The new <a href="/pkg/go/types#Alias"><code>Alias</code></a> type represents type aliases.
      Previously, type aliases were not represented explicitly, so a reference to a type alias was equivalent
      to spelling out the aliased type, and the name of the alias was lost.
      The new representation retains the intermediate <code>Alias</code>.

initialization in the presence of multiple goroutines
through the use of the <code>Once</code> type.
Multiple threads can execute <code>once.Do(f)</code> for a particular <code>f</code>,
but only one will run <code>f()</code>, and the other calls block
until <code>f()</code> has returned.
</p>

<p class="rule">
The completion of a single call of <code>f()</code> from <code>once.Do(f)</code>

Type declarations come in two forms: alias declarations and type definitions.
</p>

<pre class="ebnf">
TypeDecl = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
TypeSpec = AliasDecl | TypeDef .
</pre>

<h4 id="Alias_declarations">Alias declarations</h4>

<p>
An alias declaration binds an identifier to the given type
[<a href="#Go_1.9">Go 1.9</a>].
</p>

Type declarations come in two forms: alias declarations and type definitions.
</p>

<pre class="ebnf">
TypeDecl = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
TypeSpec = AliasDecl | TypeDef .
</pre>

<h4 id="Alias_declarations">Alias declarations</h4>

<p>
An alias declaration binds an identifier to the given type.
</p>

<pre class="ebnf">

</p>

<p>
The <code>SP</code> pseudo-register is a virtual stack pointer
used to refer to frame-local variables and the arguments being
prepared for function calls.
It points to the highest address within the local stack frame, so references should use negative offsets
in the range [−framesize, 0):
<code>x-8(SP)</code>, <code>y-4(SP)</code>, and so on.
</p>

<p>