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<p style="margin: 0px 0px 1.2em !important;">On 14/02/2023 01:06,
Dan Smith wrote:</p>
<p style="margin: 0px 0px 1.2em !important;"></p>
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<p></p>
<blockquote type="cite" cite="mid:D6A4B805-E2A3-4F87-BF09-FEF6AF0263AA@oracle.com">
<div>LS isn't always clear about which of these two signatures
it's talking about, but in this case, given the use of
different phrases in the third and fourth rules, and the
fact of javac's longstanding behavior, I think that's the
intent.</div>
<div><br>
</div>
<div>(It makes sense, too, because the underlying problem is
that you don't want the descriptors to clash in the class
file. And they don't, because one has descriptor '(Object)V'
and the other is '(Class)V'. Eventually, somebody might try
to override something and need a bridge method that *would*
clash, but in that case there would be another method for
which this error check should apply.)</div>
</blockquote>
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<p style="margin: 0px 0px 1.2em !important;"></p>
<p style="margin: 0px 0px 1.2em !important;">Exactly.</p>
<p style="margin: 0px 0px 1.2em !important;">The checks in 8.4.8
are there to ensure you can’t accidentally override a bridge
method. As Dan points out, the underlying descriptors are
different here, so no real problem occurs. When writing the
checks for 8.4.8 I had to scan these rules multiple times - and
I agree that some clarification could be in order here. I think
reading them with the glasses of “no accidental bridge method
override” is generally a useful metaphore - and, since the JLS
cannot speak about bridge methods, that results in a somewhat
convoluted formulation of the rules.</p>
<p style="margin: 0px 0px 1.2em !important;">The example Archie
shown is one of those cases where there’s obviously something
“fishy” going on, but the compiler decides to go ahead with it,
kicking the can down the road, to when the abstract class will
become a concrete one. So, if a new class comes along, like
this:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code class="hljs language-java" style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;display: block; overflow-x: auto; padding: 0.5em; color: rgb(51, 51, 51); background: rgb(248, 248, 248) none repeat scroll 0% 0%; -moz-text-size-adjust: none;"><span class="hljs-class"><span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">class</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">EvenLower</span><<span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">R</span>> <span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">extends</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">Lower</span><<span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">R</span>> </span>{
<span class="hljs-function"><span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;">method</span><span class="hljs-params">(Class<?> c)</span> </span>{ }
}
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">A problem will be
reported - because the class will still need to implement <code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;">method(Class<R>)</code>
- but of course if you try to do that, you will get a clash.</p>
<p style="margin: 0px 0px 1.2em !important;">That said, your
subclass can have a raw declaration:</p>
<pre style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;font-size: 1em; line-height: 1.2em;margin: 1.2em 0px;"><code class="hljs language-java" style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;white-space: pre; overflow: auto; border-radius: 3px; border: 1px solid rgb(204, 204, 204); padding: 0.5em 0.7em; display: block !important;display: block; overflow-x: auto; padding: 0.5em; color: rgb(51, 51, 51); background: rgb(248, 248, 248) none repeat scroll 0% 0%; -moz-text-size-adjust: none;"> <span class="hljs-class"><span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">class</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">EvenLower</span><<span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">R</span>> <span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">extends</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">Lower</span><<span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;color: rgb(68, 85, 136); font-weight: bold;">R</span>> </span>{
<span class="hljs-function"><span class="hljs-keyword" style="color: rgb(51, 51, 51); font-weight: bold;">void</span> <span class="hljs-title" style="color: rgb(153, 0, 0); font-weight: bold;">method</span><span class="hljs-params">(Class c)</span> </span>{ }
}
</code></pre>
<p style="margin: 0px 0px 1.2em !important;">In which case
everything is ok (beause <code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;">method(Class)</code>
is a subsignature of the sharper <code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace;margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-radius: 3px; display: inline;">method(Class<R>)</code>).</p>
<p style="margin: 0px 0px 1.2em !important;">Maurizio</p>
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