interp: fix use of interfaces in composite types

The representation of non empty interfaces defined in the interpreter is now identical between refType() and frameType() functions, which are used to generate interpreter objects.

Fixes #1447 and #1426.

Author: mvertes

_test/assert2.go

@@ -5,8 +5,8 @@ import (
 	"sync"
 )
 
-// Defined an interface of stringBuilder that compatible with
-// strings.Builder(go 1.10) and bytes.Buffer(< go 1.10)
+// Define an interface of stringBuilder that is compatible with
+// strings.Builder(go 1.10) and bytes.Buffer(< go 1.10).
 type stringBuilder interface {
 	WriteRune(r rune) (n int, err error)
 	WriteString(s string) (int, error)

_test/issue-1447.go

@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+type I interface {
+	Name() string
+}
+
+type S struct {
+	iMap map[string]I
+}
+
+func main() {
+	s := S{}
+	s.iMap = map[string]I{}
+	fmt.Println(s)
+}
+
+// Output:
+// {map[]}

interp/run.go

@@ -553,7 +553,7 @@ func convert(n *node) {
 	if c.isNil() { // convert nil to type
 		// TODO(mpl): Try to completely remove, as maybe frameType already does the job for interfaces.
 		if isInterfaceSrc(n.child[0].typ) && !isEmptyInterface(n.child[0].typ) {
-			typ = reflect.TypeOf((*valueInterface)(nil)).Elem()
+			typ = valueInterfaceType
 		}
 		n.exec = func(f *frame) bltn {
 			dest(f).Set(reflect.New(typ).Elem())
@@ -713,7 +713,7 @@ func assign(n *node) {
 		case isFuncSrc(typ):
 			t = reflect.TypeOf((*node)(nil))
 		case isInterfaceSrc(typ):
-			t = reflect.TypeOf((*valueInterface)(nil)).Elem()
+			t = valueInterfaceType
 		default:
 			t = typ.TypeOf()
 		}
@@ -1007,7 +1007,7 @@ func genFunctionWrapper(n *node) func(*frame) reflect.Value {
 				}
 				typ := def.typ.arg[i]
 				switch {
-				case isEmptyInterface(typ):
+				case isEmptyInterface(typ) || typ.TypeOf() == valueInterfaceType:
 					d[i].Set(arg)
 				case isInterfaceSrc(typ):
 					d[i].Set(reflect.ValueOf(valueInterface{value: arg.Elem()}))
@@ -1560,12 +1560,9 @@ func callBin(n *node) {
 			case isInterfaceSrc(c.typ):
 				values = append(values, genValueInterfaceValue(c))
 			case c.typ.cat == arrayT || c.typ.cat == variadicT:
-				switch {
-				case isEmptyInterface(c.typ.val):
+				if isEmptyInterface(c.typ.val) {
 					values = append(values, genValueArray(c))
-				case isInterfaceSrc(c.typ.val):
-					values = append(values, genValueInterfaceArray(c))
-				default:
+				} else {
 					values = append(values, genInterfaceWrapper(c, defType))
 				}
 			case isPtrSrc(c.typ):
@@ -2703,8 +2700,6 @@ func doComposite(n *node, hasType bool, keyed bool) {
 			values[fieldIndex] = func(*frame) reflect.Value { return reflect.New(rft).Elem() }
 		case isFuncSrc(val.typ):
 			values[fieldIndex] = genValueAsFunctionWrapper(val)
-		case isArray(val.typ) && val.typ.val != nil && isInterfaceSrc(val.typ.val) && !isEmptyInterface(val.typ.val):
-			values[fieldIndex] = genValueInterfaceArray(val)
 		case isInterfaceSrc(ft) && (!isEmptyInterface(ft) || len(val.typ.method) > 0):
 			values[fieldIndex] = genValueInterface(val)
 		case isInterface(ft):
@@ -3585,7 +3580,7 @@ func convertLiteralValue(n *node, t reflect.Type) {
 	case n.typ.cat == nilT:
 		// Create a zero value of target type.
 		n.rval = reflect.New(t).Elem()
-	case !(n.kind == basicLit || n.rval.IsValid()) || t == nil || t.Kind() == reflect.Interface || t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Interface:
+	case !(n.kind == basicLit || n.rval.IsValid()) || t == nil || t.Kind() == reflect.Interface || t == valueInterfaceType || t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Interface:
 		// Skip non-constant values, undefined target type or interface target type.
 	case n.rval.IsValid():
 		// Convert constant value to target type.
@@ -3946,7 +3941,7 @@ func isNotNil(n *node) {
 	dest := genValue(n)
 
 	if n.fnext == nil {
-		if isInterfaceSrc(c0.typ) {
+		if isInterfaceSrc(c0.typ) && c0.typ.TypeOf() != valueInterfaceType {
 			if isInterface {
 				n.exec = func(f *frame) bltn {
 					dest(f).Set(reflect.ValueOf(!value(f).IsNil()).Convert(typ))
@@ -3991,7 +3986,7 @@ func isNotNil(n *node) {
 
 	fnext := getExec(n.fnext)
 
