Changeset 98a8290

Timestamp:

Jun 4, 2019, 2:03:25 PM (6 years ago)

Author:

Thierry Delisle <tdelisle@…>

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:

1867c96, bc4bea8, de8dfac2

Parents:

0e315a5 (diff), 4ae2364 (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:

• AST/Decl.hpp (modified) (1 diff)
• AST/Node.hpp (modified) (3 diffs)
• AST/Type.hpp (modified) (1 diff)
• AST/TypeEnvironment.cpp (modified) (14 diffs)
• AST/TypeEnvironment.hpp (modified) (2 diffs)
• AST/TypeSubstitution.cpp (modified) (2 diffs)
• AST/porting.md (modified) (1 diff)
• ResolvExpr/CommonType.cc (modified) (1 diff)
• ResolvExpr/FindOpenVars.cc (modified) (1 diff)
• ResolvExpr/FindOpenVars.h (modified) (1 diff)
• ResolvExpr/TypeEnvironment.cc (modified) (9 diffs)
• ResolvExpr/TypeEnvironment.h (modified) (1 diff)
• ResolvExpr/Unify.cc (modified) (28 diffs)
• ResolvExpr/Unify.h (modified) (3 diffs)
• ResolvExpr/WidenMode.h (modified) (1 diff)
• ResolvExpr/typeops.h (modified) (5 diffs)
• include/cassert (modified) (2 diffs)

src/AST/Decl.hpp

@@ -102 +102 @@
         ptr<Expr> bitfieldWidth;
 
-        ObjectDecl( const CodeLocation & loc, const std::string & name, const Type * type, Init * init = nullptr,
-                Storage::Classes storage = {}, Linkage::Spec linkage = Linkage::C, Expr * bitWd = nullptr,
-                std::vector< ptr<Attribute> > && attrs = {}, Function::Specs fs = {})
+        ObjectDecl( const CodeLocation & loc, const std::string & name, const Type * type, 
+                Init * init = nullptr, Storage::Classes storage = {}, Linkage::Spec linkage = Linkage::C, 
+                Expr * bitWd = nullptr, std::vector< ptr<Attribute> > && attrs = {}, 
+                Function::Specs fs = {} )
         : DeclWithType( loc, name, storage, linkage, std::move(attrs), fs ), type( type ),
           init( init ), bitfieldWidth( bitWd ) {}

src/AST/Node.hpp

@@ -10 +10 @@
 // Created On       : Wed May 8 10:27:04 2019
 // Last Modified By : Andrew Beach
-// Last Modified On : Thu May 23 16:00:00 2019
-// Update Count     : 4
+// Last Modified On : Mon Jun  3 13:26:00 2019
+// Update Count     : 5
 //
 
@@ -107 +107 @@
         ptr_base() : node(nullptr) {}
         ptr_base( const node_t * n ) : node(n) { if( node ) _inc(node); }
-        ~ptr_base() { if( node ) _dec(node); }
+        ~ptr_base() { if( node ) { auto tmp = node; node = nullptr; _dec(tmp); } }
 
         ptr_base( const ptr_base & o ) : node(o.node) {
@@ -127 +127 @@
         template<typename o_node_t>
         ptr_base & operator=( const o_node_t * node ) {
-                assign( node ? strict_dynamic_cast<const node_t *>(node) : nullptr );
+                assign( strict_dynamic_cast<const node_t *, nullptr>(node) );
                 return *this;
         }

src/AST/Type.hpp

@@ -48 +48 @@
 
         Type * set_const( bool v ) { qualifiers.is_const = v; return this; }
+        Type * set_volatile( bool v ) { qualifiers.is_volatile = v; return this; }
         Type * set_restrict( bool v ) { qualifiers.is_restrict = v; return this; }
         Type * set_lvalue( bool v ) { qualifiers.is_lvalue = v; return this; }

src/AST/TypeEnvironment.cpp

@@ -46 +46 @@
 }
 
-void print( std::ostream & out, const OpenVarSet & openVars, Indenter indent ) {
+void print( std::ostream & out, const OpenVarSet & open, Indenter indent ) {
         out << indent;
         bool first = true;
-        for ( const auto & i : openVars ) {
+        for ( const auto & i : open ) {
                 if ( first ) { first = false; } else { out << ' '; }
                 out << i.first << "(" << i.second << ")";
@@ -166 +166 @@
 
 bool TypeEnvironment::combine( 
-                const TypeEnvironment & o, OpenVarSet & openVars, const SymbolTable & symtab ) {
+                const TypeEnvironment & o, OpenVarSet & open, const SymbolTable & symtab ) {
         // short-circuit easy cases
         if ( o.empty() ) return true;
@@ -189 +189 @@
                         EqvClass & r = *rt;
                         // merge bindings
-                        if ( ! mergeBound( r, c, openVars, symtab ) ) return false;
+                        if ( ! mergeBound( r, c, open, symtab ) ) return false;
                         // merge previous unbound variables into this class, checking occurs if needed
                         if ( r.bound ) for ( const auto & u : c.vars ) {
@@ -204 +204 @@
                                 } else if ( st != rt ) {
                                         // bound, but not to the same class
-                                        if ( ! mergeClasses( rt, st, openVars, symtab ) ) return false;
+                                        if ( ! mergeClasses( rt, st, open, symtab ) ) return false;
                                 }       // ignore bound into the same class
                         }
@@ -216 +216 @@
 }
 
-void TypeEnvironment::extractOpenVars( OpenVarSet & openVars ) const {
+void TypeEnvironment::extractOpenVars( OpenVarSet & open ) const {
         for ( const auto & clz : env ) {
                 for ( const auto & var : clz.vars ) {
-                        openVars[ var ] = clz.data;
-                }
-        }
-}
-
-void TypeEnvironment::addActual( const TypeEnvironment & actualEnv, OpenVarSet & openVars ) {
+                        open[ var ] = clz.data;
+                }
+        }
+}
+
+void TypeEnvironment::addActual( const TypeEnvironment & actualEnv, OpenVarSet & open ) {
         for ( const auto & clz : actualEnv ) {
                 EqvClass c = clz;
                 c.allowWidening = false;
                 for ( const auto & var : c.vars ) {
-                        openVars[ var ] = c.data;
+                        open[ var ] = c.data;
                 }
                 env.emplace_back( std::move(c) );
@@ -268 +268 @@
 bool TypeEnvironment::bindVar( 
                 const TypeInstType * typeInst, const Type * bindTo, const TypeDecl::Data & data, 
-                AssertionSet & need, AssertionSet & have, const OpenVarSet & openVars, 
-                WidenMode widenMode, const SymbolTable & symtab ) {
+                AssertionSet & need, AssertionSet & have, const OpenVarSet & open, WidenMode widen, 
+                const SymbolTable & symtab 
+) {
         // remove references from bound type, so that type variables can only bind to value types
-        bindTo = bindTo->stripReferences();
-        auto tyvar = openVars.find( typeInst->name );
-        assert( tyvar != openVars.end() );
-        if ( ! tyVarCompatible( tyvar->second, bindTo ) ) return false;
-        if ( occurs( bindTo, typeInst->name, *this ) ) return false;
+        ptr<Type> target = bindTo->stripReferences();
+        auto tyvar = open.find( typeInst->name );
+        assert( tyvar != open.end() );
+        if ( ! tyVarCompatible( tyvar->second, target ) ) return false;
+        if ( occurs( target, typeInst->name, *this ) ) return false;
 
