whisper: fix megacheck warnings (#14925)

* whisper: fix megacheck warnings

* whisper/whisperv5: regenerate json codec to fix unused override type

whisper/whisperv5/gen_criteria_json.go

@@ -8,6 +8,8 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
+var _ = (*criteriaOverride)(nil)
+
 func (c Criteria) MarshalJSON() ([]byte, error) {
 	type Criteria struct {
 		SymKeyID     string        `json:"symKeyID"`

whisper/whisperv5/gen_message_json.go

@@ -8,6 +8,8 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
+var _ = (*messageOverride)(nil)
+
 func (m Message) MarshalJSON() ([]byte, error) {
 	type Message struct {
 		Sig       hexutil.Bytes `json:"sig,omitempty"`

whisper/whisperv5/gen_newmessage_json.go

@@ -8,6 +8,8 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
+var _ = (*newMessageOverride)(nil)
+
 func (n NewMessage) MarshalJSON() ([]byte, error) {
 	type NewMessage struct {
 		SymKeyID   string        `json:"symKeyID"`

whisper/whisperv5/message_test.go

@@ -25,11 +25,6 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-func copyFromBuf(dst []byte, src []byte, beg int) int {
-	copy(dst, src[beg:])
-	return beg + len(dst)
-}
-
 func generateMessageParams() (*MessageParams, error) {
 	// set all the parameters except p.Dst and p.Padding
 
@@ -158,7 +153,7 @@ func TestMessageWrap(t *testing.T) {
 	params.TTL = 1000000
 	params.WorkTime = 1
 	params.PoW = 10000000.0
-	env, err = msg2.Wrap(params)
+	_, err = msg2.Wrap(params)
 	if err == nil {
 		t.Fatalf("unexpectedly reached the PoW target with seed %d.", seed)
 	}

whisper/whisperv5/whisper_test.go

@@ -424,7 +424,7 @@ func TestWhisperSymKeyManagement(t *testing.T) {
 
 	randomKey = make([]byte, aesKeyLength+1)
 	mrand.Read(randomKey)
-	id1, err = w.AddSymKeyDirect(randomKey)
+	_, err = w.AddSymKeyDirect(randomKey)
 	if err == nil {
 		t.Fatalf("added the key with wrong size, seed %d.", seed)
 	}
@@ -541,6 +541,9 @@ func TestCustomization(t *testing.T) {
 	const smallPoW = 0.00001
 
 	f, err := generateFilter(t, true)
+	if err != nil {
+		t.Fatalf("failed generateMessageParams with seed %d: %s.", seed, err)
+	}
 	params, err := generateMessageParams()
 	if err != nil {
 		t.Fatalf("failed generateMessageParams with seed %d: %s.", seed, err)
@@ -607,6 +610,9 @@ func TestCustomization(t *testing.T) {
 
 	// check w.messages()
 	id, err := w.Subscribe(f)
+	if err != nil {
+		t.Fatalf("failed subscribe with seed %d: %s.", seed, err)
+	}
 	time.Sleep(5 * time.Millisecond)
 	mail := f.Retrieve()
 	if len(mail) > 0 {