Grammar.bnf

{
  classHeader="license.txt"
  generate=[java="8" names="long" visitor-value="R"]

  parserClass="org.intellij.grammar.parser.GrammarParser"
  parserUtilClass="org.intellij.grammar.parser.GrammarParserUtil"

  implements="org.intellij.grammar.psi.BnfComposite"
  extends="org.intellij.grammar.psi.impl.BnfCompositeImpl"

  psiClassPrefix="Bnf"
  psiImplClassSuffix="Impl"
  psiPackage="org.intellij.grammar.psi"
  psiImplPackage="org.intellij.grammar.psi.impl"
  psiImplUtilClass="org.intellij.grammar.psi.impl.GrammarPsiImplUtil"

  elementTypeHolderClass="org.intellij.grammar.psi.BnfTypes"
  elementTypePrefix="BNF_"
  elementTypeClass="org.intellij.grammar.psi.BnfCompositeElementType"
  tokenTypeClass="org.intellij.grammar.psi.BnfTokenType"
  
  tokens = [
    OP_EQ="="
    OP_IS="::="
    OP_OR="|"
    OP_OPT="?"
    OP_ONEMORE="+"
    OP_ZEROMORE="*"
    OP_AND="&"
    OP_NOT="!"
    SEMICOLON=";"
    LEFT_BRACE="{"
    RIGHT_BRACE="}"
    LEFT_BRACKET="["
    RIGHT_BRACKET="]"
    LEFT_PAREN="("
    RIGHT_PAREN=")"
    EXTERNAL_START="<<"
    EXTERNAL_END=">>"

    space='regexp:\s+'
    id="regexp:\w+"
    string="regexp:('([^'\\]|\\.)*'|\"([^\"\\]|\\\"|\\\'|\\)*\")"
    number="regexp:\d+"
    line_comment="regexp://.*"
    block_comment="regexp:/\*(.|\n)*\*/"
  ]

  implements("rule|attr")="org.intellij.grammar.psi.BnfNamedElement"
  extends("rule|attr")="org.intellij.grammar.psi.impl.BnfNamedImpl"
  mixin("reference_or_token")="org.intellij.grammar.psi.impl.BnfRefOrTokenImpl"
  mixin("string_literal_expression")="org.intellij.grammar.psi.impl.BnfStringImpl"
  extends("paren_.*expression")=parenthesized
}

external grammar ::= parseGrammar grammar_element
//grammar ::= grammar_element * // live preview root

private grammar_element ::= !<<eof>> (attrs | rule) {
  pin=1 recoverWhile=grammar_element_recover
}
private grammar_element_recover::=!('{'|rule_start)

rule ::= rule_start expression attrs? ';'? {pin=2}
private rule_start ::= modifier* id '::='
modifier ::= 'private' | 'external' | 'meta'
  | 'inner' | 'left' | 'upper' | 'fake'

attrs ::= '{' attr * '}' {pin=1}
attr ::= attr_start attr_value ';'? {
  pin=1 recoverWhile=attr_recover
}
private attr_start ::= id (attr_pattern '=' | '=') {
  pin(".*")="attr_pattern"
}
private attr_start_simple ::= id attr_pattern? '='
private attr_recover ::= !('}' | attr_start)
private attr_value ::= attr_value_inner !'='
private attr_value_inner ::= reference_or_token
  | literal_expression
  | value_list
attr_pattern ::= '(' string_literal_expression ')' {
  pin=1 methods=[literalExpression="string_literal_expression"]
}

value_list ::= '[' list_entry * ']' {pin=1 extends=expression}
list_entry ::= (id list_entry_tail? | string_literal_expression) ';'? {
  recoverWhile=list_entry_recover
  methods=[getReferences literalExpression="string_literal_expression"]
}
private list_entry_tail ::= '=' string_literal_expression {pin=1}
private list_entry_recover ::= !(']' | '}' | id | string)

expression ::= sequence choice?
sequence ::= option * {
  extends=expression recoverWhile=sequence_recover
}
private sequence_recover ::=
  !(';'|'|'|'('|')'|'['|']'|'{'|'}') grammar_element_recover
private option ::= predicate | paren_opt_expression | simple quantified?

left choice ::= ( '|' sequence ) + {pin(".*")=1 extends=expression}
left quantified ::= quantifier {extends=expression }
quantifier ::= '?' | '+' | '*'

predicate ::= predicate_sign simple {extends=expression}
predicate_sign ::= '&' | '!'

fake parenthesized ::= '(' expression ')' {extends=expression}
private simple ::= !(modifier* id '::=' ) reference_or_token
  | literal_expression
  | external_expression
  | paren_expression
external_expression ::= '<<' reference_or_token option * '>>' {
  pin=2 extends=expression methods=[refElement='/expression[0]' getArguments]
}
reference_or_token ::= id  {extends=expression methods=[resolveRule]}
literal_expression ::= string_literal_expression | number {extends=expression }
string_literal_expression ::= string {extends=literal_expression}
paren_expression ::= '(' expression ')' | '{' alt_choice_element '}' {pin(".*")=2}
paren_opt_expression ::= '[' expression ']' {pin=2}
private alt_choice_element ::= !attr_start_simple expression