         auto it = internal_lookup( typeInst->name );
@@ -282 +283 @@
                         // attempt to unify equivalence class type with type to bind to.
                         // equivalence class type has stripped qualifiers which must be restored
-                        const Type * common = nullptr;
+                        ptr<Type> common;
                         ptr<Type> newType = it->bound;
                         newType.get_and_mutate()->qualifiers = typeInst->qualifiers;
                         if ( unifyInexact( 
-                                        newType, bindTo, *this, need, have, openVars, 
-                                        widenMode & WidenMode{ it->allowWidening, true }, symtab, common ) ) {
+                                        newType, target, *this, need, have, open, 
+                                        widen & WidenMode{ it->allowWidening, true }, symtab, common ) ) {
                                 if ( common ) {
-                                        it->bound = common;
+                                        it->bound = std::move(common);
                                         clear_qualifiers( it->bound );
                                 }
                         } else return false;
                 } else {
-                        it->bound = bindTo;
+                        it->bound = std::move(target);
                         clear_qualifiers( it->bound );
-                        it->allowWidening = widenMode.widenFirst && widenMode.widenSecond;
+                        it->allowWidening = widen.first && widen.second;
                 }
         } else {
                 env.emplace_back( 
-                        typeInst->name, bindTo, widenMode.widenFirst && widenMode.widenSecond, data );
+                        typeInst->name, target, widen.first && widen.second, data );
         }
         return true;
@@ -307 +308 @@
 bool TypeEnvironment::bindVarToVar( 
                 const TypeInstType * var1, const TypeInstType * var2, TypeDecl::Data && data, 
-                AssertionSet & need, AssertionSet & have, const OpenVarSet & openVars, 
-                WidenMode widenMode, const SymbolTable & symtab ) {
+                AssertionSet & need, AssertionSet & have, const OpenVarSet & open, 
+                WidenMode widen, const SymbolTable & symtab 
+) {
         auto c1 = internal_lookup( var1->name );
         auto c2 = internal_lookup( var2->name );
@@ -314 +316 @@
         // exit early if variables already bound together
         if ( c1 != env.end() && c1 == c2 ) {
-                c1->allowWidening &= widenMode;
+                c1->allowWidening &= widen;
                 return true;
         }
@@ -327 +329 @@
                         type1 = c1->bound;
                 }
-                widen1 = widenMode.widenFirst && c1->allowWidening;
+                widen1 = widen.first && c1->allowWidening;
         }
         if ( c2 != env.end() ) {
@@ -334 +336 @@
                         type2 = c2->bound;
                 }
-                widen2 = widenMode.widenSecond && c2->allowWidening;
+                widen2 = widen.second && c2->allowWidening;
         }
 
@@ -341 +343 @@
                 ptr<Type> newType1{ type1 }, newType2{ type2 };
                 WidenMode newWidenMode{ widen1, widen2 };
-                const Type * common = nullptr;
+                ptr<Type> common;
 
                 if ( unifyInexact(
-                                newType1, newType2, *this, need, have, openVars, newWidenMode, symtab, common ) ) {
+                                newType1, newType2, *this, need, have, open, newWidenMode, symtab, common ) ) {
                         c1->vars.insert( c2->vars.begin(), c2->vars.end() );
                         c1->allowWidening = widen1 && widen2;
                         if ( common ) {
-                                c1->bound = common;
+                                c1->bound = std::move(common);
                                 clear_qualifiers( c1->bound );
                         }
@@ -395 +397 @@
 
 bool TypeEnvironment::mergeBound( 
-                EqvClass & to, const EqvClass & from, OpenVarSet & openVars, const SymbolTable & symtab ) {
+                EqvClass & to, const EqvClass & from, OpenVarSet & open, const SymbolTable & symtab ) {
         if ( from.bound ) {
                 if ( to.bound ) {
                         // attempt to unify bound types
                         ptr<Type> toType{ to.bound }, fromType{ from.bound };
-                        WidenMode widenMode{ to.allowWidening, from.allowWidening };
-                        const Type * common = nullptr;
+                        WidenMode widen{ to.allowWidening, from.allowWidening };
+                        ptr<Type> common;
                         AssertionSet need, have;
 
                         if ( unifyInexact( 
-                                        toType, fromType, *this, need, have, openVars, widenMode, symtab, common ) ) {
+                                        toType, fromType, *this, need, have, open, widen, symtab, common ) ) {
                                 // unifies, set common type if necessary
                                 if ( common ) {
-                                        to.bound = common;
+                                        to.bound = std::move(common);
                                         clear_qualifiers( to.bound );
                                 }
@@ -423 +425 @@
 
 bool TypeEnvironment::mergeClasses( 
-                ClassList::iterator to, ClassList::iterator from, OpenVarSet & openVars, 
-                const SymbolTable & symtab ) {
+        ClassList::iterator to, ClassList::iterator from, OpenVarSet & open, const SymbolTable & symtab
+) {
         EqvClass & r = *to, & s = *from;
 
         // ensure bounds match
-        if ( ! mergeBound( r, s, openVars, symtab ) ) return false;
+        if ( ! mergeBound( r, s, open, symtab ) ) return false;
 
         // check safely bindable

src/AST/TypeEnvironment.hpp

@@ -178 +178 @@
                 const TypeInstType * typeInst, const Type * bindTo, const TypeDecl::Data & data, 
                 AssertionSet & need, AssertionSet & have, const OpenVarSet & openVars, 
-                ResolvExpr::WidenMode widenMode, const SymbolTable & symtab );
+                ResolvExpr::WidenMode widen, const SymbolTable & symtab );
         
         /// Binds the type classes represented by `var1` and `var2` together; will add one or both 
@@ -185 +185 @@
                 const TypeInstType * var1, const TypeInstType * var2, TypeDecl::Data && data, 
                 AssertionSet & need, AssertionSet & have, const OpenVarSet & openVars, 
-                ResolvExpr::WidenMode widenMode, const SymbolTable & symtab );
+                ResolvExpr::WidenMode widen, const SymbolTable & symtab );
 
         /// Disallows widening for all bindings in the environment

src/AST/TypeSubstitution.cpp

@@ -9 +9 @@
 // Author           : Richard C. Bilson
 // Created On       : Mon May 18 07:44:20 2015
-// Last Modified By : Peter A. Buhr
-// Last Modified On : Thu Mar 16 15:54:35 2017
-// Update Count     : 4
+// Last Modified By : Andrew Beach
+// Last Modified On : Mon Jun  3 13:26:00 2017
+// Update Count     : 5
 //
 
@@ -26 +26 @@
 }
 
-TypeSubstitution::~TypeSubstitution() {
-        for ( TypeEnvType::iterator i = typeEnv.begin(); i != typeEnv.end(); ++i ) {
-                delete( i->second );
-        }
-        for ( VarEnvType::iterator i = varEnv.begin(); i != varEnv.end(); ++i ) {
-                delete( i->second );
-        }
-}
+TypeSubstitution::~TypeSubstitution() {}
 
 TypeSubstitution &TypeSubstitution::operator=( const TypeSubstitution &other ) {

src/AST/porting.md

@@ -291 +291 @@
 * moved to be helper function in `TypeEnvironment.cpp` (its only use)
 
+`WidenMode`
+* changed `widenFirst`, `widenSecond` => `first`, `second`
+* changed `WidenMode widenMode` => `WidenMode widen`
+
 [1] https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Type-Attributes.html#Type-Attributes
 

src/ResolvExpr/CommonType.cc

@@ -176 +176 @@
         }
 
+        const ast::Type * commonType(
+                        const ast::Type * type1, const ast::Type * type2, WidenMode widen, 
+                        const ast::SymbolTable & symtab, ast::TypeEnvironment & env, 
+                        const ast::OpenVarSet & open ) {
+                #warning unimplemented
+                (void)type1; (void)type2; (void)widen; (void)symtab; (void)env; (void)open;
+                assert(false);
+                return nullptr;
+        }
+
         // GENERATED START, DO NOT EDIT
         // GENERATED BY BasicTypes-gen.cc

src/ResolvExpr/FindOpenVars.cc

@@ -93 +93 @@
                 common_action( tupleType );
         }
+
+        void findOpenVars( 
+                        const ast::Type * type, ast::OpenVarSet & open, ast::OpenVarSet & closed, 
+                        ast::AssertionSet & need, ast::AssertionSet & have, FirstMode firstIsOpen ) {
+                #warning unimplemented
+                (void)type; (void)open; (void)closed; (void)need; (void)have; (void)firstIsOpen;
+                assert(false);
+        }
 } // namespace ResolvExpr
 

