all: update error type checking

accounts/keystore/keystore_test.go

@@ -17,6 +17,7 @@
 package keystore
 
 import (
+	"errors"
 	"math/rand"
 	"os"
 	"runtime"
@@ -127,7 +128,7 @@ func TestTimedUnlock(t *testing.T) {
 
 	// Signing without passphrase fails because account is locked
 	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
-	if err != ErrLocked {
+	if !errors.Is(err, ErrLocked) {
 		t.Fatal("Signing should've failed with ErrLocked before unlocking, got ", err)
 	}
 
@@ -145,7 +146,7 @@ func TestTimedUnlock(t *testing.T) {
 	// Signing fails again after automatic locking
 	time.Sleep(250 * time.Millisecond)
 	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
-	if err != ErrLocked {
+	if !errors.Is(err, ErrLocked) {
 		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
 	}
 }
@@ -185,7 +186,7 @@ func TestOverrideUnlock(t *testing.T) {
 	// Signing fails again after automatic locking
 	time.Sleep(250 * time.Millisecond)
 	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
-	if err != ErrLocked {
+	if !errors.Is(err, ErrLocked) {
 		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
 	}
 }
@@ -206,7 +207,7 @@ func TestSignRace(t *testing.T) {
 	}
 	end := time.Now().Add(500 * time.Millisecond)
 	for time.Now().Before(end) {
-		if _, err := ks.SignHash(accounts.Account{Address: a1.Address}, testSigData); err == ErrLocked {
+		if _, err := ks.SignHash(accounts.Account{Address: a1.Address}, testSigData); errors.Is(err, ErrLocked) {
 			return
 		} else if err != nil {
 			t.Errorf("Sign error: %v", err)

accounts/keystore/plain_test.go

@@ -19,6 +19,7 @@ package keystore
 import (
 	"crypto/rand"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"path/filepath"
 	"reflect"
@@ -90,7 +91,7 @@ func TestKeyStorePassphraseDecryptionFail(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if _, err = ks.GetKey(k1.Address, account.URL.Path, "bar"); err != ErrDecrypt {
+	if _, err = ks.GetKey(k1.Address, account.URL.Path, "bar"); !errors.Is(err, ErrDecrypt) {
 		t.Fatalf("wrong error for invalid password\ngot %q\nwant %q", err, ErrDecrypt)
 	}
 }

accounts/usbwallet/ledger.go

@@ -119,7 +119,7 @@ func (w *ledgerDriver) Open(device io.ReadWriter, passphrase string) error {
 	_, err := w.ledgerDerive(accounts.DefaultBaseDerivationPath)
 	if err != nil {
 		// Ethereum app is not running or in browser mode, nothing more to do, return
-		if err == errLedgerReplyInvalidHeader {
+		if errors.Is(err, errLedgerReplyInvalidHeader) {
 			w.browser = true
 		}
 		return nil
@@ -141,7 +141,7 @@ func (w *ledgerDriver) Close() error {
 // Heartbeat implements usbwallet.driver, performing a sanity check against the
 // Ledger to see if it's still online.
 func (w *ledgerDriver) Heartbeat() error {
-	if _, err := w.ledgerVersion(); err != nil && err != errLedgerInvalidVersionReply {
+	if _, err := w.ledgerVersion(); err != nil && !errors.Is(err, errLedgerInvalidVersionReply) {
 		w.failure = err
 		return err
 	}

beacon/light/committee_chain_test.go

@@ -18,6 +18,7 @@ package light
 
 import (
 	"crypto/rand"
+	"errors"
 	"testing"
 	"time"
 
@@ -259,13 +260,13 @@ func (c *committeeChainTest) setClockPeriod(period float64) {
 }
 
 func (c *committeeChainTest) addFixedCommitteeRoot(tc *testCommitteeChain, period uint64, expErr error) {
-	if err := c.chain.addFixedCommitteeRoot(period, tc.periods[period].committee.Root()); err != expErr {
+	if err := c.chain.addFixedCommitteeRoot(period, tc.periods[period].committee.Root()); !errors.Is(err, expErr) {
 		c.t.Errorf("Incorrect error output from addFixedCommitteeRoot at period %d (expected %v, got %v)", period, expErr, err)
 	}
 }
 
 func (c *committeeChainTest) addCommittee(tc *testCommitteeChain, period uint64, expErr error) {
-	if err := c.chain.addCommittee(period, tc.periods[period].committee); err != expErr {
+	if err := c.chain.addCommittee(period, tc.periods[period].committee); !errors.Is(err, expErr) {
 		c.t.Errorf("Incorrect error output from addCommittee at period %d (expected %v, got %v)", period, expErr, err)
 	}
 }
@@ -275,7 +276,7 @@ func (c *committeeChainTest) insertUpdate(tc *testCommitteeChain, period uint64,
 	if addCommittee {
 		committee = tc.periods[period+1].committee
 	}
-	if err := c.chain.InsertUpdate(tc.periods[period].update, committee); err != expErr {
+	if err := c.chain.InsertUpdate(tc.periods[period].update, committee); !errors.Is(err, expErr) {
 		c.t.Errorf("Incorrect error output from InsertUpdate at period %d (expected %v, got %v)", period, expErr, err)
 	}
 }

cmd/evm/main.go

@@ -18,6 +18,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"math/big"
 	"os"
@@ -248,7 +249,8 @@ func init() {
 func main() {
 	if err := app.Run(os.Args); err != nil {
 		code := 1
-		if ec, ok := err.(*t8ntool.NumberedError); ok {
+		var ec *t8ntool.NumberedError
+		if errors.As(err, &ec) {
 			code = ec.ExitCode()
 		}
 		fmt.Fprintln(os.Stderr, err)

cmd/geth/accountcmd.go

@@ -17,6 +17,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"os"
 
@@ -233,11 +234,12 @@ func unlockAccount(ks *keystore.KeyStore, address string, i int, passwords []str
 			log.Info("Unlocked account", "address", account.Address.Hex())
 			return account, password
 		}
-		if err, ok := err.(*keystore.AmbiguousAddrError); ok {
+		var err *keystore.AmbiguousAddrError
+		if errors.As(err, &err) {
 			log.Info("Unlocked account", "address", account.Address.Hex())
 			return ambiguousAddrRecovery(ks, err, password), password
 		}
-		if err != keystore.ErrDecrypt {
+		if !errors.Is(err, keystore.ErrDecrypt) {
 			// No need to prompt again if the error is not decryption-related.
 			break
 		}

cmd/geth/config.go

@@ -106,7 +106,8 @@ func loadConfig(file string, cfg *gethConfig) error {
 
 	err = tomlSettings.NewDecoder(bufio.NewReader(f)).Decode(cfg)
 	// Add file name to errors that have a line number.
-	if _, ok := err.(*toml.LineError); ok {
+	var lineError *toml.LineError
+	if errors.As(err, &lineError) {
 		err = errors.New(file + ", " + err.Error())
 	}
 	return err

common/bitutil/compress_test.go

@@ -18,6 +18,7 @@ package bitutil
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"math/rand"
 	"testing"
@@ -143,7 +144,7 @@ func TestCompression(t *testing.T) {
 		t.Errorf("decoding mismatch for dense data: have %x, want %x, error %v", data, in, err)
 	}
 	// Check that decompressing a longer input than the target fails
-	if _, err := DecompressBytes([]byte{0xc0, 0x01, 0x01}, 2); err != errExceededTarget {
+	if _, err := DecompressBytes([]byte{0xc0, 0x01, 0x01}, 2); !errors.Is(err, errExceededTarget) {
 		t.Errorf("decoding error mismatch for long data: have %v, want %v", err, errExceededTarget)
 	}
 }

common/hexutil/hexutil.go

@@ -32,6 +32,7 @@ package hexutil
 
 import (
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"math/big"
 	"strconv"
@@ -223,18 +224,20 @@ func decodeNibble(in byte) uint64 {
 }
 
 func mapError(err error) error {
-	if err, ok := err.(*strconv.NumError); ok {
+	var numErr *strconv.NumError
-		switch err.Err {
+	if errors.As(err, &numErr) {
-		case strconv.ErrRange:
+		switch {
+		case errors.Is(numErr.Err, strconv.ErrRange):
 			return ErrUint64Range
-		case strconv.ErrSyntax:
+		case errors.Is(numErr.Err, strconv.ErrSyntax):
 			return ErrSyntax
 		}
 	}
-	if _, ok := err.(hex.InvalidByteError); ok {
+	var invalidByteError hex.InvalidByteError
+	if errors.As(err, &invalidByteError) {
 		return ErrSyntax
 	}
-	if err == hex.ErrLength {
+	if errors.Is(err, hex.ErrLength) {
 		return ErrOddLength
 	}
 	return err

