mipsevm,cli: step fn fixes, fix lint

cmd/run.go

@@ -214,9 +214,9 @@ func Run(ctx *cli.Context) error {
 	proofFmt := ctx.String(RunProofFmtFlag.Name)
 	snapshotFmt := ctx.String(RunSnapshotFmtFlag.Name)
 
-	step := us.Step
+	stepFn := us.Step
 	if po.cmd != nil {
-		step = Guard(po.cmd.ProcessState, step)
+		stepFn = Guard(po.cmd.ProcessState, stepFn)
 	}
 
 	for !state.Exited {
@@ -241,7 +241,7 @@ func Run(ctx *cli.Context) error {
 
 		if proofAt(state) {
 			preStateHash := crypto.Keccak256Hash(state.EncodeWitness())
-			witness, err := us.Step(true)
+			witness, err := stepFn(true)
 			if err != nil {
 				return fmt.Errorf("failed at proof-gen step %d (PC: %08x): %w", step, state.PC, err)
 			}

mipsevm/state_test.go

@@ -74,7 +74,8 @@ func TestState(t *testing.T) {
 				if us.state.PC == endAddr {
 					break
 				}
-				us.Step(false)
+				_, err := us.Step(false)
+				require.NoError(t, err)
 			}
 			require.Equal(t, uint32(endAddr), us.state.PC, "must reach end")
 			// inspect test result
@@ -109,7 +110,8 @@ func TestHello(t *testing.T) {
 		if us.state.Exited {
 			break
 		}
-		us.Step(false)
+		_, err := us.Step(false)
+		require.NoError(t, err)
 	}
 
 	require.True(t, state.Exited, "must complete program")
@@ -215,7 +217,8 @@ func TestClaim(t *testing.T) {
 		if us.state.Exited {
 			break
 		}
-		us.Step(false)
+		_, err := us.Step(false)
+		require.NoError(t, err)
 	}
 
 	require.True(t, state.Exited, "must complete program")