Revisit formatter changes with introduction of 'when' clause in switch pattern expressions

[eclipse-jdt]

Revisit formatter changes with introduction of 'when' clause in switch pattern expressions

[mateusz-matela]

I tried to enable the test and change the line
case Triangle t&&(t.calculateArea() > 100) ->
into
case Triangle t when t.calculateArea() > 100 ->.
The formatter now crashes, because the when token is not of type TokenNameRestrictedIdentifierWhen (131), it's TokenNameIdentifier (19). Is this something to be fixed in the Scanner? I see it has a method called disambiguatedRestrictedIdentifierWhen(), so it looks like it attempts to take care of it.

After we resolve this, I wonder how to handle whitespace around the when keyboard. Using the settings for logical_operator is no longer intuitive. I think we can always add spaces, they're usually necessary anyway (except for when the pattern or expression is in parentheis).
Also, in JEP some examples keep the when clause in the same line as the case clause, while others put in in a new line, I guess we'll need a new formatter setting for that.

[jarthana]

Thanks @mateusz-matela. I will look into that and report back. There's no rush to work on the formatter yet as we are still in early stages of compiler support. You don't mind keeping this on your list till then, do you?

[jarthana]

Scanner went through some changes for this keyword. I tried this again but still tests are failing but looks like a different error now.

[mateusz-matela]

I checked again and it turned out that the Scanner returns proper tokens when previewEnabled is set to true, so I did that in the failing test and it works now. It's possible that was the problem from the beginning.
Please verify in the PR that I set this option properly (will it stay there forever, or be removed when we're out of beta? maybe it should be set somewhere else globally?)

[jarthana]

Looks good. Whenever the feature moves from preview to standard, we can remove the option. So, we can close this now?

[mateusz-matela]

I think so, as long as we don't forget to remove the option when appropriate :)