By jjg on Oct 06, 2008
A while back, we created a new OpenJDK project, Compiler Grammar, so that we could investigate integrating an ANTLR grammar for Java into javac. Thanks to some hard work by our intern Yang Jiang, with assistance from Terence Parr, the initial results of that work are now available.
The grammar currently supports Java version 1.5, although the goal is to fully support the -source option and support older (and newer) versions of the language as well. Right now, the performance is slower than that of standard javac, so this will not be the default lexer and parser for javac for a while, but even so, it should prove an interesting code base for anyone wishing to experiment with potential new language features. And, it does mean that the grammar files being used have been fully tested\* in the context of a complete Java compiler.
We are also looking to align the grammar more closely with the grammar found in JLS.
This version of javac is in the langtools component of the compiler-grammar set of Mercurial OpenJDK repositories.
\*There are currently a few test failures in the regression test suite. Some are to be expected, because the error messages generated by the parser do not match the errors given by the standard version of javac; the other failures are being investigated.