func (g *ObjcGen) genWrite(varName string, t types.Type, mode varMode) {
	switch t := t.(type) {
	case *types.Basic:
		switch t.Kind() {
		case types.String:
			g.Printf("nstring _%s = go_seq_from_objc_string(%s);\n", varName, varName)
		default:
			g.Printf("%s _%s = (%s)%s;\n", g.cgoType(t), varName, g.cgoType(t), varName)
		}
	case *types.Slice:
		switch e := t.Elem().(type) {
		case *types.Basic:
			switch e.Kind() {
			case types.Uint8: // Byte.
				g.Printf("nbyteslice _%s = go_seq_from_objc_bytearray(%s, %d);\n", varName, varName, toCFlag(mode == modeRetained))
			default:
				g.errorf("unsupported type: %s", t)
			}
		default:
			g.errorf("unsupported type: %s", t)
		}
	case *types.Named:
		switch u := t.Underlying().(type) {
		case *types.Interface:
			g.genRefWrite(varName)
		default:
			g.errorf("unsupported named type: %s / %T", u, u)
		}
	case *types.Pointer:
		g.genRefWrite(varName)
	default:
		g.Printf("%s _%s = (%s)%s;\n", g.cgoType(t), varName, g.cgoType(t), varName)
	}
}

// lockPath returns a typePath describing the location of a lock value
// contained in typ. If there is no contained lock, it returns nil.
func lockPath(tpkg *types.Package, typ types.Type) typePath {
	if typ == nil {
		return nil
	}

	// We're only interested in the case in which the underlying
	// type is a struct. (Interfaces and pointers are safe to copy.)
	styp, ok := typ.Underlying().(*types.Struct)
	if !ok {
		return nil
	}

	// We're looking for cases in which a reference to this type
	// can be locked, but a value cannot. This differentiates
	// embedded interfaces from embedded values.
	if plock := types.NewMethodSet(types.NewPointer(typ)).Lookup(tpkg, "Lock"); plock != nil {
		if lock := types.NewMethodSet(typ).Lookup(tpkg, "Lock"); lock == nil {
			return []types.Type{typ}
		}
	}

	nfields := styp.NumFields()
	for i := 0; i < nfields; i++ {
		ftyp := styp.Field(i).Type()
		subpath := lockPath(tpkg, ftyp)
		if subpath != nil {
			return append(subpath, typ)
		}
	}

	return nil
}

func asmKindForType(t types.Type, size int) asmKind {
	switch t := t.Underlying().(type) {
	case *types.Basic:
		switch t.Kind() {
		case types.String:
			return asmString
		case types.Complex64, types.Complex128:
			return asmComplex
		}
		return asmKind(size)
	case *types.Pointer, *types.Chan, *types.Map, *types.Signature:
		return asmKind(size)
	case *types.Struct:
		return asmStruct
	case *types.Interface:
		if t.Empty() {
			return asmEmptyInterface
		}
		return asmInterface
	case *types.Array:
		return asmArray
	case *types.Slice:
		return asmSlice
	}
	panic("unreachable")
}

// javaTypeDefault returns a string that represents the default value of the mapped java type.
// TODO(hyangah): Combine javaType and javaTypeDefault?
func (g *javaGen) javaTypeDefault(T types.Type) string {
	switch T := T.(type) {
	case *types.Basic:
		switch T.Kind() {
		case types.Bool:
			return "false"
		case types.Int, types.Int8, types.Int16, types.Int32,
			types.Int64, types.Uint8:
			return "0"
		case types.Float32, types.Float64:
			return "0.0"
		case types.String:
			return "null"
		default:
			g.errorf("unsupported return type: %s", T)
			return "TODO"
		}
	case *types.Slice, *types.Pointer, *types.Named:
		return "null"

	default:
		g.errorf("unsupported javaType: %#+v, %s\n", T, T)
		return "TODO"
	}
}

func (f Field) UnderlyingTarget() fieldser {
	var t types.Type
	switch v := f.v.Type().(type) {
	case elemer:
		t = v.Elem()
	case *types.Named:
		t = v
	}
	if _, ok := t.(underlyinger); !ok {
		return nil
	}
	u := t.(underlyinger).Underlying()
	switch t := u.(type) {
	case *types.Struct:
		return fields{
			g:      f.gen,
			target: t,
		}
	case *types.Pointer:
		return fields{
			g:      f.gen,
			target: t.Elem().(*types.Named).Underlying().(*types.Struct),
		}
	}
	return nil
}

