Use unexported sentinel error and require.ErrorIs

Author: qdm12

libevm/legacy/legacy.go

@@ -19,11 +19,16 @@
 package legacy
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/ava-labs/libevm/core/vm"
 )
 
+var (
+	errRemainingGasExceedsSuppliedGas = errors.New("remaining gas exceeds supplied gas")
+)
+
 // PrecompiledStatefulContract is the legacy signature of
 // [vm.PrecompiledStatefulContract], which explicitly accepts and returns gas
 // values. Instances SHOULD NOT use the [vm.PrecompileEnvironment]
@@ -36,7 +41,7 @@ func (c PrecompiledStatefulContract) Upgrade() vm.PrecompiledStatefulContract {
 		gas := env.Gas()
 		ret, remainingGas, err := c(env, input, gas)
 		if remainingGas > gas {
-			return nil, fmt.Errorf("remaining gas %d exceeds supplied gas %d", remainingGas, gas)
+			return nil, fmt.Errorf("%w: %d > %d", errRemainingGasExceedsSuppliedGas, remainingGas, gas)
 		}
 		if used := gas - remainingGas; used > 0 {
 			env.UseGas(used)

libevm/legacy/legacy_test.go

@@ -47,29 +47,31 @@ func (s *stubPrecompileEnvironment) UseGas(gas uint64) bool {
 func TestPrecompiledStatefulContract_Upgrade(t *testing.T) {
 	t.Parallel()
 
+	errTest := errors.New("test error")
+
 	tests := map[string]struct {
 		envGas        uint64
 		precompileRet []byte
 		remainingGas  uint64
 		precompileErr error
 		wantRet       []byte
-		wantErr       string
+		wantErr       error
 		wantGasUsed   uint64
 	}{
 		"call_error": {
 			envGas:        10,
 			precompileRet: []byte{2},
 			remainingGas:  6,
-			precompileErr: errors.New("test error"),
+			precompileErr: errTest,
 			wantRet:       []byte{2},
-			wantErr:       "test error",
+			wantErr:       errTest,
 			wantGasUsed:   4,
 		},
 		"remaining_gas_exceeds_supplied_gas": {
 			envGas:        10,
 			precompileRet: []byte{2},
 			remainingGas:  11,
-			wantErr:       "remaining gas 11 exceeds supplied gas 10",
+			wantErr:       errRemainingGasExceedsSuppliedGas,
 		},
 		"zero_remaining_gas": {
 			envGas:        10,
@@ -103,11 +105,7 @@ func TestPrecompiledStatefulContract_Upgrade(t *testing.T) {
 			input := []byte("unused")
 
 			ret, err := upgraded(env, input)
-			if testCase.wantErr == "" {
-				require.NoError(t, err)
-			} else {
-				require.EqualError(t, err, testCase.wantErr)
-			}
+			require.ErrorIs(t, err, testCase.wantErr)
 			assert.Equal(t, testCase.wantRet, ret, "bytes returned by upgraded contract")
 			assert.Equalf(t, testCase.wantGasUsed, env.gasUsed, "sum of %T.UseGas() calls", env)
 		})