common/hexutil/json.go

@@ -19,6 +19,7 @@ package hexutil
 import (
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"math/big"
 	"reflect"
@@ -355,7 +356,7 @@ func (b *Uint) UnmarshalJSON(input []byte) error {
 func (b *Uint) UnmarshalText(input []byte) error {
 	var u64 Uint64
 	err := u64.UnmarshalText(input)
-	if u64 > Uint64(^uint(0)) || err == ErrUint64Range {
+	if u64 > Uint64(^uint(0)) || errors.Is(err, ErrUint64Range) {
 		return ErrUintRange
 	} else if err != nil {
 		return err
@@ -410,7 +411,8 @@ func checkNumberText(input []byte) (raw []byte, err error) {
 }
 
 func wrapTypeError(err error, typ reflect.Type) error {
-	if _, ok := err.(*decError); ok {
+	var de *decError
+	if errors.As(err, &de) {
 		return &json.UnmarshalTypeError{Value: err.Error(), Type: typ}
 	}
 	return err

common/test_utils.go

@@ -18,6 +18,7 @@ package common
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 )
@@ -29,7 +30,8 @@ func LoadJSON(file string, val interface{}) error {
 		return err
 	}
 	if err := json.Unmarshal(content, val); err != nil {
-		if syntaxerr, ok := err.(*json.SyntaxError); ok {
+		var syntaxerr *json.SyntaxError
+		if errors.As(err, &syntaxerr) {
 			line := findLine(content, syntaxerr.Offset)
 			return fmt.Errorf("JSON syntax error at %v:%v: %v", file, line, err)
 		}

console/bridge.go

@@ -434,11 +434,13 @@ func (b *bridge) Send(call jsre.Call) (goja.Value, error) {
 		} else {
 			code := -32603
 			var data interface{}
-			if err, ok := err.(rpc.Error); ok {
+			var rpcErr rpc.Error
-				code = err.ErrorCode()
+			if errors.As(err, &rpcErr) {
+				code = rpcErr.ErrorCode()
 			}
-			if err, ok := err.(rpc.DataError); ok {
+			var dataErr rpc.DataError
-				data = err.ErrorData()
+			if errors.As(err, &dataErr) {
+				data = dataErr.ErrorData()
 			}
 			setError(resp, code, err.Error(), data)
 		}

console/console.go

@@ -149,7 +149,8 @@ func (c *Console) init(preload []string) error {
 	for _, path := range preload {
 		if err := c.jsre.Exec(path); err != nil {
 			failure := err.Error()
-			if gojaErr, ok := err.(*goja.Exception); ok {
+			var gojaErr *goja.Exception
+			if errors.As(err, &gojaErr) {
 				failure = gojaErr.String()
 			}
 			return fmt.Errorf("%s: %v", path, failure)
@@ -206,7 +207,8 @@ func (c *Console) initExtensions() error {
 	const methodNotFound = -32601
 	apis, err := c.client.SupportedModules()
 	if err != nil {
-		if rpcErr, ok := err.(rpc.Error); ok && rpcErr.ErrorCode() == methodNotFound {
+		var rpcErr rpc.Error
+		if errors.As(err, &rpcErr) && rpcErr.ErrorCode() == methodNotFound {
 			log.Warn("Server does not support method rpc_modules, using default API list.")
 			apis = defaultAPIs
 		} else {

core/blockchain.go

@@ -275,7 +275,8 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis
 	// to database if the genesis block is not present yet, or load the
 	// stored one from database.
 	chainConfig, genesisHash, genesisErr := SetupGenesisBlockWithOverride(db, triedb, genesis, overrides)
-	if _, ok := genesisErr.(*params.ConfigCompatError); genesisErr != nil && !ok {
+	var configCompatError *params.ConfigCompatError
+	if genesisErr != nil && !errors.As(genesisErr, &configCompatError) {
 		return nil, genesisErr
 	}
 	log.Info("")
@@ -455,7 +456,8 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, genesis *Genesis
 	go bc.updateFutureBlocks()
 
 	// Rewind the chain in case of an incompatible config upgrade.
-	if compat, ok := genesisErr.(*params.ConfigCompatError); ok {
+	var compat *params.ConfigCompatError
+	if errors.As(genesisErr, &compat) {
 		log.Warn("Rewinding chain to upgrade configuration", "err", compat)
 		if compat.RewindToTime > 0 {
 			bc.SetHeadWithTimestamp(compat.RewindToTime)
@@ -1282,7 +1284,7 @@ func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain [
 	// Write downloaded chain data and corresponding receipt chain data
 	if len(ancientBlocks) > 0 {
 		if n, err := writeAncient(ancientBlocks, ancientReceipts); err != nil {
-			if err == errInsertionInterrupted {
+			if errors.Is(err, errInsertionInterrupted) {
 				return 0, nil
 			}
 			return n, err
@@ -1290,7 +1292,7 @@ func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain [
 	}
 	if len(liveBlocks) > 0 {
 		if n, err := writeLive(liveBlocks, liveReceipts); err != nil {
-			if err == errInsertionInterrupted {
+			if errors.Is(err, errInsertionInterrupted) {
 				return 0, nil
 			}
 			return n, err

core/blockchain_test.go

@@ -154,7 +154,7 @@ func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 			err = blockchain.validator.ValidateBody(block)
 		}
 		if err != nil {
-			if err == ErrKnownBlock {
+			if errors.Is(err, ErrKnownBlock) {
 				continue
 			}
 			return err

core/rawdb/freezer_table_test.go

@@ -19,6 +19,7 @@ package rawdb
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math/rand"
 	"os"
@@ -68,7 +69,7 @@ func TestFreezerBasics(t *testing.T) {
 	}
 	// Check that we cannot read too far
 	_, err = f.Retrieve(uint64(255))
-	if err != errOutOfBounds {
+	if !errors.Is(err, errOutOfBounds) {
 		t.Fatal(err)
 	}
 }
@@ -1361,7 +1362,8 @@ func runRandTest(rt randTest) bool {
 
 func TestRandom(t *testing.T) {
 	if err := quick.Check(runRandTest, nil); err != nil {
-		if cerr, ok := err.(*quick.CheckError); ok {
+		var cerr *quick.CheckError
+		if errors.As(err, &cerr) {
 			t.Fatalf("random test iteration %d failed: %s", cerr.Count, spew.Sdump(cerr.In))
 		}
 		t.Fatal(err)

core/rawdb/freezer_test.go

@@ -373,7 +373,7 @@ func checkAncientCount(t *testing.T, f *Freezer, kind string, n uint64) {
 	}
 	if _, err := f.Ancient(kind, index); err == nil {
 		t.Errorf("Ancient(%q, %d) didn't return expected error", kind, index)
-	} else if err != errOutOfBounds {
+	} else if !errors.Is(err, errOutOfBounds) {
 		t.Errorf("Ancient(%q, %d) returned unexpected error %q", kind, index, err)
 	}
 }

core/state/snapshot/disklayer_test.go

@@ -18,6 +18,7 @@ package snapshot
 
 import (
 	"bytes"
+	"errors"
 	"testing"
 
 	"github.com/VictoriaMetrics/fastcache"
@@ -311,7 +312,7 @@ func TestDiskPartialMerge(t *testing.T) {
 		assertAccount := func(account common.Hash, data []byte) {
 			t.Helper()
 			blob, err := base.AccountRLP(account)
-			if bytes.Compare(account[:], genMarker) > 0 && err != ErrNotCoveredYet {
+			if bytes.Compare(account[:], genMarker) > 0 && !errors.Is(err, ErrNotCoveredYet) {
 				t.Fatalf("test %d: post-marker (%x) account access (%x) succeeded: %x", i, genMarker, account, blob)
 			}
 			if bytes.Compare(account[:], genMarker) <= 0 && !bytes.Equal(blob, data) {
@@ -327,7 +328,7 @@ func TestDiskPartialMerge(t *testing.T) {
 		assertStorage := func(account common.Hash, slot common.Hash, data []byte) {
 			t.Helper()
 			blob, err := base.Storage(account, slot)
-			if bytes.Compare(append(account[:], slot[:]...), genMarker) > 0 && err != ErrNotCoveredYet {
+			if bytes.Compare(append(account[:], slot[:]...), genMarker) > 0 && !errors.Is(err, ErrNotCoveredYet) {
 				t.Fatalf("test %d: post-marker (%x) storage access (%x:%x) succeeded: %x", i, genMarker, account, slot, blob)
 			}
 			if bytes.Compare(append(account[:], slot[:]...), genMarker) <= 0 && !bytes.Equal(blob, data) {

core/state/snapshot/generate.go

@@ -687,7 +687,8 @@ func (dl *diskLayer) generate(stats *generatorStats) {
 
 	if err := generateAccounts(ctx, dl, accMarker); err != nil {
 		// Extract the received interruption signal if exists
-		if aerr, ok := err.(*abortErr); ok {
+		var aerr *abortErr
+		if errors.As(err, &aerr) {
 			abort = aerr.abort
 		}
 		// Aborted by internal error, wait the signal

