltList exploded;
-                Tuples::explode( actuals, indexer, back_inserter( exploded ) );
-
-                AltList::iterator actualExpr = exploded.begin();
-                AltList::iterator actualEnd = exploded.end();
-                for ( DeclarationWithType * formal : formals ) {
-                        // match flattened actuals with formal parameters - actuals will be grouped to match
-                        // with formals as appropriate
-                        Cost cost = Cost::zero;
-                        std::list< Expression * > newExprs;
-                        ObjectDecl * obj = strict_dynamic_cast< ObjectDecl * >( formal );
-                        if ( ! instantiateArgument( obj->get_type(), obj->get_init(), actualExpr, actualEnd, openVars, resultEnv, resultNeed, resultHave, indexer, cost, back_inserter( newExprs ) ) ) {
-                                deleteAll( newExprs );
-                                return false;
-                        }
-                        // success - produce argument as a new alternative
-                        assert( newExprs.size() == 1 );
-                        out.push_back( Alternative( newExprs.front(), resultEnv, cost ) );
-                }
-                if ( actualExpr != actualEnd ) {
-                        // there are still actuals remaining, but we've run out of formal parameters to match against
-                        // this is okay only if the function is variadic
-                        if ( ! isVarArgs ) {
-                                return false;
-                        }
-                        out.splice( out.end(), exploded, actualExpr, actualEnd );
-                }
-                return true;
         }
 
