Make Value an empty interface.

This addresses #573. The implementations of Value are not yet changed.

edit/binding_table.go

@@ -54,7 +54,7 @@ func (bt BindingTable) Repr(indent int) string {
 		if err != nil {
 			panic(err)
 		}
-		builder.WritePair(parse.Quote(k.String()), indent+2, v.Repr(indent+2))
+		builder.WritePair(parse.Quote(k.String()), indent+2, types.Repr(v, indent+2))
 	}
 
 	return builder.String()

edit/compl_getopt.go

@@ -26,7 +26,7 @@ func complGetopt(ec *eval.Frame, a []types.Value, o map[string]types.Value) {
 	elemsv.Iterate(func(v types.Value) bool {
 		elem, ok := v.(types.String)
 		if !ok {
-			throwf("arg should be string, got %s", v.Kind())
+			throwf("arg should be string, got %s", types.Kind(v))
 		}
 		elems = append(elems, string(elem))
 		return true
@@ -34,7 +34,7 @@ func complGetopt(ec *eval.Frame, a []types.Value, o map[string]types.Value) {
 	optsv.Iterate(func(v types.Value) bool {
 		m, ok := v.(types.MapLike)
 		if !ok {
-			throwf("opt should be map-like, got %s", v.Kind())
+			throwf("opt should be map-like, got %s", types.Kind(v))
 		}
 		get := func(ks string) (string, bool) {
 			kv := types.String(ks)
@@ -82,7 +82,7 @@ func complGetopt(ec *eval.Frame, a []types.Value, o map[string]types.Value) {
 		}
 		arg, ok := v.(eval.Fn)
 		if !ok {
-			throwf("argument handler should be fn, got %s", v.Kind())
+			throwf("argument handler should be fn, got %s", types.Kind(v))
 		}
 		args = append(args, arg)
 		return true

edit/edit.go

@@ -131,7 +131,7 @@ func NewEditor(in *os.File, out *os.File, sigs chan os.Signal, ev *eval.Evaler)
 	// Forward reads from notifyChan to notification.
 	go func() {
 		for v := range notifyChan {
-			ed.Notify("[value out] %s", v.Repr(types.NoPretty))
+			ed.Notify("[value out] %s", types.Repr(v, types.NoPretty))
 		}
 	}()
 

edit/hooks.go

@@ -48,7 +48,7 @@ type hookOp struct {
 func (op *hookOp) Invoke(fm *eval.Frame) error {
 	fn, ok := op.hook.(eval.Fn)
 	if !ok {
-		fmt.Fprintf(os.Stderr, "not a function: %s\n", op.hook.Repr(types.NoPretty))
+		fmt.Fprintf(os.Stderr, "not a function: %s\n", types.Repr(op.hook, types.NoPretty))
 		return nil
 	}
 	err := fm.PCall(fn, op.args, eval.NoOpts)

eval/builtin_fn.go

@@ -100,7 +100,7 @@ func kindOf(ec *Frame, args []types.Value, opts map[string]types.Value) {
 	TakeNoOpt(opts)
 	out := ec.ports[1].Chan
 	for _, a := range args {
-		out <- types.String(a.Kind())
+		out <- types.String(types.Kind(a))
 	}
 }
 
@@ -136,7 +136,7 @@ func eq(ec *Frame, args []types.Value, opts map[string]types.Value) {
 	TakeNoOpt(opts)
 	result := true
 	for i := 0; i+1 < len(args); i++ {
-		if !args[i].Equal(args[i+1]) {
+		if !types.Equal(args[i], args[i+1]) {
 			result = false
 			break
 		}
@@ -148,7 +148,7 @@ func notEq(ec *Frame, args []types.Value, opts map[string]types.Value) {
 	TakeNoOpt(opts)
 	result := true
 	for i := 0; i+1 < len(args); i++ {
-		if args[i].Equal(args[i+1]) {
+		if types.Equal(args[i], args[i+1]) {
 			result = false
 			break
 		}

