which are unordered by happens before
(that is, neither <i>r</i> happens before <i>w</i>
nor <i>w</i> happens before <i>r</i>).
</p>

<p>
A <i>write-write data race</i> on memory location <i>x</i>
consists of two write-like memory operations <i>w</i> and <i>w'</i> on <i>x</i>,
at least one of which is non-synchronizing,
which are unordered by happens before.
</p>

<p>

components have identical types. In detail:
</p>

<ul>
	<li>Two array types are identical if they have identical element types and
	    the same array length.</li>

	<li>Two slice types are identical if they have identical element types.</li>

	<li>Two struct types are identical if they have the same sequence of fields,
	    and if corresponding fields have the same names, and identical types,

and declares <code>runtime·tlsoffset</code>, a 4-byte, implicitly zeroed variable that
contains no pointers.
</p>

<p>
There may be one or two arguments to the directives.
If there are two, the first is a bit mask of flags,
which can be written as numeric expressions, added or or-ed together,
or can be set symbolically for easier absorption by a human.

	<li>Two interface types are identical if they define the same type set.
	</li>

	<li>Two map types are identical if they have identical key and element types.</li>

	<li>Two channel types are identical if they have identical element types and
	    the same direction.</li>

	<li>Two <a href="#Instantiations">instantiated</a> types are identical if