Add IsNil function for checking nil values in Go (#399)

type_manipulation.go

@@ -7,6 +7,12 @@ func ToPtr[T any](x T) *T {
 	return &x
 }
 
+// IsNil checks if a value is nil or if it's a reference type with a nil underlying value.
+func IsNil(x any) bool {
+	defer func() { recover() }()
+	return x == nil || reflect.ValueOf(x).IsNil()
+}
+
 // EmptyableToPtr returns a pointer copy of value if it's nonzero.
 // Otherwise, returns nil pointer.
 func EmptyableToPtr[T any](x T) *T {

type_manipulation_test.go

@@ -15,6 +15,30 @@ func TestToPtr(t *testing.T) {
 	is.Equal(*result1, []int{1, 2})
 }
 
+func TestIsNil(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	var x int
+	is.False(IsNil(x))
+
+	var k struct{}
+	is.False(IsNil(k))
+
+	var s *string
+	is.True(IsNil(s))
+
+	var i *int
+	is.True(IsNil(i))
+
+	var b *bool
+	is.True(IsNil(b))
+
+	var ifaceWithNilValue interface{} = (*string)(nil)
+	is.True(IsNil(ifaceWithNilValue))
+	is.True(ifaceWithNilValue != nil)
+}
+
 func TestEmptyableToPtr(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)