eval/builtin_fn_container.go

@@ -185,7 +185,7 @@ func hasValue(ec *Frame, args []types.Value, opts map[string]types.Value) {
 			return !found
 		})
 	default:
-		throw(fmt.Errorf("argument of type '%s' is not iterable", container.Kind()))
+		throw(fmt.Errorf("argument of type '%s' is not iterable", types.Kind(container)))
 	}
 
 	ec.ports[1].Chan <- types.Bool(found)
@@ -207,7 +207,7 @@ func hasKey(ec *Frame, args []types.Value, opts map[string]types.Value) {
 		_, _, _, err := types.ParseAndFixListIndex(types.ToString(key), container.Len())
 		found = (err == nil)
 	default:
-		throw(fmt.Errorf("couldn't get key or index of type '%s'", container.Kind()))
+		throw(fmt.Errorf("couldn't get key or index of type '%s'", types.Kind(container)))
 	}
 
 	ec.ports[1].Chan <- types.Bool(found)
@@ -234,7 +234,7 @@ func count(ec *Frame, args []types.Value, opts map[string]types.Value) {
 				return true
 			})
 		} else {
-			throw(fmt.Errorf("cannot get length of a %s", v.Kind()))
+			throw(fmt.Errorf("cannot get length of a %s", types.Kind(v)))
 		}
 	default:
 		throw(errors.New("want 0 or 1 argument"))

eval/builtin_fn_io.go

@@ -72,7 +72,7 @@ func pprint(ec *Frame, args []types.Value, opts map[string]types.Value) {
 	TakeNoOpt(opts)
 	out := ec.ports[1].File
 	for _, arg := range args {
-		out.WriteString(arg.Repr(0))
+		out.WriteString(types.Repr(arg, 0))
 		out.WriteString("\n")
 	}
 }
@@ -84,7 +84,7 @@ func repr(ec *Frame, args []types.Value, opts map[string]types.Value) {
 		if i > 0 {
 			out.WriteString(" ")
 		}
-		out.WriteString(arg.Repr(types.NoPretty))
+		out.WriteString(types.Repr(arg, types.NoPretty))
 	}
 	out.WriteString("\n")
 }

eval/builtin_fn_str.go

@@ -92,7 +92,7 @@ func joins(ec *Frame, args []types.Value, opts map[string]types.Value) {
 			}
 			buf.WriteString(string(s))
 		} else {
-			throwf("join wants string input, got %s", v.Kind())
+			throwf("join wants string input, got %s", types.Kind(v))
 		}
 	})
 	out := ec.ports[1].Chan

eval/compile_op.go

@@ -354,7 +354,7 @@ func (op *formOp) Invoke(ec *Frame) (errRet error) {
 		if ks, ok := k.(types.String); ok {
 			convertedOpts[string(ks)] = v
 		} else {
-			errOpt = fmt.Errorf("Option key must be string, got %s", k.Kind())
+			errOpt = fmt.Errorf("Option key must be string, got %s", types.Kind(k))
 			return false
 		}
 		return true
@@ -559,7 +559,7 @@ func (op *redirOp) Invoke(ec *Frame) error {
 				CloseFile: false,
 			}
 		default:
-			srcUnwrap.error("string or file", "%s", src.Kind())
+			srcUnwrap.error("string or file", "%s", types.Kind(src))
 		}
 	}
 	return nil

eval/compile_value.go

@@ -139,7 +139,8 @@ func cat(lhs, rhs types.Value) (types.Value, error) {
 			return lhs, nil
 		}
 	}
-	return nil, fmt.Errorf("unsupported concat: %s and %s", lhs.Kind(), rhs.Kind())
+	return nil, fmt.Errorf("unsupported concat: %s and %s",
+		types.Kind(lhs), types.Kind(rhs))
 }
 
