I have a simple grammar (for demonstration)
grammar Test;
program
: expression* EOF
;
expression
: Identifier
| expression '(' expression? ')'
| '(' expression ')'
;
Identifier
: [a-zA-Z_] [a-zA-Z_0-9?]*
;
WS
: [ \r\t\n]+ -> channel(HIDDEN)
;
Obviously the second and third alternatives in the expression
rule are ambiguous. I want to resolve this ambiguity by permitting the second alternative only if an expression is immediately followed by a '('
.
So the following
bar(foo)
should match the second alternative while
bar
(foo)
should match the 1st and 3rd alternatives (even if the token between them is in the HIDDEN channel).
How can I do that? I have seen these ambiguities, between call expressions and parenthesized expressions, present in languages that have no (or have optional) expression terminator tokens (or rules) - example