Changeset 9d5089e

Timestamp:

Jun 17, 2019, 7:14:58 PM (5 years ago)

Author:

Aaron Moss <a3moss@…>

Branches:

ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, pthread-emulation, qualifiedEnum

Children:

ea05f8d

Parents:

aba20d2

Message:

Port CandidateFinder::makeFunctionCandidates() and deps

Location:

src

Files:

• AST/TypeEnvironment.hpp (modified) (1 diff)
• AST/porting.md (modified) (1 diff)
• ResolvExpr/AlternativeFinder.cc (modified) (2 diffs)
• ResolvExpr/Candidate.hpp (modified) (1 diff)
• ResolvExpr/CandidateFinder.cpp (modified) (12 diffs)
• ResolvExpr/ConversionCost.cc (modified) (3 diffs)
• ResolvExpr/PolyCost.cc (modified) (2 diffs)
• ResolvExpr/SpecCost.cc (modified) (2 diffs)
• ResolvExpr/typeops.h (modified) (3 diffs)

src/AST/TypeEnvironment.hpp

@@ -215 +215 @@
 std::ostream & operator<<( std::ostream & out, const TypeEnvironment & env );
 
-}
+} // namespace ast
 
 // Local Variables: //

src/AST/porting.md

@@ -302 +302 @@
 * `ExplodedActual.h` => `ExplodedArg.hpp`
 
+`polyCost`
+* switched order of `env`, `symtab` parameters for better consistency
+
 [1] https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Type-Attributes.html#Type-Attributes
 

src/ResolvExpr/AlternativeFinder.cc

@@ -227 +227 @@
         }
 
-        const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
-                if ( expr->result.as< ast::ReferenceType >() ) {
-                        // cast away reference from expr
-                        cost.incReference();
-                        return new ast::CastExpr{ expr->location, expr, expr->result->stripReferences() };
-                }
-                
-                return expr;
-        }
-
         template< typename InputIterator, typename OutputIterator >
         void AlternativeFinder::findSubExprs( InputIterator begin, InputIterator end, OutputIterator out ) {
@@ -518 +508 @@
         }
 
-        /// Unique identifier for matching expression resolutions to their requesting expression
-        UniqueId globalResnSlot = 0;
+        /// Unique identifier for matching expression resolutions to their requesting expression (located in CandidateFinder.cpp)
+        extern UniqueId globalResnSlot;
 
         template< typename OutputIterator >

src/ResolvExpr/Candidate.hpp

@@ -58 +58 @@
 
         Candidate(
+                const ast::Expr * x, const ast::TypeEnvironment & e, const ast::OpenVarSet & o, 
+                const ast::AssertionSet & n, const Cost & c, const Cost & cvt = Cost::zero )
+        : expr( x ), cost( c ), cvtCost( cvt ), env( e ), open( o ), need( n.begin(), n.end() ) {}
+
+        Candidate(
                 const ast::Expr * x, ast::TypeEnvironment && e, ast::OpenVarSet && o,
                 ast::AssertionSet && n, const Cost & c, const Cost & cvt = Cost::zero )

src/ResolvExpr/CandidateFinder.cpp

@@ -29 +29 @@
 #include "Resolver.h"
 #include "SatisfyAssertions.hpp"
-#include "typeops.h"              // for adjustExprType
+#include "typeops.h"              // for adjustExprType, conversionCost, polyCost, specCost
 #include "Unify.h"
 #include "AST/Expr.hpp"
@@ -44 +44 @@
 namespace ResolvExpr {
 
+using std::move;
+
+/// partner to move that copies any copyable type
+template<typename T>
+T copy( const T & x ) { return x; }
+
+const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost ) {
+        if ( expr->result.as< ast::ReferenceType >() ) {
+                // cast away reference from expr
+                cost.incReference();
+                return new ast::CastExpr{ expr->location, expr, expr->result->stripReferences() };
+        }
+        
+        return expr;
+}
+
+/// Unique identifier for matching expression resolutions to their requesting expression
+UniqueId globalResnSlot = 0;
+
 namespace {
-
         /// First index is which argument, second is which alternative, third is which exploded element
         using ExplodedArgs_new = std::deque< std::vector< ExplodedArg > >;
@@ -65 +83 @@
         }
 