src/ResolvExpr/FindOpenVars.h

@@ -16 +16 @@
 #pragma once
 
+#include "AST/TypeEnvironment.hpp"  // for AssertionSet, OpenVarSet
 #include "ResolvExpr/TypeEnvironment.h"  // for AssertionSet, OpenVarSet
 
 class Type;
+namespace ast {
+        class Type;
+}
 
 namespace ResolvExpr {
         // Updates open and closed variables and their associated assertions
         void findOpenVars( Type *type, OpenVarSet &openVars, OpenVarSet &closedVars, AssertionSet &needAssertions, AssertionSet &haveAssertions, bool firstIsOpen );
+
+        enum FirstMode { FirstClosed, FirstOpen };
+
+        // Updates open and closed variables and their associated assertions
+        void findOpenVars( 
+                const ast::Type * type, ast::OpenVarSet & open, ast::OpenVarSet & closed, 
+                ast::AssertionSet & need, ast::AssertionSet & have, FirstMode firstIsOpen );
 } // namespace ResolvExpr
 

src/ResolvExpr/TypeEnvironment.cc

@@ -205 +205 @@
                                 // attempt to unify bound types
                                 std::unique_ptr<Type> toType{ to.type->clone() }, fromType{ from.type->clone() };
-                                WidenMode widenMode{ to.allowWidening, from.allowWidening };
+                                WidenMode widen{ to.allowWidening, from.allowWidening };
                                 Type* common = nullptr;
                                 AssertionSet need, have;
-                                if ( unifyInexact( toType.get(), fromType.get(), *this, need, have, openVars, widenMode, indexer, common ) ) {
+                                if ( unifyInexact( toType.get(), fromType.get(), *this, need, have, openVars, widen, indexer, common ) ) {
                                         // unifies, set common type if necessary
                                         if ( common ) {
@@ -343 +343 @@
         }
 
-        bool TypeEnvironment::bindVar( TypeInstType *typeInst, Type *bindTo, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer ) {
+        bool TypeEnvironment::bindVar( TypeInstType *typeInst, Type *bindTo, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer ) {
 
                 // remove references from other, so that type variables can only bind to value types
@@ -362 +362 @@
                                 std::unique_ptr< Type > newType( curClass->type->clone() );
                                 newType->get_qualifiers() = typeInst->get_qualifiers();
-                                if ( unifyInexact( newType.get(), bindTo, *this, need, have, openVars, widenMode & WidenMode( curClass->allowWidening, true ), indexer, common ) ) {
+                                if ( unifyInexact( newType.get(), bindTo, *this, need, have, openVars, widen & WidenMode( curClass->allowWidening, true ), indexer, common ) ) {
                                         if ( common ) {
                                                 common->get_qualifiers() = Type::Qualifiers{};
@@ -372 +372 @@
                                 newType->get_qualifiers() = Type::Qualifiers{};
                                 curClass->set_type( newType );
-                                curClass->allowWidening = widenMode.widenFirst && widenMode.widenSecond;
+                                curClass->allowWidening = widen.first && widen.second;
                         } // if
                 } else {
@@ -379 +379 @@
                         newClass.type = bindTo->clone();
                         newClass.type->get_qualifiers() = Type::Qualifiers();
-                        newClass.allowWidening = widenMode.widenFirst && widenMode.widenSecond;
+                        newClass.allowWidening = widen.first && widen.second;
                         newClass.data = data;
                         env.push_back( std::move(newClass) );
@@ -388 +388 @@
         bool TypeEnvironment::bindVarToVar( TypeInstType *var1, TypeInstType *var2, 
                         TypeDecl::Data && data, AssertionSet &need, AssertionSet &have, 
-                        const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer ) {
+                        const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer ) {
 
                 auto class1 = internal_lookup( var1->get_name() );
@@ -395 +395 @@
                 // exit early if variables already bound together
                 if ( class1 != env.end() && class1 == class2 ) {
-                        class1->allowWidening &= widenMode;
+                        class1->allowWidening &= widen;
                         return true;
                 }
@@ -408 +408 @@
                                 type1 = class1->type;
                         } // if
-                        widen1 = widenMode.widenFirst && class1->allowWidening;
+                        widen1 = widen.first && class1->allowWidening;
                 } // if
                 if ( class2 != env.end() ) {
@@ -415 +415 @@
                                 type2 = class2->type;
                         } // if
-                        widen2 = widenMode.widenSecond && class2->allowWidening;
+                        widen2 = widen.second && class2->allowWidening;
                 } // if
 

src/ResolvExpr/TypeEnvironment.h

@@ -136 +136 @@
                 /// Binds the type class represented by `typeInst` to the type `bindTo`; will add 
                 /// the class if needed. Returns false on failure.
-                bool bindVar( TypeInstType *typeInst, Type *bindTo, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );
+                bool bindVar( TypeInstType *typeInst, Type *bindTo, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
                 
                 /// Binds the type classes represented by `var1` and `var2` together; will add 
                 /// one or both classes if needed. Returns false on failure.
-                bool bindVarToVar( TypeInstType *var1, TypeInstType *var2, TypeDecl::Data && data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );
+                bool bindVarToVar( TypeInstType *var1, TypeInstType *var2, TypeDecl::Data && data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
 
                 /// Disallows widening for all bindings in the environment

src/ResolvExpr/Unify.cc

@@ -14 +14 @@
 //
 
+#include "Unify.h"
+
 #include <cassert>                  // for assertf, assert
 #include <iterator>                 // for back_insert_iterator, back_inserter
@@ -23 +25 @@
 #include <vector>
 
+#include "AST/Decl.hpp"
 #include "AST/Node.hpp"
+#include "AST/Pass.hpp"
 #include "AST/Type.hpp"
 #include "AST/TypeEnvironment.hpp"
@@ -37 +41 @@
 #include "Tuples/Tuples.h"          // for isTtype
 #include "TypeEnvironment.h"        // for EqvClass, AssertionSet, OpenVarSet
-#include "Unify.h"
 #include "typeops.h"                // for flatten, occurs, commonType
+
+namespace ast {
+        class SymbolTable;
+}
 
 namespace SymTab {
@@ -48 +55 @@
 namespace ResolvExpr {
 
-        struct Unify : public WithShortCircuiting {
-                Unify( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );
+        struct Unify_old : public WithShortCircuiting {
+                Unify_old( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
 
                 bool get_result() const { return result; }
@@ -81 +88 @@
                 AssertionSet &haveAssertions;
                 const OpenVarSet &openVars;
-                WidenMode widenMode;
+                WidenMode widen;
                 const SymTab::Indexer &indexer;
         };
@@ -87 +94 @@
         /// Attempts an inexact unification of type1 and type2.
         /// Returns false if no such unification; if the types can be unified, sets common (unless they unify exactly and have identical type qualifiers)
-        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer, Type *&common );
-        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );
+        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer, Type *&common );
+        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer );
+
+        bool unifyExact( 
+                const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env, 
+                ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                WidenMode widen, const ast::SymbolTable & symtab );
 
         bool typesCompatible( Type *first, Type *second, const SymTab::Indexer &indexer, const TypeEnvironment &env ) {
@@ -112 +124 @@
                         const ast::Type * first, const ast::Type * second, const ast::SymbolTable & symtab, 
                         const ast::TypeEnvironment & env ) {
-                #warning unimplemented
-                assert((first, second, symtab, env, false));
-                return false;
+                ast::TypeEnvironment newEnv;
+                ast::OpenVarSet open, closed;
+                ast::AssertionSet need, have;
+
+                ast::ptr<ast::Type> newFirst{ first }, newSecond{ second };
+                env.apply( newFirst );
+                env.apply( newSecond );
+
+                findOpenVars( newFirst, open, closed, need, have, FirstClosed );
+                findOpenVars( newSecond, open, closed, need, have, FirstOpen );
+
+                return unifyExact( 
+                        newFirst, newSecond, newEnv, need, have, open, WidenMode{ false, false }, symtab );
         }
 
