Make StringLiteral.getLiteralValue thread safe

[martinlippert]

Fixes #3424 + slightly improved tests from #3509

The exact same issue happens for CharacterLiteral.charValue, for which I added a test case and a fix as well.

[jukzi]

As this PR adds API it would be good to get a review from someone else too. @mpalat

[mpalat]

@jukzi : I will take a look. @SarikaSinha had moved out of Eclipse Team "officially" sometime back although she contributes at her "free" time occasionally. So wouldn't bother her unless its really required and hence removed her name from the review.

[mpalat]

@martinlippert - As mentioned in the review comment in the AST, would not prefer this change. Since its just a couple of places - StringLiteral and CharacterLiteral, creating a new scanner from this.ast.scanner values would be better than having a convenience method at an API level. In case we need such similar changes later in other places, we can think of a convenience method in Scanner class (or a nested sub-class similar to VanguardScanner) - that would not constitute an API change since they are internal classes. So in short, would request to remove the API changes and create new Scanners at the charValue() and StringValue() methods.

[jukzi]

LGTM and no new API

[martinlippert]

And thanks a lot @jukzi and @mpalat for your quick feedback and the reviews here. Really awesome. And very much appreciated!!!

[mpalat]

Thanks @martinlippert for removing the new addition to API. However, about the addition of methods to Scanner, given @szarnekow feedback as well, I believe it's best to inline for now rather than adding methods to Scanner.

[martinlippert]

Thanks @martinlippert for removing the new addition to API. However, about the addition of methods to Scanner, given @szarnekow feedback as well, I believe it's best to inline for now rather than adding methods to Scanner.

Yepp, no problem. Last commit reverted, back at inline scanner creation now.

[iloveeclipse]

@martinlippert : could you please squash all 5 commits to a single one with appropriate commit message?
See https://github.com/eclipse-jdt/.github/blob/main/CONTRIBUTING.md#commit-message-recommendations

[martinlippert]

@martinlippert : could you please squash all 5 commits to a single one with appropriate commit message? See https://github.com/eclipse-jdt/.github/blob/main/CONTRIBUTING.md#commit-message-recommendations

Done

[iloveeclipse]

@mpalat : could you pleas update your review? Thanks.

[mpalat]

Yepp, no problem. Last commit reverted, back at inline scanner creation now.
Thanks @martinlippert !