 func outerProduct(vs []types.Value, us []types.Value, f func(types.Value, types.Value) (types.Value, error)) ([]types.Value, error) {
@@ -200,7 +201,7 @@ func doTilde(v types.Value) types.Value {
 		}
 		return v
 	default:
-		throw(fmt.Errorf("tilde doesn't work on value of type %s", v.Kind()))
+		throw(fmt.Errorf("tilde doesn't work on value of type %s", types.Kind(v)))
 		panic("unreachable")
 	}
 }
@@ -236,7 +237,7 @@ func (op *indexingOp) Invoke(ec *Frame) ([]types.Value, error) {
 		for _, v := range vs {
 			indexer, ok := v.(types.Indexer)
 			if !ok {
-				return nil, fmt.Errorf("a %s not indexable", v.Kind())
+				return nil, fmt.Errorf("a %s not indexable", types.Kind(v))
 			}
 			for _, index := range indicies {
 				result, err := indexer.Index(index)
@@ -306,7 +307,7 @@ func (op variableOp) Invoke(ec *Frame) ([]types.Value, error) {
 		iterator, ok := value.(types.Iterator)
 		if !ok {
 			// Use qname[1:] to skip the leading "@"
-			return nil, fmt.Errorf("variable $%s:%s (kind %s) cannot be exploded", op.ns, op.name, value.Kind())
+			return nil, fmt.Errorf("variable $%s:%s (kind %s) cannot be exploded", op.ns, op.name, types.Kind(value))
 		}
 		return types.CollectFromIterator(iterator), nil
 	}

eval/conversion.go

@@ -86,7 +86,7 @@ func scanValueToGo(src types.Value, dstPtr interface{}) {
 		if reflect.TypeOf(src).ConvertibleTo(dstReflect.Type()) {
 			dstReflect.Set(reflect.ValueOf(src).Convert(dstReflect.Type()))
 		} else {
-			throwf("need %s argument, got %s", dstReflect.Type().Name(), src.Kind())
+			throwf("need %s argument, got %s", dstReflect.Type().Name(), types.Kind(src))
 		}
 	}
 }

eval/evaler_ports.go

@@ -39,7 +39,7 @@ func newEvalerPorts(stdin, stdout, stderr *os.File, prefix *string) evalerPorts
 func relayChanToFile(ch <-chan types.Value, file *os.File, prefix *string, w *sync.WaitGroup) {
 	for v := range ch {
 		file.WriteString(*prefix)
-		file.WriteString(v.Repr(initIndent))
+		file.WriteString(types.Repr(v, initIndent))
 		file.WriteString("\n")
 	}
 	w.Done()

eval/re/re.go

@@ -99,7 +99,7 @@ func replace(ec *eval.Frame, args []types.Value, opts map[string]types.Value) {
 		repl, ok := argRepl.(types.String)
 		if !ok {
 			throwf("replacement must be string when literal is set, got %s",
-				argRepl.Kind())
+				types.Kind(argRepl))
 		}
 		result = pattern.ReplaceAllLiteralString(string(argSource), string(repl))
 	} else {
@@ -116,14 +116,15 @@ func replace(ec *eval.Frame, args []types.Value, opts map[string]types.Value) {
 				}
 				output, ok := values[0].(types.String)
 				if !ok {
-					throwf("replacement function must output one string, got %s", values[0].Kind())
+					throwf("replacement function must output one string, got %s",
+						types.Kind(values[0]))
 				}
 				return string(output)
 			}
 			result = pattern.ReplaceAllStringFunc(string(argSource), replFunc)
 		default:
 			throwf("replacement must be string or function, got %s",
-				argRepl.Kind())
+				types.Kind(argRepl))
 		}
 	}
 	out <- types.String(result)