@@ -144 +166 @@
                         const ast::Type * first, const ast::Type * second, const ast::SymbolTable & symtab, 
                         const ast::TypeEnvironment & env ) {
-                #warning unimplemented
-                assert((first, second, symtab, env, false));
-                return false;
+                ast::TypeEnvironment newEnv;
+                ast::OpenVarSet open;
+                ast::AssertionSet need, have;
+                
+                ast::ptr<ast::Type> newFirst{ first }, newSecond{ second };
+                env.apply( newFirst );
+                env.apply( newSecond );
+                clear_qualifiers( newFirst );
+                clear_qualifiers( newSecond );
+
+                return unifyExact( 
+                        newFirst, newSecond, newEnv, need, have, open, WidenMode{ false, false }, symtab );
         }
 
@@ -171 +202 @@
         }
 
-        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer ) {
+        bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer ) {
 #ifdef DEBUG
                 TypeEnvironment debugEnv( env );
@@ -198 +229 @@
                                 result = env.bindVarToVar(
                                         var1, var2, TypeDecl::Data{ entry1->second, entry2->second }, needAssertions,
-                                        haveAssertions, openVars, widenMode, indexer );
+                                        haveAssertions, openVars, widen, indexer );
                         }
                 } else if ( isopen1 ) {
-                        result = env.bindVar( var1, type2, entry1->second, needAssertions, haveAssertions, openVars, widenMode, indexer );
-                } else if ( isopen2 ) { // TODO: swap widenMode values in call, since type positions are flipped?
-                        result = env.bindVar( var2, type1, entry2->second, needAssertions, haveAssertions, openVars, widenMode, indexer );
+                        result = env.bindVar( var1, type2, entry1->second, needAssertions, haveAssertions, openVars, widen, indexer );
+                } else if ( isopen2 ) { // TODO: swap widen values in call, since type positions are flipped?
+                        result = env.bindVar( var2, type1, entry2->second, needAssertions, haveAssertions, openVars, widen, indexer );
                 } else {
-                        PassVisitor<Unify> comparator( type2, env, needAssertions, haveAssertions, openVars, widenMode, indexer );
+                        PassVisitor<Unify_old> comparator( type2, env, needAssertions, haveAssertions, openVars, widen, indexer );
                         type1->accept( comparator );
                         result = comparator.pass.get_result();
@@ -230 +261 @@
         }
 
-        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer, Type *&common ) {
+        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer, Type *&common ) {
                 Type::Qualifiers tq1 = type1->get_qualifiers(), tq2 = type2->get_qualifiers();
                 type1->get_qualifiers() = Type::Qualifiers();
@@ -242 +273 @@
                 std::cerr << std::endl;
 #endif
-                if ( ! unifyExact( type1, type2, env, needAssertions, haveAssertions, openVars, widenMode, indexer ) ) {
+                if ( ! unifyExact( type1, type2, env, needAssertions, haveAssertions, openVars, widen, indexer ) ) {
 #ifdef DEBUG
                         std::cerr << "unifyInexact: no exact unification found" << std::endl;
 #endif
-                        if ( ( common = commonType( type1, type2, widenMode.widenFirst, widenMode.widenSecond, indexer, env, openVars ) ) ) {
+                        if ( ( common = commonType( type1, type2, widen.first, widen.second, indexer, env, openVars ) ) ) {
                                 common->get_qualifiers() = tq1 | tq2;
 #ifdef DEBUG
@@ -262 +293 @@
                 } else {
                         if ( tq1 != tq2 ) {
-                                if ( ( tq1 > tq2 || widenMode.widenFirst ) && ( tq2 > tq1 || widenMode.widenSecond ) ) {
+                                if ( ( tq1 > tq2 || widen.first ) && ( tq2 > tq1 || widen.second ) ) {
                                         common = type1->clone();
                                         common->get_qualifiers() = tq1 | tq2;
@@ -280 +311 @@
         }
 
-        bool unifyInexact( 
-                        const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env, 
-                        ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & openVars, 
-                        WidenMode widenMode, const ast::SymbolTable & symtab, const ast::Type *& common ) {
-                #warning unimplemented
-                assert((type1, type2, env, need, have, openVars, widenMode, symtab, common, false));
-                return false;
-        }
-
-        Unify::Unify( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer )
-                : result( false ), type2( type2 ), env( env ), needAssertions( needAssertions ), haveAssertions( haveAssertions ), openVars( openVars ), widenMode( widenMode ), indexer( indexer ) {
-        }
-
-        void Unify::postvisit( __attribute__((unused)) VoidType *voidType) {
+        Unify_old::Unify_old( Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer )
+                : result( false ), type2( type2 ), env( env ), needAssertions( needAssertions ), haveAssertions( haveAssertions ), openVars( openVars ), widen( widen ), indexer( indexer ) {
+        }
+
+        void Unify_old::postvisit( __attribute__((unused)) VoidType *voidType) {
                 result = dynamic_cast< VoidType* >( type2 );
         }
 
-        void Unify::postvisit(BasicType *basicType) {
+        void Unify_old::postvisit(BasicType *basicType) {
                 if ( BasicType *otherBasic = dynamic_cast< BasicType* >( type2 ) ) {
                         result = basicType->get_kind() == otherBasic->get_kind();
@@ -325 +347 @@
         }
 
-        void Unify::postvisit(PointerType *pointerType) {
+        void Unify_old::postvisit(PointerType *pointerType) {
                 if ( PointerType *otherPointer = dynamic_cast< PointerType* >( type2 ) ) {
                         result = unifyExact( pointerType->get_base(), otherPointer->get_base(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
@@ -333 +355 @@
         }
 
-        void Unify::postvisit(ReferenceType *refType) {
+        void Unify_old::postvisit(ReferenceType *refType) {
                 if ( ReferenceType *otherRef = dynamic_cast< ReferenceType* >( type2 ) ) {
                         result = unifyExact( refType->get_base(), otherRef->get_base(), env, needAssertions, haveAssertions, openVars, WidenMode( false, false ), indexer );
@@ -341 +363 @@
         }
 
-        void Unify::postvisit(ArrayType *arrayType) {
+        void Unify_old::postvisit(ArrayType *arrayType) {
                 ArrayType *otherArray = dynamic_cast< ArrayType* >( type2 );
                 // to unify, array types must both be VLA or both not VLA
@@ -421 +443 @@
         /// If this isn't done then argument lists can have wildly different
         /// size and structure, when they should be compatible.
-        struct TtypeExpander : public WithShortCircuiting {
+        struct TtypeExpander_old : public WithShortCircuiting {
                 TypeEnvironment & tenv;
-                TtypeExpander( TypeEnvironment & tenv ) : tenv( tenv ) {}
+                TtypeExpander_old( TypeEnvironment & tenv ) : tenv( tenv ) {}
                 void premutate( TypeInstType * ) { visit_children = false; }
                 Type * postmutate( TypeInstType * typeInst ) {
@@ -442 +464 @@
                 dst.clear();
                 for ( DeclarationWithType * dcl : src ) {
-                        PassVisitor<TtypeExpander> expander( env );
+                        PassVisitor<TtypeExpander_old> expander( env );
                         dcl->acceptMutator( expander );
                         std::list< Type * > types;
@@ -457 +479 @@
         }
 
-        void Unify::postvisit(FunctionType *functionType) {
+        void Unify_old::postvisit(FunctionType *functionType) {
                 FunctionType *otherFunction = dynamic_cast< FunctionType* >( type2 );
                 if ( otherFunction && functionType->get_isVarArgs() == otherFunction->get_isVarArgs() ) {
@@ -468 +490 @@
 
