Consider this very simple grammar to recognize strings with no embedded '"'.
ANTLR seems to be generating an incorrect lexer for StringPart.
grammar small;
defaults
: StringPart EOF
;
StringPart
: ( ~ NonStringChars) *
;
fragment
NonStringChars
: '"'
;
Look inside smallLexer.java, and
// $ANTLR start "StringPart"
public final void mStringPart() throws RecognitionException {
try {
int _type = StringPart;
int _channel = DEFAULT_TOKEN_CHANNEL;
// /home/aph/ceylon/small.g:8:5: ( (~ NonStringChars )* )
// /home/aph/ceylon/small.g:8:10: (~ NonStringChars )*
{
// /home/aph/ceylon/small.g:8:10: (~ NonStringChars )*
loop1:
do {
int alt1=2;
int LA1_0 = input.LA(1);
if ( ((LA1_0>='\u0000' && LA1_0<='!')||(LA1_0>='#' &&
LA1_0<='\uFFFF')) ) {
alt1=1;
}
switch (alt1) {
case 1 :
// /home/aph/ceylon/small.g:8:12: ~ NonStringChars
{
// ********************************************** Here's the bug:
if ( (input.LA(1)>='\u0000' &&
input.LA(1)<='\u0004')||(input.LA(1)>='\u0006' && input.LA(1)<='\uFFFF') ) {
input.consume();
// **************************************************************
}
else {
MismatchedSetException mse = new
MismatchedSetException(null,input);
What on Earth is
input.LA(1)<='\u0004')||(input.LA(1)>='\u0006'
supposed to do? It clearly excludes control character 5, but why? If
I change the grammar for StringPart to
StringPart
: ( ~ '"') *
;
I get
if ( (input.LA(1)>='\u0000' &&
input.LA(1)<='!')||(input.LA(1)>='#' && input.LA(1)<='\uFFFF') ) {
input.consume();
which is right, I think. So, replacing NonStringChars with '"' in the
grammar fixes the problem.
This is all very strange. It seems that the parser generator is
inlining NonStringChars but getting it wrong.
This is ANTLR 3.2, by the way.
Andrew.
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