<div dir="ltr"><div><div><div><div>Thank you all!<br><br></div><div>I agree with Remi, the problem no longer exists when using a switch expression.<br></div><div>I thought I could not do it with our (obviously more contrived) code, but I have managed to do it in the end.<br></div><div><br></div>That said, after sending the email, I actually wondered if this problem was actually linked to the use of the "old switch" statement, and a possible lack of understanding of the control flow?<br></div>I am ready to be told "we cannot fix it because of JLS rule 4.5.6.7" or something like that.<br><br></div>Thank you again for taking a look at it,<br></div>Jean-Noël<br><br><br><div><div><div><div><br></div></div></div></div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Wed, Dec 11, 2024 at 3:05 PM Angelos Bimpoudis <<a href="mailto:angelos.bimpoudis@oracle.com">angelos.bimpoudis@oracle.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-688562241304480375">
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Filed it here: <a href="https://bugs.openjdk.org/browse/JDK-8345997" target="_blank">https://bugs.openjdk.org/browse/JDK-8345997</a></div>
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<div style="font-size:11pt;color:rgb(0,0,0)">
Thank you for reaching out! </div>
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Thx Remi for the minimized example as well.</div>
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<div id="m_-3490843587185937718divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> amber-dev <<a href="mailto:amber-dev-retn@openjdk.org" target="_blank">amber-dev-retn@openjdk.org</a>> on behalf of Remi Forax <<a href="mailto:forax@univ-mlv.fr" target="_blank">forax@univ-mlv.fr</a>><br>
<b>Sent:</b> 11 December 2024 13:44<br>
<b>To:</b> Gavin Bierman <<a href="mailto:gavin.bierman@oracle.com" target="_blank">gavin.bierman@oracle.com</a>><br>
<b>Cc:</b> Jean-Noël Rouvignac (ForgeRock) <<a href="mailto:jean-noel.rouvignac@pingidentity.com" target="_blank">jean-noel.rouvignac@pingidentity.com</a>>; amber-dev <<a href="mailto:amber-dev@openjdk.org" target="_blank">amber-dev@openjdk.org</a>><br>
<b>Subject:</b> Re: Enum: difference of behaviour between exhaustive switch vs. using default:</font>
<div> </div>
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<div>
<div style="font-family:arial,helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<div>Hello,<br>
</div>
<div>I think it can be reduced to</div>
<div>
<div style="background-color:rgb(255,255,255);color:rgb(8,8,8)">
<pre style="font-family:"JetBrains Mono",monospace;font-size:9.8pt"><span style="color:rgb(0,51,179)">public enum </span><span style="color:rgb(0,0,0)">Action </span>{ <span style="color:rgb(135,16,148);font-style:italic">IGNORE</span>, <span style="color:rgb(135,16,148);font-style:italic">REJECT </span>}</pre>
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<div style="background-color:rgb(255,255,255);color:rgb(8,8,8)">
<pre style="font-family:"JetBrains Mono",monospace;font-size:9.8pt"><span style="color:rgb(0,51,179)">private static void </span><span style="color:rgb(0,98,122)">bad</span>() {<br> <span style="color:rgb(0,0,0)">String s</span>;<br> <span style="color:rgb(0,51,179)">switch </span>(<span style="font-style:italic">getAction</span>()) {<br> <span style="color:rgb(0,51,179)">case </span><span style="color:rgb(135,16,148);font-style:italic">IGNORE</span>:<br> <span style="color:rgb(0,0,0)">s </span>= <span style="color:rgb(6,125,23)">"foo"</span>;<br> <span style="color:rgb(0,51,179)">break</span>;<br> <span style="color:rgb(0,51,179)">case </span><span style="color:rgb(135,16,148);font-style:italic">REJECT</span>:<span style="color:rgb(140,140,140);font-style:italic"><br></span><span style="color:rgb(140,140,140);font-style:italic"> </span><span style="color:rgb(0,51,179)">throw new </span>RuntimeException(<span style="color:rgb(6,125,23)">"REJECTED"</span>);<br> };<br> <span style="color:rgb(0,0,0)">System</span>.