[#absl-down_cast-048]
= xref:absl.adoc[absl]::down_cast
:relfileprefix: ../
:mrdocs:

Overload of down_cast for references. Use like this: absl::down_cast<T&>(foo). The code is slightly convoluted because we're still using the pointer form of dynamic cast. (The reference form throws an exception if it fails.)

== Synopsis

Declared in `<absl/base/casts.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename To,
    typename From>
[[nodiscard]]
To
down_cast(From& f);
----

== Description

There's no need for a special const overload either for the pointer or the reference form. If you call down_cast with a const T&, the compiler will just bind From to const T.

== Return Value

`f`, downcast to `To`.

[NOTE]
====
The return value https://en.cppreference.com/cpp/language/attributes/nodiscard[should not be discarded^].
====
== Parameters

[cols="1,4"]
|===
| Name| Description
| *f*
| The source reference to downcast.
|===


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