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<p class="MsoNormal"><span lang="EN-GB">Hi experts<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">A while back I was reading the new amber spec on switch pattern matching, and read something that felt off, but after checking the normal spec, I noticed the issue existed there too.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">It was late when I sent my review of the amber spec to their group, so I wanted to sent this the day after but I managed to forget it.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">In 5.2, the concept of "assignment compatible" is introduced:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> If the type of an expression can be converted to the type of a variable by assignment conversion, we say the expression (or its value) is assignable to the variable or, equivalently, that the type of the expression
is assignment compatible with the type of the variable.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">It is a useful concept that is used a total of 16 times in the spec for java 18 (and the current 19 spec).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Although this concept is introduced as a relation between two types, in the switch statement specifications (14.11) the following appears:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> 14.11.1 Switch Blocks<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> ...<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> The switch block of a switch statement or a switch expression is compatible with<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">the type of the selector expression, T, if both of the following are true:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> * If T is not an enum type, then **every case constant associated with the switch<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">block is assignment compatible with T (§5.2)**.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> * ...<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Here the relation is used between a constant and a type, which seems to be incorrect.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">For the Amber experts, this section has been rewritten due to there being more valid possible selector types, but the issue remains:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">> A case constant c is switch compatible with a type T where T is either char, byte, short, int, Character, Byte, Short, Integer, or String if c is assignment compatible with T (5.2).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Greetings<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Robbe Pincket</span><span lang="EN-GB"><o:p></o:p></span></p>
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