core/state/snapshot/snapshot_test.go

@@ -19,6 +19,7 @@ package snapshot
 import (
 	crand "crypto/rand"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math/rand"
 	"testing"
@@ -118,10 +119,10 @@ func TestDiskLayerExternalInvalidationFullFlatten(t *testing.T) {
 		t.Fatalf("failed to merge diff layer onto disk: %v", err)
 	}
 	// Since the base layer was modified, ensure that data retrievals on the external reference fail
-	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
+	if acc, err := ref.Account(common.HexToHash("0x01")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
 	}
-	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
+	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
 	}
 	if n := len(snaps.layers); n != 1 {
@@ -168,10 +169,10 @@ func TestDiskLayerExternalInvalidationPartialFlatten(t *testing.T) {
 		t.Fatalf("failed to merge accumulator onto disk: %v", err)
 	}
 	// Since the base layer was modified, ensure that data retrievals on the external reference fail
-	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
+	if acc, err := ref.Account(common.HexToHash("0x01")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
 	}
-	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
+	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
 	}
 	if n := len(snaps.layers); n != 2 {
@@ -230,10 +231,10 @@ func TestDiffLayerExternalInvalidationPartialFlatten(t *testing.T) {
 		t.Fatalf("failed to flatten diff layer into accumulator: %v", err)
 	}
 	// Since the accumulator diff layer was modified, ensure that data retrievals on the external reference fail
-	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
+	if acc, err := ref.Account(common.HexToHash("0x01")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
 	}
-	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
+	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); !errors.Is(err, ErrSnapshotStale) {
 		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
 	}
 	if n := len(snaps.layers); n != 3 {

core/state/statedb_fuzz_test.go

@@ -384,10 +384,9 @@ func (test *stateTest) verify(root common.Hash, next common.Hash, db *triedb.Dat
 func TestStateChanges(t *testing.T) {
 	config := &quick.Config{MaxCount: 1000}
 	err := quick.Check((*stateTest).run, config)
-	if cerr, ok := err.(*quick.CheckError); ok {
+	var cerr *quick.CheckError
+	if errors.As(err, &cerr) {
 		test := cerr.In[0].(*stateTest)
 		t.Errorf("%v:\n%s", test.err, test)
-	} else if err != nil {
-		t.Error(err)
 	}
 }

core/state/statedb_test.go

@@ -227,7 +227,8 @@ func TestCopy(t *testing.T) {
 func TestSnapshotRandom(t *testing.T) {
 	config := &quick.Config{MaxCount: 1000}
 	err := quick.Check((*snapshotTest).run, config)
-	if cerr, ok := err.(*quick.CheckError); ok {
+	var cerr *quick.CheckError
+	if errors.As(err, &cerr) {
 		test := cerr.In[0].(*snapshotTest)
 		t.Errorf("%v:\n%s", test.err, test)
 	} else if err != nil {

core/types/receipt_test.go

@@ -19,6 +19,7 @@ package types
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"math"
 	"math/big"
 	"reflect"
@@ -300,7 +301,7 @@ func TestDecodeEmptyTypedReceipt(t *testing.T) {
 	input := []byte{0x80}
 	var r Receipt
 	err := rlp.DecodeBytes(input, &r)
-	if err != errShortTypedReceipt {
+	if !errors.Is(err, errShortTypedReceipt) {
 		t.Fatal("wrong error:", err)
 	}
 }

core/types/transaction_test.go

@@ -75,7 +75,7 @@ func TestDecodeEmptyTypedTx(t *testing.T) {
 	input := []byte{0x80}
 	var tx Transaction
 	err := rlp.DecodeBytes(input, &tx)
-	if err != errShortTypedTx {
+	if !errors.Is(err, errShortTypedTx) {
 		t.Fatal("wrong error:", err)
 	}
 }

core/vm/evm.go

@@ -17,6 +17,7 @@
 package vm
 
 import (
+	"errors"
 	"math/big"
 	"sync/atomic"
 
@@ -246,7 +247,7 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 	// when we're in homestead this also counts for code storage gas errors.
 	if err != nil {
 		evm.StateDB.RevertToSnapshot(snapshot)
-		if err != ErrExecutionReverted {
+		if !errors.Is(err, ErrExecutionReverted) {
 			gas = 0
 		}
 		// TODO: consider clearing up unused snapshots:
@@ -299,7 +300,7 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
 	}
 	if err != nil {
 		evm.StateDB.RevertToSnapshot(snapshot)
-		if err != ErrExecutionReverted {
+		if !errors.Is(err, ErrExecutionReverted) {
 			gas = 0
 		}
 	}
@@ -343,7 +344,7 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
 	}
 	if err != nil {
 		evm.StateDB.RevertToSnapshot(snapshot)
-		if err != ErrExecutionReverted {
+		if !errors.Is(err, ErrExecutionReverted) {
 			gas = 0
 		}
 	}
@@ -399,7 +400,7 @@ func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte
 	}
 	if err != nil {
 		evm.StateDB.RevertToSnapshot(snapshot)
-		if err != ErrExecutionReverted {
+		if !errors.Is(err, ErrExecutionReverted) {
 			gas = 0
 		}
 	}
@@ -492,9 +493,9 @@ func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64,
 	// When an error was returned by the EVM or when setting the creation code
 	// above we revert to the snapshot and consume any gas remaining. Additionally
 	// when we're in homestead this also counts for code storage gas errors.
-	if err != nil && (evm.chainRules.IsHomestead || err != ErrCodeStoreOutOfGas) {
+	if err != nil && (evm.chainRules.IsHomestead || !errors.Is(err, ErrCodeStoreOutOfGas)) {
 		evm.StateDB.RevertToSnapshot(snapshot)
-		if err != ErrExecutionReverted {
+		if !errors.Is(err, ErrExecutionReverted) {
 			contract.UseGas(contract.Gas)
 		}
 	}

core/vm/gas_table_test.go

@@ -18,6 +18,7 @@ package vm
 
 import (
 	"bytes"
+	"errors"
 	"math"
 	"math/big"
 	"sort"
@@ -43,8 +44,8 @@ func TestMemoryGasCost(t *testing.T) {
 	}
 	for i, tt := range tests {
 		v, err := memoryGasCost(&Memory{}, tt.size)
-		if (err == ErrGasUintOverflow) != tt.overflow {
+		if (errors.Is(err, ErrGasUintOverflow)) != tt.overflow {
-			t.Errorf("test %d: overflow mismatch: have %v, want %v", i, err == ErrGasUintOverflow, tt.overflow)
+			t.Errorf("test %d: overflow mismatch: have %v, want %v", i, errors.Is(err, ErrGasUintOverflow), tt.overflow)
 		}
 		if v != tt.cost {
 			t.Errorf("test %d: gas cost mismatch: have %v, want %v", i, v, tt.cost)

core/vm/instructions.go

@@ -17,6 +17,7 @@
 package vm
 
 import (
+	"errors"
 	"math"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -597,9 +598,9 @@ func opCreate(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]b
 	// homestead we must check for CodeStoreOutOfGasError (homestead only
 	// rule) and treat as an error, if the ruleset is frontier we must
 	// ignore this error and pretend the operation was successful.
-	if interpreter.evm.chainRules.IsHomestead && suberr == ErrCodeStoreOutOfGas {
+	if interpreter.evm.chainRules.IsHomestead && errors.Is(suberr, ErrCodeStoreOutOfGas) {
 		stackvalue.Clear()
-	} else if suberr != nil && suberr != ErrCodeStoreOutOfGas {
+	} else if suberr != nil && !errors.Is(suberr, ErrCodeStoreOutOfGas) {
 		stackvalue.Clear()
 	} else {
 		stackvalue.SetBytes(addr.Bytes())
@@ -607,7 +608,7 @@ func opCreate(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]b
 	scope.Stack.push(&stackvalue)
 	scope.Contract.Gas += returnGas
 
-	if suberr == ErrExecutionReverted {
+	if errors.Is(suberr, ErrExecutionReverted) {
 		interpreter.returnData = res // set REVERT data to return data buffer
 		return res, nil
 	}
@@ -642,7 +643,7 @@ func opCreate2(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]
 	scope.Stack.push(&stackvalue)
 	scope.Contract.Gas += returnGas
 