+        /// Computes conversion cost between two types
+        Cost computeConversionCost( 
+                const ast::Type * argType, const ast::Type * paramType, const ast::SymbolTable & symtab, 
+                const ast::TypeEnvironment & env 
+        ) {
+                PRINT(
+                        std::cerr << std::endl << "converting ";
+                        ast::print( std::cerr, argType, 2 );
+                        std::cerr << std::endl << " to ";
+                        ast::print( std::cerr, paramType, 2 );
+                        std::cerr << std::endl << "environment is: ";
+                        ast::print( std::cerr, env, 2 );
+                        std::cerr << std::endl;
+                )
+                Cost convCost = conversionCost( argType, paramType, symtab, env );
+                PRINT(
+                        std::cerr << std::endl << "cost is " << convCost << std::endl;
+                )
+                if ( convCost == Cost::infinity ) return convCost;
+                convCost.incPoly( polyCost( paramType, symtab, env ) + polyCost( argType, symtab, env ) );
+                PRINT(
+                        std::cerr << "cost with polycost is " << convCost << std::endl;
+                )
+                return convCost;
+        }
+
+        /// Computes conversion cost for a given expression to a given type
+        const ast::Expr * computeExpressionConversionCost( 
+                const ast::Expr * arg, const ast::Type * paramType, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env, Cost & outCost 
+        ) {
+                Cost convCost = computeConversionCost( arg->result, paramType, symtab, env );
+                outCost += convCost;
+
+                // If there is a non-zero conversion cost, ignoring poly cost, then the expression requires 
+                // conversion. Ignore poly cost for now, since this requires resolution of the cast to 
+                // infer parameters and this does not currently work for the reason stated below
+                Cost tmpCost = convCost;
+                tmpCost.incPoly( -tmpCost.get_polyCost() );
+                if ( tmpCost != Cost::zero ) {
+                        ast::ptr< ast::Type > newType = paramType;
+                        env.apply( newType );
+                        return new ast::CastExpr{ arg->location, arg, newType };
+
+                        // xxx - *should* be able to resolve this cast, but at the moment pointers are not 
+                        // castable to zero_t, but are implicitly convertible. This is clearly inconsistent, 
+                        // once this is fixed it should be possible to resolve the cast.
+                        // xxx - this isn't working, it appears because type1 (parameter) is seen as widenable, 
+                        // but it shouldn't be because this makes the conversion from DT* to DT* since 
+                        // commontype(zero_t, DT*) is DT*, rather than nothing
+
+                        // CandidateFinder finder{ symtab, env };
+                        // finder.find( arg, ResolvMode::withAdjustment() );
+                        // assertf( finder.candidates.size() > 0, 
+                        //      "Somehow castable expression failed to find alternatives." );
+                        // assertf( finder.candidates.size() == 1, 
+                        //      "Somehow got multiple alternatives for known cast expression." );
+                        // return finder.candidates.front()->expr;
+                }
+
+                return arg;
+        }
+
         /// Computes conversion cost for a given candidate
         Cost computeApplicationConversionCost( 
-                const CandidateRef & cand, const ast::SymbolTable & symtab 
+                CandidateRef cand, const ast::SymbolTable & symtab 
         ) {
-                #warning unimplemented
-                (void)cand; (void)symtab;
-                assert(false);
-                return Cost::infinity;
+                auto appExpr = cand->expr.strict_as< ast::ApplicationExpr >();
+                auto pointer = appExpr->func->result.strict_as< ast::PointerType >();
+                auto function = pointer->base.strict_as< ast::FunctionType >();
+
+                Cost convCost = Cost::zero;
+                const auto & params = function->params;
+                auto param = params.begin();
+                auto & args = appExpr->args;
+
+                for ( unsigned i = 0; i < args.size(); ++i ) {
+                        const ast::Type * argType = args[i]->result;
+                        PRINT(
+                                std::cerr << "arg expression:" << std::endl;
+                                ast::print( std::cerr, args[i], 2 );
+                                std::cerr << "--- results are" << std::endl;
+                                ast::print( std::cerr, argType, 2 );
+                        )
+
+                        if ( param == params.end() ) {
+                                if ( function->isVarArgs ) {
+                                        convCost.incUnsafe();
+                                        PRINT( std::cerr << "end of params with varargs function: inc unsafe: " 
+                                                << convCost << std::endl; ; )
+                                        // convert reference-typed expressions into value-typed expressions
+                                        cand->expr = ast::mutate_field_index( 
+                                                appExpr, &ast::ApplicationExpr::args, i, 
+                                                referenceToRvalueConversion( args[i], convCost ) );
+                                        continue;
+                                } else return Cost::infinity;
+                        }
+
+                        if ( auto def = args[i].as< ast::DefaultArgExpr >() ) {
+                                // Default arguments should be free - don't include conversion cost.
+                                // Unwrap them here because they are not relevant to the rest of the system
+                                cand->expr = ast::mutate_field_index( 
+                                        appExpr, &ast::ApplicationExpr::args, i, def->expr );
+                                ++param;
+                                continue;
+                        }
+
+                        // mark conversion cost and also specialization cost of param type
+                        const ast::Type * paramType = (*param)->get_type();
+                        cand->expr = ast::mutate_field_index( 
+                                appExpr, &ast::ApplicationExpr::args, i, 
+                                computeExpressionConversionCost( 
+                                        args[i], paramType, symtab, cand->env, convCost ) );
+                        convCost.decSpec( specCost( paramType ) );
+                        ++param;  // can't be in for-loop update because of the continue
+                }