@@ -675 +559 @@
         }
 
-        template< typename OutputIterator >
-        void AlternativeFinder::makeFunctionAlternatives( const Alternative &func, FunctionType *funcType, const AltList &actualAlt, OutputIterator out ) {
-                OpenVarSet openVars;
-                AssertionSet resultNeed, resultHave;
-                TypeEnvironment resultEnv( func.env );
-                makeUnifiableVars( funcType, openVars, resultNeed );
-                resultEnv.add( funcType->get_forall() ); // add all type variables as open variables now so that those not used in the parameter list are still considered open
-                AltList instantiatedActuals; // filled by instantiate function
+        /// Gets a default value from an initializer, nullptr if not present
+        ConstantExpr* getDefaultValue( Initializer* init ) {
+                if ( SingleInit* si = dynamic_cast<SingleInit*>( init ) ) {
+                        if ( CastExpr* ce = dynamic_cast<CastExpr*>( si->get_value() ) ) {
+                                return dynamic_cast<ConstantExpr*>( ce->get_arg() );
+                        }
+                }
+                return nullptr;
+        }
+
+        /// State to iteratively build a match of parameter expressions to arguments
+        struct ArgPack {
+                AltList actuals;                 ///< Arguments included in this pack
+                TypeEnvironment env;             ///< Environment for this pack
+                AssertionSet need;               ///< Assertions outstanding for this pack
+                AssertionSet have;               ///< Assertions found for this pack
+                OpenVarSet openVars;             ///< Open variables for this pack
+                unsigned nextArg;                ///< Index of next argument in arguments list
+                std::vector<Alternative> expls;  ///< Exploded actuals left over from last match
+                unsigned nextExpl;               ///< Index of next exploded alternative to use
+                std::vector<unsigned> tupleEls;  /// Number of elements in current tuple element(s)
+
+                ArgPack(const TypeEnvironment& env, const AssertionSet& need, const AssertionSet& have, 
+                                const OpenVarSet& openVars)
+                        : actuals(), env(env), need(need), have(have), openVars(openVars), nextArg(0),
+                          expls(), nextExpl(0), tupleEls() {}
+                
+                /// Starts a new tuple expression
+                void beginTuple() {
+                        if ( ! tupleEls.empty() ) ++tupleEls.back();
+                        tupleEls.push_back(0);
+                }
+
+                /// Ends a tuple expression, consolidating the appropriate actuals
+                void endTuple() {
+                        // set up new Tuple alternative
+                        std::list<Expression*> exprs;
+                        Cost cost = Cost::zero;
+
+                        // transfer elements into alternative
+                        for (unsigned i = 0; i < tupleEls.back(); ++i) {
+                                exprs.push_front( actuals.back().expr );
+                                actuals.back().expr = nullptr;
+                                cost += actuals.back().cost;
+                                actuals.pop_back();
+                        }
+                        tupleEls.pop_back();
+
+                        // build new alternative
+                        actuals.emplace_back( new TupleExpr( exprs ), this->env, cost );
+                }
+
+                /// Clones and adds an actual, returns this
+                ArgPack& withArg( Expression* expr, Cost cost = Cost::zero ) {
+                        actuals.emplace_back( expr->clone(), this->env, cost );
+                        if ( ! tupleEls.empty() ) ++tupleEls.back();
+                        return *this;
+                }
+        };
+
+        /// Instantiates an argument to match a formal, returns false if no results left
+        bool instantiateArgument( Type* formalType, Initializer* initializer, 
+                        const std::vector< AlternativeFinder >& args, 
+                        std::vector<ArgPack>& results, std::vector<ArgPack>& nextResults, 
+                        const SymTab::Indexer& indexer ) {
+                if ( TupleType* tupleType = dynamic_cast<TupleType*>( formalType ) ) {
+                        // formalType is a TupleType - group actuals into a TupleExpr
+                        for ( ArgPack& result : results ) { result.beginTuple(); }
+                        for ( Type* type : *tupleType ) {
+                                // xxx - dropping initializer changes behaviour from previous, but seems correct
+                                if ( ! instantiateArgument( type, nullptr, args, results, nextResults, indexer ) ) 
+                                        return false;
+                        }
+                        for ( ArgPack& result : results ) { result.endTuple(); }
+                        return true;
+                } else if ( TypeInstType* ttype = Tuples::isTtype( formalType ) ) {
+                        // formalType is a ttype, consumes all remaining arguments
+                        // xxx - mixing default arguments with variadic??
+                        std::vector<ArgPack> finalResults{};  /// list of completed tuples
+                        // start tuples
+                        for ( ArgPack& result : results ) {
+                                result.beginTuple();
+
+                                // use rest of exploded tuple if present
+                                while ( result.nextExpl < result.expls.size() ) {
+                                        const Alternative& actual = result.expls[result.nextExpl];
+                                        result.env.addActual( actual.env, result.openVars );
+                                        result.withArg( actual.expr );
+                                        ++result.nextExpl;
+                                }
+                        }
+                        // iterate until all results completed
+                        while ( ! results.empty() ) {
+                                // add another argument to results
+                                for ( ArgPack& result : results ) {
+                                        // finish result when out of arguments
+                                        if ( result.nextArg >= args.size() ) {
+                                                Type* argType = result.actuals.back().expr->get_result();
+                                                if ( result.tupleEls.back() == 1 && Tuples::isTtype( argType ) ) {
+                                                        // the case where a ttype value is passed directly is special, e.g. for 
+                                                        // argument forwarding purposes
+                                                        // xxx - what if passing multiple arguments, last of which is ttype?
+                                                        // xxx - what would happen if unify was changed so that unifying tuple 
+                                                        // types flattened both before unifying lists? then pass in TupleType
+                                                        // (ttype) below.
+                                                        result.tupleEls.pop_back();
+                                                } else {
+                                                        // collapse leftover arguments into tuple
+                                                        result.endTuple();
+                                                        argType = result.actuals.back().expr->get_result();
+                                                }
+                                                // check unification for ttype before adding to final
+                                                if ( unify( ttype, argType, result.env, result.need, result.have, 
+                                                                result.openVars, indexer ) ) {
+                                                        finalResults.push_back( std::move(result) );
+                                                }
+                                                continue;
+                                        }
+
+                                        // add each possible next argument
