Antlr4 Grammar for Function Application - antlr

Question

I'm trying to write a simple lambda calculus grammar (show below). The issue I am having is that function application seems to be treated as right associative instead of left associative e.g. "f 1 2" is parsed as (f (1 2)) instead of ((f 1) 2). ANTLR has an assoc option for tokens, but I don't see how that helps here since there is no operator for function application. Does anyone see a solution?
LAMBDA : '\\';
DOT : '.';
OPEN_PAREN : '(';
CLOSE_PAREN : ')';
fragment ID_START : [A-Za-z+\-*/_];
fragment ID_BODY : ID_START | DIGIT;
fragment DIGIT : [0-9];
ID : ID_START ID_BODY*;
NUMBER : DIGIT+ (DOT DIGIT+)?;
WS : [ \t\r\n]+ -> skip;
parse : expr EOF;
expr : variable #VariableExpr
| number #ConstantExpr
| function_def #FunctionDefinition
| expr expr #FunctionApplication
| OPEN_PAREN expr CLOSE_PAREN #ParenExpr
;
function_def : LAMBDA ID DOT expr;
number : NUMBER;
variable : ID;
Thanks!

Answer 1

this breaks 4.1's pattern matcher for left-recursion. cleaned up in main branch I believe. try downloading last master and build. CUrrently 4.1 generates:
expr[int _p]
: ( {} variable
| number
| function_def
| OPEN_PAREN expr CLOSE_PAREN
)
(
{2 >= $_p}? expr
)*
;
for that rule. expr ref in loop is expr[0] actually, which isn't right.