+
+                if ( param != params.end() ) return Cost::infinity;
+
+                // specialization cost of return types can't be accounted for directly, it disables 
+                // otherwise-identical calls, like this example based on auto-newline in the I/O lib:
+                //
+                //   forall(otype OS) {
+                //     void ?|?(OS&, int);  // with newline
+                //     OS&  ?|?(OS&, int);  // no newline, always chosen due to more specialization
+                //   }
+
+                // mark type variable and specialization cost of forall clause
+                convCost.incVar( function->forall.size() );
+                for ( const ast::TypeDecl * td : function->forall ) {
+                        convCost.decSpec( td->assertions.size() );
+                }
+
+                return convCost;
+        }
+
+        void makeUnifiableVars( 
+                const ast::ParameterizedType * type, ast::OpenVarSet & unifiableVars, 
+                ast::AssertionSet & need 
+        ) {
+                for ( const ast::TypeDecl * tyvar : type->forall ) {
+                        unifiableVars[ tyvar->name ] = ast::TypeDecl::Data{ tyvar };
+                        for ( const ast::DeclWithType * assn : tyvar->assertions ) {
+                                need[ assn ].isUsed = true;
+                        }
+                }
+        }
+
+        /// Gets a default value from an initializer, nullptr if not present
+        const ast::ConstantExpr * getDefaultValue( const ast::Init * init ) {
+                if ( auto si = dynamic_cast< const ast::SingleInit * >( init ) ) {
+                        if ( auto ce = si->value.as< ast::CastExpr >() ) {
+                                return ce->arg.as< ast::ConstantExpr >();
+                        } else {
+                                return si->value.as< ast::ConstantExpr >();
+                        }
+                }
+                return nullptr;
+        }
+
+        /// State to iteratively build a match of parameter expressions to arguments
+        struct ArgPack {
+                std::size_t parent;          ///< Index of parent pack
+                ast::ptr< ast::Expr > expr;  ///< The argument stored here
+                Cost cost;                   ///< The cost of this argument
+                ast::TypeEnvironment env;    ///< Environment for this pack
+                ast::AssertionSet need;      ///< Assertions outstanding for this pack
+                ast::AssertionSet have;      ///< Assertions found for this pack
+                ast::OpenVarSet open;        ///< Open variables for this pack
+                unsigned nextArg;            ///< Index of next argument in arguments list
+                unsigned tupleStart;         ///< Number of tuples that start at this index
+                unsigned nextExpl;           ///< Index of next exploded element
+                unsigned explAlt;            ///< Index of alternative for nextExpl > 0
+
+                ArgPack()
+                : parent( 0 ), expr(), cost( Cost::zero ), env(), need(), have(), open(), nextArg( 0 ), 
+                  tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
+                
+                ArgPack( 
+                        const ast::TypeEnvironment & env, const ast::AssertionSet & need, 
+                        const ast::AssertionSet & have, const ast::OpenVarSet & open )
+                : parent( 0 ), expr(), cost( Cost::zero ), env( env ), need( need ), have( have ), 
+                  open( open ), nextArg( 0 ), tupleStart( 0 ), nextExpl( 0 ), explAlt( 0 ) {}
+                
+                ArgPack(
+                        std::size_t parent, const ast::Expr * expr, ast::TypeEnvironment && env, 
+                        ast::AssertionSet && need, ast::AssertionSet && have, ast::OpenVarSet && open, 
+                        unsigned nextArg, unsigned tupleStart = 0, Cost cost = Cost::zero, 
+                        unsigned nextExpl = 0, unsigned explAlt = 0 )
+                : parent(parent), expr( expr ), cost( cost ), env( move( env ) ), need( move( need ) ),
+                  have( move( have ) ), open( move( open ) ), nextArg( nextArg ), tupleStart( tupleStart ),
+                  nextExpl( nextExpl ), explAlt( explAlt ) {}
+                
+                ArgPack(
+                        const ArgPack & o, ast::TypeEnvironment && env, ast::AssertionSet && need, 
+                        ast::AssertionSet && have, ast::OpenVarSet && open, unsigned nextArg, Cost added )
+                : parent( o.parent ), expr( o.expr ), cost( o.cost + added ), env( move( env ) ), 
+                  need( move( need ) ), have( move( have ) ), open( move( open ) ), nextArg( nextArg ), 
+                  tupleStart( o.tupleStart ), nextExpl( 0 ), explAlt( 0 ) {}
+                
+                /// true if this pack is in the middle of an exploded argument
+                bool hasExpl() const { return nextExpl > 0; }
+
+                /// Gets the list of exploded candidates for this pack
+                const ExplodedArg & getExpl( const ExplodedArgs_new & args ) const {
+                        return args[ nextArg-1 ][ explAlt ];
+                }
+                
+                /// Ends a tuple expression, consolidating the appropriate args
+                void endTuple( const std::vector< ArgPack > & packs ) {
+                        // add all expressions in tuple to list, summing cost
+                        std::deque< const ast::Expr * > exprs;
+                        const ArgPack * pack = this;
+                        if ( expr ) { exprs.emplace_front( expr ); }
+                        while ( pack->tupleStart == 0 ) {
+                                pack = &packs[pack->parent];
+                                exprs.emplace_front( pack->expr );
+                                cost += pack->cost;
+                        }
+                        // reset pack to appropriate tuple
+                        std::vector< ast::ptr< ast::Expr > > exprv( exprs.begin(), exprs.end() );
+                        expr = new ast::TupleExpr{ expr->location, move( exprv ) };
+                        tupleStart = pack->tupleStart - 1;
+                        parent = pack->parent;
+                }
+        };
+
+        /// Instantiates an argument to match a parameter, returns false if no matching results left
+        bool instantiateArgument( 
+                const ast::Type * paramType, const ast::Init * init, const ExplodedArgs_new & args, 
+                std::vector< ArgPack > & results, std::size_t & genStart, const ast::SymbolTable & symtab, 
+                unsigned nTuples = 0 
+        ) {
+                if ( auto tupleType = dynamic_cast< const ast::TupleType * >( paramType ) ) {
+                        // paramType is a TupleType -- group args into a TupleExpr
+                        ++nTuples;
+                        for ( const ast::Type * type : *tupleType ) {
