RFR: 8267580: The method JavacParser#peekToken is wrong when the first parameter is not zero

[Maurizio Cimadamore]

On Sun, 23 May 2021 14:38:18 GMT, Guoxiong Li <gli at openjdk.org> wrote:

> Hi all,
> 
> The method `JavacParser#peekToken(int lookahead, Predicate<TokenKind>... kinds)` succeeds only when the first parameter `lookahead` is zero. If the `lookahead` is not zero, it is wrong and returns unexpected result.
> 
> The parameter `kinds` should not be dereferenced by `lookahead` and should be always started at zero.
> 
> But currently, the method `JavacParser#peekToken(int lookahead, Predicate<TokenKind>... kinds)` has not been used so that this issue doesn't effect the parser.
> 
> An alternative way:  remove the following methods, because they are not used.
> 
>     protected boolean peekToken(Predicate<TokenKind>... kinds)
>     protected boolean peekToken(int lookahead, Predicate<TokenKind>... kinds) 
> 
> 
> To test this patch, we can comment out the following methods  and  run the tests locally.
> Note: some methods may need to add `@SuppressWarnings("unchecked")`.
> 
>     protected boolean peekToken(Predicate<TokenKind> tk1, Predicate<TokenKind> tk2, Predicate<TokenKind> tk3) {
>         return peekToken(0, tk1, tk2, tk3);
>     }
> 
>     protected boolean peekToken(int lookahead, Predicate<TokenKind> tk1, Predicate<TokenKind> tk2, Predicate<TokenKind> tk3) {
>         return tk1.test(S.token(lookahead + 1).kind) &&
>                 tk2.test(S.token(lookahead + 2).kind) &&
>                 tk3.test(S.token(lookahead + 3).kind);
>     }
> 
> 
> Thanks for your review.
> 
> Best Regards,
> -- Guoxiong

Looks good - I wonder if we could rewrite all the other routines in terms of this one, rather than having a bunch of different related methods bottoming out in the same code?

-------------

Marked as reviewed by mcimadamore (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4158