Antlr4 expressions are chaining - antlr4

Question

from what i have read the way i defined my 'expression' this should provide me with the following:
This is my input:
xyz = a + b + c + d
This should be my output:
xyz = ( ( a + b ) + ( c + d) )
But instead i get:
xyz = ( a + (b + (c + d) ) )
I bet this has been solved before and i just wasnt able to find the solution.
statementList : s=statement sl=statementList #multipleStatementList
| s=statement #singleStatementList
;
statement : statementAssign
| statementIf
;
statementAssign : var=VAR ASSIGN expr=expression #overwriteStatementAssign
| var=VAR PLUS ASSIGN expr=expression #addStatementAssign
| var=VAR MINUS ASSIGN expr=expression #subStatementAssign
;
;
expression : BRACKET_OPEN expr=expression BRACKET_CLOSE #priorityExp
| left=expression operand=('*'|'/') right=expression #mulDivExp
| left=expression operand=('+'|'-') right=expression #addSubExp
| <assoc=right> left=expression POWER right=expression #powExp
| variable=VAR #varExp
| number=NUMBER #numExp
;
BRACKET_OPEN : '(' ;
BRACKET_CLOSE : ')' ;
ASTERISK : '*' ;
SLASH : '/' ;
PLUS : '+' ;
MINUS : '-' ;
POWER : '^' ;
MODULO : '%' ;
ASSIGN : '=' ;
NUMBER : [0-9]+ ;
VAR : [a-z][a-zA-Z0-9\-]* ;
WS : [ \t\r\n]+ -> skip ; // skip spaces, tabs, newlines

Answer 1

If you want the expression
xyz = ( ( a + b ) + ( c + d) )
Then you'll need to control the binding of the + operator with parentheses just as you've done in your expected output. Otherwise, with
xyz = ( a + (b + (c + d) ) )
is the way the parser is going to parse it because all the + operators have the same precedence, and the parser continues parsing until it reaches the end of the expression.
It recursively applies
left=expression operand=('+'|'-') right=expression
until the expression is completed.
and you get the grouping you got. So use those parentheses, that's what they're for if you want to force the order of expression evaluation. ;)
If you change your input to
xyz = a * b + c + d
you'll see what I mean about the precedence, because the multiplication rule appears before the addition rule -- and hence binds earlier -- which is a mathematical convention (lacking parentheses to group terms.)
You're doing it right and the parser is too. Just group what you want if you want a specific binding order.