+                                // xxx - dropping initializer changes behaviour from previous, but seems correct
+                                // ^^^ need to handle the case where a tuple has a default argument
+                                if ( ! instantiateArgument( 
+                                        type, nullptr, args, results, genStart, symtab, nTuples ) ) return false;
+                                nTuples = 0;
+                        }
+                        // re-constitute tuples for final generation
+                        for ( auto i = genStart; i < results.size(); ++i ) {
+                                results[i].endTuple( results );
+                        }
+                        return true;
+                } else if ( const ast::TypeInstType * ttype = Tuples::isTtype( paramType ) ) {
+                        // paramType is a ttype, consumes all remaining arguments
+                        
+                        // completed tuples; will be spliced to end of results to finish
+                        std::vector< ArgPack > finalResults{};
+
+                        // iterate until all results completed
+                        std::size_t genEnd;
+                        ++nTuples;
+                        do {
+                                genEnd = results.size();
+
+                                // add another argument to results
+                                for ( std::size_t i = genStart; i < genEnd; ++i ) {
+                                        unsigned nextArg = results[i].nextArg;
+                                        
+                                        // use next element of exploded tuple if present
+                                        if ( results[i].hasExpl() ) {
+                                                const ExplodedArg & expl = results[i].getExpl( args );
+
+                                                unsigned nextExpl = results[i].nextExpl + 1;
+                                                if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
+
+                                                results.emplace_back(
+                                                        i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
+                                                        copy( results[i].need ), copy( results[i].have ), 
+                                                        copy( results[i].open ), nextArg, nTuples, Cost::zero, nextExpl,
+                                                        results[i].explAlt );
+
+                                                continue;
+                                        }
+
+                                        // finish result when out of arguments
+                                        if ( nextArg >= args.size() ) {
+                                                ArgPack newResult{
+                                                        results[i].env, results[i].need, results[i].have, results[i].open };
+                                                newResult.nextArg = nextArg;
+                                                const ast::Type * argType = nullptr;
+
+                                                if ( nTuples > 0 || ! results[i].expr ) {
+                                                        // first iteration or no expression to clone,
+                                                        // push empty tuple expression
+                                                        newResult.parent = i;
+                                                        std::vector< ast::ptr< ast::Expr > > emptyList;
+                                                        newResult.expr = 
+                                                                new ast::TupleExpr{ CodeLocation{}, move( emptyList ) };
+                                                        argType = newResult.expr->result;
+                                                } else {
+                                                        // clone result to collect tuple
+                                                        newResult.parent = results[i].parent;
+                                                        newResult.cost = results[i].cost;
+                                                        newResult.tupleStart = results[i].tupleStart;
+                                                        newResult.expr = results[i].expr;
+                                                        argType = newResult.expr->result;
+
+                                                        if ( results[i].tupleStart > 0 && 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.
+                                                                --newResult.tupleStart;
+                                                        } else {
+                                                                // collapse leftover arguments into tuple
+                                                                newResult.endTuple( results );
+                                                                argType = newResult.expr->result;
+                                                        }
+                                                }
+
+                                                // check unification for ttype before adding to final
+                                                if ( 
+                                                        unify( 
+                                                                ttype, argType, newResult.env, newResult.need, newResult.have,
+                                                                newResult.open, symtab ) 
+                                                ) {
+                                                        finalResults.emplace_back( move( newResult ) );
+                                                }
+
+                                                continue;
+                                        }
+
+                                        // add each possible next argument
+                                        for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
+                                                const ExplodedArg & expl = args[nextArg][j];
+
+                                                // fresh copies of parent parameters for this iteration
+                                                ast::TypeEnvironment env = results[i].env;
+                                                ast::OpenVarSet open = results[i].open;
+
+                                                env.addActual( expl.env, open );
+
+                                                // skip empty tuple arguments by (nearly) cloning parent into next gen
+                                                if ( expl.exprs.empty() ) {
+                                                        results.emplace_back(
+                                                                results[i], move( env ), copy( results[i].need ), 
