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Visit website Recent posts Updated on $DATE date lightning-talk Personal blog, for development work Zola 2026-01-21T14:00:00+00:00 https://kemitix.net/tags/lightning-talk/atom.xml 2026-01-21T14:00:00+00:00 2026-01-21T14:00:00+00:00 Paul Campbell https://kemitix.net/blog/tree-type-lightning-talk/ <p>I just presented the following Lightning Talk for my <a href="https://crates.io/crates/tree-type">tree-type</a> crate.</p> <hr /> <h2 id="the-problem-string-based-paths-are-error-prone">The Problem: String-Based Paths Are Error-Prone</h2> <p>When working with filesystem paths in code, we typically use strings:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">update_project</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">root</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>Path</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Easy to make typos </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> changelog <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>CHANGLOG.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Oops! Missing &#39;E&#39; </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Easy to get case wrong </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> cargo <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Should be &quot;Cargo.toml&quot; </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> No IDE autocomplete </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> config <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>config<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>settings.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Errors discovered at runtime (or in production!) </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> content <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">fs<span class="z-punctuation z-accessor z-rust">::</span></span>read_to_string<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Runtime error! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p><strong>Problems:</strong></p> <ul> <li>❌ Typos caught at runtime</li> <li>❌ No IDE autocomplete</li> <li>❌ Easy to mix up similar paths</li> <li>❌ Refactoring is error-prone</li> <li>❌ No compile-time validation</li> </ul> <hr /> <h2 id="the-solution-tree-type">The Solution: tree-type</h2> <p>Define your project structure once, get type safety everywhere:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-keyword z-other z-rust">use</span> <span class="z-meta z-path z-rust">tree_type<span class="z-punctuation z-accessor z-rust">::</span></span>tree_type<span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> CurrentRoot <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>CHANGELOG.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> ChangeLogFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Cargo.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> CargoFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> config<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">settings</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>settings.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> SettingsFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></code></pre> <p>Now use it safely:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">update_project</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">root</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>CurrentRoot</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Type-safe access - impossible to typo! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> changelog<span class="z-punctuation z-separator z-rust">:</span> ChangeLogFile <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> IDE autocomplete works </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> cargo<span class="z-punctuation z-separator z-rust">:</span> CargoFile <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Nested navigation is type-safe </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> settings<span class="z-punctuation z-separator z-rust">:</span> SettingsFile <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">config</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">settings</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Compiler catches mistakes before code runs </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> content <span class="z-keyword z-operator z-assignment z-rust">=</span> changelog<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_to_string</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p><strong>Benefits:</strong></p> <ul> <li>✅ Compile-time path validation</li> <li>✅ IDE autocomplete for all paths</li> <li>✅ Impossible to typo filenames</li> <li>✅ Refactoring is safe</li> <li>✅ Each path has its own type</li> </ul> <hr /> <h2 id="real-example-cairn-project">Real Example: Cairn Project</h2> <p>From the <a href="https://codeberg.org/kemitix/cairn">cairn</a> release automation tool:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> CurrentRoot <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> jj<span class="z-keyword z-operator z-arithmetic z-rust">/</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>.jj<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> JujutsuRepoDir<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> git<span class="z-keyword z-operator z-arithmetic z-rust">/</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>.git<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> GitRepoDir<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>CHANGELOG.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> ChangeLogFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Cargo.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> CargoFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">ci_cache</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>.cairn-ci-cache<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> CiCacheFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Usage throughout the codebase </span></span><span class="z-source z-rust"><span class="z-keyword z-control z-rust">if</span> <span class="z-keyword z-operator z-logical z-rust">!