                         // sizes don't have to match if ttypes are involved; need to be more precise wrt where the ttype is to prevent errors
-                        if ( (flatFunc->parameters.size() == flatOther->parameters.size() && flatFunc->returnVals.size() == flatOther->returnVals.size()) || flatFunc->isTtype() || flatOther->isTtype() ) {
+                        if ( 
+                                        (flatFunc->parameters.size() == flatOther->parameters.size() && 
+                                                flatFunc->returnVals.size() == flatOther->returnVals.size()) 
+                                        || flatFunc->isTtype() 
+                                        || flatOther->isTtype() 
+                        ) {
                                 if ( unifyDeclList( flatFunc->parameters.begin(), flatFunc->parameters.end(), flatOther->parameters.begin(), flatOther->parameters.end(), env, needAssertions, haveAssertions, openVars, indexer ) ) {
                                         if ( unifyDeclList( flatFunc->returnVals.begin(), flatFunc->returnVals.end(), flatOther->returnVals.begin(), flatOther->returnVals.end(), env, needAssertions, haveAssertions, openVars, indexer ) ) {
@@ -484 +511 @@
 
         template< typename RefType >
-        void Unify::handleRefType( RefType *inst, Type *other ) {
+        void Unify_old::handleRefType( RefType *inst, Type *other ) {
                 // check that other type is compatible and named the same
                 RefType *otherStruct = dynamic_cast< RefType* >( other );
@@ -491 +518 @@
 
         template< typename RefType >
-        void Unify::handleGenericRefType( RefType *inst, Type *other ) {
+        void Unify_old::handleGenericRefType( RefType *inst, Type *other ) {
                 // Check that other type is compatible and named the same
                 handleRefType( inst, other );
@@ -559 +586 @@
         }
 
-        void Unify::postvisit(StructInstType *structInst) {
+        void Unify_old::postvisit(StructInstType *structInst) {
                 handleGenericRefType( structInst, type2 );
         }
 
-        void Unify::postvisit(UnionInstType *unionInst) {
+        void Unify_old::postvisit(UnionInstType *unionInst) {
                 handleGenericRefType( unionInst, type2 );
         }
 
-        void Unify::postvisit(EnumInstType *enumInst) {
+        void Unify_old::postvisit(EnumInstType *enumInst) {
                 handleRefType( enumInst, type2 );
         }
 
-        void Unify::postvisit(TraitInstType *contextInst) {
+        void Unify_old::postvisit(TraitInstType *contextInst) {
                 handleRefType( contextInst, type2 );
         }
 
-        void Unify::postvisit(TypeInstType *typeInst) {
+        void Unify_old::postvisit(TypeInstType *typeInst) {
                 assert( openVars.find( typeInst->get_name() ) == openVars.end() );
                 TypeInstType *otherInst = dynamic_cast< TypeInstType* >( type2 );
@@ -630 +657 @@
         }
 
-        void Unify::postvisit(TupleType *tupleType) {
+        void Unify_old::postvisit(TupleType *tupleType) {
                 if ( TupleType *otherTuple = dynamic_cast< TupleType* >( type2 ) ) {
                         std::unique_ptr<TupleType> flat1( tupleType->clone() );
@@ -636 +663 @@
                         std::list<Type *> types1, types2;
 
-                        PassVisitor<TtypeExpander> expander( env );
+                        PassVisitor<TtypeExpander_old> expander( env );
                         flat1->acceptMutator( expander );
                         flat2->acceptMutator( expander );
@@ -647 +674 @@
         }
 
-        void Unify::postvisit( __attribute__((unused)) VarArgsType *varArgsType ) {
+        void Unify_old::postvisit( __attribute__((unused)) VarArgsType *varArgsType ) {
                 result = dynamic_cast< VarArgsType* >( type2 );
         }
 
-        void Unify::postvisit( __attribute__((unused)) ZeroType *zeroType ) {
+        void Unify_old::postvisit( __attribute__((unused)) ZeroType *zeroType ) {
                 result = dynamic_cast< ZeroType* >( type2 );
         }
 
-        void Unify::postvisit( __attribute__((unused)) OneType *oneType ) {
+        void Unify_old::postvisit( __attribute__((unused)) OneType *oneType ) {
                 result = dynamic_cast< OneType* >( type2 );
         }
@@ -673 +700 @@
         }
 
