From 21674c05e5251b9d1218e11da2ca98d0911a5659 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@mit.edu>
Date: Wed, 27 Jun 2018 16:56:49 -0700
Subject: [PATCH] channeldb/codec: add concrete error for unknown types

---
 channeldb/codec.go | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/channeldb/codec.go b/channeldb/codec.go
index 12d14627..03d2b416 100644
--- a/channeldb/codec.go
+++ b/channeldb/codec.go
@@ -43,6 +43,19 @@ func readOutpoint(r io.Reader, o *wire.OutPoint) error {
 	return nil
 }
 
+// UnknownElementType is an error returned when the codec is unable to encode or
+// decode a particular type.
+type UnknownElementType struct {
+	method  string
+	element interface{}
+}
+
+// Error returns the name of the method that encountered the error, as well as
+// the type that was unsupported.
+func (e UnknownElementType) Error() string {
+	return fmt.Sprintf("Unknown type in %s: %T", e.method, e.element)
+}
+
 // WriteElement is a one-stop shop to write the big endian representation of
 // any element which is to be serialized for storage on disk. The passed
 // io.Writer should be backed by an appropriately sized byte slice, or be able
@@ -164,7 +177,7 @@ func WriteElement(w io.Writer, element interface{}) error {
 		}
 
 	default:
-		return fmt.Errorf("Unknown type in WriteElement: %T", e)
+		return UnknownElementType{"WriteElement", e}
 	}
 
 	return nil
@@ -343,7 +356,7 @@ func ReadElement(r io.Reader, element interface{}) error {
 		}
 
 	default:
-		return fmt.Errorf("Unknown type in ReadElement: %T", e)
+		return UnknownElementType{"ReadElement", e}
 	}
 
 	return nil