ListenerConn: Report better errors from sendSimpleQuery

ErrBadConns here are completely useless, since there's no database/sql
to talk to.

conn.go

@@ -119,22 +119,11 @@ func Open(name string) (_ driver.Conn, err error) {
 }
 
 func DialOpen(d Dialer, name string) (_ driver.Conn, err error) {
-	defer func() {
-		// Handle any panics during connection initialization.  Note that we
-		// specifically do *not* want to use errRecover(), as that would turn
-		// any connection errors into ErrBadConns, hiding the real error
-		// message from the user.
-		e := recover()
-		if e == nil {
-			// Do nothing
-			return
-		}
-		var ok bool
-		err, ok = e.(error)
-		if !ok {
-			err = fmt.Errorf("pq: unexpected error: %#v", e)
-		}
-	}()
+	// Handle any panics during connection initialization.  Note that we
+	// specifically do *not* want to use errRecover(), as that would turn any
+	// connection errors into ErrBadConns, hiding the real error message from
+	// the user.
+	defer errRecoverNoErrBadConn(&err)
 
 	o := make(values)
 

error.go

@@ -459,6 +459,19 @@ func errorf(s string, args ...interface{}) {
 	panic(fmt.Errorf("pq: %s", fmt.Sprintf(s, args...)))
 }
 
+func errRecoverNoErrBadConn(err *error) {
+	e := recover()
+	if e == nil {
+		// Do nothing
+		return
+	}
+	var ok bool
+	err, ok = e.(error)
+	if !ok {
+		err = fmt.Errorf("pq: unexpected error: %#v", e)
+	}
+}
+
 func (c *conn) errRecover(err *error) {
 	e := recover()
 	switch v := e.(type) {

notify.go

@@ -128,7 +128,7 @@ func (l *ListenerConn) setState(newState int32) bool {
 // away or should be discarded because we couldn't agree on the state with the
 // server backend.
 func (l *ListenerConn) listenerConnLoop() (err error) {
-	defer l.cn.errRecover(&err)
+	defer errRecoverNoErrBadConn(&err)
 
 	r := &readBuf{}
 	for {
@@ -244,7 +244,7 @@ func (l *ListenerConn) Ping() error {
 // The caller must be holding senderLock (see acquireSenderLock and
 // releaseSenderLock).
 func (l *ListenerConn) sendSimpleQuery(q string) (err error) {
-	defer l.cn.errRecover(&err)
+	defer errRecoverNoErrBadConn(&err)
 
 	// must set connection state before sending the query
 	if !l.setState(connStateExpectResponse) {