Genbank parser rewrite

io/genbank/error.go

@@ -0,0 +1,27 @@
+package genbank
+
+import "fmt"
+
+// A GenbankSyntaxError denotes a sytntax error in
+// a Genbank flatfile.
+type GenbankSyntaxError struct {
+	Line     uint
+	Context  string
+	Msg      string
+	InnerErr error
+}
+
+// Error returns a human-readable error message.
+func (gse GenbankSyntaxError) Error() string {
+	msg := gse.Msg
+	if gse.InnerErr != nil {
+		msg = fmt.Errorf("%v: %w", msg, gse.InnerErr).Error()
+	}
+
+	return fmt.Sprintf("syntax error at line %v: %v\n%v\t%v", gse.Line, msg, gse.Line, gse.Context)
+}
+
+// Unwrap returns any errors underlying the syntax error, if applicable.
+func (gse GenbankSyntaxError) Unwrap() error {
+	return gse.InnerErr
+}