RFR: 8294943: Implement record patterns in enhanced for [v15]

[Maurizio Cimadamore]

On Thu, 24 Nov 2022 13:43:02 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Aggelos Biboudis has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add @enablePreview
>
> src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java line 3016:
> 
>> 3014:                             return ForInitResult.LocalVarDecl;
>> 3015:                         }
>> 3016:                         else if(peekToken(lookahead, COLON)) {
> 
> Does this logic works with nested record patterns? You don't seem to "count" the parenthesis... I do see tests with it though...

This is an example I found where classification goes wrong:


for (m(a ? b() : c) ; ;) {}

This used to parse correctly, but now parsing fails because the classification sees ")" followed by a ":".

This a nasty one: we can't just bail out on "?" as that is useful for generic types. But once you accept "?" then it could be a conditional as well, and conditionals also feature a ":" which means here we have a problem.

I think "?" should only conditionally be accepted if we're inside generic brackets. But then again, you could still have `a < b ? c() : d` which is not a type.

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PR: https://git.openjdk.org/jdk/pull/10798