+                                        for ( const Alternative& actual : args[result.nextArg] ) {
+                                                ArgPack aResult = result;  // copy to clone everything
+                                                // add details of actual to result
+                                                aResult.env.addActual( actual.env, aResult.openVars );
+                                                Cost cost = actual.cost;
+                
+                                                // explode argument
+                                                std::vector<Alternative> exploded;
+                                                Tuples::explode( actual, indexer, back_inserter( exploded ) );
+                                                
+                                                // add exploded argument to tuple
+                                                for ( Alternative& aActual : exploded ) {
+                                                        aResult.withArg( aActual.expr, cost );
+                                                        cost = Cost::zero;
+                                                }
+                                                ++aResult.nextArg;
+                                                nextResults.push_back( std::move(aResult) );
+                                        }
+                                }
+
+                                // reset for next round
+                                results.swap( nextResults );
+                                nextResults.clear();
+                        }
+                        results.swap( finalResults );
+                        return ! results.empty();
+                }
+                
+                // iterate each current subresult
+                for ( unsigned iResult = 0; iResult < results.size(); ++iResult ) {
+                        ArgPack& result = results[iResult];
+
+                        if ( result.nextExpl < result.expls.size() ) {
+                                // use remainder of exploded tuple if present
+                                const Alternative& actual = result.expls[result.nextExpl];
+                                result.env.addActual( actual.env, result.openVars );
+                                Type* actualType = actual.expr->get_result();
+
+                                PRINT(
+                                        std::cerr << "formal type is ";
+                                        formalType->print( std::cerr );
+                                        std::cerr << std::endl << "actual type is ";
+                                        actualType->print( std::cerr );
+                                        std::cerr << std::endl;
+                                )
+                                
+                                if ( unify( formalType, actualType, result.env, result.need, result.have, 
+                                                result.openVars, indexer ) ) {
+                                        ++result.nextExpl;
+                                        nextResults.push_back( std::move(result.withArg( actual.expr )) );
+                                }
+
+                                continue;
+                        } else if ( result.nextArg >= args.size() ) {
+                                // use default initializers if out of arguments
+                                if ( ConstantExpr* cnstExpr = getDefaultValue( initializer ) ) {
+                                        if ( Constant* cnst = dynamic_cast<Constant*>( cnstExpr->get_constant() ) ) {
+                                                if ( unify( formalType, cnst->get_type(), result.env, result.need, 
+                                                                result.have, result.openVars, indexer ) ) {
+                                                        nextResults.push_back( std::move(result.withArg( cnstExpr )) );
+                                                }
+                                        }
+                                }
+                                continue;
+                        }
+
+                        // Check each possible next argument
+                        for ( const Alternative& actual : args[result.nextArg] ) {
+                                ArgPack aResult = result;  // copy to clone everything
+                                // add details of actual to result
+                                aResult.env.addActual( actual.env, aResult.openVars );
+
+                                // explode argument
+                                std::vector<Alternative> exploded;
+                                Tuples::explode( actual, indexer, back_inserter( exploded ) );
+                                if ( exploded.empty() ) {
+                                        // skip empty tuple arguments
+                                        ++aResult.nextArg;
+                                        results.push_back( std::move(aResult) );
+                                        continue;
+                                }
+
+                                // consider only first exploded actual
+                                const Alternative& aActual = exploded.front();
+                                Type* actualType = aActual.expr->get_result()->clone();
+
+                                PRINT(
+                                        std::cerr << "formal type is ";
+                                        formalType->print( std::cerr );
+                                        std::cerr << std::endl << "actual type is ";
+                                        actualType->print( std::cerr );
+                                        std::cerr << std::endl;
+                                )
+
+                                // attempt to unify types
+                                if ( unify( formalType, actualType, aResult.env, aResult.need, aResult.have, aResult.openVars, indexer ) ) {
+                                        // add argument
+                                        aResult.withArg( aActual.expr, actual.cost );
+                                        ++aResult.nextArg;
+                                        if ( exploded.size() > 1 ) {
+                                                // other parts of tuple left over
+                                                aResult.expls = std::move( exploded );
+                                                aResult.nextExpl = 1;
+                                        }
+                                        nextResults.push_back( std::move(aResult) );
+                                }
+                        }
+                }
+
+                // reset for next parameter
+                results.swap( nextResults );
+                nextResults.clear();
+                
+                return ! results.empty();
+        }       
+
+        template<typename OutputIterator>
+        void AlternativeFinder::makeFunctionAlternatives( const Alternative &func, 
+                        FunctionType *funcType, const std::vector< AlternativeFinder > &args, 
+                        OutputIterator out ) {
+                OpenVarSet funcOpenVars;
+                AssertionSet funcNeed, funcHave;
+                TypeEnvironment funcEnv( func.env );
+                makeUnifiableVars( funcType, funcOpenVars, funcNeed );
+                // add all type variables as open variables now so that those not used in the parameter 
+                // list are still considered open.
+                funcEnv.add( funcType->get_forall() );
+                
                 if ( targetType && ! targetType->isVoid() && ! funcType->get_returnVals().empty() ) {
                         // attempt to narrow based on expected target type
                         Type * returnType = funcType->get_returnVals().front()->get_type();
-                        if ( ! unify( returnType, targetType, resultEnv, resultNeed, resultHave, openVars, indexer ) ) {
-                                // unification failed, don't pursue this alternative
+                        if ( ! unify( returnType, targetType, funcEnv, funcNeed, funcHave, funcOpenVars, 
+                                        indexer ) ) {
+                                // unification failed, don't pursue this function alternative
                                 return;
                         }
                 }
 