+        class Unify_new : public ast::WithShortCircuiting {
+                const ast::Type * type2;
+                ast::TypeEnvironment & tenv;
+                ast::AssertionSet & need;
+                ast::AssertionSet & have;
+                const ast::OpenVarSet & open;
+                WidenMode widen;
+                const ast::SymbolTable & symtab;
+        public:
+                bool result;
+
+                Unify_new( 
+                        const ast::Type * type2, ast::TypeEnvironment & env, ast::AssertionSet & need, 
+                        ast::AssertionSet & have, const ast::OpenVarSet & open, WidenMode widen, 
+                        const ast::SymbolTable & symtab )
+                : type2(type2), tenv(env), need(need), have(have), open(open), widen(widen), 
+                  symtab(symtab), result(false) {}
+
+                void previsit( const ast::Node * ) { visit_children = false; }
+                
+                void previsit( const ast::VoidType * ) {
+                        visit_children = false;
+                        result = dynamic_cast< const ast::VoidType * >( type2 );
+                }
+
+                void previsit( const ast::BasicType * basic ) {
+                        visit_children = false;
+                        if ( auto basic2 = dynamic_cast< const ast::BasicType * >( type2 ) ) {
+                                result = basic->kind == basic2->kind;
+                        }
+                }
+
+                void previsit( const ast::PointerType * pointer ) {
+                        visit_children = false;
+                        if ( auto pointer2 = dynamic_cast< const ast::PointerType * >( type2 ) ) {
+                                result = unifyExact( 
+                                        pointer->base, pointer2->base, tenv, need, have, open, 
+                                        WidenMode{ false, false }, symtab );
+                        }
+                }
+
+                void previsit( const ast::ArrayType * array ) {
+                        visit_children = false;
+                        auto array2 = dynamic_cast< const ast::ArrayType * >( type2 );
+                        if ( ! array2 ) return;
+
+                        // to unify, array types must both be VLA or both not VLA and both must have a 
+                        // dimension expression or not have a dimension
+                        if ( array->isVarLen != array2->isVarLen ) return;
+                        if ( ! array->isVarLen && ! array2->isVarLen 
+                                        && array->dimension && array2->dimension ) {
+                                auto ce1 = array->dimension.as< ast::ConstantExpr >();
+                                auto ce2 = array2->dimension.as< ast::ConstantExpr >();
+
+                                // see C11 Reference Manual 6.7.6.2.6
+                                // two array types with size specifiers that are integer constant expressions are 
+                                // compatible if both size specifiers have the same constant value
+                                if ( ce1 && ce2 && ce1->intValue() != ce2->intValue() ) return;
+                        }
+
+                        result = unifyExact( 
+                                array->base, array2->base, tenv, need, have, open, WidenMode{ false, false }, 
+                                symtab );
+                }
+
+                void previsit( const ast::ReferenceType * ref ) {
+                        visit_children = false;
+                        if ( auto ref2 = dynamic_cast< const ast::ReferenceType * >( type2 ) ) {
+                                result = unifyExact( 
+                                        ref->base, ref2->base, tenv, need, have, open, WidenMode{ false, false }, 
+                                        symtab );
+                        }
+                }
+
+        private:
+                /// Replaces ttype variables with their bound types.
+                /// If this isn't done when satifying ttype assertions, then argument lists can have 
+                /// different size and structure when they should be compatible.
+                struct TtypeExpander_new : public ast::WithShortCircuiting {
+                        ast::TypeEnvironment & tenv;
+
+                        TtypeExpander_new( ast::TypeEnvironment & env ) : tenv( env ) {}
+
+                        const ast::Type * postmutate( const ast::TypeInstType * typeInst ) {
+                                if ( const ast::EqvClass * clz = tenv.lookup( typeInst->name ) ) {
+                                        // expand ttype parameter into its actual type
+                                        if ( clz->data.kind == ast::TypeVar::Ttype && clz->bound ) {
+                                                return clz->bound;
+                                        }
+                                }
+                                return typeInst;
+                        }
+                };
+
+                /// returns flattened version of `src`
+                static std::vector< ast::ptr< ast::DeclWithType > > flattenList(
+                        const std::vector< ast::ptr< ast::DeclWithType > > & src, ast::TypeEnvironment & env
+                ) {
+                        std::vector< ast::ptr< ast::DeclWithType > > dst;
+                        dst.reserve( src.size() );
+                        for ( const ast::DeclWithType * d : src ) {
+                                ast::Pass<TtypeExpander_new> expander{ env };
+                                d = d->accept( expander );
+                                auto types = flatten( d->get_type() );
+                                for ( ast::ptr< ast::Type > & t : types ) {
+                                        // outermost const, volatile, _Atomic qualifiers in parameters should not play 
+                                        // a role in the unification of function types, since they do not determine 
+                                        // whether a function is callable.
+                                        // NOTE: **must** consider at least mutex qualifier, since functions can be 
+                                        // overloaded on outermost mutex and a mutex function has different 
+                                        // requirements than a non-mutex function
+                                        t.get_and_mutate()->qualifiers 
+                                                -= ast::CV::Const | ast::CV::Volatile | ast::CV::Atomic;
+                                        dst.emplace_back( new ast::ObjectDecl{ d->location, "", t } );
+                                }
+                        }
+                        return dst;
+                }
+
+                /// Creates a tuple type based on a list of DeclWithType
+                template< typename Iter >
+                static ast::ptr< ast::Type > tupleFromDecls( Iter crnt, Iter end ) {
+                        std::vector< ast::ptr< ast::Type > > types;
+                        while ( crnt != end ) {
+                                // it is guaranteed that a ttype variable will be bound to a flat tuple, so ensure 
+                                // that this results in a flat tuple
+                                flatten( (*crnt)->get_type(), types );
+
+                                ++crnt;
+                        }
+
+                        return { new ast::TupleType{ std::move(types) } };
+                }
+
+                template< typename Iter >
+                static bool unifyDeclList( 
+                        Iter crnt1, Iter end1, Iter crnt2, Iter end2, ast::TypeEnvironment & env, 
+                        ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                        const ast::SymbolTable & symtab
+                ) {
+                        while ( crnt1 != end1 && crnt2 != end2 ) {
+                                const ast::Type * t1 = (*crnt1)->get_type();
+                                const ast::Type * t2 = (*crnt2)->get_type();
+                                bool isTuple1 = Tuples::isTtype( t1 );
+                                bool isTuple2 = Tuples::isTtype( t2 );
+
+                                // assumes here that ttype *must* be last parameter
+                                if ( isTuple1 && ! isTuple2 ) {
+                                        // combine remainder of list2, then unify
+                                        return unifyExact( 
+                                                t1, tupleFromDecls( crnt2, end2 ), env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                                } else if ( ! isTuple1 && isTuple2 ) {
+                                        // combine remainder of list1, then unify
+                                        return unifyExact( 
+                                                tupleFromDecls( crnt1, end1 ), t2, env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                                }
+
+                                if ( ! unifyExact( 
+                                        t1, t2, env, need, have, open, WidenMode{ false, false }, symtab ) 
+                                ) return false;
+
+                                ++crnt1; ++crnt2;
+                        }
+
+                        // May get to the end of one argument list before the other. This is only okay if the 
+                        // other is a ttype
+                        if ( crnt1 != end1 ) {
+                                // try unifying empty tuple with ttype
+                                const ast::Type * t1 = (*crnt1)->get_type();
+                                if ( ! Tuples::isTtype( t1 ) ) return false;
+                                return unifyExact( 
+                                        t1, tupleFromDecls( crnt2, end2 ), env, need, have, open, 
+                                        WidenMode{ false, false }, symtab );
+                        } else if ( crnt2 != end2 ) {
+                                // try unifying empty tuple with ttype
+                                const ast::Type * t2 = (*crnt2)->get_type();
+                                if ( ! Tuples::isTtype( t2 ) ) return false;
+                                return unifyExact( 
+                                        tupleFromDecls( crnt1, end1 ), t2, env, need, have, open, 
+                                        WidenMode{ false, false }, symtab );
+                        }
+
+                        return true;
+                }
+
+                static bool unifyDeclList( 
+                        const std::vector< ast::ptr< ast::DeclWithType > > & list1, 
+                        const std::vector< ast::ptr< ast::DeclWithType > > & list2, 
+                        ast::TypeEnvironment & env, ast::AssertionSet & need, ast::AssertionSet & have, 
+                        const ast::OpenVarSet & open, const ast::SymbolTable & symtab
+                ) {
+                        return unifyDeclList( 
+                                list1.begin(), list1.end(), list2.begin(), list2.end(), env, need, have, open, 
+                                symtab );
+                }
+
+                static void markAssertionSet( ast::AssertionSet & assns, const ast::DeclWithType * assn ) {
+                        auto i = assns.find( assn );
+                        if ( i != assns.end() ) {
+                                i->second.isUsed = true;
+                        }
+                }
+
+                /// mark all assertions in `type` used in both `assn1` and `assn2`
+                static void markAssertions( 
+                        ast::AssertionSet & assn1, ast::AssertionSet & assn2, 
+                        const ast::ParameterizedType * type 
+                ) {
+                        for ( const auto & tyvar : type->forall ) {
+                                for ( const ast::DeclWithType * assert : tyvar->assertions ) {
+                                        markAssertionSet( assn1, assert );
+                                        markAssertionSet( assn2, assert );
+                                }
+                        }
+                }
+
+        public:
+                void previsit( const ast::FunctionType * func ) {
+                        visit_children = false;
+                        auto func2 = dynamic_cast< const ast::FunctionType * >( type2 );
+                        if ( ! func2 ) return;
+
+                        if ( func->isVarArgs != func2->isVarArgs ) return;
+                        
+                        // Flatten the parameter lists for both functions so that tuple structure does not 
+                        // affect unification. Does not actually mutate function parameters.
+                        auto params = flattenList( func->params, tenv );
+                        auto params2 = flattenList( func2->params, tenv );
+
+                        // sizes don't have to match if ttypes are involved; need to be more precise w.r.t. 
+                        // where the ttype is to prevent errors
+                        if ( 
+                                ( params.size() != params2.size() || func->returns.size() != func2->returns.size() )
+                                && ! func->isTtype()
+                                && ! func2->isTtype()
+                        ) return;
+
+                        if ( ! unifyDeclList( params, params2, tenv, need, have, open, symtab ) ) return;
+                        if ( ! unifyDeclList( 
+                                func->returns, func2->returns, tenv, need, have, open, symtab ) ) return;
+                        
+                        markAssertions( have, need, func );
+                        markAssertions( have, need, func2 );
+
+                        result = true;
+                }
+        
+        private:
+                template< typename RefType >
+                const RefType * handleRefType( const RefType * inst, const ast::Type * other ) {
+                        visit_children = false;