</span><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span>root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">exists</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">return</span> <span class="z-support z-type z-rust">Err</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>CHANGELOG.md not found<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> content <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span>root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_to_string</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span>root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">ci_cache</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">write</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>cache_data</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p>Each file has its own type with built-in methods:</p> <ul> <li><code>.read_to_string()</code> - Read file contents</li> <li><code>.write()</code> - Write to file</li> <li><code>.exists()</code> - Check existence</li> <li><code>.remove()</code> - Delete file</li> <li>And more…</li> </ul> <hr /> <h2 id="feature-type-safe-navigation-with-parent">Feature: Type-Safe Navigation with parent()</h2> <p><strong>The Problem with Generic Paths:</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Generic approach - returns Option </span></span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> dir <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">GenericDir<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>/path/to/dir<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> parent <span class="z-keyword z-operator z-assignment z-rust">=</span> dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">parent</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Returns Option&lt;GenericDir&gt; </span></span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-keyword z-control z-rust">if</span> <span class="z-storage z-type z-rust">let</span> <span class="z-support z-type z-rust">Some</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>p</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-assignment z-rust">=</span> parent <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Have to handle None case </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></code></pre> <p><strong>tree-type Solution - Exact Parent Types:</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> ProjectRoot <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> src<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">lib</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>lib.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> LibFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">main</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>main.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> MainFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> project <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">ProjectRoot<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>/project<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> src <span class="z-keyword z-operator z-assignment z-rust">=</span> project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">src</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> lib_file <span class="z-keyword z-operator z-assignment z-rust">=</span> src<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lib</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> parent() returns exact parent type - no Option! </span></span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> src_dir<span class="z-punctuation z-separator z-rust">:</span> ProjectRootSrc <span class="z-keyword z-operator z-assignment z-rust">=</span> lib_file<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">parent</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> project_root<span class="z-punctuation z-separator z-rust">:</span> ProjectRoot <span class="z-keyword z-operator z-assignment z-rust">=</span> src_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">parent</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p><strong>Why this matters:</strong></p> <ul> <li>Compiler knows the structure</li> <li>No runtime checks needed</li> <li>Can’t accidentally navigate to wrong parent</li> <li>Type system enforces correct relationships</li> </ul> <hr /> <h2 id="feature-type-safe-directory-iteration-with-children">Feature: Type-Safe Directory Iteration with children()</h2> <p><strong>The Problem with read_dir():</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Generic read_dir returns untyped entries </span></span><span class="z-source z-rust"><span class="z-keyword z-control z-rust">for</span> entry <span class="z-keyword z-operator z-rust">in</span> src_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_dir</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> entry <span class="z-keyword z-operator z-assignment z-rust">=</span> entry<span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> What type is this? File? Directory? Which one? </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> No type safety, have to check at runtime </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></code></pre> <p><strong>tree-type Solution - Typed Children:</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> ProjectRoot <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> src<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">lib</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>lib.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> LibFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">main</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>main.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> MainFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">utils</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>utils.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> UtilsFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> src <span class="z-keyword z-operator z-assignment z-rust">=</span> project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">src</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> children() returns an iterator of the correct types! </span></span><span class="z-source z-rust"><span class="z-keyword z-control z-rust">for</span> child <span class="z-keyword z-operator z-rust">in</span> src<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">children</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">match</span> child <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">ProjectRootSrcChild<span class="z-punctuation z-accessor z-rust">::</span></span>Lib<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>lib_file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">=&gt;</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> lib_file is LibFile type </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Found lib: <span class="z-constant z-other z-placeholder z-rust">{}</span><span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-separator z-rust">,</span> lib_file<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_path</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">display</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">ProjectRootSrcChild<span class="z-punctuation z-accessor z-rust">::</span></span>Main<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>main_file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">=&gt;</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> main_file