tape/dynamic.go

@@ -14,6 +14,14 @@ import "reflect"
 var dummyMap map[uint16] any
 var dummyBuffer []byte
 
+type errCantAssign string
+func (err errCantAssign) Error() string {
+	return string(err)
+}
+func errCantAssignf(format string, v ...any) errCantAssign {
+	return errCantAssign(fmt.Sprintf(format, v...))
+}
+
 // EncodeAny encodes an "any" value. Returns an error if the underlying type is
 // unsupported. Supported types are:
 //
@@ -83,20 +91,34 @@ type unknownSlicePlaceholder struct { }
 var unknownSlicePlaceholderType = reflect.TypeOf(unknownSlicePlaceholder { })
 
 // decodeAny is internal to [DecodeAny]. It takes in an addressable
-// [reflect.Value] as the destination.
+// [reflect.Value] as the destination. If the decoded value cannot fit in the
+// destination, it skims over the payload, leaves the destination empty, and
+// returns without an error.
 func decodeAny(decoder *Decoder, destination reflect.Value, tag Tag) (n int, err error) {
-	errWrongDestinationType := func(expected string) error {
+	n, err = decodeAnyOrError(decoder, destination, tag)
-		panic(fmt.Errorf(
+	if _, ok := err.(errCantAssign); ok {
-		// return fmt.Errorf(
+		if n > 0 { panic(fmt.Sprintf("decodeAnyOrError decoded more than it should: %d", n)) }
-			"expected %s destination, not %v",
+		nn, err := Skim(decoder, tag)
-			expected, destination))
+		n += nn; if err != nil { return n, err }
+		return n, nil
 	}
+	return n, err
+}
+
+// decodeAnyOrError is internal to [decodeAny]. It takes in an addressable
+// [reflect.Value] as the destination. If the decoded value cannot fit in the
+// destination, it decodes nothing and returns an error of type errCantAssign,
+// except for the case of a mismatched OTA element tag, wherein it will skim
+// over the rest of the payload, leave the destination empty, and return without
+// an error.
+func decodeAnyOrError(decoder *Decoder, destination reflect.Value, tag Tag) (n int, err error) {
+	err = canSet(destination.Type(), tag)
+	if err != nil { return n, err }
 	
 	switch tag.WithoutCN() {
 	case SI:
 		// SI: (none)
-		err = setInt(destination, uint64(tag.CN()))
+		setInt(destination, uint64(tag.CN()))
-		if err != nil { return n, err }
 	case LI:
 		// LI: <value: IntN>
 		nn, err := decodeAndSetUint(decoder, destination, tag.CN() + 1)