-                if ( instantiateFunction( funcType->get_parameters(), actualAlt, funcType->get_isVarArgs(), openVars, resultEnv, resultNeed, resultHave, instantiatedActuals ) ) {
+                // iteratively build matches, one parameter at a time
+                std::vector<ArgPack> results{ ArgPack{ funcEnv, funcNeed, funcHave, funcOpenVars } };
+                std::vector<ArgPack> nextResults{};
+                for ( DeclarationWithType* formal : funcType->get_parameters() ) {
+                        ObjectDecl* obj = strict_dynamic_cast< ObjectDecl* >( formal );
+                        if ( ! instantiateArgument( 
+                                        obj->get_type(), obj->get_init(), args, results, nextResults, indexer ) )
+                                return;
+                }
+
+                // filter out results that don't use all the arguments, and aren't variadic
+                std::vector<ArgPack> finalResults{};
+                if ( funcType->get_isVarArgs() ) {
+                        for ( ArgPack& result : results ) {
+                                // use rest of exploded tuple if present
+                                while ( result.nextExpl < result.expls.size() ) {
+                                        const Alternative& actual = result.expls[result.nextExpl];
+                                        result.env.addActual( actual.env, result.openVars );
+                                        result.withArg( actual.expr );
+                                        ++result.nextExpl;
+                                }
+                        }
+
+                        while ( ! results.empty() ) {
+                                // build combinations for all remaining arguments
+                                for ( ArgPack& result : results ) {
+                                        // keep if used all arguments
+                                        if ( result.nextArg >= args.size() ) {
+                                                finalResults.push_back( std::move(result) );
+                                                continue;
+                                        }
+
+                                        // add each possible next argument
+                                        for ( const Alternative& actual : args[result.nextArg] ) {
+                                                ArgPack aResult = result; // copy to clone everything
+                                                // add details of actual to result
+                                                aResult.env.addActual( actual.env, aResult.openVars );
+                                                Cost cost = actual.cost;
+
+                                                // explode argument
+                                                std::vector<Alternative> exploded;
+                                                Tuples::explode( actual, indexer, back_inserter( exploded ) );
+
+                                                // add exploded argument to arg list
+                                                for ( Alternative& aActual : exploded ) {
+                                                        aResult.withArg( aActual.expr, cost );
+                                                        cost = Cost::zero;
+                                                }
+                                                ++aResult.nextArg;
+                                                nextResults.push_back( std::move(aResult) );
+                                        }
+                                }
+
+                                // reset for next round
+                                results.swap( nextResults );
+                                nextResults.clear();
+                        }
+                } else {
+                        // filter out results that don't use all the arguments
+                        for ( ArgPack& result : results ) {
+                                if ( result.nextExpl >= result.expls.size() && result.nextArg >= args.size() ) {
+                                        finalResults.push_back( std::move(result) );
+                                }
+                        }
+                }
+
+                // validate matching combos, add to final result list
+                for ( ArgPack& result : finalResults ) {
                         ApplicationExpr *appExpr = new ApplicationExpr( func.expr->clone() );
-                        Alternative newAlt( appExpr, resultEnv, sumCost( instantiatedActuals ) );
-                        makeExprList( instantiatedActuals, appExpr->get_args() );
+                        Alternative newAlt( appExpr, result.env, sumCost( result.actuals ) );
+                        makeExprList( result.actuals, appExpr->get_args() );
                         PRINT(
                                 std::cerr << "instantiate function success: " << appExpr << std::endl;
                                 std::cerr << "need assertions:" << std::endl;
-                                printAssertionSet( resultNeed, std::cerr, 8 );
+                                printAssertionSet( result.need, std::cerr, 8 );
                         )
-                        inferParameters( resultNeed, resultHave, newAlt, openVars, out );
+                        inferParameters( result.need, result.have, newAlt, result.openVars, out );
                 }
         }
@@ -711 +903 @@
                 if ( funcFinder.alternatives.empty() ) return;
 