is MainFile type </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Found main: <span class="z-constant z-other z-placeholder z-rust">{}</span><span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-separator z-rust">,</span> main_file<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_path</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">display</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">ProjectRootSrcChild<span class="z-punctuation z-accessor z-rust">::</span></span>Utils<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>utils_file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">=&gt;</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> utils_file is UtilsFile type </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Found utils: <span class="z-constant z-other z-placeholder z-rust">{}</span><span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-separator z-rust">,</span> utils_file<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_path</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">display</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></code></pre> <p><strong>Benefits:</strong></p> <ul> <li>✅ Each child has its correct type</li> <li>✅ Exhaustive pattern matching</li> <li>✅ Compiler ensures you handle all cases</li> <li>✅ No runtime type checking needed</li> </ul> <hr /> <h2 id="feature-dynamic-ids-for-runtime-paths">Feature: Dynamic IDs for Runtime Paths</h2> <p>Sometimes you need paths determined at runtime. Here’s a real example from fireforge:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> AppDataDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> repos<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> AppReposDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span>owner<span class="z-punctuation z-separator z-rust">:</span> RepositoryOwner<span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> RepoOwnerDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span>name<span class="z-punctuation z-separator z-rust">:</span> RepositoryName<span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> RepoBaseDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> metadata<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> RepoMetadataDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>info.json<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> RepoMetadataFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> issues<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> RepoIssuesDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span>issue<span class="z-punctuation z-separator z-rust">:</span> IssueId<span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> RepoIssueDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>issue.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> RepoIssueFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Type-safe navigation with runtime IDs </span></span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> app_data <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">AppDataDir<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>/data<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> owner_dir <span class="z-keyword z-operator z-assignment z-rust">=</span> app_data<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">repos</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">owner</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>kemitix<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> repo_dir <span class="z-keyword z-operator z-assignment z-rust">=</span> owner_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">name</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>tree-type<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> metadata<span class="z-punctuation z-separator z-rust">:</span> RepoMetadataFile <span class="z-keyword z-operator z-assignment z-rust">=</span> repo_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">metadata</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> issue_dir <span class="z-keyword z-operator z-assignment z-rust">=</span> repo_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">metadata</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">issues</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">issue</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-constant z-numeric z-integer z-decimal z-rust">42</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> issue_file<span class="z-punctuation z-separator z-rust">:</span> RepoIssueFile <span class="z-keyword z-operator z-assignment z-rust">=</span> issue_dir<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">file</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Each level is still type-safe! </span></span><span class="z-source z-rust"><span class="z-support z-macro z-rust">assert_eq!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> issue_file<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_path</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-separator z-rust">,</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> <span class="z-meta z-path z-rust">Path<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>/data/repos/kemitix/tree-type/metadata/issues/42/issue.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p><strong>Benefits:</strong></p> <ul> <li>✅ Runtime flexibility with compile-time safety</li> <li>✅ Nested dynamic IDs (multiple levels) - unlimited with <code>codegen-v2</code> feature</li> <li>✅ Type-safe navigation at every level</li> <li>✅ IDE autocomplete still works</li> </ul> <p><strong>Note:</strong> Default code generation supports up to 3 levels of dynamic ID nesting. Enable the <code>codegen-v2</code> feature for unlimited nesting depth.</p> <hr /> <h2 id="feature-extending-generated-types-with-custom-methods">Feature: Extending Generated Types with Custom Methods</h2> <p>Since generated types exist in your crate, you can add your own methods:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> ProjectRoot <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Cargo.