So you can see in the example above

So you can see in the example above that the AST for a WhileStatement looks kind of like this (excluding that expression gibberish for clarity):
If you were to add curly braces around the call to buz.doSomething()and click "Go" again, you'd see that the AST would change a bit. It'd look like this:
WhileStatement
Expression
Statement
Block
BlockStatement
Statement
StatementExpression

Ah ha! We see that the curly braces add a couple more AST nodes - a Block and a BlockStatement. So all we have to do is write a rule to detect a WhileStatement that has a Statement that's not followed by a Block, and we've got a rule violation.

By the way, all this structural information - i.e., the fact that a Statement may be followed a Block - is concisely defined in the EBNF grammar. So, for example, the Statement definition looks like this:
void Statement() :
{}
{
LOOKAHEAD( { isNextTokenAnAssert() } ) AssertStatement()
| LOOKAHEAD(2) LabeledStatement()
| Block()
| EmptyStatement()
| StatementExpression() ";"
| SwitchStatement()
| IfStatement()
| WhileStatement()
| DoStatement()
| ForStatement()
| BreakStatement()
| ContinueStatement()
| ReturnStatement()
| ThrowStatement()
| SynchronizedStatement()
| TryStatement()
}

結果 (中国語) 1:

所以你可以看到上面的示例中为 WhileStatement AST 看起来有点像这个 （不包括为清楚起见，表达胡言乱语）：如果你是添加大括号对 buz.doSomething () 的调用，并再次单击"转到"，你会看到 AST 会有点改变。看起来会像这样：WhileStatement表达式声明块BlockStatement声明StatementExpression啊哈哈 ！我们看到的大括号添加一对夫妇更多的 AST 节点-块和 BlockStatement。因此，所有我们要做是写一个规则来检测已不跟着一个块，声明的 WhileStatement 和我们有违反规则的行为。顺便问一下，这个结构的信息 — — 即事实的声明可能是跟着一个块 EBNF 语法中简要定义。因此，例如，语句定义看起来像这样：无效的 Statement()：{}{预测先行 ({isNextTokenAnAssert()}) AssertStatement()|LOOKAHEAD(2) LabeledStatement()|Block()|EmptyStatement()|StatementExpression()";"|SwitchStatement()|IfStatement()|WhileStatement()|DoStatement()|ForStatement()|BreakStatement()|ContinueStatement()|ReturnStatement()|ThrowStatement()|SynchronizedStatement()|TryStatement()}

結果 (中国語) 3:

所以你可以看到在上面的例子中，一个whilestatement AST看起来像这个（不包括表达清晰
胡言乱语）：如果你在调用布斯加花括号（）。然后单击“走”了，你会发现AST会改变一点。它会看起来像这样：
whilestatement
表达
声明
块
blockstatement
声明
statementexpression

啊啊啊啊啊！我们看到，大括号加几AST节点-一块和blockstatement。所以我们要做的是一个规则来检测whilestatement已经声明，这不是跟着一块写，我们已经有了一个违反规则。

的方式，所有这些结构信息-即，事实上，一个语句可以跟着一块简单的EBNF语法定义。所以，例如，语句定义看起来像这样：
无效statement()：
{ } {

前瞻（{ isnexttokenanassert() }）assertstatement()
|先行（2）labeledstatement()
| block()
| emptystatement()
| statementexpression()”；“
| switchstatement()
| ifstatement()
| whilestatement()
| dostatement()
| forstatement()
| breakstatement()
| continuestatement()
| returnstatement()
| throwstatement()
| synchronizedstatement()
| trystatement()
}