-                std::list< AlternativeFinder > argAlternatives;
-                findSubExprs( untypedExpr->begin_args(), untypedExpr->end_args(), back_inserter( argAlternatives ) );
-
-                std::list< AltList > possibilities;
-                combos( argAlternatives.begin(), argAlternatives.end(), back_inserter( possibilities ) );
+                std::vector< AlternativeFinder > argAlternatives;
+                findSubExprs( untypedExpr->begin_args(), untypedExpr->end_args(), 
+                        back_inserter( argAlternatives ) );
 
                 // take care of possible tuple assignments
                 // if not tuple assignment, assignment is taken care of as a normal function call
-                Tuples::handleTupleAssignment( *this, untypedExpr, possibilities );
+                Tuples::handleTupleAssignment( *this, untypedExpr, argAlternatives );
 
                 // find function operators
@@ -744 +934 @@
                                                 Alternative newFunc( *func );
                                                 referenceToRvalueConversion( newFunc.expr );
-                                                for ( std::list< AltList >::iterator actualAlt = possibilities.begin(); actualAlt != possibilities.end(); ++actualAlt ) {
-                                                        // XXX
-                                                        //Designators::check_alternative( function, *actualAlt );
-                                                        makeFunctionAlternatives( newFunc, function, *actualAlt, std::back_inserter( candidates ) );
-                                                }
+                                                makeFunctionAlternatives( newFunc, function, argAlternatives, 
+                                                        std::back_inserter( candidates ) );
                                         }
                                 } else if ( TypeInstType *typeInst = dynamic_cast< TypeInstType* >( func->expr->get_result()->stripReferences() ) ) { // handle ftype (e.g. *? on function pointer)
@@ -756 +943 @@
                                                         Alternative newFunc( *func );
                                                         referenceToRvalueConversion( newFunc.expr );
-                                                        for ( std::list< AltList >::iterator actualAlt = possibilities.begin(); actualAlt != possibilities.end(); ++actualAlt ) {
-                                                                makeFunctionAlternatives( newFunc, function, *actualAlt, std::back_inserter( candidates ) );
-                                                        } // for
+                                                        makeFunctionAlternatives( newFunc, function, argAlternatives, 
+                                                                std::back_inserter( candidates ) );
                                                 } // if
                                         } // if
-                                }
-
-                                // try each function operator ?() with the current function alternative and each of the argument combinations
-                                for ( AltList::iterator funcOp = funcOpFinder.alternatives.begin(); funcOp != funcOpFinder.alternatives.end(); ++funcOp ) {
-                                        // check if the type is pointer to function
-                                        if ( PointerType *pointer = dynamic_cast< PointerType* >( funcOp->expr->get_result()->stripReferences() ) ) {
-                                                if ( FunctionType *function = dynamic_cast< FunctionType* >( pointer->get_base() ) ) {
+                                }                       
+                        } catch ( SemanticError &e ) {
+                                errors.append( e );
+                        }
+                } // for
+
+                // try each function operator ?() with each function alternative
+                if ( ! funcOpFinder.alternatives.empty() ) {
+                        // add function alternatives to front of argument list
+                        argAlternatives.insert( argAlternatives.begin(), std::move(funcFinder) );
+
+                        for ( AltList::iterator funcOp = funcOpFinder.alternatives.begin();
+                                        funcOp != funcOpFinder.alternatives.end(); ++funcOp ) {
+                                try {
+                                        // check if type is a pointer to function
+                                        if ( PointerType* pointer = dynamic_cast<PointerType*>( 
+                                                        funcOp->expr->get_result()->stripReferences() ) ) {
+                                                if ( FunctionType* function = 
+                                                                dynamic_cast<FunctionType*>( pointer->get_base() ) ) {
                                                         Alternative newFunc( *funcOp );
                                                         referenceToRvalueConversion( newFunc.expr );
-                                                        for ( std::list< AltList >::iterator actualAlt = possibilities.begin(); actualAlt != possibilities.end(); ++actualAlt ) {
-                                                                AltList currentAlt;
-                                                                currentAlt.push_back( *func );
-                                                                currentAlt.insert( currentAlt.end(), actualAlt->begin(), actualAlt->end() );
-                                                                makeFunctionAlternatives( newFunc, function, currentAlt, std::back_inserter( candidates ) );
-                                                        } // for
-                                                } // if
-                                        } // if
-                                } // for
-                        } catch ( SemanticError &e ) {
-                                errors.append( e );
-                        }
-                } // for
+                                                        makeFunctionAlternatives( newFunc, function, argAlternatives, 
+                                                                std::back_inserter( candidates ) );
+                                                }
+                                        }
+                                } catch ( SemanticError &e ) {
+                                        errors.append( e );
+                                }
+                        }
+                }
 
                 // Implement SFINAE; resolution errors are only errors if there aren't any non-erroneous resolutions

src/ResolvExpr/AlternativeFinder.h

@@ -34 +34 @@
           public:
                 AlternativeFinder( const SymTab::Indexer &indexer, const TypeEnvironment &env );
+
+                AlternativeFinder( const AlternativeFinder& o )
+                        : indexer(o.indexer), alternatives(o.alternatives), env(o.env), 
+                          targetType(o.targetType) {}
+                
+                AlternativeFinder( AlternativeFinder&& o )
+                        : indexer(o.indexer), alternatives(std::move(o.alternatives)), env(o.env), 
+                          targetType(o.targetType) {}
+                
+                AlternativeFinder& operator= ( const AlternativeFinder& o ) {
+                        if (&o == this) return *this;
+                        
+                        // horrific nasty hack to rebind references...
+                        alternatives.~AltList();
+                        new(this) AlternativeFinder(o);
+                        return *this;
+                }
+
+                AlternativeFinder& operator= ( AlternativeFinder&& o ) {
+                        if (&o == this) return *this;
+                        
+                        // horrific nasty hack to rebind references...
+                        alternatives.~AltList();
+                        new(this) AlternativeFinder(std::move(o));
+                        return *this;
+                }
+
                 void find( Expression *expr, bool adjust = false, bool prune = true, bool failFast = true );
                 /// Calls find with the adjust flag set; adjustment turns array and function types into equivalent pointer types
@@ -99 +126 @@
                 /// Adds alternatives for offsetof expressions, given the base type and name of the member
                 template< typename StructOrUnionType > void addOffsetof( StructOrUnionType *aggInst, const std::string &name );
-                bool instantiateFunction( std::list< DeclarationWithType* >& formals, const AltList &actuals, bool isVarArgs, OpenVarSet& openVars, TypeEnvironment &resultEnv, AssertionSet &resultNeed, AssertionSet &resultHave, AltList & out );
-                template< typename OutputIterator >
-                void makeFunctionAlternatives( const Alternative &func, FunctionType *funcType, const AltList &actualAlt, OutputIterator out );
+                template<typename OutputIterator>
+                void makeFunctionAlternatives( const Alternative &func, FunctionType *funcType, const std::vector< AlternativeFinder >& args, OutputIterator out );
                 template< typename OutputIterator >
                 void inferParameters( const AssertionSet &need, AssertionSet &have, const Alternative &newAlt, OpenVarSet &openVars, OutputIterator out );

src/ResolvExpr/TypeEnvironment.cc

@@ -201 +201 @@
         }
 
+        void TypeEnvironment::addActual( const TypeEnvironment& actualEnv, OpenVarSet& openVars ) {
+                for ( const EqvClass& c : actualEnv ) {
+                        EqvClass c2 = c;
+                        c2.allowWidening = false;
+                        for ( const std::string& var : c2.vars ) {
+                                openVars[ var ] = c2.data;
+                        }
+                        env.push_back( std::move(c2) );
+                }
+        }
+
 } // namespace ResolvExpr
 

src/ResolvExpr/TypeEnvironment.h

@@ -86 +86 @@
                 TypeEnvironment *clone() const { return new TypeEnvironment( *this ); }
 
