feat: add isNil helper function.

Author: ghosind

util.go

@@ -0,0 +1,21 @@
+package assert
+
+import "reflect"
+
+// isNil checks whether a value is nil or not. It'll always return false if the value is not a
+// channel, a function, a map, a point, an unsafe point, an interface, or a slice.
+func isNil(val any) bool {
+	if val == nil {
+		return true
+	}
+
+	v := reflect.ValueOf(val)
+
+	switch v.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Map, reflect.Pointer, reflect.UnsafePointer,
+		reflect.Interface, reflect.Slice:
+		return v.IsNil()
+	default:
+		return false
+	}
+}

util_test.go

@@ -0,0 +1,14 @@
+package assert
+
+import "testing"
+
+func TestIsNil(t *testing.T) {
+	assert := New(t)
+
+	assert.DeepEqual(isNil(1), false)  // int
+	assert.DeepEqual(isNil(""), false) // string
+	assert.DeepEqual(isNil(nil), true)
+	var testAssert *Assertion
+	assert.DeepEqual(isNil(testAssert), true)
+	assert.DeepEqual(isNil(assert), false)
+}