RFR: 8268320: Better error recovery for broken patterns in switch

[Vicente Romero]

On Wed, 9 Jun 2021 19:50:00 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

> Trying to improve error recovery in case the user wanted to use a type-pattern in the switch construct, but didn't put a binding variable name after the type name. E.g.:
> 
> $ cat test/langtools/tools/javac/diags/examples/PatternExpected.java
> [snip]
> class PatternSwitch {
>     private void doSwitch(Object o) {
>         switch (o) {
>             case String: break;
>             default: break;
>         }
>     }
> }
> $ javac --enable-preview -source 17  test/langtools/tools/javac/diags/examples/PatternExpected.java
> test/langtools/tools/javac/diags/examples/PatternExpected.java:32: error: type pattern expected
>             case String: break;
>                  ^
> Note: test/langtools/tools/javac/diags/examples/PatternExpected.java uses preview features of Java SE 17.
> Note: Recompile with -Xlint:preview for details.
> 1 error

test/langtools/tools/javac/patterns/SwitchErrors-no-preview.out line 1:

> 1: SwitchErrors.java:35:31: compiler.err.preview.feature.disabled.plural: (compiler.misc.feature.pattern.switch)

I don't get why you want to test what happens when the `--enable-preview + source` options are not passed

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PR: https://git.openjdk.java.net/jdk/pull/4441