+                                                                copy( results[i].have ), move( open ), nextArg + 1, expl.cost );
+                                                        
+                                                        continue;
+                                                }
+
+                                                // add new result
+                                                results.emplace_back(
+                                                        i, expl.exprs.front(), move( env ), copy( results[i].need ), 
+                                                        copy( results[i].have ), move( open ), nextArg + 1, nTuples, 
+                                                        expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
+                                        }
+                                }
+
+                                // reset for next round
+                                genStart = genEnd;
+                                nTuples = 0;
+                        } while ( genEnd != results.size() );
+
+                        // splice final results onto results
+                        for ( std::size_t i = 0; i < finalResults.size(); ++i ) {
+                                results.emplace_back( move( finalResults[i] ) );
+                        }
+                        return ! finalResults.empty();
+                }
+
+                // iterate each current subresult
+                std::size_t genEnd = results.size();
+                for ( std::size_t i = genStart; i < genEnd; ++i ) {
+                        unsigned nextArg = results[i].nextArg;
+
+                        // use remainder of exploded tuple if present
+                        if ( results[i].hasExpl() ) {
+                                const ExplodedArg & expl = results[i].getExpl( args );
+                                const ast::Expr * expr = expl.exprs[ results[i].nextExpl ];
+
+                                ast::TypeEnvironment env = results[i].env;
+                                ast::AssertionSet need = results[i].need, have = results[i].have;
+                                ast::OpenVarSet open = results[i].open;
+
+                                const ast::Type * argType = expr->result;
+
+                                PRINT(
+                                        std::cerr << "param type is ";
+                                        ast::print( std::cerr, paramType );
+                                        std::cerr << std::endl << "arg type is ";
+                                        ast::print( std::cerr, argType );
+                                        std::cerr << std::endl;
+                                )
+
+                                if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
+                                        unsigned nextExpl = results[i].nextExpl + 1;
+                                        if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
+
+                                        results.emplace_back(
+                                                i, expr, move( env ), move( need ), move( have ), move( open ), nextArg, 
+                                                nTuples, Cost::zero, nextExpl, results[i].explAlt );
+                                }
+
+                                continue;
+                        }
+
+                        // use default initializers if out of arguments
+                        if ( nextArg >= args.size() ) {
+                                if ( const ast::ConstantExpr * cnst = getDefaultValue( init ) ) {
+                                        ast::TypeEnvironment env = results[i].env;
+                                        ast::AssertionSet need = results[i].need, have = results[i].have;
+                                        ast::OpenVarSet open = results[i].open;
+
+                                        if ( unify( paramType, cnst->result, env, need, have, open, symtab ) ) {
+                                                results.emplace_back(
+                                                        i, new ast::DefaultArgExpr{ cnst->location, cnst }, move( env ), 
+                                                        move( need ), move( have ), move( open ), nextArg, nTuples );
+                                        }
+                                }
+
+                                continue;
+                        }
+
+                        // Check each possible next argument
+                        for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
+                                const ExplodedArg & expl = args[nextArg][j];
+
+                                // fresh copies of parent parameters for this iteration
+                                ast::TypeEnvironment env = results[i].env;
+                                ast::AssertionSet need = results[i].need, have = results[i].have;
+                                ast::OpenVarSet open = results[i].open;
+
+                                env.addActual( expl.env, open );
+
+                                // skip empty tuple arguments by (nearly) cloning parent into next gen
+                                if ( expl.exprs.empty() ) {
+                                        results.emplace_back(
+                                                results[i], move( env ), move( need ), move( have ), move( open ), 
+                                                nextArg + 1, expl.cost );
+                                        
+                                        continue;
+                                }
+
+                                // consider only first exploded arg
+                                const ast::Expr * expr = expl.exprs.front();
+                                const ast::Type * argType = expr->result;
+
+                                PRINT(
+                                        std::cerr << "param type is ";
+                                        ast::print( std::cerr, paramType );
+                                        std::cerr << std::endl << "arg type is ";
+                                        ast::print( std::cerr, argType );
+                                        std::cerr << std::endl;
+                                )
+
+                                // attempt to unify types
+                                if ( unify( paramType, argType, env, need, have, open, symtab ) ) {
+                                        // add new result
+                                        results.emplace_back(
+                                                i, expr, move( env ), move( need ), move( have ), move( open ), 
+                                                nextArg + 1, nTuples, expl.cost, expl.exprs.size() == 1 ? 0 : 1, j );
+                                }
+                        }
+                }
+
+                // reset for next parameter
+                genStart = genEnd;
+
+                return genEnd != results.size();
         }
 