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> CargoFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> src<span class="z-keyword z-operator z-arithmetic z-rust">/</span> <span class="z-keyword z-operator z-rust">as</span> SrcDir <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">lib</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>lib.rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-rust">as</span> LibFile<span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Add custom methods to generated types </span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-storage z-type z-impl z-rust">impl</span> </span><span class="z-meta z-impl z-rust"><span class="z-entity z-name z-impl z-rust">CargoFile</span> </span><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-modifier z-rust">pub</span> <span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">parse_version</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-support z-type z-rust">String</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> content <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_to_string</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Parse version from Cargo.toml </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-type z-rust">Ok</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-support z-function z-rust">extract_version</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>content</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-modifier z-rust">pub</span> <span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">update_version</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span>, <span class="z-variable z-parameter z-rust">new_version</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span><span class="z-storage z-type z-rust">str</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> content <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_to_string</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> updated <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-support z-function z-rust">replace_version</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>content<span class="z-punctuation z-separator z-rust">,</span> new_version</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">write</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>updated</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-storage z-type z-impl z-rust">impl</span> </span><span class="z-meta z-impl z-rust"><span class="z-entity z-name z-impl z-rust">SrcDir</span> </span><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-modifier z-rust">pub</span> <span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">count_rust_files</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-storage z-type z-rust">usize</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-type z-rust">Ok</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">read_dir</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">filter</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-function z-closure z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">|</span></span></span><span class="z-meta z-function z-closure z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-variable z-parameter z-rust">e</span><span class="z-punctuation z-section z-parameters z-end z-rust">|</span></span> </span><span class="z-meta z-function z-closure z-rust">e<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">path</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">extension</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-keyword z-operator z-comparison z-rust">==</span> <span class="z-support z-type z-rust">Some</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>rs<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">count</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Use your custom methods </span></span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> project <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">ProjectRoot<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>/project<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> version <span class="z-keyword z-operator z-assignment z-rust">=</span> project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">parse_version</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">update_version</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>0.2.0<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> file_count <span class="z-keyword z-operator z-assignment z-rust">=</span> project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">src</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">count_rust_files</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p><strong>Benefits:</strong></p> <ul> <li>✅ Domain-specific operations on your types</li> <li>✅ Encapsulate business logic with filesystem structure</li> <li>✅ Type safety extends to your custom methods</li> <li>✅ Clean API that combines navigation and operations</li> </ul> <hr /> <h2 id="feature-file-operations-with-compile-time-safety">Feature: File Operations with Compile-Time Safety</h2> <p><strong>Before (string-based):</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">process_files</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">root</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>Path</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Can pass wrong file to wrong function </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> changelog <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>CHANGELOG.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> cargo <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>Cargo.toml<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Compiler can&#39;t help if you mix them up </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">parse_cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Runtime error! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">update_changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Runtime error! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p><strong>After (tree-type):</strong></p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">process_files</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">root</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>CurrentRoot</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> changelog<span class="z-punctuation z-separator z-rust">:</span> ChangeLogFile <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> cargo<span class="z-punctuation z-separator z-rust">:</span> CargoFile <span class="z-keyword z-operator z-assignment z-rust">=</span> root<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Compiler enforces correct types </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">parse_cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>cargo</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> ✅ Correct </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">update_changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>changelog</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> ✅ Correct </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> These won&#39;t compile: </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> parse_cargo(&amp;changelog)?; // ❌ Compile error! