all: use errors.As instead of .(type)

2 files changed, 7 insertions, 6 deletions

diff --git a/vm/vmimpl/merger_test.go b/vm/vmimpl/merger_test.go
index 8308aff5e..ef5570509 100644
--- a/vm/vmimpl/merger_test.go
+++ b/vm/vmimpl/merger_test.go
@@ -5,6 +5,7 @@ package vmimpl
 
 import (
 	"bytes"
+	"errors"
 	"io"
 	"testing"
 	"time"
@@ -62,9 +63,10 @@ func TestMerger(t *testing.T) {
 		t.Fatalf("bad line: '%s', want '%s'", got, want)
 	}
 
+	var merr MergerError
 	if err := <-merger.Err; err == nil {
 		t.Fatalf("merger did not produce an error on pipe close")
-	} else if merr := err.(MergerError); merr.Name != "pipe1" || merr.R != rp1 || merr.Err != io.EOF {
+	} else if !errors.As(err, &merr) || merr.Name != "pipe1" || merr.R != rp1 || merr.Err != io.EOF {
 		t.Fatalf("merger produced wrong error: %v", err)
 	}
 
diff --git a/vm/vmimpl/vmimpl.go b/vm/vmimpl/vmimpl.go
index 9dbd61a92..0a4ada028 100644
--- a/vm/vmimpl/vmimpl.go
+++ b/vm/vmimpl/vmimpl.go
@@ -93,12 +93,11 @@ type BootError struct {
 }
 
 func MakeBootError(err error, output []byte) error {
-	switch err1 := err.(type) {
-	case *osutil.VerboseError:
-		return BootError{err1.Title, append(err1.Output, output...)}
-	default:
-		return BootError{err.Error(), output}
+	var verboseError *osutil.VerboseError
+	if errors.As(err, &verboseError) {
+		return BootError{verboseError.Title, append(verboseError.Output, output...)}
 	}
+	return BootError{err.Error(), output}
 }
 
 func (err BootError) Error() string {