From f5cd2b14ccf8dd06fb3562d4d88f8ecde2ca0b79 Mon Sep 17 00:00:00 2001
From: Joel Kek <joel.kek@gmail.com>
Date: Tue, 9 Sep 2014 00:55:40 +0800
Subject: [PATCH] UnmarshalJSON in null.Bool, null.Float, and null.String now
 return an error message when asked to unmarshal from an invalid type. This is
 in line with the behavior of the built-in sql library's null values.

---
 bool.go   | 7 ++++---
 float.go  | 4 ++++
 string.go | 4 ++++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/bool.go b/bool.go
index 86950a1..b913777 100644
--- a/bool.go
+++ b/bool.go
@@ -4,7 +4,8 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
-	// "fmt"
+	"fmt"
+	"reflect"
 )
 
 // Bool is an even nuller nullable bool.
@@ -53,8 +54,8 @@ func (b *Bool) UnmarshalJSON(data []byte) error {
 	case nil:
 		b.Valid = false
 		return nil
-		// default:
-		// 	err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.Bool", v.(type).Name())
+	default:
+		err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.Bool", reflect.TypeOf(v).Name())
 	}
 	b.Valid = err == nil
 	return err
diff --git a/float.go b/float.go
index 42c5cdd..5b722b1 100644
--- a/float.go
+++ b/float.go
@@ -3,6 +3,8 @@ package null
 import (
 	"database/sql"
 	"encoding/json"
+	"fmt"
+	"reflect"
 	"strconv"
 )
 
@@ -52,6 +54,8 @@ func (f *Float) UnmarshalJSON(data []byte) error {
 	case nil:
 		f.Valid = false
 		return nil
+	default:
+		err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.Float", reflect.TypeOf(v).Name())
 	}
 	f.Valid = err == nil
 	return err
diff --git a/string.go b/string.go
index c646908..630616a 100644
--- a/string.go
+++ b/string.go
@@ -6,6 +6,8 @@ package null
 import (
 	"database/sql"
 	"encoding/json"
+	"fmt"
+	"reflect"
 )
 
 // String is an even nuller nullable string.
@@ -51,6 +53,8 @@ func (s *String) UnmarshalJSON(data []byte) error {
 	case nil:
 		s.Valid = false
 		return nil
+	default:
+		err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.String", reflect.TypeOf(v).Name())
 	}
 	s.Valid = (err == nil) && (s.String != "")
 	return err