checkInitializer_(type, declaration) {
    if (this.options_.blockBinding && type === CONST &&
        declaration.initializer === null) {
      this.reportError_(declaration.location,
                        'const variables must have an initializer');
      return false;
    }
    return true;
  }
Checks variable declaration

@param {TokenType} type
@param {VariableDeclaration} declaration
@return {boolan} Whether the initializer is correct.
@private