[antlr-interest] AST rewrite rules issue with -> ^('+' $elts+)

[Damien]

Hello,

I'm writing a grammar for a calculator.

I have the following working:

mulExpr    :    atom ('*' (atom))+ -> ^('*' atom+);

which is equivalent to the following, also working:

mulExpr    :    elts+=atom ('*' (elts+=atom))+ -> ^('*' $elts+);

I have an issue with the following:

addExpr    :     (elts+=mulExpr | elts+=atom) ('+'  (elts+=mulExpr | 
elts+=atom))* -> ^('+' $elts+);

If I don't comment out the rewite rule above, the AST is empty.

Why is this wrong?

Thanks a lot


Complete grammar:
grammar Expr;

options { output=AST; backtrack=true; } //k=2;

prog    :    stmt+;

stmt    :    expr (NEWLINE | EOF);

expr    :    addExpr;

parExpr    :    '(' e=expr ')' -> $e
    ;

addExpr    :    //'-'? (mulExpr | atom) (('+' | '-')  (mulExpr | atom))*
        (elts+=mulExpr | elts+=atom) ('+' (elts+=mulExpr | elts+=atom))* 
-> ^('+' $elts+)
    ;

mulExpr    :    atom ('*' (atom))+ -> ^('*' atom+)
        ;

functionExpr
    :    ID '(' expr (',' expr)* ')' -> ^(ID expr+)
    ;

atom    :    INT | ID | functionExpr | parExpr
    ;
   
ID    :    ('a'..'z')+;
INT    :    '0'..'9'+;
NEWLINE    :    '\r'? '\n';
WS    :    (' ')+ {skip();};