-	if suberr == ErrExecutionReverted {
+	if errors.Is(suberr, ErrExecutionReverted) {
 		interpreter.returnData = res // set REVERT data to return data buffer
 		return res, nil
 	}
@@ -676,7 +677,7 @@ func opCall(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byt
 		temp.SetOne()
 	}
 	stack.push(&temp)
-	if err == nil || err == ErrExecutionReverted {
+	if err == nil || errors.Is(err, ErrExecutionReverted) {
 		scope.Memory.Set(retOffset.Uint64(), retSize.Uint64(), ret)
 	}
 	scope.Contract.Gas += returnGas
@@ -708,7 +709,7 @@ func opCallCode(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([
 		temp.SetOne()
 	}
 	stack.push(&temp)
-	if err == nil || err == ErrExecutionReverted {
+	if err == nil || errors.Is(err, ErrExecutionReverted) {
 		scope.Memory.Set(retOffset.Uint64(), retSize.Uint64(), ret)
 	}
 	scope.Contract.Gas += returnGas
@@ -736,7 +737,7 @@ func opDelegateCall(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext
 		temp.SetOne()
 	}
 	stack.push(&temp)
-	if err == nil || err == ErrExecutionReverted {
+	if err == nil || errors.Is(err, ErrExecutionReverted) {
 		scope.Memory.Set(retOffset.Uint64(), retSize.Uint64(), ret)
 	}
 	scope.Contract.Gas += returnGas
@@ -764,7 +765,7 @@ func opStaticCall(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext)
 		temp.SetOne()
 	}
 	stack.push(&temp)
-	if err == nil || err == ErrExecutionReverted {
+	if err == nil || errors.Is(err, ErrExecutionReverted) {
 		scope.Memory.Set(retOffset.Uint64(), retSize.Uint64(), ret)
 	}
 	scope.Contract.Gas += returnGas

core/vm/interpreter.go

@@ -17,6 +17,7 @@
 package vm
 
 import (
+	"errors"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -234,7 +235,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		pc++
 	}
 
-	if err == errStopToken {
+	if errors.Is(err, errStopToken) {
 		err = nil // clear stop token error
 	}
 

crypto/crypto.go

@@ -182,7 +182,8 @@ func FromECDSAPub(pub *ecdsa.PublicKey) []byte {
 // HexToECDSA parses a secp256k1 private key.
 func HexToECDSA(hexkey string) (*ecdsa.PrivateKey, error) {
 	b, err := hex.DecodeString(hexkey)
-	if byteErr, ok := err.(hex.InvalidByteError); ok {
+	var byteErr hex.InvalidByteError
+	if errors.As(err, &byteErr) {
 		return nil, fmt.Errorf("invalid hex character %q in private key", byte(byteErr))
 	} else if err != nil {
 		return nil, errors.New("invalid hex data for private key")

crypto/crypto_test.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/ecdsa"
 	"encoding/hex"
+	"errors"
 	"math/big"
 	"os"
 	"reflect"
@@ -66,11 +67,11 @@ func BenchmarkSha3(b *testing.B) {
 
 func TestUnmarshalPubkey(t *testing.T) {
 	key, err := UnmarshalPubkey(nil)
-	if err != errInvalidPubkey || key != nil {
+	if !errors.Is(err, errInvalidPubkey) || key != nil {
 		t.Fatalf("expected error, got %v, %v", err, key)
 	}
 	key, err = UnmarshalPubkey([]byte{1, 2, 3})
-	if err != errInvalidPubkey || key != nil {
+	if !errors.Is(err, errInvalidPubkey) || key != nil {
 		t.Fatalf("expected error, got %v, %v", err, key)
 	}
 

crypto/ecies/ecies_test.go

@@ -152,12 +152,12 @@ func TestTooBigSharedKey(t *testing.T) {
 	}
 
 	_, err = prv1.GenerateShared(&prv2.PublicKey, 32, 32)
-	if err != ErrSharedKeyTooBig {
+	if !errors.Is(err, ErrSharedKeyTooBig) {
 		t.Fatal("ecdh: shared key should be too large for curve")
 	}
 
 	_, err = prv2.GenerateShared(&prv1.PublicKey, 32, 32)
-	if err != ErrSharedKeyTooBig {
+	if !errors.Is(err, ErrSharedKeyTooBig) {
 		t.Fatal("ecdh: shared key should be too large for curve")
 	}
 }
@@ -355,7 +355,7 @@ func TestBasicKeyValidation(t *testing.T) {
 	for _, b := range badBytes {
 		ct[0] = b
 		_, err := prv.Decrypt(ct, nil, nil)
-		if err != ErrInvalidPublicKey {
+		if !errors.Is(err, ErrInvalidPublicKey) {
 			t.Fatal("ecies: validated an invalid key")
 		}
 	}

crypto/secp256k1/secp256_test.go

@@ -13,6 +13,7 @@ import (
 	"crypto/elliptic"
 	"crypto/rand"
 	"encoding/hex"
+	"errors"
 	"io"
 	"testing"
 )
@@ -92,7 +93,7 @@ func TestInvalidRecoveryID(t *testing.T) {
 	sig, _ := Sign(msg, seckey)
 	sig[64] = 99
 	_, err := RecoverPubkey(msg, sig)
-	if err != ErrInvalidRecoveryID {
+	if !errors.Is(err, ErrInvalidRecoveryID) {
 		t.Fatalf("got %q, want %q", err, ErrInvalidRecoveryID)
 	}
 }

eth/downloader/downloader.go

@@ -1547,7 +1547,7 @@ func (d *Downloader) processSnapSyncContent() error {
 	}()
 
 	closeOnErr := func(s *stateSync) {
-		if err := s.Wait(); err != nil && err != errCancelStateFetch && err != errCanceled && err != snap.ErrCancelled {
+		if err := s.Wait(); err != nil && !errors.Is(err, errCancelStateFetch) && !errors.Is(err, errCanceled) && !errors.Is(err, snap.ErrCancelled) {
 			d.queue.Close() // wake up Results
 		}
 	}

eth/downloader/downloader_test.go

@@ -17,6 +17,7 @@
 package downloader
 
 import (
+	"errors"
 	"fmt"
 	"math/big"
 	"os"
@@ -614,7 +615,7 @@ func testBoundedForkedSync(t *testing.T, protocol uint, mode SyncMode) {
 	assertOwnChain(t, tester, len(chainA.blocks))
 
 	// Synchronise with the second peer and ensure that the fork is rejected to being too old
-	if err := tester.sync("rewriter", nil, mode); err != errInvalidAncestor {
+	if err := tester.sync("rewriter", nil, mode); !errors.Is(err, errInvalidAncestor) {
 		t.Fatalf("sync failure mismatch: have %v, want %v", err, errInvalidAncestor)
 	}
 }
@@ -649,7 +650,7 @@ func testBoundedHeavyForkedSync(t *testing.T, protocol uint, mode SyncMode) {
 
 	tester.newPeer("heavy-rewriter", protocol, chainB.blocks[1:])
 	// Synchronise with the second peer and ensure that the fork is rejected to being too old
-	if err := tester.sync("heavy-rewriter", nil, mode); err != errInvalidAncestor {
+	if err := tester.sync("heavy-rewriter", nil, mode); !errors.Is(err, errInvalidAncestor) {
 		t.Fatalf("sync failure mismatch: have %v, want %v", err, errInvalidAncestor)
 	}
 }
@@ -854,7 +855,7 @@ func testHighTDStarvationAttack(t *testing.T, protocol uint, mode SyncMode) {
 
 	chain := testChainBase.shorten(1)
 	tester.newPeer("attack", protocol, chain.blocks[1:])
-	if err := tester.sync("attack", big.NewInt(1000000), mode); err != errStallingPeer {
+	if err := tester.sync("attack", big.NewInt(1000000), mode); !errors.Is(err, errStallingPeer) {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
 	}
 }

eth/downloader/skeleton.go

@@ -278,25 +278,25 @@ func (s *skeleton) startup() {
 				// signalling as the sync loop should never terminate (TM).
 				newhead, err := s.sync(head)
 				switch {
-				case err == errSyncLinked:
+				case errors.Is(err, errSyncLinked):
 					// Sync cycle linked up to the genesis block, or the existent chain
 					// segment. Tear down the loop and restart it so, it can properly
 					// notify the backfiller. Don't account a new head.
 					head = nil
 
-				case err == errSyncMerged:
+				case errors.Is(err, errSyncMerged):
 					// Subchains were merged, we just need to reinit the internal
 					// start to continue on the tail of the merged chain. Don't
 					// announce a new head,
 					head = nil
 
-				case err == errSyncReorged:
+				case errors.Is(err, errSyncReorged):
 					// The subchain being synced got modified at the head in a
 					// way that requires resyncing it. Restart sync with the new
 					// head to force a cleanup.
 					head = newhead
 
-				case err == errTerminated:
+				case errors.Is(err, errTerminated):
 					// Sync was requested to be terminated from within, stop and
 					// return (no need to pass a message, was already done internally)
 					return

eth/filters/filter_system_test.go

@@ -468,7 +468,7 @@ func TestInvalidGetRangeLogsRequest(t *testing.T) {
 		api    = NewFilterAPI(sys, false)
 	)
 
