do not generate null checks for record patterns

[vicente-romero-oracle]

do not generate null checks for record patterns

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do not generate null checks for record patterns

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[vicente-romero-oracle]

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;
        }
    };
}

[mcimadamore]

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.

[vicente-romero-oracle]

superseded by: #1902

[mcimadamore]

Looks good!