RFR: 8253584: Redunant errors for partial member selects

[Jan Lahoda]

For code like:
package t;

class Test {

    void t() {
        if (true) {
            s().
        } else {
        }
    }

    String s() {
        return null;
    }
}

(note the missing member name after `s().`), javac will produce a number of compile-time errors:
$ javac /tmp/Test.java

            s().
                ^

            s().
               ^

        } else {
         ^

        } else {
          ^

    String s() {
            ^

}
 ^
6 errors

The reason is that after not seeing an identifier after the `.` javac will skip the token that follows the dot. This
was done to improve errors in https://bugs.openjdk.java.net/browse/JDK-8081769 . But here, reading the next token will
skip the closing `}`, and the parser will de-synchronize with the braces, leading to the follow-up errors.

The proposal here is to handle incorrect `.class` specially, and avoid reading the next token when an identifier is no
specified in a member select, except when the next token is `class`.

The errors with this patch are:
$ javac /tmp/Test.java

            s().
                ^

            s().
               ^
2 errors

This seems much better.

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

Commit messages:
 - 8253584: Redunant errors for partial member selects

Changes: https://git.openjdk.java.net/jdk/pull/333/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=333&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253584
  Stats: 51 lines in 2 files changed: 48 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/333.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/333/head:pull/333

PR: https://git.openjdk.java.net/jdk/pull/333