-	if _, err := api.GetLogs(context.Background(), FilterCriteria{FromBlock: big.NewInt(2), ToBlock: big.NewInt(1)}); err != errInvalidBlockRange {
+	if _, err := api.GetLogs(context.Background(), FilterCriteria{FromBlock: big.NewInt(2), ToBlock: big.NewInt(1)}); !errors.Is(err, errInvalidBlockRange) {
 		t.Errorf("Expected Logs for invalid range return error, but got: %v", err)
 	}
 }

eth/state_accessor.go

@@ -117,8 +117,9 @@ func (eth *Ethereum) hashState(ctx context.Context, block *types.Block, reexec u
 			}
 		}
 		if err != nil {
-			switch err.(type) {
+			var missingNodeError *trie.MissingNodeError
-			case *trie.MissingNodeError:
+			switch {
+			case errors.As(err, &missingNodeError):
 				return nil, nil, fmt.Errorf("required historical state unavailable (reexec=%d)", reexec)
 			default:
 				return nil, nil, err

ethclient/ethclient_test.go

@@ -398,7 +398,7 @@ func testTransactionInBlock(t *testing.T, client *rpc.Client) {
 	}
 
 	// Test tx in block not found.
-	if _, err := ec.TransactionInBlock(context.Background(), block.Hash(), 20); err != ethereum.NotFound {
+	if _, err := ec.TransactionInBlock(context.Background(), block.Hash(), 20); !errors.Is(err, ethereum.NotFound) {
 		t.Fatal("error should be ethereum.NotFound")
 	}
 

ethdb/leveldb/leveldb.go

@@ -21,7 +21,9 @@
 package leveldb
 
 import (
+	"errors"
 	"fmt"
+	dberrors "github.com/syndtr/goleveldb/leveldb/errors"
 	"strings"
 	"sync"
 	"time"
@@ -31,7 +33,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/syndtr/goleveldb/leveldb"
-	"github.com/syndtr/goleveldb/leveldb/errors"
 	"github.com/syndtr/goleveldb/leveldb/filter"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/util"
@@ -120,7 +121,8 @@ func NewCustom(file string, namespace string, customize func(options *opt.Option
 
 	// Open the db and recover any potential corruptions
 	db, err := leveldb.OpenFile(file, options)
-	if _, corrupted := err.(*errors.ErrCorrupted); corrupted {
+	var errCorrupted *dberrors.ErrCorrupted
+	if errors.As(err, &errCorrupted) {
 		db, err = leveldb.RecoverFile(file, nil)
 	}
 	if err != nil {

event/event_test.go

@@ -17,6 +17,7 @@
 package event
 
 import (
+	"errors"
 	"math/rand"
 	"sync"
 	"testing"
@@ -59,7 +60,7 @@ func TestMuxErrorAfterStop(t *testing.T) {
 	if _, isopen := <-sub.Chan(); isopen {
 		t.Errorf("subscription channel was not closed")
 	}
-	if err := mux.Post(testEvent(0)); err != ErrMuxClosed {
+	if err := mux.Post(testEvent(0)); !errors.Is(err, ErrMuxClosed) {
 		t.Errorf("Post error mismatch, got: %s, expected: %s", err, ErrMuxClosed)
 	}
 }

event/subscription_test.go

@@ -56,7 +56,7 @@ loop:
 				t.Fatalf("wrong int %d, want %d", got, want)
 			}
 		case err := <-sub.Err():
-			if err != errInts {
+			if !errors.Is(err, errInts) {
 				t.Fatalf("wrong error: got %q, want %q", err, errInts)
 			}
 			if want != 2 {

internal/build/util.go

@@ -19,6 +19,7 @@ package build
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"flag"
 	"fmt"
 	"go/parser"
@@ -98,7 +99,8 @@ func RunGit(args ...string) string {
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout, cmd.Stderr = &stdout, &stderr
 	if err := cmd.Run(); err != nil {
-		if e, ok := err.(*exec.Error); ok && e.Err == exec.ErrNotFound {
+		var e *exec.Error
+		if errors.As(err, &e) && errors.Is(e.Err, exec.ErrNotFound) {
 			if !warnedAboutGit {
 				log.Println("Warning: can't find 'git' in PATH")
 				warnedAboutGit = true

internal/cmdtest/test_cmd.go

@@ -19,6 +19,7 @@ package cmdtest
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -206,7 +207,8 @@ func (tt *TestCmd) Interrupt() {
 // It will only return a valid value after the process has finished.
 func (tt *TestCmd) ExitStatus() int {
 	if tt.Err != nil {
-		exitErr := tt.Err.(*exec.ExitError)
+		var exitErr *exec.ExitError
+		errors.As(tt.Err, &exitErr)
 		if exitErr != nil {
 			if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
 				return status.ExitStatus()

internal/jsre/pretty.go

@@ -17,6 +17,7 @@
 package jsre
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"reflect"
@@ -60,7 +61,8 @@ func prettyPrint(vm *goja.Runtime, value goja.Value, w io.Writer) {
 // prettyError writes err to standard output.
 func prettyError(vm *goja.Runtime, err error, w io.Writer) {
 	failure := err.Error()
-	if gojaErr, ok := err.(*goja.Exception); ok {
+	var gojaErr *goja.Exception
+	if errors.As(err, &gojaErr) {
 		failure = gojaErr.String()
 	}
 	fmt.Fprint(w, ErrorColor("%s", failure))

node/errors.go

@@ -33,7 +33,8 @@ var (
 )
 
 func convertFileLockError(err error) error {
-	if errno, ok := err.(syscall.Errno); ok && datadirInUseErrnos[uint(errno)] {
+	var errno syscall.Errno
+	if errors.As(err, &errno) && datadirInUseErrnos[uint(errno)] {
 		return ErrDatadirUsed
 	}
 	return err

node/node_test.go

@@ -55,7 +55,7 @@ func TestNodeCloseMultipleTimes(t *testing.T) {
 
 	// Ensure that a stopped node can be stopped again
 	for i := 0; i < 3; i++ {
-		if err := stack.Close(); err != ErrNodeStopped {
+		if err := stack.Close(); !errors.Is(err, ErrNodeStopped) {
 			t.Fatalf("iter %d: stop failure mismatch: have %v, want %v", i, err, ErrNodeStopped)
 		}
 	}
@@ -71,14 +71,14 @@ func TestNodeStartMultipleTimes(t *testing.T) {
 	if err := stack.Start(); err != nil {
 		t.Fatalf("failed to start node: %v", err)
 	}
-	if err := stack.Start(); err != ErrNodeRunning {
+	if err := stack.Start(); !errors.Is(err, ErrNodeRunning) {
 		t.Fatalf("start failure mismatch: have %v, want %v ", err, ErrNodeRunning)
 	}
 	// Ensure that a node can be stopped, but only once
 	if err := stack.Close(); err != nil {
 		t.Fatalf("failed to stop node: %v", err)
 	}
-	if err := stack.Close(); err != ErrNodeStopped {
+	if err := stack.Close(); !errors.Is(err, ErrNodeStopped) {
 		t.Fatalf("stop failure mismatch: have %v, want %v ", err, ErrNodeStopped)
 	}
 }
@@ -100,7 +100,7 @@ func TestNodeUsedDataDir(t *testing.T) {
 
 	// Create a second node based on the same data directory and ensure failure
 	_, err = New(&Config{DataDir: dir})
-	if err != ErrDatadirUsed {
+	if !errors.Is(err, ErrDatadirUsed) {
 		t.Fatalf("duplicate datadir failure mismatch: have %v, want %v", err, ErrDatadirUsed)
 	}
 }

p2p/dial.go

@@ -474,7 +474,8 @@ func (t *dialTask) run(d *dialScheduler) {
 	err := t.dial(d, t.dest)
 	if err != nil {
 		// For static nodes, resolve one more time if dialing fails.
-		if _, ok := err.(*dialError); ok && t.flags&staticDialedConn != 0 {
+		var dialError *dialError
+		if errors.As(err, &dialError) && t.flags&staticDialedConn != 0 {
 			if t.resolve(d) {
 				t.dial(d, t.dest)
 			}
@@ -537,7 +538,8 @@ func (t *dialTask) String() string {
 }
 
 func cleanupDialErr(err error) error {
-	if netErr, ok := err.(*net.OpError); ok && netErr.Op == "dial" {
+	var netErr *net.OpError
+	if errors.As(err, &netErr) && netErr.Op == "dial" {
 		return netErr.Err
 	}
 	return err

p2p/discover/v4_udp_test.go

@@ -111,7 +111,7 @@ func (test *udpTest) waitPacketOut(validate interface{}) (closed bool) {
 	test.t.Helper()
 
 	dgram, err := test.pipe.receive()
-	if err == errClosed {
+	if errors.Is(err, errClosed) {
 		return true
 	} else if err != nil {
 		test.t.Error("packet receive error:", err)
@@ -150,7 +150,7 @@ func TestUDPv4_pingTimeout(t *testing.T) {
 	key := newkey()
 	toaddr := &net.UDPAddr{IP: net.ParseIP("1.2.3.4"), Port: 2222}
 	node := enode.NewV4(&key.PublicKey, toaddr.IP, 0, toaddr.Port)
-	if _, err := test.udp.ping(node); err != errTimeout {
+	if _, err := test.udp.ping(node); !errors.Is(err, errTimeout) {
 		t.Error("expected timeout error, got", err)
 	}
 }
@@ -210,7 +210,7 @@ func TestUDPv4_responseTimeouts(t *testing.T) {
 	for i := 0; i < nReqs; i++ {
 		select {
 		case err := <-timeoutErr:
-			if err != errTimeout {
+			if !errors.Is(err, errTimeout) {
 				t.Fatalf("got non-timeout error on timeoutErr %d: %v", i, err)
 			}
 			nTimeoutsRecv++
@@ -240,7 +240,7 @@ func TestUDPv4_findnodeTimeout(t *testing.T) {
 	toid := enode.ID{1, 2, 3, 4}
 	target := v4wire.Pubkey{4, 5, 6, 7}
 	result, err := test.udp.findnode(toid, toaddr, target)
-	if err != errTimeout {
+	if !errors.Is(err, errTimeout) {
 		t.Error("expected timeout error, got", err)
 	}
 	if len(result) > 0 {

p2p/discover/v5_udp_test.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/ecdsa"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math/rand"
 	"net"
@@ -239,7 +240,7 @@ func TestUDPv5_pingCall(t *testing.T) {
 		done <- err
 	}()
 	test.waitPacketOut(func(p *v5wire.Ping, addr *net.UDPAddr, _ v5wire.Nonce) {})
-	if err := <-done; err != errTimeout {
+	if err := <-done; !errors.Is(err, errTimeout) {
 		t.Fatalf("want errTimeout, got %q", err)
 	}
 
