htlcswitch: use distinct error for unreadable failures

routing/payment_lifecycle.go

@@ -17,7 +17,7 @@ import (
 type errNoRoute struct {
 	// lastError is the error encountered during the last payment attempt,
 	// if at least one attempt has been made.
-	lastError *htlcswitch.ForwardingError
+	lastError error
 }
 
 // Error returns a string representation of the error.
@@ -37,7 +37,7 @@ type paymentLifecycle struct {
 	finalCLTVDelta uint16
 	attempt        *channeldb.PaymentAttemptInfo
 	circuit        *sphinx.Circuit
-	lastError      *htlcswitch.ForwardingError
+	lastError      error
 }
 
 // resumePayment resumes the paymentLifecycle from the current state.
@@ -341,25 +341,16 @@ func (p *paymentLifecycle) sendPaymentAttempt(firstHop lnwire.ShortChannelID,
 // handleSendError inspects the given error from the Switch and determines
 // whether we should make another payment attempt.
 func (p *paymentLifecycle) handleSendError(sendErr error) error {
-	var reason channeldb.FailureReason
 
-	// If an internal, non-forwarding error occurred, we can stop trying.
-	fErr, ok := sendErr.(*htlcswitch.ForwardingError)
-	if !ok {
-		reason = channeldb.FailureReasonError
-	} else {
-		var final bool
-		final, reason = p.router.processSendError(
-			p.paySession, &p.attempt.Route, fErr,
-		)
+	final, reason := p.router.processSendError(
+		p.paySession, &p.attempt.Route, sendErr,
+	)
+	if !final {
+		// Save the forwarding error so it can be returned if
+		// this turns out to be the last attempt.
+		p.lastError = sendErr
 
-		if !final {
-			// Save the forwarding error so it can be returned if
-			// this turns out to be the last attempt.
-			p.lastError = fErr
-
-			return nil
-		}
+		return nil
 	}
 
 	log.Debugf("Payment %x failed: final_outcome=%v, raw_err=%v",