eval/scan.go

@@ -56,7 +56,7 @@ func ScanArgsOptionalInput(ec *Frame, src []types.Value, dstArgs ...interface{})
 		value := src[len(dstArgs)]
 		iterable, ok := value.(types.Iterator)
 		if !ok {
-			throwf("need iterable argument, got %s", value.Kind())
+			throwf("need iterable argument, got %s", types.Kind(value))
 		}
 		return func(f func(types.Value)) {
 			iterable.Iterate(func(v types.Value) bool {

eval/scan_test.go

@@ -201,7 +201,7 @@ var scanArgTestCases = []struct {
 func TestScanArg(t *testing.T) {
 	for _, tc := range scanArgTestCases {
 		scanValueToGo(tc.source, tc.destPtr)
-		if !equals(indirect(tc.destPtr), tc.want) {
+		if !types.Equal(indirect(tc.destPtr), tc.want) {
 			t.Errorf("scanArg(%s) got %q, want %v", tc.source,
 				indirect(tc.destPtr), tc.want)
 		}

eval/testutils.go

@@ -213,7 +213,7 @@ func matchOut(want, got []types.Value) bool {
 		return false
 	}
 	for i := range got {
-		if !got[i].Equal(want[i]) {
+		if !types.Equal(got[i], want[i]) {
 			return false
 		}
 	}
@@ -234,18 +234,9 @@ func compareSlice(wantValues, gotValues []interface{}) error {
 			len(wantValues), len(gotValues))
 	}
 	for i, want := range wantValues {
-		if !equals(want, gotValues[i]) {
+		if !types.Equal(want, gotValues[i]) {
 			return fmt.Errorf("want [%d] = %s, got %s", i, want, gotValues[i])
 		}
 	}
 	return nil
 }
-
-// equals compares two values. It uses Eq if want is a Value instance, or
-// reflect.DeepEqual otherwise.
-func equals(a, b interface{}) bool {
-	if aValue, ok := a.(types.Value); ok {
-		return aValue.Equal(b)
-	}
-	return reflect.DeepEqual(a, b)
-}

eval/types/equal.go

@@ -1,5 +1,17 @@
 package types
 
-func Equal(x, y interface{}) bool {
-	return x.(Equaler).Equal(y)
+import "reflect"
+
+// Equaler wraps the Equal method.
+type Equaler interface {
+	// Equal compares the receiver to another value. Two equal values must have
+	// the same hash code.
+	Equal(other interface{}) bool
+}
+
+func Equal(x, y interface{}) bool {
+	if equaler, ok := x.(Equaler); ok {
+		return equaler.Equal(y)
+	}
+	return reflect.DeepEqual(x, y)
 }

eval/types/hash.go

@@ -1,5 +1,14 @@
 package types
 
-func Hash(v interface{}) uint32 {
-	return v.(Hasher).Hash()
+// Hasher wraps the Hash method.
+type Hasher interface {
+	// Hash computes the hash code of the receiver.
+	Hash() uint32
+}
+
+func Hash(v interface{}) uint32 {
+	if hasher, ok := v.(Hasher); ok {
+		return hasher.Hash()
+	}
+	return 0
 }

eval/types/kind.go

@@ -0,0 +1,13 @@
+package types
+
+// Kinder wraps the Kind method.
+type Kinder interface {
+	Kind() string
+}
+
+func Kind(v interface{}) string {
+	if kinder, ok := v.(Kinder); ok {
+		return kinder.Kind()
+	}
+	return "unknown"
+}

eval/types/list.go

@@ -62,7 +62,7 @@ func (l List) Repr(indent int) string {
 	b.Indent = indent
 	for it := l.inner.Iterator(); it.HasElem(); it.Next() {
 		v := it.Elem().(Value)
-		b.WriteElem(v.Repr(indent + 1))
+		b.WriteElem(Repr(v, indent+1))
 	}
 	return b.String()
 }