@@ -264,7 +265,7 @@ func TestUDPv5_pingCall(t *testing.T) {
 		wrongAddr := &net.UDPAddr{IP: net.IP{33, 44, 55, 22}, Port: 10101}
 		test.packetInFrom(test.remotekey, wrongAddr, &v5wire.Pong{ReqID: p.ReqID})
 	})
-	if err := <-done; err != errTimeout {
+	if err := <-done; !errors.Is(err, errTimeout) {
 		t.Fatalf("want errTimeout for reply from wrong IP, got %q", err)
 	}
 }
@@ -377,7 +378,7 @@ func TestUDPv5_multipleHandshakeRounds(t *testing.T) {
 	test.waitPacketOut(func(p *v5wire.Ping, addr *net.UDPAddr, nonce v5wire.Nonce) {
 		test.packetIn(&v5wire.Whoareyou{Nonce: nonce})
 	})
-	if err := <-done; err != errTimeout {
+	if err := <-done; !errors.Is(err, errTimeout) {
 		t.Fatalf("unexpected ping error: %q", err)
 	}
 }
@@ -486,7 +487,7 @@ func TestUDPv5_talkRequest(t *testing.T) {
 		done <- err
 	}()
 	test.waitPacketOut(func(p *v5wire.TalkRequest, addr *net.UDPAddr, _ v5wire.Nonce) {})
-	if err := <-done; err != errTimeout {
+	if err := <-done; !errors.Is(err, errTimeout) {
 		t.Fatalf("want errTimeout, got %q", err)
 	}
 
@@ -817,10 +818,10 @@ func (test *udpV5Test) waitPacketOut(validate interface{}) (closed bool) {
 	exptype := fn.Type().In(0)
 
 	dgram, err := test.pipe.receive()
-	if err == errClosed {
+	if errors.Is(err, errClosed) {
 		return true
 	}
-	if err == errTimeout {
+	if errors.Is(err, errTimeout) {
 		test.t.Fatalf("timed out waiting for %v", exptype)
 		return false
 	}

p2p/discover/v5wire/encoding.go

@@ -128,7 +128,7 @@ var (
 // returns false, it is pretty certain that the packet causing the error does not belong
 // to discv5.
 func IsInvalidHeader(err error) bool {
-	return err == errTooShort || err == errInvalidHeader || err == errMsgTooShort
+	return errors.Is(err, errTooShort) || errors.Is(err, errInvalidHeader) || errors.Is(err, errMsgTooShort)
 }
 
 // Packet sizes.

p2p/dnsdisc/error.go

@@ -47,7 +47,8 @@ type nameError struct {
 }
 
 func (err nameError) Error() string {
-	if ee, ok := err.err.(entryError); ok {
+	var ee entryError
+	if errors.As(err.err, &ee) {
 		return fmt.Sprintf("invalid %s entry at %s: %v", ee.typ, err.name, ee.err)
 	}
 	return err.name + ": " + err.err.Error()

p2p/enode/nodedb.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/rand"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -28,7 +29,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/syndtr/goleveldb/leveldb"
-	"github.com/syndtr/goleveldb/leveldb/errors"
+	dberrors "github.com/syndtr/goleveldb/leveldb/errors"
 	"github.com/syndtr/goleveldb/leveldb/iterator"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/storage"
@@ -98,7 +99,8 @@ func newMemoryDB() (*DB, error) {
 func newPersistentDB(path string) (*DB, error) {
 	opts := &opt.Options{OpenFilesCacheCapacity: 5}
 	db, err := leveldb.OpenFile(path, opts)
-	if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
+	var errCorrupted *dberrors.ErrCorrupted
+	if errors.As(err, &errCorrupted) {
 		db, err = leveldb.RecoverFile(path, nil)
 	}
 	if err != nil {
@@ -110,15 +112,14 @@ func newPersistentDB(path string) (*DB, error) {
 	currentVer = currentVer[:binary.PutVarint(currentVer, int64(dbVersion))]
 
 	blob, err := db.Get([]byte(dbVersionKey), nil)
-	switch err {
+	switch {
-	case leveldb.ErrNotFound:
+	case errors.Is(err, leveldb.ErrNotFound):
 		// Version not found (i.e. empty cache), insert it
 		if err := db.Put([]byte(dbVersionKey), currentVer, nil); err != nil {
 			db.Close()
 			return nil, err
 		}
-
+	case err == nil:
-	case nil:
 		// Version present, flush if different
 		if !bytes.Equal(blob, currentVer) {
 			db.Close()

p2p/enr/enr_test.go

@@ -19,6 +19,7 @@ package enr
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"math/rand"
 	"testing"
@@ -97,8 +98,8 @@ func TestLoadErrors(t *testing.T) {
 	// Check error for invalid keys.
 	var list []uint
 	err = r.Load(WithEntry(ip4.ENRKey(), &list))
-	kerr, ok := err.(*KeyError)
+	var kerr *KeyError
-	if !ok {
+	if !errors.As(err, &kerr) {
 		t.Fatalf("expected KeyError, got %T", err)
 	}
 	assert.Equal(t, kerr.Key, ip4.ENRKey())
@@ -149,7 +150,7 @@ func TestSortedGetAndSet(t *testing.T) {
 func TestDirty(t *testing.T) {
 	var r Record
 
-	if _, err := rlp.EncodeToBytes(r); err != errEncodeUnsigned {
+	if _, err := rlp.EncodeToBytes(r); !errors.Is(err, errEncodeUnsigned) {
 		t.Errorf("expected errEncodeUnsigned, got %#v", err)
 	}
 
@@ -164,7 +165,7 @@ func TestDirty(t *testing.T) {
 	if len(r.signature) != 0 {
 		t.Error("signature still set after modification")
 	}
-	if _, err := rlp.EncodeToBytes(r); err != errEncodeUnsigned {
+	if _, err := rlp.EncodeToBytes(r); !errors.Is(err, errEncodeUnsigned) {
 		t.Errorf("expected errEncodeUnsigned, got %#v", err)
 	}
 }
@@ -248,7 +249,7 @@ func TestRecordTooBig(t *testing.T) {
 
 	// set a big value for random key, expect error
 	r.Set(WithEntry(key, randomString(SizeLimit)))
-	if err := signTest([]byte{5}, &r); err != errTooBig {
+	if err := signTest([]byte{5}, &r); !errors.Is(err, errTooBig) {
 		t.Fatalf("expected to get errTooBig, got %#v", err)
 	}
 

p2p/enr/entries.go

@@ -175,7 +175,7 @@ type KeyError struct {
 
 // Error implements error.
 func (err *KeyError) Error() string {
-	if err.Err == errNotFound {
+	if errors.Is(err.Err, errNotFound) {
 		return fmt.Sprintf("missing ENR key %q", err.Key)
 	}
 	return fmt.Sprintf("ENR key %q: %v", err.Key, err.Err)
@@ -190,7 +190,7 @@ func (err *KeyError) Unwrap() error {
 func IsNotFound(err error) bool {
 	var ke *KeyError
 	if errors.As(err, &ke) {
-		return ke.Err == errNotFound
+		return errors.Is(ke.Err, errNotFound)
 	}
 	return false
 }

p2p/message_test.go

@@ -18,6 +18,7 @@ package p2p
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"runtime"
@@ -55,7 +56,7 @@ loop:
 		go func() {
 			if err := SendItems(rw1, 1); err == nil {
 				t.Error("EncodeMsg returned nil error")
-			} else if err != ErrPipeClosed {
+			} else if !errors.Is(err, ErrPipeClosed) {
 				t.Errorf("EncodeMsg returned wrong error: got %v, want %v", err, ErrPipeClosed)
 			}
 			close(done)