func needWrapType(typ types.Type) bool {
	switch typ := typ.(type) {
	case *types.Basic:
		return false
	case *types.Struct:
		return true
	case *types.Named:
		switch ut := typ.Underlying().(type) {
		case *types.Basic:
			return false
		default:
			return needWrapType(ut)
		}
	case *types.Array:
		return true
	case *types.Map:
		return true
	case *types.Slice:
		return true
	case *types.Interface:
		wrap := true
		if typ.Underlying() == universe.syms["error"].GoType().Underlying() {
			wrap = false
		}
		return wrap
	case *types.Signature:
		return true
	case *types.Pointer:
		return needWrapType(typ.Elem())
	}
	return false
}

func (g *goGen) genWrite(valName, seqName string, T types.Type) {
	if isErrorType(T) {
		g.Printf("if %s == nil {\n", valName)
		g.Printf("    %s.WriteString(\"\");\n", seqName)
		g.Printf("} else {\n")
		g.Printf("    %s.WriteString(%s.Error());\n", seqName, valName)
		g.Printf("}\n")
		return
	}
	switch T := T.(type) {
	case *types.Pointer:
		// TODO(crawshaw): test *int
		// TODO(crawshaw): test **Generator
		switch T := T.Elem().(type) {
		case *types.Named:
			obj := T.Obj()
			if obj.Pkg() != g.pkg {
				g.errorf("type %s not defined in package %s", T, g.pkg)
				return
			}
			g.Printf("%s.WriteGoRef(%s)\n", seqName, valName)
		default:
			g.errorf("unsupported type %s", T)
		}
	case *types.Named:
		switch u := T.Underlying().(type) {
		case *types.Interface, *types.Pointer:
			g.Printf("%s.WriteGoRef(%s)\n", seqName, valName)
		default:
			g.errorf("unsupported, direct named type %s: %s", T, u)
		}
	default:
		g.Printf("%s.Write%s(%s);\n", seqName, seqType(T), valName)
	}
}

func (f *File) validVarDeclType(typ types.Type) *Error {
	if e := f.validResultType(typ); e != nil {
		switch typ.(type) {
		default:
			return e
		case *types.Interface:
			return f.validVarDeclType(typ.Underlying())
		case *types.Named:
			named, ok := typ.(*types.Named)
			if !ok {
				panic("ERROR can't cast to named type")
			}
			tname := named.Obj()
			/*i := Int(0)
			simdInt := reflect.TypeOf(i)
			var i4 Int4
			simdInt4 := reflect.TypeOf(i4)
			switch tname.Name() {
			default:*/
			return &Error{errors.New(fmt.Sprintf("invalid type (%v)", tname.Name())), 0}
			/*case simdInt.Name():
				return nil
			case simdInt4.Name():
				return nil
			}*/
		}
	}
	return nil
}

// MethodSet returns the method set of type T.  It is thread-safe.
//
// If cache is nil, this function is equivalent to types.NewMethodSet(T).
// Utility functions can thus expose an optional *MethodSetCache
// parameter to clients that care about performance.
//
func (cache *MethodSetCache) MethodSet(T types.Type) *types.MethodSet {
	if cache == nil {
		return types.NewMethodSet(T)
	}
	cache.mu.Lock()
	defer cache.mu.Unlock()

	switch T := T.(type) {
	case *types.Named:
		return cache.lookupNamed(T).value

	case *types.Pointer:
		if N, ok := T.Elem().(*types.Named); ok {
			return cache.lookupNamed(N).pointer
		}
	}

	// all other types
	// (The map uses pointer equivalence, not type identity.)
	mset := cache.others[T]
	if mset == nil {
		mset = types.NewMethodSet(T)
		if cache.others == nil {
			cache.others = make(map[types.Type]*types.MethodSet)
		}
		cache.others[T] = mset
	}
	return mset
}

func (sym *symtab) addInterfaceType(pkg *types.Package, obj types.Object, t types.Type, kind symkind, id, n string) {
	fn := sym.typename(t, nil)
	typ := t.Underlying().(*types.Interface)
	kind |= skInterface
	// special handling of 'error'
	if isErrorType(typ) {
		return
	}

	sym.syms[fn] = &symbol{
		gopkg:   pkg,
		goobj:   obj,
		gotyp:   t,
		kind:    kind,
		id:      id,
		goname:  n,
		cgoname: "cgo_type_" + id,
		cpyname: "cpy_type_" + id,
		pyfmt:   "O&",
		pybuf:   "P",
		pysig:   "object",
		c2py:    "cgopy_cnv_c2py_" + id,
		py2c:    "cgopy_cnv_py2c_" + id,
		pychk:   fmt.Sprintf("cpy_func_%[1]s_check(%%s)", id),
	}

