Fix BPChar.AssignTo **rune

https://github.com/jackc/pgtype/issues/123

bpchar.go

@@ -2,6 +2,7 @@ package pgtype
 
 import (
 	"database/sql/driver"
+	"fmt"
 )
 
 // BPChar is fixed-length, blank padded char type
@@ -20,7 +21,8 @@ func (dst BPChar) Get() interface{} {
 
 // AssignTo assigns from src to dst.
 func (src *BPChar) AssignTo(dst interface{}) error {
-	if src.Status == Present {
+	switch src.Status {
+	case Present:
 		switch v := dst.(type) {
 		case *rune:
 			runes := []rune(src.String)
@@ -28,9 +30,24 @@ func (src *BPChar) AssignTo(dst interface{}) error {
 				*v = runes[0]
 				return nil
 			}
+		case *string:
+			*v = src.String
+			return nil
+		case *[]byte:
+			*v = make([]byte, len(src.String))
+			copy(*v, src.String)
+			return nil
+		default:
+			if nextDst, retry := GetAssignToDstType(dst); retry {
+				return src.AssignTo(nextDst)
 			}
+			return fmt.Errorf("unable to assign to %T", dst)
 		}
-	return (*Text)(src).AssignTo(dst)
+	case Null:
+		return NullAssignTo(dst)
+	}
+
+	return fmt.Errorf("cannot decode %#v into %T", src, dst)
 }
 
 func (BPChar) PreferredResultFormat() int16 {