p2p/netutil/error_test.go

@@ -17,6 +17,7 @@
 package netutil
 
 import (
+	"errors"
 	"net"
 	"testing"
 	"time"
@@ -52,7 +53,8 @@ func TestIsPacketTooBig(t *testing.T) {
 		listener.SetDeadline(time.Now().Add(1 * time.Second))
 		n, _, err := listener.ReadFrom(buf)
 		if err != nil {
-			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
+			var nerr net.Error
+			if errors.As(err, &nerr) && nerr.Timeout() {
 				continue
 			}
 			if !isPacketTooBig(err) {

p2p/peer.go

@@ -272,7 +272,8 @@ loop:
 			}
 			writeStart <- struct{}{}
 		case err = <-readErr:
-			if r, ok := err.(DiscReason); ok {
+			var r DiscReason
+			if errors.As(err, &r) {
 				remoteRequested = true
 				reason = r
 			} else {

p2p/peer_error.go

@@ -100,13 +100,15 @@ func (d DiscReason) Error() string {
 }
 
 func discReasonForError(err error) DiscReason {
-	if reason, ok := err.(DiscReason); ok {
+	var reason DiscReason
+	if errors.As(err, &reason) {
 		return reason
 	}
 	if errors.Is(err, errProtocolReturned) {
 		return DiscQuitting
 	}
-	peerError, ok := err.(*peerError)
+	var peerError *peerError
+	ok := errors.As(err, &peerError)
 	if ok {
 		switch peerError.code {
 		case errInvalidMsgCode, errInvalidMsg:

p2p/peer_test.go

@@ -138,7 +138,7 @@ func TestPeerProtoReadMsg(t *testing.T) {
 
 	select {
 	case err := <-errc:
-		if err != errProtocolReturned {
+		if !errors.Is(err, errProtocolReturned) {
 			t.Errorf("peer returned error: %v", err)
 		}
 	case <-time.After(2 * time.Second):

p2p/transport.go

@@ -19,6 +19,7 @@ package p2p
 import (
 	"bytes"
 	"crypto/ecdsa"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -113,7 +114,8 @@ func (t *rlpxTransport) close(err error) {
 	// We only bother doing this if the underlying connection supports
 	// setting a timeout tough.
 	if t.conn != nil {
-		if r, ok := err.(DiscReason); ok && r != DiscNetworkError {
+		var r DiscReason
+		if errors.As(err, &r) && !errors.Is(r, DiscNetworkError) {
 			deadline := time.Now().Add(discWriteTimeout)
 			if err := t.conn.SetWriteDeadline(deadline); err == nil {
 				// Connection supports write deadline.

rlp/decode.go

@@ -141,7 +141,8 @@ func wrapStreamError(err error, typ reflect.Type) error {
 }
 
 func addErrorContext(err error, ctx string) error {
-	if decErr, ok := err.(*decodeError); ok {
+	var decErr *decodeError
+	if errors.As(err, &decErr) {
 		decErr.ctx = append(decErr.ctx, ctx)
 	}
 	return err
@@ -326,7 +327,7 @@ func decodeSliceElems(s *Stream, val reflect.Value, elemdec decoder) error {
 			val.SetLen(i + 1)
 		}
 		// decode into element
-		if err := elemdec(s, val.Index(i)); err == EOL {
+		if err := elemdec(s, val.Index(i)); errors.Is(err, EOL) {
 			break
 		} else if err != nil {
 			return addErrorContext(err, fmt.Sprint("[", i, "]"))
@@ -345,7 +346,7 @@ func decodeListArray(s *Stream, val reflect.Value, elemdec decoder) error {
 	vlen := val.Len()
 	i := 0
 	for ; i < vlen; i++ {
-		if err := elemdec(s, val.Index(i)); err == EOL {
+		if err := elemdec(s, val.Index(i)); errors.Is(err, EOL) {
 			break
 		} else if err != nil {
 			return addErrorContext(err, fmt.Sprint("[", i, "]"))
@@ -417,7 +418,7 @@ func makeStructDecoder(typ reflect.Type) (decoder, error) {
 		}
 		for i, f := range fields {
 			err := f.info.decoder(s, val.Field(f.index))
-			if err == EOL {
+			if errors.Is(err, EOL) {
 				if f.optional {
 					// The field is optional, so reaching the end of the list before
 					// reaching the last field is acceptable. All remaining undecoded
@@ -757,7 +758,7 @@ func (s *Stream) uint(maxbits int) (uint64, error) {
 		}
 		v, err := s.readUint(byte(size))
 		switch {
-		case err == ErrCanonSize:
+		case errors.Is(err, ErrCanonSize):
 			// Adjust error because we're not reading a size right now.
 			return 0, ErrCanonInt
 		case err != nil:
@@ -948,7 +949,8 @@ func (s *Stream) Decode(val interface{}) error {
 	}
 
 	err = decoder(s, rval.Elem())
-	if decErr, ok := err.(*decodeError); ok && len(decErr.ctx) > 0 {
+	var decErr *decodeError
+	if errors.As(err, &decErr) && len(decErr.ctx) > 0 {
 		// Add decode target type to error so context has more meaning.
 		decErr.ctx = append(decErr.ctx, fmt.Sprint("(", rtyp.Elem(), ")"))
 	}

rlp/decode_test.go

@@ -250,7 +250,7 @@ func TestStreamList(t *testing.T) {
 		}
 	}
 
-	if _, err := s.Uint(); err != EOL {
+	if _, err := s.Uint(); !errors.Is(err, EOL) {
 		t.Errorf("Uint error mismatch, got %v, want %v", err, EOL)
 	}
 	if err = s.ListEnd(); err != nil {
@@ -331,16 +331,16 @@ func TestStreamReadBytes(t *testing.T) {
 func TestDecodeErrors(t *testing.T) {
 	r := bytes.NewReader(nil)
 
-	if err := Decode(r, nil); err != errDecodeIntoNil {
+	if err := Decode(r, nil); !errors.Is(err, errDecodeIntoNil) {
 		t.Errorf("Decode(r, nil) error mismatch, got %q, want %q", err, errDecodeIntoNil)
 	}
 
 	var nilptr *struct{}
-	if err := Decode(r, nilptr); err != errDecodeIntoNil {
+	if err := Decode(r, nilptr); !errors.Is(err, errDecodeIntoNil) {
 		t.Errorf("Decode(r, nilptr) error mismatch, got %q, want %q", err, errDecodeIntoNil)
 	}
 
-	if err := Decode(r, struct{}{}); err != errNoPointer {
+	if err := Decode(r, struct{}{}); !errors.Is(err, errNoPointer) {
 		t.Errorf("Decode(r, struct{}{}) error mismatch, got %q, want %q", err, errNoPointer)
 	}
 

rlp/typecache.go

@@ -17,6 +17,7 @@
 package rlp
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"sync"
@@ -142,7 +143,8 @@ func structFields(typ reflect.Type) (fields []field, err error) {
 	// Filter/validate fields.
 	structFields, structTags, err := rlpstruct.ProcessFields(allStructFields)
 	if err != nil {
-		if tagErr, ok := err.(rlpstruct.TagError); ok {
+		var tagErr rlpstruct.TagError
+		if errors.As(err, &tagErr) {
 			tagErr.StructType = typ.String()
 			return nil, tagErr
 		}

rpc/client.go

@@ -712,7 +712,8 @@ func (c *Client) drainRead() {
 func (c *Client) read(codec ServerCodec) {
 	for {
 		msgs, batch, err := codec.readBatch()
-		if _, ok := err.(*json.SyntaxError); ok {
+		var syntaxError *json.SyntaxError
+		if errors.As(err, &syntaxError) {
 			msg := errorMessage(&parseError{err.Error()})
 			codec.writeJSON(context.Background(), msg, true)
 		}

rpc/client_test.go

@@ -106,17 +106,19 @@ func TestClientErrorData(t *testing.T) {
 	// The method handler returns an error value which implements the rpc.Error
 	// interface, i.e. it has a custom error code. The server returns this error code.
 	expectedCode := testError{}.ErrorCode()
-	if e, ok := err.(Error); !ok {
+	var e Error
+	if !errors.As(err, &e) {
 		t.Fatalf("client did not return rpc.Error, got %#v", e)
 	} else if e.ErrorCode() != expectedCode {
 		t.Fatalf("wrong error code %d, want %d", e.ErrorCode(), expectedCode)
 	}
 
 	// Check data.
-	if e, ok := err.(DataError); !ok {
+	var de DataError
+	if !errors.As(err, &de) {
 		t.Fatalf("client did not return rpc.DataError, got %#v", e)
-	} else if e.ErrorData() != (testError{}.ErrorData()) {
+	} else if de.ErrorData() != (testError{}.ErrorData()) {
-		t.Fatalf("wrong error data %#v, want %#v", e.ErrorData(), testError{}.ErrorData())
+		t.Fatalf("wrong error data %#v, want %#v", de.ErrorData(), testError{}.ErrorData())
 	}
 }
 