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> update_changelog(&amp;cargo)?; // ❌ Compile error! </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">parse_cargo</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">file</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>CargoFile</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-comment z-block z-rust"><span class="z-punctuation z-definition z-comment z-rust">/*</span> ... <span class="z-punctuation z-definition z-comment z-rust">*/</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">update_changelog</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-variable z-parameter z-rust">file</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-keyword z-operator z-rust">&amp;</span>ChangeLogFile</span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-comment z-block z-rust"><span class="z-punctuation z-definition z-comment z-rust">/*</span> ... <span class="z-punctuation z-definition z-comment z-rust">*/</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p><strong>What you get:</strong></p> <ul> <li>Different types for different files</li> <li>Can’t accidentally pass wrong file to wrong function</li> <li>Compiler catches mistakes before code runs</li> <li>Refactoring is safe - rename type, compiler finds all uses</li> </ul> <hr /> <h2 id="summary-why-tree-type">Summary: Why tree-type?</h2> <p><strong>Type Safety Benefits:</strong></p> <ol> <li><strong>Compile-time validation</strong> - Catch path errors before runtime</li> <li><strong>IDE autocomplete</strong> - Discover available paths as you type</li> <li><strong>Refactoring safety</strong> - Rename types, compiler finds all uses</li> <li><strong>Impossible to typo</strong> - Filenames defined once, used safely everywhere</li> <li><strong>Type-safe navigation</strong> - <code>parent()</code> returns exact types, no Option needed</li> <li><strong>Dynamic flexibility</strong> - Runtime IDs with compile-time structure</li> <li><strong>Function safety</strong> - Can’t pass wrong file type to wrong function</li> </ol> <p><strong>When to use:</strong></p> <ul> <li>✅ Projects with fixed directory structures</li> <li>✅ Build tools and automation</li> <li>✅ Configuration management</li> <li>✅ Test fixtures and data directories</li> <li>✅ Any code that works with known filesystem layouts</li> </ul> <p><strong>When NOT to use:</strong></p> <ul> <li>❌ Completely dynamic/unknown directory structures</li> <li>❌ User-provided arbitrary paths</li> <li>❌ Simple scripts with 1-2 paths</li> </ul> <hr /> <h2 id="getting-started">Getting Started</h2> <pre data-lang="toml" class="language-toml z-code"><code class="language-toml" data-lang="toml"><span class="z-source z-toml"><span class="z-punctuation z-definition z-table z-begin z-toml">[</span><span class="z-meta z-tag z-table z-toml"><span class="z-entity z-name z-table z-toml">dependencies</span></span><span class="z-punctuation z-definition z-table z-end z-toml">]</span> </span><span class="z-source z-toml"><span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">tree-type</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>0.4<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span> </span><span class="z-source z-toml"> </span><span class="z-source z-toml"><span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> Optional features</span> </span><span class="z-source z-toml"><span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> tree-type = { version = &quot;0.4&quot;, features = [&quot;serde&quot;, &quot;enhanced-errors&quot;, &quot;walk&quot;, &quot;pattern-validation&quot;, &quot;codegen-v2&quot;] }</span> </span></code></pre> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-keyword z-other z-rust">use</span> <span class="z-meta z-path z-rust">tree_type<span class="z-punctuation z-accessor z-rust">::</span></span>tree_type<span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">tree_type!</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> MyProject <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> src<span class="z-keyword z-operator z-arithmetic z-rust">/</span><span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> target<span class="z-keyword z-operator z-arithmetic z-rust">/</span><span class="z-punctuation z-separator z-rust">,</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-support z-function z-rust">readme</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>README.md<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> project <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">MyProject<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>project_root</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">project<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">sync</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Creates all directories and required files </span></span></code></pre> <p><strong>Optional Features:</strong></p> <ul> <li><code>serde</code> - Serialize/deserialize support</li> <li><code>enhanced-errors</code> - Better error messages with context</li> <li><code>walk</code> - Directory traversal methods</li> <li><code>pattern-validation</code> - Regex validation for dynamic IDs</li> <li><code>codegen-v2</code> - Unlimited dynamic ID nesting depth</li> </ul> <p><strong>Learn more:</strong></p> <ul> <li>Crate: <a href="https://crates.io/crates/tree-type">crates.io/crates/tree-type</a></li> <li>Docs: <a href="https://docs.rs/tree-type">docs.rs/tree-type</a></li> <li>Source: <a href="https://codeberg.org/kemitix/tree-type">codeberg.org/kemitix/tree-type</a></li> </ul> <hr /> <h2 id="q-a-anticipated-questions">Q&amp;A - Anticipated Questions</h2> <p><strong>Q: Does this work with existing codebases?</strong> A: Yes! You can gradually adopt tree-type. Define types for your structure, then refactor incrementally. Old string-based code continues to work.</p> <p><strong>Q: What about performance?</strong> A: Zero runtime overhead. tree-type is a compile-time abstraction - generated code is as efficient as hand-written PathBuf operations.</p> <p><strong>Q: Can I use this with other languages?</strong> A: tree-type is Rust-specific (uses procedural macros). The concept could be adapted to other languages with strong type systems (TypeScript, Kotlin, etc.).</p> <p><strong>Q: What if my directory structure changes?</strong> A: Update the tree_type! definition, and the compiler will show you everywhere that needs updating. This is a feature - you can’t forget to update code!</p> <p><strong>Q: Does it work on Windows?</strong> A: Yes! tree-type uses Rust’s standard Path/PathBuf which handle platform differences automatically.</p> <p><strong>Q: Can I have optional files/directories?</strong> A: Yes! Use <code>#[required]</code> attribute for must-exist paths, or check <code>.exists()</code> for optional ones. The <code>sync()</code> method only creates required paths.</p> <p><strong>Q: What about symbolic links?</strong> A: Supported with <code>#[symlink(target)]</code> attribute (Unix only). tree-type handles symlink creation and validation.</p> <hr /> <p><strong>Questions?</strong></p>