Is Java grammar somehow finished?

[dims12]

Hi! I noticed that additiveExpression is never used here: https://github.com/antlr/grammars-v4/blob/master/java/java8/Java8Parser.g4#L1276`

(Used only in itself and in shiftExpression)

Is it by design of Java grammar is far from completeness?

[msagca]

Hi @dims12

additiveExpression is referenced by shiftExpression which is referenced by relationalExpression which is referenced by equalityExpression and so on. The grammar is designed this way because the operator precedence is important in order for the resulting parse tree to be correct. shiftExpression can be unfolded as follows:

shiftExpression
: unaryExpression
| shiftExpression ('*' | '/' | '%') shiftExpression
| shiftExpression ('+' | '-') shiftExpression
| shiftExpression ('<<' | '>>' | '>>>') shiftExpression
;

Similarly, we can rewrite the expression rule by performing unfold transforms and get the following more compact form:

expression
: lambdaExpression
| unaryExpression
| expression ('*' | '/' | '%') expression
| expression ('+' | '-') expression
| expression ('<<' | '>>' | '>>>') expression
| expression ('<' | '>' | '<=' | '>=' | 'instanceof') expression
| expression ('==' | '!=') expression
| expression '&' expression
| expression '^' expression
| expression '|' expression
| expression '&&' expression
| expression '||' expression
| <assoc=right> expression '?' expression ':' expression
| leftHandSide ('=' | '*=' | '/=' | '%=' | '+=' | '-=' | '<<=' | '>>=' | '>>>=' | '&=' | '^=' | '|=') expression
;

[KvanTTT]

I don't recommend using this grammar because it's slow and outdated. Use java instead.