RFR: do not generate null checks for record patterns [v3]

[Maurizio Cimadamore]

On Tue, 13 Jan 2026 19:46:48 GMT, Vicente Romero <vromero at openjdk.org> wrote:

>> Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   addressing review comments
>
> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/NullChecksWriter.java line 170:
> 
>> 168:     public void visitLetExpr(LetExpr tree) {
>> 169:         // don't recurse inside let expressions, they are backend artifacts
>> 170:         result = tree;
> 
> offline suggestion from Jan Lahoda:
> 
> this code will skip all let expressions which is too broad, as let expressions are generated also by switch expressions but could contain user code. For example there is no null check generated in this case:
> 
> void main() {
>     int i = switch (new Object()) {
>         default -> {
>             Object obj = null;
>             Object! nonNull = obj;
>             yield 0;
>         }
>     };
> }

Actually, I think we can remove this visitor. Sure, javac will add an extra, redundant null check for null-restricted type test patterns, but that's not incorrect (this check will never throw NPE because, if `null`, the pattern won't match -- thanks to your changes in `TransPatterns`). I think I prefer a redundant check than having to mark all LetExpr that might need recursion (as we will surely forget some).

Separately, we can work on removing redundant null checks -- e.g. for things that are co-compiled and such, in which case this will fall out for free.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1884#discussion_r2689983882