Introduce ++ operator into grammar

grammar/src/attributes.grm

@@ -12,5 +12,5 @@ annotation
   ;
 
 annotationEntry
-  : "@"? SimpleName{"."} typeArguments? valueArguments?
+  : "@"? ++ SimpleName{"."} typeArguments? valueArguments?
   ;

grammar/src/expressions.grm

@@ -126,11 +126,11 @@ atomicExpression
   ;
 
 labelReference
-  : "@" LabelName
+  : "@" ++ LabelName
   ;
 
 labelDefinition
-  : LabelName "@"
+  : LabelName ++ "@"
   ;
 
 literalConstant
@@ -246,9 +246,9 @@ valueArguments
 
 jump
   : "throw" expression
-  : "return" labelReference? expression?
-  : "continue" labelReference?
-  : "break" labelReference?
+  : "return" ++ labelReference? expression?
+  : "continue" ++ labelReference?
+  : "break" ++ labelReference?
 // yield ?
   ;
 

grammar/src/modifiers.grm

@@ -3,10 +3,14 @@
 */
 
 modifiers
-  : ("@"? modifier)*
+  : modifier*
   ;
 
 modifier
+  : "@"? ++ modifierKeyword
+  ;
+
+modifierKeyword
   : classModifier
   : accessModifier
   : varianceAnnotation

grammar/src/notation.grm

@@ -17,7 +17,8 @@ Operator `|` denotes _alternative_.<br>
 Operator `*` denotes _iteration_ (zero or more).<br>
 Operator `+` denotes _iteration_ (one or more).<br>
 Operator `?` denotes _option_ (zero or one).<br>
-alpha`{`beta`}` denotes a nonempty _beta_-separated list of _alpha_'s.
+alpha`{`beta`}` denotes a nonempty _beta_-separated list of _alpha_'s. <br>
+Operator ``++'' means that no space or comment allowed between operands.
 
 # Semicolons