@@ -633,7 +635,7 @@ func TestClientNotificationStorm(t *testing.T) {
 					t.Fatalf("(%d/%d) unexpected value %d", i, count, val)
 				}
 			case err := <-sub.Err():
-				if wantError && err != ErrSubscriptionQueueOverflow {
+				if wantError && !errors.Is(err, ErrSubscriptionQueueOverflow) {
 					t.Fatalf("(%d/%d) got error %q, want %q", i, count, err, ErrSubscriptionQueueOverflow)
 				} else if !wantError {
 					t.Fatalf("(%d/%d) got unexpected error %q", i, count, err)

rpc/http_test.go

@@ -18,6 +18,7 @@ package rpc
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -148,7 +149,8 @@ func TestHTTPErrorResponse(t *testing.T) {
 		t.Fatal("error was expected")
 	}
 
-	httpErr, ok := err.(HTTPError)
+	var httpErr HTTPError
+	ok := errors.As(err, &httpErr)
 	if !ok {
 		t.Fatalf("unexpected error type %T", err)
 	}
@@ -234,12 +236,12 @@ func TestNewContextWithHeaders(t *testing.T) {
 	ctx3 := NewContextWithHeaders(ctx2, newHdr("key-2", "val-2"))
 
 	expectedHeaders = 3
-	if err := client.CallContext(ctx3, nil, "test"); err != ErrNoResult {
+	if err := client.CallContext(ctx3, nil, "test"); !errors.Is(err, ErrNoResult) {
 		t.Error("call failed", err)
 	}
 
 	expectedHeaders = 2
-	if err := client.CallContext(ctx2, nil, "test"); err != ErrNoResult {
+	if err := client.CallContext(ctx2, nil, "test"); !errors.Is(err, ErrNoResult) {
 		t.Error("call failed:", err)
 	}
 }

rpc/json.go

@@ -125,11 +125,13 @@ func errorMessage(err error) *jsonrpcMessage {
 		Code:    errcodeDefault,
 		Message: err.Error(),
 	}}
-	ec, ok := err.(Error)
+	var ec Error
+	ok := errors.As(err, &ec)
 	if ok {
 		msg.Error.Code = ec.ErrorCode()
 	}
-	de, ok := err.(DataError)
+	var de DataError
+	ok = errors.As(err, &de)
 	if ok {
 		msg.Error.Data = de.ErrorData()
 	}

rpc/subscription.go

@@ -310,7 +310,7 @@ func (sub *ClientSubscription) run() {
 
 	// Send the error.
 	if err != nil {
-		if err == ErrClientQuit {
+		if errors.Is(err, ErrClientQuit) {
 			// ErrClientQuit gets here when Client.Close is called. This is reported as a
 			// nil error because it's not an error, but we can't close sub.err here.
 			err = nil
@@ -346,7 +346,7 @@ func (sub *ClientSubscription) forward() (unsubscribeServer bool, err error) {
 			if !recv.IsNil() {
 				err = recv.Interface().(error)
 			}
-			if err == errUnsubscribed {
+			if errors.Is(err, errUnsubscribed) {
 				// Exiting because Unsubscribe was called, unsubscribe on server.
 				return true, nil
 			}

tests/init_test.go

@@ -52,7 +52,8 @@ func readJSON(reader io.Reader, value interface{}) error {
 		return fmt.Errorf("error reading JSON file: %v", err)
 	}
 	if err = json.Unmarshal(data, &value); err != nil {
-		if syntaxerr, ok := err.(*json.SyntaxError); ok {
+		var syntaxerr *json.SyntaxError
+		if errors.As(err, &syntaxerr) {
 			line := findLine(data, syntaxerr.Offset)
 			return fmt.Errorf("JSON syntax error at line %v: %v", line, err)
 		}

trie/iterator.go

@@ -268,10 +268,11 @@ func (it *nodeIterator) NodeBlob() []byte {
 }
 
 func (it *nodeIterator) Error() error {
-	if it.err == errIteratorEnd {
+	if errors.Is(it.err, errIteratorEnd) {
 		return nil
 	}
-	if seek, ok := it.err.(seekError); ok {
+	var seek seekError
+	if errors.As(it.err, &seek) {
 		return seek.err
 	}
 	return it.err
@@ -282,10 +283,11 @@ func (it *nodeIterator) Error() error {
 // sets the Error field to the encountered failure. If `descend` is false,
 // skips iterating over any subnodes of the current node.
 func (it *nodeIterator) Next(descend bool) bool {
-	if it.err == errIteratorEnd {
+	if errors.Is(it.err, errIteratorEnd) {
 		return false
 	}
-	if seek, ok := it.err.(seekError); ok {
+	var seek seekError
+	if errors.As(it.err, &seek) {
 		if it.err = it.seek(seek.key); it.err != nil {
 			return false
 		}
@@ -307,7 +309,7 @@ func (it *nodeIterator) seek(prefix []byte) error {
 	// Move forward until we're just before the closest match to key.
 	for {
 		state, parentIndex, path, err := it.peekSeek(key)
-		if err == errIteratorEnd {
+		if errors.Is(err, errIteratorEnd) {
 			return errIteratorEnd
 		} else if err != nil {
 			return seekError{prefix, err}

trie/node.go

@@ -17,6 +17,7 @@
 package trie
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"strings"
@@ -242,7 +243,8 @@ func wrapError(err error, ctx string) error {
 	if err == nil {
 		return nil
 	}
-	if decErr, ok := err.(*decodeError); ok {
+	var decErr *decodeError
+	if errors.As(err, &decErr) {
 		decErr.stack = append(decErr.stack, ctx)
 		return decErr
 	}

trie/node_test.go

@@ -18,6 +18,7 @@ package trie
 
 import (
 	"bytes"
+	"errors"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/crypto"
@@ -59,7 +60,8 @@ func TestDecodeFullNodeWrongSizeChild(t *testing.T) {
 	rlp.Encode(buf, fullNodeData)
 
 	_, err := decodeNode([]byte("testdecode"), buf.Bytes())
-	if _, ok := err.(*decodeError); !ok {
+	var decodeError *decodeError
+	if !errors.As(err, &decodeError) {
 		t.Fatalf("decodeNode returned wrong err: %v", err)
 	}
 }
@@ -78,7 +80,8 @@ func TestDecodeFullNodeWrongNestedFullNode(t *testing.T) {
 	rlp.Encode(buf, fullNodeData)
 
 	_, err := decodeNode([]byte("testdecode"), buf.Bytes())
-	if _, ok := err.(*decodeError); !ok {
+	var decodeError *decodeError
+	if !errors.As(err, &decodeError) {
 		t.Fatalf("decodeNode returned wrong err: %v", err)
 	}
 }

trie/trie_test.go

@@ -76,7 +76,8 @@ func testMissingRoot(t *testing.T, scheme string) {
 	if trie != nil {
 		t.Error("New returned non-nil trie for invalid root")
 	}
-	if _, ok := err.(*MissingNodeError); !ok {
+	var missingNodeError *MissingNodeError
+	if !errors.As(err, &missingNodeError) {
 		t.Errorf("New returned wrong error: %v", err)
 	}
 }
@@ -146,11 +147,12 @@ func testMissingNode(t *testing.T, memonly bool, scheme string) {
 	}
 
 	_, err = trie.Get([]byte("120000"))
-	if _, ok := err.(*MissingNodeError); !ok {
+	var missingNodeError *MissingNodeError
+	if !errors.As(err, &missingNodeError) {
 		t.Errorf("Wrong error: %v", err)
 	}
 	_, err = trie.Get([]byte("120099"))
-	if _, ok := err.(*MissingNodeError); !ok {
+	if !errors.As(err, &missingNodeError) {
 		t.Errorf("Wrong error: %v", err)
 	}
 	_, err = trie.Get([]byte("123456"))
@@ -158,11 +160,11 @@ func testMissingNode(t *testing.T, memonly bool, scheme string) {
 		t.Errorf("Unexpected error: %v", err)
 	}
 	err = trie.Update([]byte("120099"), []byte("zxcv"))
-	if _, ok := err.(*MissingNodeError); !ok {
+	if !errors.As(err, &missingNodeError) {
 		t.Errorf("Wrong error: %v", err)
 	}
 	err = trie.Delete([]byte("123456"))
-	if _, ok := err.(*MissingNodeError); !ok {
+	if !errors.As(err, &missingNodeError) {
 		t.Errorf("Wrong error: %v", err)
 	}
 }
@@ -620,7 +622,8 @@ func runRandTest(rt randTest) error {
 
 func TestRandom(t *testing.T) {
 	if err := quick.Check(runRandTestBool, nil); err != nil {
-		if cerr, ok := err.(*quick.CheckError); ok {
+		var cerr *quick.CheckError
+		if errors.As(err, &cerr) {
 			t.Fatalf("random test iteration %d failed: %s", cerr.Count, spew.Sdump(cerr.In))
 		}
 		t.Fatal(err)