@@ -99 +578 @@
                 }
 
+                /// Set up candidate assertions for inference
+                void inferParameters( CandidateRef & newCand, CandidateList & out ) {
+                        // Set need bindings for any unbound assertions
+                        UniqueId crntResnSlot = 0; // matching ID for this expression's assertions
+                        for ( auto & assn : newCand->need ) {
+                                // skip already-matched assertions
+                                if ( assn.second.resnSlot != 0 ) continue;
+                                // assign slot for expression if needed
+                                if ( crntResnSlot == 0 ) { crntResnSlot = ++globalResnSlot; }
+                                // fix slot to assertion
+                                assn.second.resnSlot = crntResnSlot;
+                        }
+                        // pair slot to expression
+                        if ( crntResnSlot != 0 ) {
+                                newCand->expr.get_and_mutate()->inferred.resnSlots().emplace_back( crntResnSlot );
+                        }
+
+                        // add to output list; assertion satisfaction will occur later
+                        out.emplace_back( newCand );
+                }
+
+                /// Completes a function candidate with arguments located
+                void validateFunctionCandidate( 
+                        const CandidateRef & func, ArgPack & result, const std::vector< ArgPack > & results, 
+                        CandidateList & out 
+                ) {
+                        ast::ApplicationExpr * appExpr = 
+                                new ast::ApplicationExpr{ func->expr->location, func->expr };
+                        // sum cost and accumulate arguments
+                        std::deque< const ast::Expr * > args;
+                        Cost cost = func->cost;
+                        const ArgPack * pack = &result;
+                        while ( pack->expr ) {
+                                args.emplace_front( pack->expr );
+                                cost += pack->cost;
+                                pack = &results[pack->parent];
+                        }
+                        std::vector< ast::ptr< ast::Expr > > vargs( args.begin(), args.end() );
+                        appExpr->args = move( vargs );
+                        // build and validate new candidate
+                        auto newCand = 
+                                std::make_shared<Candidate>( appExpr, result.env, result.open, result.need, cost );
+                        PRINT(
+                                std::cerr << "instantiate function success: " << appExpr << std::endl;
+                                std::cerr << "need assertions:" << std::endl;
+                                ast::print( std::cerr, result.need, 2 );
+                        )
+                        inferParameters( newCand, out );
+                }
+
                 /// Builds a list of candidates for a function, storing them in out
                 void makeFunctionCandidates(
@@ -104 +633 @@
                         const ExplodedArgs_new & args, CandidateList & out
                 ) {
-                        #warning unimplemented
-                        (void)func; (void)funcType; (void)args; (void)out;
-                        assert(false);
+                        ast::OpenVarSet funcOpen;
+                        ast::AssertionSet funcNeed, funcHave;
+                        ast::TypeEnvironment funcEnv{ func->env };
+                        makeUnifiableVars( funcType, funcOpen, 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->forall );
+
+                        if ( targetType && ! targetType->isVoid() && ! funcType->returns.empty() ) {
+                                // attempt to narrow based on expected target type
+                                const ast::Type * returnType = funcType->returns.front()->get_type();
+                                if ( ! unify( 
+                                        returnType, targetType, funcEnv, funcNeed, funcHave, funcOpen, symtab ) 
+                                ) {
+                                        // unification failed, do not pursue this candidate
+                                        return;
+                                }
+                        }
+
+                        // iteratively build matches, one parameter at a time
+                        std::vector< ArgPack > results;
+                        results.emplace_back( funcEnv, funcNeed, funcHave, funcOpen );
+                        std::size_t genStart = 0;
+
+                        for ( const ast::DeclWithType * param : funcType->params ) {
+                                auto obj = strict_dynamic_cast< const ast::ObjectDecl * >( param );
+                                // Try adding the arguments corresponding to the current parameter to the existing 
+                                // matches
+                                if ( ! instantiateArgument( 
+                                        obj->type, obj->init, args, results, genStart, symtab ) ) return;
+                        }
+
+                        if ( funcType->isVarArgs ) {
+                                // append any unused arguments to vararg pack
+                                std::size_t genEnd;
+                                do {
+                                        genEnd = results.size();
+
+                                        // iterate results
+                                        for ( std::size_t i = genStart; i < genEnd; ++i ) {
+                                                unsigned nextArg = results[i].nextArg;
+
+                                                // use remainder of exploded tuple if present