}

func (x array) hash(t types.Type) int {
	h := 0
	tElt := t.Underlying().(*types.Array).Elem()
	for _, xi := range x {
		h += hash(tElt, xi)
	}
	return h
}

func encodeType(t types.Type) Type {
	t = t.Underlying()
	switch t.(type) {
	case *types.Basic:
		b := t.(*types.Basic)
		untyped := (b.Info() & types.IsUntyped) != 0
		return NewBasic(basicKindString(b), untyped)
	case *types.Pointer:
		p := t.(*types.Pointer)
		pt := encodeType(p.Elem())
		return NewPointer(pt)
	case *types.Array:
		a := t.(*types.Array)
		at := encodeType(a.Elem())
		return NewArray(at, a.Len())
	case *types.Slice:
		s := t.(*types.Slice)
		st := encodeType(s.Elem())
		return NewSlice(st)
	case *types.Signature:
		sig := t.(*types.Signature)
		v := sig.Recv()
		var vt *Type
		if v != nil {
			t := encodeType(v.Type())
			vt = &t
		}
		return NewSignature(
			sig.Variadic(),
			vt,
			tupleToSlice(sig.Params()),
			tupleToSlice(sig.Results()))
	case *types.Named:
		n := t.(*types.Named)
		return NewNamed(
			n.Obj().Pkg().Name(),
			n.Obj().Name(),
			n.Underlying())
	case *types.Interface:
		i := t.(*types.Interface)
		if i.Empty() {
			return NewInterface()
		} else {
			return NewUnsupported("Interfaces")
		}
	case *types.Tuple:
		return NewUnsupported("Tuples")
	case *types.Map:
		return NewUnsupported("Maps")
	case *types.Chan:
		return NewUnsupported("Channels")
	case *types.Struct:
		return NewUnsupported("Structs")
	default:
		return NewUnsupported(t.String())
	}
}

// indirect(typ) assumes that typ is a pointer type,
// or named alias thereof, and returns its base type.
// Panic ensures if it is not a pointer.
//
func indirectType(ptr types.Type) types.Type {
	if v, ok := underlyingType(ptr).(*types.Pointer); ok {
		return v.Base
	}
	// When debugging it is convenient to comment out this line
	// and let it continue to print the (illegal) SSA form.
	panic("indirect() of non-pointer type: " + ptr.String())
	return nil
}

func (x array) eq(t types.Type, _y interface{}) bool {
	y := _y.(array)
	tElt := t.Underlying().(*types.Array).Elem()
	for i, xi := range x {
		if !equals(tElt, xi, y[i]) {
			return false
		}
	}
	return true
}

func makeImplementsType(T types.Type, fset *token.FileSet) serial.ImplementsType {
	var pos token.Pos
	if nt, ok := deref(T).(*types.Named); ok { // implementsResult.t may be non-named
		pos = nt.Obj().Pos()
	}
	return serial.ImplementsType{
		Name: T.String(),
		Pos:  fset.Position(pos).String(),
		Kind: typeKind(T),
	}
}

