---
id: LANG-27
family: GR-LANG
level: core
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-lang/lang-27
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# LANG-27 — A switch compares its value; it does not evaluate it

*GR-LANG (Part I) · level: core · profiles: runtime · added in 1.0*

Despite the parameter's name, a switch gateway runs no expression engine. The value is matched against each branch as it stands.

## The rule

> **Normative.** This is the rule.
>
> 1. A switch gateway does not evaluate its `expression`.
>
> 2. The value is compared unchanged against each branch's `value` in declaration order, with no coercion: a branch matches only where the two are of the same type as well as equal.
>
> 3. The first matching branch is the sole active branch, and its name is what the gateway reports as active.
>
> 4. Where no branch matches, the branch named by `default_branch` is active; where no branch matches and no usable default is named, the node fails.

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.