+                                                if ( results[i].hasExpl() ) {
+                                                        const ExplodedArg & expl = results[i].getExpl( args );
+
+                                                        unsigned nextExpl = results[i].nextExpl + 1;
+                                                        if ( nextExpl == expl.exprs.size() ) { nextExpl = 0; }
+
+                                                        results.emplace_back(
+                                                                i, expl.exprs[ results[i].nextExpl ], copy( results[i].env ),
+                                                                copy( results[i].need ), copy( results[i].have ),
+                                                                copy( results[i].open ), nextArg, 0, Cost::zero, nextExpl,
+                                                                results[i].explAlt );
+
+                                                        continue;
+                                                }
+
+                                                // finish result when out of arguments
+                                                if ( nextArg >= args.size() ) {
+                                                        validateFunctionCandidate( func, results[i], results, out );
+
+                                                        continue;
+                                                }
+
+                                                // add each possible next argument
+                                                for ( std::size_t j = 0; j < args[nextArg].size(); ++j ) {
+                                                        const ExplodedArg & expl = args[nextArg][j];
+
+                                                        // fresh copies of parent parameters for this iteration
+                                                        ast::TypeEnvironment env = results[i].env;
+                                                        ast::OpenVarSet open = results[i].open;
+
+                                                        env.addActual( expl.env, open );
+
+                                                        // skip empty tuple arguments by (nearly) cloning parent into next gen
+                                                        if ( expl.exprs.empty() ) {
+                                                                results.emplace_back(
+                                                                        results[i], move( env ), copy( results[i].need ), 
+                                                                        copy( results[i].have ), move( open ), nextArg + 1, 
+                                                                        expl.cost );
+
+                                                                continue;
+                                                        }
+
+                                                        // add new result
+                                                        results.emplace_back(
+                                                                i, expl.exprs.front(), move( env ), copy( results[i].need ),
+                                                                copy( results[i].have ), move( open ), nextArg + 1, 0, expl.cost, 
+                                                                expl.exprs.size() == 1 ? 0 : 1, j );
+                                                }
+                                        }
+
+                                        genStart = genEnd;
+                                } while( genEnd != results.size() );
+                        } else {
+                                // filter out the results that don't use all the arguments
+                                for ( std::size_t i = genStart; i < results.size(); ++i ) {
+                                        ArgPack & result = results[i];
+                                        if ( ! result.hasExpl() && result.nextArg >= args.size() ) {
+                                                validateFunctionCandidate( func, result, results, out );
+                                        }
+                                }
+                        }
                 }
 
@@ -189 +819 @@
                                         funcE.emplace_back( *func, symtab );
                                 }
-                                argExpansions.emplace_front( std::move( funcE ) );
+                                argExpansions.emplace_front( move( funcE ) );
 
                                 for ( const CandidateRef & op : opFinder ) {
@@ -233 +863 @@
                                 if ( cvtCost != Cost::infinity ) {
                                         withFunc->cvtCost = cvtCost;
-                                        candidates.emplace_back( std::move( withFunc ) );
-                                }
-                        }
-                        found = std::move( candidates );
+                                        candidates.emplace_back( move( withFunc ) );
+                                }
+                        }
+                        found = move( candidates );
 
                         // use a new list so that candidates are not examined by addAnonConversions twice
@@ -376 +1006 @@
                                                 new ast::LogicalExpr{ 
                                                         logicalExpr->location, r1->expr, r2->expr, logicalExpr->isAnd },
-                                                std::move( env ), std::move( open ), std::move( need ), 
-                                                r1->cost + r2->cost );
+                                                move( env ), move( open ), move( need ), r1->cost + r2->cost );
                                 }
                         }
@@ -512 +1141 @@
 