eval/types/listlike.go

@@ -27,7 +27,7 @@ func eqListLike(lhs ListLike, r interface{}) bool {
 func hashListLike(l ListLike) uint32 {
 	h := hash.DJBInit
 	l.Iterate(func(v Value) bool {
-		h = hash.DJBCombine(h, v.Hash())
+		h = hash.DJBCombine(h, Hash(v))
 		return true
 	})
 	return h

eval/types/map.go

@@ -24,7 +24,7 @@ func NoSuchKey(k Value) error {
 }
 
 func (err noSuchKeyError) Error() string {
-	return "no such key: " + err.key.Repr(NoPretty)
+	return "no such key: " + Repr(err.key, NoPretty)
 }
 
 var EmptyMapInner = hashmap.New(Equal, Hash)
@@ -73,7 +73,7 @@ func (m Map) Repr(indent int) string {
 	builder.Indent = indent
 	for it := m.inner.Iterator(); it.HasElem(); it.Next() {
 		k, v := it.Elem()
-		builder.WritePair(k.(Value).Repr(indent+1), indent+2, v.(Value).Repr(indent+2))
+		builder.WritePair(Repr(k, indent+1), indent+2, Repr(v, indent+2))
 	}
 	return builder.String()
 }

eval/types/maplike.go

@@ -28,7 +28,7 @@ func EqMapLike(lhs MapLike, a interface{}) bool {
 	eq := true
 	lhs.IteratePair(func(k, v Value) bool {
 		v2, err := rhs.Index(k)
-		if err != nil || !v.Equal(v2) {
+		if err != nil || !Equal(v, v2) {
 			eq = false
 			return false
 		}
@@ -40,8 +40,8 @@ func EqMapLike(lhs MapLike, a interface{}) bool {
 func HashMapLike(m MapLike) uint32 {
 	h := hash.DJBInit
 	m.IteratePair(func(k, v Value) bool {
-		h = hash.DJBCombine(h, k.Hash())
-		h = hash.DJBCombine(h, v.Hash())
+		h = hash.DJBCombine(h, Hash(k))
+		h = hash.DJBCombine(h, Hash(v))
 		return true
 	})
 	return h

eval/types/repr.go

@@ -0,0 +1,31 @@
+package types
+
+import (
+	"fmt"
+
+	"github.com/elves/elvish/util"
+)
+
+// NoPretty can be passed to Repr to suppress pretty-printing.
+const NoPretty = util.MinInt
+
+// Reprer wraps the Repr method.
+type Reprer interface {
+	// Repr returns a string that represents a Value. The string either be a
+	// literal of that Value that is preferably deep-equal to it (like `[a b c]`
+	// for a list), or a string enclosed in "<>" containing the kind and
+	// identity of the Value(like `<fn 0xdeadcafe>`).
+	//
+	// If indent is at least 0, it should be pretty-printed with the current
+	// indentation level of indent; the indent of the first line has already
+	// been written and shall not be written in Repr. The returned string
+	// should never contain a trailing newline.
+	Repr(indent int) string
+}
+
+func Repr(v interface{}, indent int) string {
+	if reprer, ok := v.(Reprer); ok {
+		return reprer.Repr(indent)
+	}
+	return fmt.Sprint(v)
+}

eval/types/struct.go

@@ -46,7 +46,7 @@ func (s *Struct) Repr(indent int) string {
 	var builder MapReprBuilder
 	builder.Indent = indent
 	for i, name := range s.descriptor.fieldNames {
-		builder.WritePair(parse.Quote(name), indent+2, s.fields[i].Repr(indent+2))
+		builder.WritePair(parse.Quote(name), indent+2, Repr(s.fields[i], indent+2))
 	}
 	return builder.String()
 }

eval/types/struct_test.go

@@ -22,7 +22,7 @@ func TestStructMethods(t *testing.T) {
 	if testStruct.Equal(testStruct2) {
 		t.Errorf(`testStruct.Equal(testStruct2) => true, want false`)
 	}
-	if s2, err := testStruct.Assoc(String("bar"), String("dolor")); !s2.Equal(testStruct2) {
+	if s2, err := testStruct.Assoc(String("bar"), String("dolor")); !Equal(s2, testStruct2) {
 		t.Errorf(`testStruct.Assoc(...) => %v, want %v`, s2, testStruct2)
 	} else if err != nil {
 		t.Errorf(`testStruct.Assoc(...) => error %s, want no error`, err)

eval/types/types.go

@@ -1,55 +1,11 @@
 // Package types contains basic types for the Elvish runtime.
 package types
 