+                /// Iteratively adds the environment of a new actual (with allowWidening = false), 
+                /// and extracts open variables.
+                void addActual( const TypeEnvironment& actualEnv, OpenVarSet& openVars );
+
                 typedef std::list< EqvClass >::iterator iterator;
                 iterator begin() { return env.begin(); }

src/Tuples/TupleAssignment.cc

@@ -20 +20 @@
 #include <memory>                          // for unique_ptr, allocator_trai...
 #include <string>                          // for string
+#include <vector>
 
 #include "CodeGen/OperatorTable.h"
@@ -33 +34 @@
 #include "ResolvExpr/Resolver.h"           // for resolveCtorInit
 #include "ResolvExpr/TypeEnvironment.h"    // for TypeEnvironment
+#include "ResolvExpr/typeops.h"            // for combos
 #include "SynTree/Declaration.h"           // for ObjectDecl
 #include "SynTree/Expression.h"            // for Expression, CastExpr, Name...
@@ -52 +54 @@
                 // dispatcher for Tuple (multiple and mass) assignment operations
                 TupleAssignSpotter( ResolvExpr::AlternativeFinder & );
-                void spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities );
+                void spot( UntypedExpr * expr, std::vector<ResolvExpr::AlternativeFinder> &args );
 
           private:
@@ -59 +61 @@
                 struct Matcher {
                   public:
-                        Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
+                        Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList& lhs, const 
+                                ResolvExpr::AltList& rhs );
                         virtual ~Matcher() {}
                         virtual void match( std::list< Expression * > &out ) = 0;
@@ -72 +75 @@
                 struct MassAssignMatcher : public Matcher {
                   public:
-                        MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
+                        MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList& lhs, 
+                                const ResolvExpr::AltList& rhs ) : Matcher(spotter, lhs, rhs) {}
                         virtual void match( std::list< Expression * > &out );
                 };
@@ -78 +82 @@
                 struct MultipleAssignMatcher : public Matcher {
                   public:
-                        MultipleAssignMatcher( TupleAssignSpotter &spot, const ResolvExpr::AltList & alts );
+                        MultipleAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList& lhs, 
+                                const ResolvExpr::AltList& rhs ) : Matcher(spotter, lhs, rhs) {}
                         virtual void match( std::list< Expression * > &out );
                 };
@@ -114 +119 @@
         }
 
-        void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
+        void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * expr, 
+                                std::vector<ResolvExpr::AlternativeFinder> &args ) {
                 TupleAssignSpotter spotter( currentFinder );
-                spotter.spot( expr, possibilities );
+                spotter.spot( expr, args );
         }
 
@@ -122 +128 @@
                 : currentFinder(f) {}
 
-        void TupleAssignSpotter::spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
+        void TupleAssignSpotter::spot( UntypedExpr * expr, 
+                        std::vector<ResolvExpr::AlternativeFinder> &args ) {
                 if (  NameExpr *op = dynamic_cast< NameExpr * >(expr->get_function()) ) {
                         if ( CodeGen::isCtorDtorAssign( op->get_name() ) ) {
-                               fname = op->get_name();
-                                PRINT( std::cerr << "TupleAssignment: " << fname << std::endl; )
-                                for ( std::list<ResolvExpr::AltList>::const_iterator ali = possibilities.begin(); ali != possibilities.end(); ++ali ) {
-                                        if ( ali->size() == 0 ) continue; // AlternativeFinder will natrually handle this case, if it's legal
-                                        if ( ali->size() <= 1 && CodeGen::isAssignment( op->get_name() ) ) {
-                                                // what does it mean if an assignment takes 1 argument? maybe someone defined such a function, in which case AlternativeFinder will naturally handle it
-                                                continue;
+                                fname = op->get_name();
+
+                                // AlternativeFinder will naturally handle this case case, if it's legal
+                                if ( args.size() == 0 ) return;
+
+                                // if an assignment only takes 1 argument, that's odd, but maybe someone wrote 
+                                // the function, in which case AlternativeFinder will handle it normally
+                                if ( args.size() == 1 && CodeGen::isAssignment( fname ) ) return;
+
+                                // look over all possible left-hand-sides
+                                for ( ResolvExpr::Alternative& lhsAlt : args[0] ) {
+                                        // skip non-tuple LHS
+                                        if ( ! refToTuple(lhsAlt.expr) ) continue;
+
+                                        // explode is aware of casts - ensure every LHS expression is sent into explode 
+                                        // with a reference cast
+                                        // xxx - this seems to change the alternatives before the normal 
+                                        //  AlternativeFinder flow; maybe this is desired?
+                                        if ( ! dynamic_cast<CastExpr*>( lhsAlt.expr ) ) {
+                                                lhsAlt.expr = new CastExpr( lhsAlt.expr, 
+                                                                new ReferenceType( Type::Qualifiers(), 
+                                                                        lhsAlt.expr->get_result()->clone() ) );
                                         }
 
-                                        assert( ! ali->empty() );
-                                        // grab args 2-N and group into a TupleExpr
-                                        const ResolvExpr::Alternative & alt1 = ali->front();
-                                        auto begin = std::next(ali->begin(), 1), end = ali->end();
-                                        PRINT( std::cerr << "alt1 is " << alt1.expr << std::endl; )
-                                        if ( refToTuple(alt1.expr) ) {
-                                                PRINT( std::cerr << "and is reference to tuple" << std::endl; )
-                                                if ( isMultAssign( begin, end ) ) {
-                                                        PRINT( std::cerr << "possible multiple assignment" << std::endl; )
-                                                        matcher.reset( new MultipleAssignMatcher( *this, *ali ) );
-                                                } else {
-                                                        // mass assignment
-                                                        PRINT( std::cerr << "possible mass assignment" << std::endl; )
-                                                        matcher.reset( new MassAssignMatcher( *this,  *ali ) );
+                                        // explode the LHS so that each field of a tuple-valued-expr is assigned
+                                        ResolvExpr::AltList lhs;
+                                        explode( lhsAlt, currentFinder.get_indexer(), back_inserter(lhs), true );
+                                        for ( ResolvExpr::Alternative& alt : lhs ) {
+                                                // each LHS value must be a reference - some come in with a cast expression, 
+                                                // if not just cast to reference here
+                                                if ( ! dynamic_cast<ReferenceType*>( alt.expr->get_result() ) ) {
+                                                        alt.expr = new CastExpr( alt.expr, 
+                                                                new ReferenceType( Type::Qualifiers(), 
+                                                                        alt.expr->get_result()->clone() ) );
                                                 }
+                                        }
+
+                                        if ( args.size() == 1 ) {
+                                                // mass default-initialization/destruction
+                                                ResolvExpr::AltList rhs{};
+                                                matcher.reset( new MassAssignMatcher( *this, lhs, rhs ) );
                                                 match();
+                                        } else if ( args.size() > 2 ) {
+                                                // expand all possible RHS possibilities
+                                                // TODO build iterative version of this instead of using combos
+                                                std::vector< ResolvExpr::AltList > rhsAlts;
+                                                combos( std::next(args.begin(), 1), args.end(), 
+                                                        std::back_inserter( rhsAlts ) );
+                                                for ( const ResolvExpr::AltList& rhsAlt : rhsAlts ) {
+                                                        // multiple assignment
+                                                        ResolvExpr::AltList rhs;
+                                                        explode( rhsAlt, currentFinder.get_indexer(), 
+                                                                std::back_inserter(rhs), true );
+                                                        matcher.reset( new MultipleAssignMatcher( *this, lhs, rhs ) );
+                                                        match();
+                                                }
+                                        } else {
+                                                for ( const ResolvExpr::Alternative& rhsAlt : args[1] ) {
+                                                        ResolvExpr::AltList rhs;
+                                                        if ( isTuple(rhsAlt.expr) ) {
+                                                                // multiple assignment
+                                                                explode( rhsAlt, currentFinder.get_indexer(),  
+                                                                        std::back_inserter(rhs), true );
+                                                                matcher.reset( new MultipleAssignMatcher( *this, lhs, rhs ) );
+                                                        } else {
+                                                                // mass assignment
+                                                                rhs.push_back( rhsAlt );
+                                                                matcher.reset( new MassAssignMatcher( *this, lhs, rhs ) );
+                                                        }
+                                                        match();
+                                                }
                                         }
                                 }
@@ -169 +222 @@
                 ResolvExpr::AltList current;
                 // now resolve new assignments
-                for ( std::list< Expression * >::iterator i = new_assigns.begin(); i != new_assigns.end(); ++i ) {
+                for ( std::list< Expression * >::iterator i = new_assigns.begin(); 
+                                i != new_assigns.end(); ++i ) {
                         PRINT(
                                 std::cerr << "== resolving tuple assign ==" << std::endl;
@@ -175 +229 @@
                         )
 
-                        ResolvExpr::AlternativeFinder finder( currentFinder.get_indexer(), currentFinder.get_environ() );
+                        ResolvExpr::AlternativeFinder finder{ currentFinder.get_indexer(), 
+                                currentFinder.get_environ() };
                         try {
                                 finder.findWithAdjustment(*i);
@@ -196 +251 @@
                 // combine assignment environments into combined expression environment
                 simpleCombineEnvironments( current.begin(), current.end(), matcher->compositeEnv );
-                currentFinder.get_alternatives().push_front( ResolvExpr::Alternative(new TupleAssignExpr(solved_assigns, matcher->tmpDecls), matcher->compositeEnv, ResolvExpr::sumCost( current  ) + matcher->baseCost ) );
-        }
-
-        TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList &alts ) : spotter(spotter), baseCost( ResolvExpr::sumCost( alts ) ) {
-                assert( ! alts.empty() );
-                // combine argument environments into combined expression environment
-                simpleCombineEnvironments( alts.begin(), alts.end(), compositeEnv );
-
-                ResolvExpr::Alternative lhsAlt = alts.front();
-                // explode is aware of casts - ensure every LHS expression is sent into explode with a reference cast
-                if ( ! dynamic_cast< CastExpr * >( lhsAlt.expr ) ) {
-                        lhsAlt.expr = new CastExpr( lhsAlt.expr, new ReferenceType( Type::Qualifiers(), lhsAlt.expr->get_result()->clone() ) );
-                }
-
-                // explode the lhs so that each field of the tuple-valued-expr is assigned.
-                explode( lhsAlt, spotter.currentFinder.get_indexer(), back_inserter(lhs), true );
-
-                for ( ResolvExpr::Alternative & alt : lhs ) {
-                        // every LHS value must be a reference - some come in with a cast expression, if it doesn't just cast to reference here.
-                        if ( ! dynamic_cast< ReferenceType * >( alt.expr->get_result() ) ) {
-                                alt.expr = new CastExpr( alt.expr, new ReferenceType( Type::Qualifiers(), alt.expr->get_result()->clone() ) );
-                        }
-                }
-        }
-
-        TupleAssignSpotter::MassAssignMatcher::MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
-                assert( alts.size() == 1 || alts.size() == 2 );
-                if ( alts.size() == 2 ) {
-                        rhs.push_back( alts.back() );
-                }
-        }
-
-        TupleAssignSpotter::MultipleAssignMatcher::MultipleAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
-                // explode the rhs so that each field of the tuple-valued-expr is assigned.
-                explode( std::next(alts.begin(), 1), alts.end(), spotter.currentFinder.get_indexer(), back_inserter(rhs), true );
+                currentFinder.get_alternatives().push_front( ResolvExpr::Alternative(
+                        new TupleAssignExpr(solved_assigns, matcher->tmpDecls), matcher->compositeEnv, 
+                        ResolvExpr::sumCost( current ) + matcher->baseCost ) );
+        }
+
+        TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter, 
+                const ResolvExpr::AltList &lhs, const ResolvExpr::AltList &rhs ) 
+        : lhs(lhs), rhs(rhs), spotter(spotter), 
+          baseCost( ResolvExpr::sumCost( lhs ) + ResolvExpr::sumCost( rhs ) ) {
+                simpleCombineEnvironments( lhs.begin(), lhs.end(), compositeEnv );
+                simpleCombineEnvironments( rhs.begin(), rhs.end(), compositeEnv );
         }
 

src/Tuples/Tuples.h

@@ -17 +17 @@
 
 #include <string>
+#include <vector>
 
 #include "SynTree/Expression.h"
@@ -26 +27 @@
 namespace Tuples {
         // TupleAssignment.cc
-        void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * assign, const std::list<ResolvExpr::AltList> & possibilities );
-
+        void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * assign, 
+                std::vector< ResolvExpr::AlternativeFinder >& args );
+        
         // TupleExpansion.cc
         /// expands z.[a, b.[x, y], c] into [z.a, z.b.x, z.b.y, z.c], inserting UniqueExprs as appropriate

src/prelude/builtins.c

@@ -80 +80 @@
 } // ?\?
 
-static inline forall( otype T | { void ?{}( T & this, one_t ); T ?*?( T, T ); double ?/?( double, T ); } )
-double ?\?( T x, signed long int y ) {
-    if ( y >=  0 ) return (double)(x \ (unsigned long int)y);
-    else return 1.0 / x \ (unsigned long int)(-y);
-} // ?\?
+// FIXME (x \ (unsigned long int)y) relies on X ?\?(T, unsigned long) a function that is neither 
+// defined, nor passed as an assertion parameter. Without user-defined conversions, cannot specify 
+// X as a type that casts to double, yet it doesn't make sense to write functions with that type 
+// signature where X is double.
+
+// static inline forall( otype T | { void ?{}( T & this, one_t ); T ?*?( T, T ); double ?/?( double, T ); } )
+// double ?\?( T x, signed long int y ) {
+//     if ( y >=  0 ) return (double)(x \ (unsigned long int)y);
+//     else return 1.0 / x \ (unsigned long int)(-y);
+// } // ?\?
 
 static inline long int ?\=?( long int & x, unsigned long int y ) { x = x \ y; return x; }