                                 addCandidate(
-                                        new ast::TupleExpr{ tupleExpr->location, std::move( exprs ) }, 
-                                        std::move( env ), std::move( open ), std::move( need ), sumCost( subs ) );
+                                        new ast::TupleExpr{ tupleExpr->location, move( exprs ) }, 
+                                        move( env ), move( open ), move( need ), sumCost( subs ) );
                         }
                 }
@@ -628 +1257 @@
                         cand->env.applyFree( newResult );
                         cand->expr = ast::mutate_field(
-                                cand->expr.get(), &ast::Expr::result, std::move( newResult ) );
+                                cand->expr.get(), &ast::Expr::result, move( newResult ) );
                         
                         out.emplace_back( cand );
@@ -666 +1295 @@
 
                 // reset candidates
-                candidates = std::move( satisfied );
+                candidates = move( satisfied );
         }
 
@@ -690 +1319 @@
 
                 auto oldsize = candidates.size();
-                candidates = std::move( pruned );
+                candidates = move( pruned );
 
                 PRINT(

src/ResolvExpr/ConversionCost.cc

@@ -85 +85 @@
                         });
                 } else {
-                        PassVisitor<ConversionCost> converter( dest, indexer, env, conversionCost );
+                        PassVisitor<ConversionCost> converter( 
+                                dest, indexer, env, 
+                                (Cost (*)(Type*, Type*, const SymTab::Indexer&, const TypeEnvironment&))
+                                        conversionCost );
                         src->accept( converter );
                         if ( converter.pass.get_cost() == Cost::infinity ) {
@@ -134 +137 @@
                         } else {
                                 PRINT( std::cerr << "reference to rvalue conversion" << std::endl; )
-                                PassVisitor<ConversionCost> converter( dest, indexer, env, conversionCost );
+                                PassVisitor<ConversionCost> converter( 
+                                        dest, indexer, env, 
+                                        (Cost (*)(Type*, Type*, const SymTab::Indexer&, const TypeEnvironment&))
+                                                conversionCost );
                                 src->accept( converter );
                                 return converter.pass.get_cost();
@@ -482 +488 @@
                 } // if
         }
+
+        Cost conversionCost( 
+                const ast::Type * src, const ast::Type * dst, const ast::SymbolTable & symtab, 
+                const ast::TypeEnvironment & env
+        ) {
+                #warning unimplemented
+                (void)src; (void)dst; (void)symtab; (void)env;
+                assert(false);
+                return Cost::zero;
+        }
 } // namespace ResolvExpr
 

src/ResolvExpr/PolyCost.cc

@@ -14 +14 @@
 //
 
+#include "AST/SymbolTable.hpp"
+#include "AST/Type.hpp"
+#include "AST/TypeEnvironment.hpp"
 #include "Common/PassVisitor.h"
 #include "SymTab/Indexer.h"   // for Indexer
@@ -54 +57 @@
         }
 
+        int polyCost( 
+                const ast::Type * type, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env 
+        ) {
+                #warning unimplemented
+                (void)type; (void)symtab; (void)env;
+                assert(false);
+                return 0;
+        }
+
 } // namespace ResolvExpr
 

src/ResolvExpr/SpecCost.cc

@@ -17 +17 @@
 #include <list>
 
+#include "AST/Type.hpp"
 #include "Common/PassVisitor.h"
 #include "SynTree/Declaration.h"
@@ -111 +112 @@
                 return counter.pass.get_count();
         }
+
+        int specCost( const ast::Type * ty ) {
+                #warning unimplmented
+                (void)ty;
+                assert(false);
+                return 0;
+        }
 } // namespace ResolvExpr
 

src/ResolvExpr/typeops.h

@@ -81 +81 @@
         // in ConversionCost.cc
         Cost conversionCost( Type *src, Type *dest, const SymTab::Indexer &indexer, const TypeEnvironment &env );
+        Cost conversionCost( 
+                const ast::Type * src, const ast::Type * dst, const ast::SymbolTable & symtab, 
+                const ast::TypeEnvironment & env );
 
         // in AlternativeFinder.cc
@@ -127 +130 @@
         // in PolyCost.cc
         int polyCost( Type *type, const TypeEnvironment &env, const SymTab::Indexer &indexer );
+        int polyCost( 
+                const ast::Type * type, const ast::SymbolTable & symtab, const ast::TypeEnvironment & env );
 
         // in SpecCost.cc
         int specCost( Type *type );
+        int specCost( const ast::Type * type );
 
         // in Occurs.cc
@@ -146 +152 @@
         // in AlternativeFinder.cc
         void referenceToRvalueConversion( Expression *& expr, Cost & cost );
+        // in CandidateFinder.cpp
         const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost );