With the latest hourly build (antlr-03-16-2007.10):
lexer grammar x;
LT:
'<' ' '*
| ('<' IDENT) =>
'<' IDENT '>';
IDENT: 'a'+;
Produces the following error:
error(100): x.g:0:0: syntax error: buildnfa: <AST>:5:8: unexpected AST node: synpred1