On Tue, 18 Apr 2023 09:13:01 GMT, Jan Lahoda <jlah...@openjdk.org> wrote:
>> This is the first draft of a patch for JEP 440 and JEP 441. Changes included:
>>
>> - the pattern matching for switch and record patterns features are made
>> final, together with updates to tests.
>> - parenthesized patterns are removed.
>> - qualified enum constants are supported for case labels.
>>
>> This change herein also includes removal record patterns in for each loop,
>> which may be split into a separate PR in the future.
>
> Jan Lahoda has updated the pull request incrementally with six additional
> commits since the last revision:
>
> - Fixing infinite loop where a binding pattern is replaced with a binding
> pattern for the same type.
> - Reflecting review comments.
> - Fixing exhaustiveness for unsealed supertype pattern.
> - No need to enable features after error reported.
> - SwitchBootstraps.typeSwitch should not initialize enum classes.
> - A prototype of avoiding enum initialization.
src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java line 812:
> 810: if (l instanceof JCPatternCaseLabel patternLabel) {
> 811: for (Type component : components(selector.type))
> {
> 812: patterns =
> patterns.prepend(PatternDescription.from(types, component, patternLabel.pat));
I noted that this code ends up adding redundant pattern descriptions to the
list - for instance:
class Test {
sealed interface I1 permits B, C { }
sealed interface I2 permits B, C { }
static final class B implements I1, I2 { }
static final class C implements I1, I2 { }
<Z extends I1 & I2> int test(Z z) {
return switch (z) {
case B c -> 2;
case C d -> 3;
};
}
}
In this case the list ends up with 6 elements, [ B, B, B, C, C, C ]. Given that
the complexity of the algorithm depends on the number of patterns in the list,
it would probably be better to use a set here and try to make the list as small
as possible from early on.
src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java line 915:
> 913:
> 914: for (PatternDescription pdOther : patterns) {
> 915: if (pdOther instanceof BindingPattern
> bpOther) {
This code redundantly checks a pattern against itself, which I think we can
avoid.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1170062325
PR Review Comment: https://git.openjdk.org/jdk/pull/13074#discussion_r1170062982