func (g *goGen) genWrite(toVar, fromVar string, t types.Type, mode varMode) {
	if isErrorType(t) {
		g.Printf("var %s_str string\n", toVar)
		g.Printf("if %s == nil {\n", fromVar)
		g.Printf("    %s_str = \"\"\n", toVar)
		g.Printf("} else {\n")
		g.Printf("    %s_str = %s.Error()\n", toVar, fromVar)
		g.Printf("}\n")
		g.genWrite(toVar, toVar+"_str", types.Typ[types.String], mode)
		return
	}
	switch t := t.(type) {
	case *types.Basic:
		switch t.Kind() {
		case types.String:
			g.Printf("%s := encodeString(%s)\n", toVar, fromVar)
		case types.Bool:
			g.Printf("var %s C.%s = 0\n", toVar, g.cgoType(t))
			g.Printf("if %s { %s = 1 }\n", fromVar, toVar)
		default:
			g.Printf("%s := C.%s(%s)\n", toVar, g.cgoType(t), fromVar)
		}
	case *types.Slice:
		switch e := t.Elem().(type) {
		case *types.Basic:
			switch e.Kind() {
			case types.Uint8: // Byte.
				g.Printf("%s := fromSlice(%s, %v)\n", toVar, fromVar, mode == modeRetained)
			default:
				g.errorf("unsupported type: %s", t)
			}
		default:
			g.errorf("unsupported type: %s", t)
		}
	case *types.Pointer:
		// TODO(crawshaw): test *int
		// TODO(crawshaw): test **Generator
		switch t := t.Elem().(type) {
		case *types.Named:
			g.genToRefNum(toVar, fromVar)
		default:
			g.errorf("unsupported type %s", t)
		}
	case *types.Named:
		switch u := t.Underlying().(type) {
		case *types.Interface, *types.Pointer:
			g.genToRefNum(toVar, fromVar)
		default:
			g.errorf("unsupported, direct named type %s: %s", t, u)
		}
	default:
		g.errorf("unsupported type %s", t)
	}
}

// usesBuiltinMap returns true if the built-in hash function and
// equivalence relation for type t are consistent with those of the
// interpreter's representation of type t.  Such types are: all basic
// types (bool, numbers, string), pointers and channels.
//
// usesBuiltinMap returns false for types that require a custom map
// implementation: interfaces, arrays and structs.
//
// Panic ensues if t is an invalid map key type: function, map or slice.
func usesBuiltinMap(t types.Type) bool {
	switch t := t.(type) {
	case *types.Basic, *types.Chan, *types.Pointer:
		return true
	case *types.Named:
		return usesBuiltinMap(t.Underlying())
	case *types.Interface, *types.Array, *types.Struct:
		return false
	}
	panic(fmt.Sprintf("invalid map key type: %T", t))
}

// CanHaveDynamicTypes reports whether the type T can "hold" dynamic types,
// i.e. is an interface (incl. reflect.Type) or a reflect.Value.
//
func CanHaveDynamicTypes(T types.Type) bool {
	switch T := T.(type) {
	case *types.Named:
		if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
			return true // reflect.Value
		}
		return CanHaveDynamicTypes(T.Underlying())
	case *types.Interface:
		return true
	}
	return false
}

// javaType returns a string that can be used as a Java type.
func (g *javaGen) javaType(T types.Type) string {
	switch T := T.(type) {
	case *types.Basic:
		switch T.Kind() {
		case types.Bool:
			return "boolean"
		case types.Int:
			return "long"
		case types.Int8:
			return "byte"
		case types.Int16:
			return "short"
		case types.Int32:
			return "int"
		case types.Int64:
			return "long"
		case types.Uint8:
			// TODO(crawshaw): Java bytes are signed, so this is
			// questionable, but vital.
			return "byte"
		// TODO(crawshaw): case types.Uint, types.Uint16, types.Uint32, types.Uint64:
		case types.Float32:
			return "float"
		case types.Float64:
			return "double"
		case types.String:
			return "String"
		default:
			g.errorf("unsupported return type: %s", T)
			return "TODO"
		}
	case *types.Slice:
		elem := g.javaType(T.Elem())
		return elem + "[]"

	case *types.Pointer:
		if _, ok := T.Elem().(*types.Named); ok {
			return g.javaType(T.Elem())
		}
		panic(fmt.Sprintf("unsupporter pointer to type: %s", T))
	case *types.Named:
		n := T.Obj()
		if n.Pkg() != g.pkg {
			panic(fmt.Sprintf("type %s is in package %s, must be defined in package %s", n.Name(), n.Pkg().Name(), g.pkg.Name()))
		}
		// TODO(crawshaw): more checking here
		return n.Name()
	default:
		g.errorf("unsupported javaType: %#+v, %s\n", T, T)
		return "TODO"
	}
}

func newVar(p *Package, typ types.Type, objname, name, doc string) *Var {
	sym := p.syms.symtype(typ)
	if sym == nil {
		panic(fmt.Errorf("could not find symbol for type [%s]!", typ.String()))
	}
	return &Var{
		pkg:  p,
		sym:  sym,
		id:   p.Name() + "_" + objname,
		doc:  doc,
		name: name,
	}
}