ANTLR4 - Mutually left-recursive grammar

Question

I am getting the error: The following sets of rules are mutually left-recursive [symbolExpression]. In my grammar, symbolExpression is directly left-recursive so shouldn't ANTLR4 be handling this?

Here are the relevant parts of my parser:

operation: 
       OPERATOR '(' (operation | values | value | symbolExpression) ')'                       #OperatorExpression
     | bracketedSymbolExpression                                                              #BracketedOperatorExpression
     ;

symbolExpression:
     (operation | values | value | symbolExpression) SYMBOL (operation | values | value | symbolExpression);

bracketedSymbolExpression:
     '(' (operation | values | value | symbolExpression) SYMBOL (operation | values | value | symbolExpression) ')';

list: '[' (operation | value) (',' (operation | value))* ']';

values: (operation | value) (',' (operation | value))+;

value:
     NUMBER
   | IDENTIFIER
   | list
   | object;

Answer 1

The elements 'symbolExpression' and 'operation' in the rule 'symbolExpression' are interdependently left recursive.

Without knowing the language specification, it is impossible to say whether the language itself is irrecoverably ambiguous.

Nonetheless, one avenue to try is to refactor the grammar to move repeated clauses, like

( operation | value )

and

(operation | values | value | symbolExpression)

to their own rules with the goal of unifying the 'operation' and 'symbolExpression' (and perhaps 'bracketedSymbolExpression') rules into a single rule -- a rule that is at most self left-recursive. Something like

a : value
  | LPAREN a* RPAREN
  | LBRACK a* LBRACK
  | a SYMBOL a
  | a ( COMMA a )+
  ;