<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div><br></div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"Brian Goetz" <brian.goetz@oracle.com><br><b>To: </b>"Remi Forax" <forax@univ-mlv.fr><br><b>Cc: </b>"amber-spec-experts" <amber-spec-experts@openjdk.java.net><br><b>Sent: </b>Friday, September 9, 2022 10:12:21 PM<br><b>Subject: </b>Re: Primitives in instanceof and patterns<br></blockquote></div><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;">I have a question about your example. I'm not trying to be clever
and play "whatabout", I'm looking for a straight answer why you
think the two cases are different. <br>
<br>
<blockquote cite="mid:1873318389.2133206.1662737744430.JavaMail.zimbra@u-pem.fr">
<div><span style="font-size: large;"><span style="font-family:
monospace;"><br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;">If we take a simple example<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> record Point(int x, int y) { }<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> Point point = ...<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> switch(point) {<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> case Point(int i, int j) -> ...<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> ...<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> }<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"><br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;">let say know that we change Point to use longs<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"> record Point(long x, long y) { }<br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;"><br></span></span></div>
<div><span style="font-size: large;"><span style="font-family:
monospace;">With the semantics you propose, the code still
compile but the pattern is now transformed to a partial
pattern that will not match all Points but only the ones
with x and y in between Integer.MIN_VALUE and
Integer.MAX_VALUE.</span></span></div>
</blockquote>
<br>
The same is true when I start with<br>
<br>
record Foo(String s) { ... }<br>
<br>
and later change it to<br>
<br>
record Foo(Object s) { ... }<br>
<br>
(both are incompatible changes, but we won't dwell on that.) <br>
<br>
My question is: why does it not bother you that use-site patterns
like `Foo(String s)` are reinterpreted as partial after the String
-> Object change, but the analogous change with long -> int
bothers you so much that you'd use it to argue against being able to
ask whether a long is also an int? <br>
<br>
You obviously think that these two examples are radically
different. Can you explain why? Is it anything more than "that's
the way its always been"? <br></blockquote><div><br></div><div>I think i've been a little over my head with this example.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>I've forgotten that in both cases, the patterns move from being a total pattern to be a partial pattern so the enclosing switch will not be exhaustive anymore, thus not compile.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Rémi<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div></div></div></body></html>