groovy-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jesper Steen Møller <>
Subject More Antlr4-based Groovy parser status update
Date Sun, 28 Feb 2016 11:55:16 GMT
Hi Groovy-Dev

Here’s another update on the progress on the Antlr4 parser, as maintained on
(in the antlr4 branch).
To play with it, try:

$ git clone -b antlr4
$ cd groovy
$ gradle -PuseAntlr4=true console

I’ve fixed a number of issues:
Support method pointer operator
Attributes/method/property names as strings/gstrings
Real support for unary plus and minus (mimics old parser’s behaviour)
Compilation units not ending with semicolon or newline
Slashy strings could span lines, confusing division statements and comments
I can now explore the new grammar and AST building using the Console, which is fun, but it’s
very easy to find unsupported constructs. Mapping out the full Groovy grammar from the documentation
alone is quite a task. Just today, I discovered lacking support for ‘assert’ and for ’super’-calls.
The smaller issues currently are:
Full Unicode letter support  for identifiers
Support identifiers as property names and map literal entry names

The bigger issue is with converting the ASTBuilder to pure Java, a task I havn’t started
yet. Actually, this poses a different question for AST generation: Whether to switch from
tree-walking the parse tree (so whole tree must be kept in memory), to the listener-based
approach, where the AST is built mostly bottom-up, ensuring smaller memory footprint.

So you can help me with a couple of answers:
Memory: Is this an issue I should be focusing on — and is there a test to baseline against?
I’ve discovered a small issue with unary syntax. Currently, nested unary expressions are
not supported without parenthesis: Try e.g. - -1 or + -1. Is this intentional, or just an
artifact of the precedence-refactored Java grammar?


View raw message