feat(downloader): wire as_* downcasts for file/archive/path/git downloaders

Override DownloaderInterface's as_change_report_interface /
as_vcs_capable_downloader_interface / as_dvcs_downloader_interface so
PHP-style instanceof checks resolve to the concrete sub-interface:
FileDownloader and the six archive downloaders (Zip/Tar/Gzip/Xz/Rar/Phar)
plus PathDownloader gain ChangeReportInterface (archives/path delegate to
the inner FileDownloader), PathDownloader exposes VcsCapableDownloaderInterface,
and GitDownloader exposes DvcsDownloaderInterface.

The default None impls remain correct for downloaders that do not
implement a given sub-interface, so their stale TODO markers are dropped.
VCS downloaders' ChangeReport/VcsCapable conformance follows separately.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

10 files changed, 121 insertions, 3 deletions

diff --git a/crates/shirabe/src/downloader/downloader_interface.rs b/crates/shirabe/src/downloader/downloader_interface.rs
index 986db28..873438e 100644
--- a/crates/shirabe/src/downloader/downloader_interface.rs
+++ b/crates/shirabe/src/downloader/downloader_interface.rs
@@ -80,19 +80,16 @@ pub trait DownloaderInterface: std::fmt::Debug {
         prev_package: Option<PackageInterfaceHandle>,
     ) -> anyhow::Result<Option<PhpMixed>>;
 
-    /// TODO(phase-b): runtime downcast helpers for PHP `instanceof` checks.
     fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
         None
     }
 
-    /// TODO(phase-b): runtime downcast helpers for PHP `instanceof` checks.
     fn as_vcs_capable_downloader_interface(
         &self,
     ) -> Option<&dyn crate::downloader::VcsCapableDownloaderInterface> {
         None
     }
 
-    /// TODO(phase-b): runtime downcast helpers for PHP `instanceof` checks.
     fn as_dvcs_downloader_interface(
         &self,
     ) -> Option<&dyn crate::downloader::DvcsDownloaderInterface> {
diff --git a/crates/shirabe/src/downloader/file_downloader.rs b/crates/shirabe/src/downloader/file_downloader.rs
index dadf8fb..5b66a9f 100644
--- a/crates/shirabe/src/downloader/file_downloader.rs
+++ b/crates/shirabe/src/downloader/file_downloader.rs
@@ -153,6 +153,10 @@ impl DownloaderInterface for FileDownloader {
         "dist".to_owned()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     /// @inheritDoc
     async fn download(
         &self,
diff --git a/crates/shirabe/src/downloader/git_downloader.rs b/crates/shirabe/src/downloader/git_downloader.rs
index ed6f913..6d545ce 100644
--- a/crates/shirabe/src/downloader/git_downloader.rs
+++ b/crates/shirabe/src/downloader/git_downloader.rs
@@ -1380,6 +1380,12 @@ impl crate::downloader::DownloaderInterface for GitDownloader {
         todo!()
     }
 
+    fn as_dvcs_downloader_interface(
+        &self,
+    ) -> Option<&dyn crate::downloader::DvcsDownloaderInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         _package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/gzip_downloader.rs b/crates/shirabe/src/downloader/gzip_downloader.rs
index 00adca9..337e298 100644
--- a/crates/shirabe/src/downloader/gzip_downloader.rs
+++ b/crates/shirabe/src/downloader/gzip_downloader.rs
@@ -3,6 +3,7 @@
 use crate::cache::Cache;
 use crate::config::Config;
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::FileDownloader;
 use crate::event_dispatcher::EventDispatcher;
 use crate::io::IOInterface;
@@ -129,12 +130,26 @@ impl GzipDownloader {
     }
 }
 
+impl ChangeReportInterface for GzipDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 #[async_trait::async_trait(?Send)]
 impl crate::downloader::DownloaderInterface for GzipDownloader {
     fn get_installation_source(&self) -> String {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/path_downloader.rs b/crates/shirabe/src/downloader/path_downloader.rs
index c50856e..3eb2a48 100644
--- a/crates/shirabe/src/downloader/path_downloader.rs
+++ b/crates/shirabe/src/downloader/path_downloader.rs
@@ -14,6 +14,7 @@ use crate::cache::Cache;
 use crate::config::Config;
 use crate::dependency_resolver::operation::InstallOperation;
 use crate::dependency_resolver::operation::UninstallOperation;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::DownloaderInterface;
 use crate::downloader::FileDownloader;
 use crate::downloader::VcsCapableDownloaderInterface;
@@ -534,6 +535,16 @@ impl VcsCapableDownloaderInterface for PathDownloader {
     }
 }
 
