An unsuccessful call has no synchronizing effect at all.
As far as the memory model is concerned,
<code>l.TryLock</code> (or <code>l.TryRLock</code>)
may be considered to be able to return false
even when the mutex <i>l</i> is unlocked.
</p>

<h3 id="once">Once</h3>

<p>
The <code>sync</code> package provides a safe mechanism for

and may therefore implement several distinct interfaces. For
instance, all types implement the <i>empty interface</i>:
</p>

<pre>
interface{}
</pre>

<p>
Similarly, consider this interface specification,
which appears within a <a href="#Type_declarations">type declaration</a>
to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()

as <code>const_bufSize</code>.
</p>

<p>
Field offsets are of the form <code><i>type</i>_<i>field</i></code>.
Struct sizes are of the form <code><i>type</i>__size</code>.
For example, consider the following Go definition:
</p>

<pre>
type reader struct {
	buf [bufSize]byte
	r   int
}
</pre>

<p>
Assembly can refer to the size of this struct

<pre>
interface{}
</pre>

<p>
For convenience, the predeclared type <code>any</code> is an alias for the empty interface.
[<a href="#Go_1.18">Go 1.18</a>]
</p>

<p>
Similarly, consider this interface specification,
which appears within a <a href="#Type_declarations">type declaration</a>
to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()