-import (
-	"github.com/elves/elvish/util"
-)
-
 // Definitions for Value interfaces, some simple Value types and some common
 // Value helpers.
 
 // Value is an Elvish value.
-type Value interface {
-	Kinder
-	Equaler
-	Hasher
-	Reprer
-}
-
-// Kinder wraps the Kind method.
-type Kinder interface {
-	Kind() string
-}
-
-// Reprer wraps the Repr method.
-type Reprer interface {
-	// Repr returns a string that represents a Value. The string either be a
-	// literal of that Value that is preferably deep-equal to it (like `[a b c]`
-	// for a list), or a string enclosed in "<>" containing the kind and
-	// identity of the Value(like `<fn 0xdeadcafe>`).
-	//
-	// If indent is at least 0, it should be pretty-printed with the current
-	// indentation level of indent; the indent of the first line has already
-	// been written and shall not be written in Repr. The returned string
-	// should never contain a trailing newline.
-	Repr(indent int) string
-}
-
-// NoPretty can be passed to Repr to suppress pretty-printing.
-const NoPretty = util.MinInt
-
-// Equaler wraps the Equal method.
-type Equaler interface {
-	// Equal compares the receiver to another value. Two equal values must have
-	// the same hash code.
-	Equal(other interface{}) bool
-}
-
-// Hasher wraps the Hash method.
-type Hasher interface {
-	// Hash computes the hash code of the receiver.
-	Hash() uint32
-}
+type Value interface{}
 
 // Booler wraps the Bool method.
 type Booler interface {
@@ -69,7 +25,7 @@ func ToString(v Value) string {
 	if s, ok := v.(Stringer); ok {
 		return s.String()
 	}
-	return v.Repr(NoPretty)
+	return Repr(v, NoPretty)
 }
 
 // Lener wraps the Len method.

eval/unwrap.go

@@ -64,7 +64,7 @@ func (u ValueUnwrapper) Any() types.Value {
 func (u ValueUnwrapper) String() types.String {
 	s, ok := u.values[0].(types.String)
 	if !ok {
-		u.error("string", "%s", u.values[0].Kind())
+		u.error("string", "%s", types.Kind(u.values[0]))
 	}
 	return s
 }
@@ -97,7 +97,7 @@ func (u ValueUnwrapper) FdOrClose() int {
 func (u ValueUnwrapper) Callable() Callable {
 	c, ok := u.values[0].(Callable)
 	if !ok {
-		u.error("callable", "%s", u.values[0].Kind())
+		u.error("callable", "%s", types.Kind(u.values[0]))
 	}
 	return c
 }
@@ -105,7 +105,7 @@ func (u ValueUnwrapper) Callable() Callable {
 func (u ValueUnwrapper) Iterable() types.Iterator {
 	it, ok := u.values[0].(types.Iterator)
 	if !ok {
-		u.error("iterable", "%s", u.values[0].Kind())
+		u.error("iterable", "%s", types.Kind(u.values[0]))
 	}
 	return it
 }

eval/value_test.go

@@ -34,7 +34,7 @@ var reprTests = []struct {
 
 func TestRepr(t *testing.T) {
 	for _, test := range reprTests {
-		repr := test.v.Repr(types.NoPretty)
+		repr := types.Repr(test.v, types.NoPretty)
 		if repr != test.want {
 			t.Errorf("Repr = %s, want %s", repr, test.want)
 		}