---
title: Enforce spacing around double colons
description: Datadog, the leading service for cloud-scale monitoring.
breadcrumbs: >-
  Docs > Datadog Security > Code Security > Static Code Analysis (SAST) > SAST
  Rules > Enforce spacing around double colons
---

# Enforce spacing around double colons

{% callout %}
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{% /callout %}

## Metadata{% #metadata %}

**ID:** `kotlin-code-style/double-colon-spacing`

**Language:** Kotlin

**Severity:** Notice

**Category:** Code Style

## Description{% #description %}

In callable references, there should be no spaces separating the class, instance, method, or property from the double colons (`::`).

An expression like `List::filter` is correct, while `List :: filter` is not.

## Non-Compliant Code Examples{% #non-compliant-code-examples %}

```kotlin
val clz1 = Foo ::class
val clz2 = Foo:: class
val clz3 = Foo :: class

val filter1 = List ::filter
val filter2 = List:: filter
val filter3 = List :: filter

val constr = :: Regex
```

## Compliant Code Examples{% #compliant-code-examples %}

```kotlin
val filter = List::filter
val clz = Foo::class
val constr = ::Regex
```
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