-	if isInterfaceSrc(c0.typ) {
+	if isInterfaceSrc(c0.typ) && c0.typ.TypeOf() != valueInterfaceType {
 		n.exec = func(f *frame) bltn {
 			if value(f).IsNil() {
 				dest(f).SetBool(false)

interp/type.go

@@ -1817,8 +1817,9 @@ func exportName(s string) string {
 
 var (
 	// TODO(mpl): generators.
-	interf   = reflect.TypeOf((*interface{})(nil)).Elem()
-	constVal = reflect.TypeOf((*constant.Value)(nil)).Elem()
+	emptyInterfaceType = reflect.TypeOf((*interface{})(nil)).Elem()
+	valueInterfaceType = reflect.TypeOf((*valueInterface)(nil)).Elem()
+	constVal           = reflect.TypeOf((*constant.Value)(nil)).Elem()
 )
 
 type fieldRebuild struct {
@@ -1971,7 +1972,12 @@ func (t *itype) refType(ctx *refTypeContext) reflect.Type {
 		}
 		t.rtype = reflect.FuncOf(in, out, variadic)
 	case interfaceT:
-		t.rtype = interf
+		if len(t.field) == 0 {
+			// empty interface, do not wrap it
+			t.rtype = emptyInterfaceType
+			break
+		}
+		t.rtype = valueInterfaceType
 	case mapT:
 		t.rtype = reflect.MapOf(t.key.refType(ctx), t.val.refType(ctx))
 	case ptrT:
@@ -2056,10 +2062,10 @@ func (t *itype) frameType() (r reflect.Type) {
 	case interfaceT:
 		if len(t.field) == 0 {
 			// empty interface, do not wrap it
-			r = reflect.TypeOf((*interface{})(nil)).Elem()
+			r = emptyInterfaceType
 			break
 		}
-		r = reflect.TypeOf((*valueInterface)(nil)).Elem()
+		r = valueInterfaceType
 	case mapT:
 		r = reflect.MapOf(t.key.frameType(), t.val.frameType())
 	case ptrT:
@@ -2072,6 +2078,14 @@ func (t *itype) frameType() (r reflect.Type) {
 
 func (t *itype) implements(it *itype) bool {
 	if isBin(t) {
+		// Note: in case of a valueInterfaceType, we
+		// miss required data which will be available
+		// later, so we optimistically return true to progress,
+		// and additional checks will be hopefully performed at
+		// runtime.
+		if rt := it.TypeOf(); rt == valueInterfaceType {
+			return true
+		}
 		return t.TypeOf().Implements(it.TypeOf())
 	}
 	return t.methods().contains(it.methods())
@@ -2127,11 +2141,15 @@ func (t *itype) defaultType(v reflect.Value, sc *scope) *itype {
 func (t *itype) isNil() bool { return t.cat == nilT }
 
 func (t *itype) hasNil() bool {
-	switch t.TypeOf().Kind() {
+	switch rt := t.TypeOf(); rt.Kind() {
 	case reflect.UnsafePointer:
 		return true
 	case reflect.Slice, reflect.Ptr, reflect.Func, reflect.Interface, reflect.Map, reflect.Chan:
 		return true
+	case reflect.Struct:
+		if rt == valueInterfaceType {
+			return true
+		}
 	}
 	return false
 }
@@ -2246,7 +2264,7 @@ func isInterfaceBin(t *itype) bool {
 }
 
 func isInterface(t *itype) bool {
-	return isInterfaceSrc(t) || t.TypeOf() != nil && t.TypeOf().Kind() == reflect.Interface
+	return isInterfaceSrc(t) || t.TypeOf() == valueInterfaceType || t.TypeOf() != nil && t.TypeOf().Kind() == reflect.Interface
 }
 
 func isBin(t *itype) bool {

interp/typecheck.go

@@ -590,7 +590,7 @@ func (check typecheck) typeAssertionExpr(n *node, typ *itype) error {
 	// https://github.com/golang/go/issues/39717 lands. It is currently impractical to
 	// type check Named types as they cannot be asserted.
 
-	if n.typ.TypeOf().Kind() != reflect.Interface {
+	if rt := n.typ.TypeOf(); rt.Kind() != reflect.Interface && rt != valueInterfaceType {
 		return n.cfgErrorf("invalid type assertion: non-interface type %s on left", n.typ.id())
 	}
 	ims := n.typ.methods()

interp/value.go

@@ -176,7 +176,7 @@ func genValue(n *node) func(*frame) reflect.Value {
 		convertConstantValue(n)
 		v := n.rval
 		if !v.IsValid() {
-			v = reflect.New(interf).Elem()
+			v = reflect.New(emptyInterfaceType).Elem()
 		}
 		return func(f *frame) reflect.Value { return v }
 	case funcDecl:
@@ -287,19 +287,6 @@ func genValueRangeArray(n *node) func(*frame) reflect.Value {
 	}
 }
 
-func genValueInterfaceArray(n *node) func(*frame) reflect.Value {
-	value := genValue(n)
-	return func(f *frame) reflect.Value {
-		vi := value(f).Interface().([]valueInterface)
-		v := reflect.MakeSlice(reflect.TypeOf([]interface{}{}), len(vi), len(vi))
-		for i, vv := range vi {
-			v.Index(i).Set(vv.value)
-		}
-
-		return v
-	}
-}
-
 func genValueInterface(n *node) func(*frame) reflect.Value {
 	value := genValue(n)
 
@@ -356,7 +343,7 @@ func getConcreteValue(val reflect.Value) reflect.Value {
 
 func zeroInterfaceValue() reflect.Value {
 	n := &node{kind: basicLit, typ: &itype{cat: nilT, untyped: true, str: "nil"}}
-	v := reflect.New(interf).Elem()
+	v := reflect.New(emptyInterfaceType).Elem()
 	return reflect.ValueOf(valueInterface{n, v})
 }