+                        // check that the other type is compatible and named the same
+                        auto otherInst = dynamic_cast< const RefType * >( other );
+                        result = otherInst && inst->name == otherInst->name;
+                        return otherInst;
+                }
+
+                /// Creates a tuple type based on a list of TypeExpr
+                template< typename Iter >
+                static const ast::Type * tupleFromExprs( 
+                        const ast::TypeExpr * param, Iter & crnt, Iter end, ast::CV::Qualifiers qs
+                ) {
+                        std::vector< ast::ptr< ast::Type > > types;
+                        do {
+                                types.emplace_back( param->type );
+
+                                ++crnt;
+                                if ( crnt == end ) break;
+                                param = strict_dynamic_cast< const ast::TypeExpr * >( crnt->get() );
+                        } while(true);
+
+                        return new ast::TupleType{ std::move(types), qs };
+                }
+
+                template< typename RefType >
+                void handleGenericRefType( const RefType * inst, const ast::Type * other ) {
+                        // check that other type is compatible and named the same
+                        const RefType * inst2 = handleRefType( inst, other );
+                        if ( ! inst2 ) return;
+                        
+                        // check that parameters of types unify, if any
+                        const std::vector< ast::ptr< ast::Expr > > & params = inst->params;
+                        const std::vector< ast::ptr< ast::Expr > > & params2 = inst2->params;
+
+                        auto it = params.begin();
+                        auto jt = params2.begin();
+                        for ( ; it != params.end() && jt != params2.end(); ++it, ++jt ) {
+                                auto param = strict_dynamic_cast< const ast::TypeExpr * >( it->get() );
+                                auto param2 = strict_dynamic_cast< const ast::TypeExpr * >( jt->get() );
+
+                                ast::ptr< ast::Type > pty = param->type;
+                                ast::ptr< ast::Type > pty2 = param2->type;
+
+                                bool isTuple = Tuples::isTtype( pty );
+                                bool isTuple2 = Tuples::isTtype( pty2 );
+
+                                if ( isTuple && isTuple2 ) {
+                                        ++it; ++jt;  // skip ttype parameters before break
+                                } else if ( isTuple ) {
+                                        // bundle remaining params into tuple
+                                        pty2 = tupleFromExprs( param2, jt, params2.end(), pty->qualifiers );
+                                        ++it;  // skip ttype parameter for break
+                                } else if ( isTuple2 ) {
+                                        // bundle remaining params into tuple
+                                        pty = tupleFromExprs( param, it, params.end(), pty2->qualifiers );
+                                        ++jt;  // skip ttype parameter for break
+                                }
+
+                                if ( ! unifyExact( 
+                                                pty, pty2, tenv, need, have, open, WidenMode{ false, false }, symtab ) ) {
+                                        result = false;
+                                        return;
+                                }
+
+                                // ttype parameter should be last
+                                if ( isTuple || isTuple2 ) break;
+                        }
+                        result = it == params.end() && jt == params2.end();
+                }
+
+        public:
+                void previsit( const ast::StructInstType * aggrType ) {
+                        handleGenericRefType( aggrType, type2 );
+                }
+
+                void previsit( const ast::UnionInstType * aggrType ) {
+                        handleGenericRefType( aggrType, type2 );
+                }
+
+                void previsit( const ast::EnumInstType * aggrType ) {
+                        handleRefType( aggrType, type2 );
+                }
+
+                void previsit( const ast::TraitInstType * aggrType ) {
+                        handleRefType( aggrType, type2 );
+                }
+
+                void previsit( const ast::TypeInstType * typeInst ) {
+                        assert( open.find( typeInst->name ) == open.end() );
+                        handleRefType( typeInst, type2 );
+                }
+
+        private:
+                /// Creates a tuple type based on a list of Type
+                static ast::ptr< ast::Type > tupleFromTypes( 
+                        const std::vector< ast::ptr< ast::Type > > & tys
+                ) {
+                        std::vector< ast::ptr< ast::Type > > out;
+                        for ( const ast::Type * ty : tys ) {
+                                // it is guaranteed that a ttype variable will be bound to a flat tuple, so ensure 
+                                // that this results in a flat tuple
+                                flatten( ty, out );
+                        }
+
+                        return { new ast::TupleType{ std::move(out) } };
+                }
+
+                static bool unifyList( 
+                        const std::vector< ast::ptr< ast::Type > > & list1, 
+                        const std::vector< ast::ptr< ast::Type > > & list2, ast::TypeEnvironment & env, 
+                        ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                        const ast::SymbolTable & symtab
+                ) {
+                        auto crnt1 = list1.begin();
+                        auto crnt2 = list2.begin();
+                        while ( crnt1 != list1.end() && crnt2 != list2.end() ) {
+                                const ast::Type * t1 = *crnt1;
+                                const ast::Type * t2 = *crnt2;
+                                bool isTuple1 = Tuples::isTtype( t1 );
+                                bool isTuple2 = Tuples::isTtype( t2 );
+
+                                // assumes ttype must be last parameter
+                                if ( isTuple1 && ! isTuple2 ) {
+                                        // combine entirety of list2, then unify
+                                        return unifyExact( 
+                                                t1, tupleFromTypes( list2 ), env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                                } else if ( ! isTuple1 && isTuple2 ) {
+                                        // combine entirety of list1, then unify
+                                        return unifyExact(
+                                                tupleFromTypes( list1 ), t2, env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                                }
+
+                                if ( ! unifyExact( 
+                                        t1, t2, env, need, have, open, WidenMode{ false, false }, symtab ) 
+                                ) return false;
+
+                                ++crnt1; ++crnt2;
+                        }
+
+                        if ( crnt1 != list1.end() ) {
+                                // try unifying empty tuple type with ttype
+                                const ast::Type * t1 = *crnt1;
+                                if ( ! Tuples::isTtype( t1 ) ) return false;
+                                // xxx - this doesn't generate an empty tuple, contrary to comment; both ported 
+                                // from Rob's code
+                                return unifyExact( 
+                                                t1, tupleFromTypes( list2 ), env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                        } else if ( crnt2 != list2.end() ) {
+                                // try unifying empty tuple with ttype
+                                const ast::Type * t2 = *crnt2;
+                                if ( ! Tuples::isTtype( t2 ) ) return false;
+                                // xxx - this doesn't generate an empty tuple, contrary to comment; both ported 
+                                // from Rob's code
+                                return unifyExact(
+                                                tupleFromTypes( list1 ), t2, env, need, have, open, 
+                                                WidenMode{ false, false }, symtab );
+                        }
+
+                        return true;
+                }
+
+        public:
+                void previsit( const ast::TupleType * tuple ) {
+                        visit_children = false;
+                        auto tuple2 = dynamic_cast< const ast::TupleType * >( type2 );
+                        if ( ! tuple2 ) return;
+
+                        ast::Pass<TtypeExpander_new> expander{ tenv };
+                        const ast::Type * flat = tuple->accept( expander );
+                        const ast::Type * flat2 = tuple2->accept( expander );
+
+                        auto types = flatten( flat );
+                        auto types2 = flatten( flat2 );
+
+                        result = unifyList( types, types2, tenv, need, have, open, symtab );
+                }
+
+                void previsit( const ast::VarArgsType * ) {
+                        visit_children = false;
+                        result = dynamic_cast< const ast::VarArgsType * >( type2 );
+                }
+
+                void previsit( const ast::ZeroType * ) {
+                        visit_children = false;
+                        result = dynamic_cast< const ast::ZeroType * >( type2 );
+                }
+
+                void previsit( const ast::OneType * ) {
+                        visit_children = false;
+                        result = dynamic_cast< const ast::OneType * >( type2 );
+                }       
+
+          private:
+                template< typename RefType > void handleRefType( RefType *inst, Type *other );
+                template< typename RefType > void handleGenericRefType( RefType *inst, Type *other );
+        };
+
+        bool unifyExact( 
+                        const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env, 
+                        ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                        WidenMode widen, const ast::SymbolTable & symtab
+        ) {
+                if ( type1->qualifiers != type2->qualifiers ) return false;
+
+                auto var1 = dynamic_cast< const ast::TypeInstType * >( type1 );
+                auto var2 = dynamic_cast< const ast::TypeInstType * >( type2 );
+                ast::OpenVarSet::const_iterator 
+                        entry1 = var1 ? open.find( var1->name ) : open.end(), 
+                        entry2 = var2 ? open.find( var2->name ) : open.end();
+                bool isopen1 = entry1 != open.end();
+                bool isopen2 = entry2 != open.end();
+
+                if ( isopen1 && isopen2 ) {
+                        if ( entry1->second.kind != entry2->second.kind ) return false;
+                        return env.bindVarToVar( 
+                                var1, var2, ast::TypeDecl::Data{ entry1->second, entry2->second }, need, have, 
+                                open, widen, symtab );
+                } else if ( isopen1 ) {
+                        return env.bindVar( var1, type2, entry1->second, need, have, open, widen, symtab );
+                } else if ( isopen2 ) {
+                        return env.bindVar( var2, type1, entry2->second, need, have, open, widen, symtab );
+                } else {
+                        ast::Pass<Unify_new> comparator{ type2, env, need, have, open, widen, symtab };
+                        type1->accept( comparator );
+                        return comparator.pass.result;
+                }
+        }
+
+        bool unifyInexact( 
+                        ast::ptr<ast::Type> & type1, ast::ptr<ast::Type> & type2, ast::TypeEnvironment & env, 
+                        ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                        WidenMode widen, const ast::SymbolTable & symtab, ast::ptr<ast::Type> & common 
+        ) {
+                ast::CV::Qualifiers q1 = type1->qualifiers, q2 = type2->qualifiers;
+                
+                // force t1 and t2 to be cloned if their qualifiers must be stripped, so that type1 and 
+                // type2 are left unchanged; calling convention forces type{1,2}->strong_ref >= 1
+                ast::ptr<ast::Type> t1{ type1 }, t2{ type2 };
+                clear_qualifiers( t1 );
+                clear_qualifiers( t2 );
+                
+                if ( unifyExact( t1, t2, env, need, have, open, widen, symtab ) ) {
+                        t1 = nullptr; t2 = nullptr; // release t1, t2 to avoid spurious clones
+
+                        // if exact unification on unqualified types, try to merge qualifiers
+                        if ( q1 == q2 || ( ( q1 > q2 || widen.first ) && ( q2 > q1 || widen.second ) ) ) {
+                                common.set_and_mutate( type1 )->qualifiers = q1 | q2;
+                                return true;
+                        } else {
+                                return false;
+                        }
+
+                } else if (( common = commonType( t1, t2, widen, symtab, env, open ) )) {
+                        t1 = nullptr; t2 = nullptr; // release t1, t2 to avoid spurious clones
+
+                        // no exact unification, but common type
+                        common.get_and_mutate()->qualifiers = q1 | q2;
+                        return true;
+                } else {
+                        return false;
+                }
+        }
+
         ast::ptr<ast::Type> extractResultType( const ast::FunctionType * func ) {
                 if ( func->returns.empty() ) return new ast::VoidType{};

