reflection: introduce UnmarshalTypeError{}

Signed-off-by: Alejandro Mery <amery@jpi.io>

reflection/error.go

@@ -42,3 +42,28 @@ func (e *InvalidUnmarshalError) Error() string {
 
 	return buf.String()
 }
+
+// An UnmarshalTypeError tells something went wrong while processing
+// a type.
+type UnmarshalTypeError struct {
+	Prefix string
+	Err    error
+
+	reflect.Type
+}
+
+func (e UnmarshalTypeError) Unwrap() error {
+	return e.Err
+}
+
+func (e UnmarshalTypeError) Error() string {
+	var buf bytes.Buffer
+
+	if e.Prefix != "" {
+		_, _ = fmt.Fprintf(&buf, "%s: ", e.Prefix)
+	}
+
+	_, _ = fmt.Fprintf(&buf, "%s: %s", e.Type.String(), e.Err)
+
+	return buf.String()
+}