TypePHP 编译器
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37 lines
5.0 KiB
37 lines
5.0 KiB
<!doctype html><html lang="zh"><head><meta charset="utf-8">
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<title>AST 转换（Lowering）</title>
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<body><div class="wrap"><h1>AST 转换（Lowering）</h1>
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<p>在 <code>doConvert()</code> 遍历 AST 时，<code>src/Transform/Visitor.php</code> 作为 <code>NodeVisitor</code> 挂载在遍历链上，对节点做<strong>编译期改写（lowering）</strong>——把 PHP 8.x 的高层语法（属性钩子、构造函数提升、getter、编译期属性等）降级为编译器能直接翻译的普通结构。</p>
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<p>Sources: <a href="file:///D:\git\php\aot-compiler\src\Transform\Visitor.php#L19-L36">src/Transform/Visitor.php</a> · <a href="file:///D:\git\php\aot-compiler\src\Translator.php#L2462">src/Translator.php</a></p>
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<h2>两个遍历钩子</h2>
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<p><code>Visitor</code> 实现 <code>enterNode()</code> 与 <code>leaveNode()</code> 两阶段处理：</p>
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<ul><li><strong>enterNode</strong>（进入节点前）：校验 + 即时 lowering。依次调用 <code>CompileTimeAttribute::validateNode</code>、<code>FunctionAttributeLowering::lower</code>、<code>GetterLowering::validateTarget</code>、<code>PropertyMethodLowering::validateTarget</code>、<code>ConstructorLowering::validateTarget</code>。</li><li><strong>leaveNode</strong>（离开节点后）：对函数/闭包做 <code>ParameterValidationLowering</code>；对类/属性做 <code>PropertyHookLowering</code>、<code>GetterLowering</code>、<code>PropertyMethodLowering</code>，把钩子属性、getter、提升属性改写成方法或标记。</li></ul>
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<p>Sources: <a href="file:///D:\git\php\aot-compiler\src\Transform\Visitor.php#L28-L80">src/Transform/Visitor.php</a></p>
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<h2>Lowering 算子清单</h2>
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<table><thead><tr><th>类</th><th>作用</th></tr></thead><tbody><tr><td><code>CompileTimeAttribute</code> / <code>CompileTimeAttributeRegistry</code></td><td>识别并校验编译期属性（如 <code>Any</code>、<code>MustUse</code>）</td></tr><tr><td><code>FunctionAttributeLowering</code></td><td>处理函数上的编译期属性</td></tr><tr><td><code>ConstructorLowering</code></td><td>处理构造函数提升参数</td></tr><tr><td><code>GetterLowering</code></td><td><code>get</code> 钩子属性 → getter 方法</td></tr><tr><td><code>PropertyHookLowering</code></td><td><code>get</code>/<code>set</code> 钩子属性 → 访问器方法</td></tr><tr><td><code>PropertyMethodLowering</code></td><td>属性 ↔ 方法互转</td></tr><tr><td><code>ParameterValidationLowering</code></td><td>参数类型校验，拒绝箭头函数误用</td></tr><tr><td><code>PrinterLowering</code> / <code>ValidateLowering</code></td><td>打印/校验相关降级</td></tr><tr><td><code>ArrayableLowering</code> / <code>NotEmptyLowering</code> / <code>NotNullLowering</code></td><td>特定表达式降级</td></tr><tr><td><code>RuntimeAttributeFactoryLowering</code></td><td>运行时工厂属性（遍历链上独立挂载）</td></tr></tbody></table>
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<p>Sources: <a href="file:///D:\git\php\aot-compiler\src\Transform">src/Transform/</a> · <a href="file:///D:\git\php\aot-compiler\src\Translator.php#L2467">src/Translator.php</a></p>
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<h2>顺序意义</h2>
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<p>Lowering 必须早于 C++ 生成：例如属性钩子若不先降级成方法，后续 <code>genClassWrapper</code> 就无法生成对应的 C++ 访问逻辑。它处在 <a href="pages/parser.html">解析器与 AST</a> 之后、<a href="pages/generator.html">代码生成</a> 之前。</p>
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<h2>相关阅读</h2>
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<ul><li>编译期属性语义 → <a href="pages/compile-time-attributes.html">编译期属性</a></li><li>降级后如何发射 C++ → <a href="pages/generator.html">生成器总览</a></li><li>常量表达式校验 → <a href="pages/type-check.html">类型检查与兼容</a></li></ul></div></body></html> |