<span style="color:rgb(135,16,148);font-style:italic">out</span>.println(<span style="color:rgb(0,0,0)">s</span>); <span style="color:rgb(140,140,140);font-style:italic">// <------- variable s might not have been initialized<br></span>}<br><br><span style="color:rgb(0,51,179)">private static void </span><span style="color:rgb(0,98,122)">ok</span>() {<br> <span style="color:rgb(0,0,0)">String s </span>= <span style="color:rgb(0,51,179)">switch </span>(<span style="font-style:italic">getAction</span>()) {<br> <span style="color:rgb(0,51,179)">case </span><span style="color:rgb(135,16,148);font-style:italic">IGNORE</span>:<br> <span style="color:rgb(0,51,179)">yield </span><span style="color:rgb(6,125,23)">"foo"</span>;<br> <span style="color:rgb(0,51,179)">case </span><span style="color:rgb(135,16,148);font-style:italic">REJECT</span>:<span style="color:rgb(140,140,140);font-style:italic"><br></span><span style="color:rgb(140,140,140);font-style:italic"> </span><span style="color:rgb(0,51,179)">throw new </span>RuntimeException(<span style="color:rgb(6,125,23)">"REJECTED"</span>);<br> };<br> <span style="color:rgb(0,0,0)">System</span>.<span style="color:rgb(135,16,148);font-style:italic">out</span>.println(<span style="color:rgb(0,0,0)">s</span>); <span style="color:rgb(140,140,140);font-style:italic">// ok !<br></span>}</pre>
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<div>so there is a bug in DA/DU rules and the workaround is to use a switch expression.<br>
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<div><br>
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<div>Rémi<br>
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<div><br>
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<blockquote style="border-left:2px solid rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
<b>From: </b>"Gavin Bierman" <<a href="mailto:gavin.bierman@oracle.com" target="_blank">gavin.bierman@oracle.com</a>><br>
<b>To: </b>"Jean-Noël Rouvignac (ForgeRock)" <<a href="mailto:jean-noel.rouvignac@pingidentity.com" target="_blank">jean-noel.rouvignac@pingidentity.com</a>><br>
<b>Cc: </b>"amber-dev" <<a href="mailto:amber-dev@openjdk.org" target="_blank">amber-dev@openjdk.org</a>><br>
<b>Sent: </b>Wednesday, December 11, 2024 1:20:15 PM<br>
<b>Subject: </b>Re: Enum: difference of behaviour between exhaustive switch vs. using default:<br>
</blockquote>
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<div>
<blockquote style="border-left:2px solid rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt">
Could you file this as a bug, and I will take a look?
<div><br>
</div>
<div>Thanks,</div>
<div>Gavin<br id="m_-3490843587185937718x_lineBreakAtBeginningOfMessage">
<div><br>
<blockquote>
<div>On 10 Dec 2024, at 16:10, Jean-Noël Rouvignac (ForgeRock) <<a href="mailto:jean-noel.rouvignac@pingidentity.com" target="_blank">jean-noel.rouvignac@pingidentity.com</a>> wrote:</div>
<br>
<div>
<div dir="ltr">
<div>Hello amber-dev experts!<br>
<br>
</div>
<div>I am modernizing our codebase by making it use enhanced / exhaustive switches.<br>
<br>
</div>
<div>In several places, I replaced `default: ` by `case THE_ONLY_UNUSED_ENUM_VALUE:`, except that I am hitting an unexpected difference in behaviour, at least from my point of view.
<br>
<br>
</div>
<div>I have reduced the code to the following reproducer (tested on the <a href="https://dev.java/playground/" target="_blank">
https://dev.java/playground/</a>), where `main1()` compiles, but `main2()` does not. And yet, I am under the impression both should be equivalent?<br clear="all">
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What do you think?<br>
Thanks a lot.<br>
<br>
<br>
<br>
import java.io.IOException;<br>
<br>
class Main {<br>
public enum Action { IGNORE, REJECT }<br>
<br>
public static void main(String[] args) {<br>
main1();<br>
main2();<br>
}<br>
<br>
private static void main1() {<br>
String s;<br>
try {<br>
s = getValue();<br>
} catch (IOException e) {<br>
switch (getAction()) {<br>
case IGNORE:<br>
return;<br>
default:<br>
throw new RuntimeException("REJECTED");<br>
}<br>
}<br>
<br>
System.out.println(s);<br>
}<br>
<br>
private static void main2() {<br>
String s;<br>
try {<br>
s = getValue();<br>
} catch (IOException e) {<br>
switch (getAction()) {<br>
case IGNORE:<br>
return;<br>
case REJECT: // <------------------- Fails compilation<br>
throw new RuntimeException("REJECTED");<br>
}<br>
}<br>
<br>
System.out.println(s); // <------- Main.java:40: error: variable s might not have been initialized<br>
}<br>
<br>
static Action getAction() {<br>
return Action.IGNORE;<br>
}<br>
<br>
static String getValue() throws IOException {<br>
return "SUCCESS";<br>
}<br>
}<br>
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