src/ResolvExpr/Unify.h

@@ -18 +18 @@
 #include <list>                   // for list
 
+#include "AST/Node.hpp"             // for ptr
 #include "AST/TypeEnvironment.hpp"  // for TypeEnvironment, AssertionSet, OpenVarSet
 #include "Common/utility.h"       // for deleteAll
@@ -39 +40 @@
         bool unify( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer, Type *&commonType );
         bool unifyExact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, OpenVarSet &openVars, const SymTab::Indexer &indexer );
-        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer, Type *&common );
+        bool unifyInexact( Type *type1, Type *type2, TypeEnvironment &env, AssertionSet &needAssertions, AssertionSet &haveAssertions, const OpenVarSet &openVars, WidenMode widen, const SymTab::Indexer &indexer, Type *&common );
 
         template< typename Iterator1, typename Iterator2 >
@@ -68 +69 @@
         }
 
+        bool unifyExact( 
+                const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env, 
+                ast::AssertionSet & need, ast::AssertionSet & have, ast::OpenVarSet & open, 
+                const ast::SymbolTable & symtab );
+
         bool unifyInexact( 
-                const ast::Type * type1, const ast::Type * type2, ast::TypeEnvironment & env, 
-                ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & openVars, 
-                WidenMode widenMode, const ast::SymbolTable & symtab, const ast::Type *& common );
+                ast::ptr<ast::Type> & type1, ast::ptr<ast::Type> & type2, ast::TypeEnvironment & env, 
+                ast::AssertionSet & need, ast::AssertionSet & have, const ast::OpenVarSet & open, 
+                WidenMode widen, const ast::SymbolTable & symtab, ast::ptr<ast::Type> & common );
 
 } // namespace ResolvExpr

src/ResolvExpr/WidenMode.h

@@ -18 +18 @@
 namespace ResolvExpr {
         struct WidenMode {
-                WidenMode( bool widenFirst, bool widenSecond ): widenFirst( widenFirst ), widenSecond( widenSecond ) {}
-                WidenMode &operator|=( const WidenMode &other ) { widenFirst |= other.widenFirst; widenSecond |= other.widenSecond; return *this; }
-                WidenMode &operator&=( const WidenMode &other ) { widenFirst &= other.widenFirst; widenSecond &= other.widenSecond; return *this; }
-                WidenMode operator|( const WidenMode &other ) { WidenMode newWM( *this ); newWM |= other; return newWM; }
-                WidenMode operator&( const WidenMode &other ) { WidenMode newWM( *this ); newWM &= other; return newWM; }
-                operator bool() { return widenFirst && widenSecond; }
+                WidenMode( bool first, bool second ): first( first ), second( second ) {}
+                
+                WidenMode &operator|=( const WidenMode &other ) {
+                        first |= other.first; second |= other.second; return *this;
+                }
 
-                bool widenFirst : 1, widenSecond : 1;
+                WidenMode &operator&=( const WidenMode &other ) {
+                        first &= other.first; second &= other.second; return *this;
+                }
+
+                WidenMode operator|( const WidenMode &other ) {
+                        WidenMode newWM( *this ); newWM |= other; return newWM;
+                }
+
+                WidenMode operator&( const WidenMode &other ) {
+                        WidenMode newWM( *this ); newWM &= other; return newWM;
+                }
+                
+                operator bool() { return first && second; }
+
+                bool first : 1, second : 1;
         };
 } // namespace ResolvExpr

src/ResolvExpr/typeops.h

@@ -18 +18 @@
 #include <vector>
 
+#include "Cost.h"
+#include "TypeEnvironment.h"
+#include "WidenMode.h"
 #include "AST/Fwd.hpp"
 #include "AST/Node.hpp"
@@ -26 +29 @@
 #include "SynTree/Type.h"
 #include "SymTab/Indexer.h"
-#include "Cost.h"
-#include "TypeEnvironment.h"
 
 namespace ResolvExpr {
@@ -117 +118 @@
         // in CommonType.cc
         Type * commonType( Type *type1, Type *type2, bool widenFirst, bool widenSecond, const SymTab::Indexer &indexer, TypeEnvironment &env, const OpenVarSet &openVars );
+        const ast::Type * commonType(
+                const ast::Type * type1, const ast::Type * type2, WidenMode widen, 
+                const ast::SymbolTable & symtab, ast::TypeEnvironment & env, const ast::OpenVarSet & open );
 
         // in PolyCost.cc
@@ -141 +145 @@
         const ast::Expr * referenceToRvalueConversion( const ast::Expr * expr, Cost & cost );
 
-        // flatten tuple type into list of types
+        /// flatten tuple type into list of types
         template< typename OutputIterator >
         void flatten( Type * type, OutputIterator out ) {
@@ -152 +156 @@
                 }
         }
+
+        /// flatten tuple type into existing list of types
+        static inline void flatten( 
+                const ast::Type * type, std::vector< ast::ptr< ast::Type > > & out 
+        ) {
+                if ( auto tupleType = dynamic_cast< const ast::TupleType * >( type ) ) {        
+                        for ( const ast::Type * t : tupleType->types ) {
+                                flatten( t, out );
+                        }
+                } else {
+                        out.emplace_back( type );
+                }
+        }
+
+        /// flatten tuple type into list of types
+        static inline std::vector< ast::ptr< ast::Type > > flatten( const ast::Type * type ) {
+                std::vector< ast::ptr< ast::Type > > out;
+                out.reserve( type->size() );
+                flatten( type, out );
+                return out;
+        }
 } // namespace ResolvExpr
 

src/include/cassert

@@ -10 +10 @@
 // Created On       : Thu Aug 18 13:19:26 2016
 // Last Modified By : Andrew Beach
-// Last Modified On : Thu May 23 15:30:00 2017
-// Update Count     : 17
+// Last Modified On : Mon Jun  3 13:11:00 2017
+// Update Count     : 18
 //
 
@@ -43 +43 @@
 #endif
 
-enum StrictAllowNull {NonNull, AllowNull};
-
-template<typename T, StrictAllowNull nullable = NonNull, typename U>
+template<typename T, typename U>
 static inline T strict_dynamic_cast( const U & src ) {
-        if (nullable == AllowNull && src == nullptr) {
-                return nullptr;
-        }
         assert(src);
         T ret = dynamic_cast<T>(src);
         assertf(ret, "%s", toString(src).c_str());
         return ret;
+}
+
+template<typename T, decltype(nullptr) null, typename U>
+static inline T strict_dynamic_cast( const U & src ) {
+        return src ? strict_dynamic_cast<T, U>( src ) : nullptr;
 }