1 files changed, 76 insertions, 0 deletions
diff --git a/spew/internal_test.go b/spew/internal_test.go
index 7a872e4..05bab97 100644
--- a/spew/internal_test.go
+++ b/spew/internal_test.go
@@ -26,6 +26,7 @@ import (
 	"bytes"
 	"reflect"
 	"testing"
+	"unsafe"
 )
 
 // dummyFmtState implements a fake fmt.State to use for testing invalid
@@ -79,3 +80,78 @@ func TestInvalidReflectValue(t *testing.T) {
 		t.Errorf("InvalidReflectValue #%d got: %s want: %s", i, s, want)
 	}
 }
+
+// flagRO, flagKindShift and flagKindWidth indicate various bit flags that the
+// reflect package uses internally to track kind and state information.
+const flagRO = 1 << 0
+const flagKindShift = 4
+const flagKindWidth = 5
+
+// changeKind uses unsafe to intentionally change the kind of a reflect.Value to
+// the maximum kind value which does not exist.  This is needed to test the
+// fallback code which punts to the standard fmt library for new types that
+// might get added to the language.
+func changeKind(v *reflect.Value, readOnly bool) {
+	rvf := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(v)) +
+		unsafe.Offsetof(reflectValue.flag)))
+	*rvf = *rvf | ((1<<flagKindWidth - 1) << flagKindShift)
+	if readOnly {
+		*rvf |= flagRO
+	} else {
+		*rvf &= ^uintptr(flagRO)
+	}
+}
+
+// TestAddedReflectValue tests functionaly of the dump and formatter code which
+// falls back to the standard fmt library for new types that might get added to
+// the language.
+func TestAddedReflectValue(t *testing.T) {
+	i := 1
+
+	// Dump using a reflect.Value that is exported.
+	v := reflect.ValueOf(int8(5))
+	changeKind(&v, false)
+	buf := new(bytes.Buffer)
+	d := dumpState{w: buf, cs: &Config}
+	d.dump(v)
+	s := buf.String()
+	want := "(int8) 5"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d\n got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Dump using a reflect.Value that is not exported.
+	changeKind(&v, true)
+	buf.Reset()
+	d.dump(v)
+	s = buf.String()
+	want = "(int8) <int8 Value>"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d\n got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Formatter using a reflect.Value that is exported.
+	changeKind(&v, false)
+	buf2 := new(dummyFmtState)
+	f := formatState{value: v, cs: &Config, fs: buf2}
+	f.format(v)
+	s = buf2.String()
+	want = "5"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Formatter using a reflect.Value that is not exported.
+	changeKind(&v, true)
+	buf2.Reset()
+	f = formatState{value: v, cs: &Config, fs: buf2}
+	f.format(v)
+	s = buf2.String()
+	want = "<int8 Value>"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d got: %s want: %s", i, s, want)
+	}
+}