+impl crate::downloader::ChangeReportInterface for PathDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> anyhow::Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 // TODO(phase-b): wire up PathDownloader trait properly. PathDownloader extends FileDownloader and
 // overrides download/install/remove with &mut self signatures that diverge from the trait. The
 // trait methods here delegate to the inner FileDownloader; the bespoke overrides on the struct
@@ -544,6 +555,16 @@ impl DownloaderInterface for PathDownloader {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
+    fn as_vcs_capable_downloader_interface(
+        &self,
+    ) -> Option<&dyn crate::downloader::VcsCapableDownloaderInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/phar_downloader.rs b/crates/shirabe/src/downloader/phar_downloader.rs
index 6a4ac97..46fdd84 100644
--- a/crates/shirabe/src/downloader/phar_downloader.rs
+++ b/crates/shirabe/src/downloader/phar_downloader.rs
@@ -3,6 +3,7 @@
 use crate::cache::Cache;
 use crate::config::Config;
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::DownloaderInterface;
 use crate::downloader::FileDownloader;
 use crate::event_dispatcher::EventDispatcher;
@@ -63,12 +64,26 @@ impl PharDownloader {
     }
 }
 
+impl ChangeReportInterface for PharDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 #[async_trait::async_trait(?Send)]
 impl DownloaderInterface for PharDownloader {
     fn get_installation_source(&self) -> String {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/rar_downloader.rs b/crates/shirabe/src/downloader/rar_downloader.rs
index 9ce6c51..4385bc3 100644
--- a/crates/shirabe/src/downloader/rar_downloader.rs
+++ b/crates/shirabe/src/downloader/rar_downloader.rs
@@ -3,6 +3,7 @@
 use crate::cache::Cache;
 use crate::config::Config;
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::FileDownloader;
 use crate::event_dispatcher::EventDispatcher;
 use crate::io::IOInterface;
@@ -143,12 +144,26 @@ impl RarDownloader {
     }
 }
 
+impl ChangeReportInterface for RarDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 #[async_trait::async_trait(?Send)]
 impl crate::downloader::DownloaderInterface for RarDownloader {
     fn get_installation_source(&self) -> String {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/tar_downloader.rs b/crates/shirabe/src/downloader/tar_downloader.rs
index 07d8a5f..6cf1176 100644
--- a/crates/shirabe/src/downloader/tar_downloader.rs
+++ b/crates/shirabe/src/downloader/tar_downloader.rs
@@ -3,6 +3,7 @@
 use crate::cache::Cache;
 use crate::config::Config;
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::DownloaderInterface;
 use crate::downloader::FileDownloader;
 use crate::event_dispatcher::EventDispatcher;
@@ -58,12 +59,26 @@ impl TarDownloader {
     }
 }
 
+impl ChangeReportInterface for TarDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 #[async_trait::async_trait(?Send)]
 impl DownloaderInterface for TarDownloader {
     fn get_installation_source(&self) -> String {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/xz_downloader.rs b/crates/shirabe/src/downloader/xz_downloader.rs
index ac8b6ba..976497a 100644
--- a/crates/shirabe/src/downloader/xz_downloader.rs
+++ b/crates/shirabe/src/downloader/xz_downloader.rs
@@ -3,6 +3,7 @@
 use crate::cache::Cache;
 use crate::config::Config;
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::FileDownloader;
 use crate::event_dispatcher::EventDispatcher;
 use crate::io::IOInterface;
@@ -77,12 +78,26 @@ impl XzDownloader {
     }
 }
 
+impl ChangeReportInterface for XzDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 #[async_trait::async_trait(?Send)]
 impl crate::downloader::DownloaderInterface for XzDownloader {
     fn get_installation_source(&self) -> String {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,
diff --git a/crates/shirabe/src/downloader/zip_downloader.rs b/crates/shirabe/src/downloader/zip_downloader.rs
index 17eeae5..3fda248 100644
--- a/crates/shirabe/src/downloader/zip_downloader.rs
+++ b/crates/shirabe/src/downloader/zip_downloader.rs
@@ -1,6 +1,7 @@
 //! ref: composer/src/Composer/Downloader/ZipDownloader.php
 
 use crate::downloader::ArchiveDownloader;
+use crate::downloader::ChangeReportInterface;
 use crate::downloader::DownloaderInterface;
 use crate::downloader::FileDownloader;
 use crate::io::IOInterface;
@@ -553,6 +554,16 @@ impl ZipDownloader {
     }
 }
 
+impl ChangeReportInterface for ZipDownloader {
+    fn get_local_changes(
+        &self,
+        package: PackageInterfaceHandle,
+        path: &str,
+    ) -> Result<Option<String>> {
+        self.inner.get_local_changes(package, path)
+    }
+}
+
 // TODO(phase-b): ZipDownloader::download is overridden with extra setup (UNZIP_COMMANDS init,
 // etc.). The trait method here delegates straight to the inner FileDownloader; the bespoke
 // override on the struct itself takes &mut self and is not yet routed through the trait.
@@ -562,6 +573,10 @@ impl crate::downloader::DownloaderInterface for ZipDownloader {
         self.inner.get_installation_source()
     }
 
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
+        Some(self)
+    }
+
     async fn download(
         &self,
         package: PackageInterfaceHandle,