feat(package): implement as_package_interface upcast

Make the Rust-only as_package_interface a required trait method and
return self from each concrete implementation, replacing the todo!()
default that PHP needs no equivalent for (implicit subtype coercion).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

6 files changed, 26 insertions, 6 deletions

diff --git a/crates/shirabe/src/package/complete_alias_package.rs b/crates/shirabe/src/package/complete_alias_package.rs
index 9e1f1f6..54b4486 100644
--- a/crates/shirabe/src/package/complete_alias_package.rs
+++ b/crates/shirabe/src/package/complete_alias_package.rs
@@ -153,4 +153,8 @@ impl CompletePackageInterface for CompleteAliasPackage {
     fn set_archive_excludes(&mut self, excludes: Vec<String>) {
         self.alias_of.set_archive_excludes(excludes);
     }
+
+    fn as_package_interface(&self) -> &dyn crate::package::PackageInterface {
+        self
+    }
 }
diff --git a/crates/shirabe/src/package/complete_package.rs b/crates/shirabe/src/package/complete_package.rs
index 033db9b..56d50d5 100644
--- a/crates/shirabe/src/package/complete_package.rs
+++ b/crates/shirabe/src/package/complete_package.rs
@@ -156,6 +156,10 @@ impl CompletePackageInterface for CompletePackage {
     fn get_archive_excludes(&self) -> Vec<String> {
         self.archive_excludes.clone()
     }
+
+    fn as_package_interface(&self) -> &dyn PackageInterface {
+        self
+    }
 }
 
 impl PackageInterface for CompletePackage {
diff --git a/crates/shirabe/src/package/complete_package_interface.rs b/crates/shirabe/src/package/complete_package_interface.rs
index 549aeb4..8a7ee25 100644
--- a/crates/shirabe/src/package/complete_package_interface.rs
+++ b/crates/shirabe/src/package/complete_package_interface.rs
@@ -56,7 +56,5 @@ pub trait CompletePackageInterface: PackageInterface {
 
     fn set_archive_excludes(&mut self, excludes: Vec<String>);
 
-    fn as_package_interface(&self) -> &dyn crate::package::PackageInterface {
-        todo!()
-    }
+    fn as_package_interface(&self) -> &dyn crate::package::PackageInterface;
 }
diff --git a/crates/shirabe/src/package/root_alias_package.rs b/crates/shirabe/src/package/root_alias_package.rs
index 9f987eb..140c96d 100644
--- a/crates/shirabe/src/package/root_alias_package.rs
+++ b/crates/shirabe/src/package/root_alias_package.rs
@@ -146,6 +146,10 @@ impl RootPackageInterface for RootAliasPackage {
     fn set_extra(&mut self, extra: IndexMap<String, PhpMixed>) {
         self.alias_of.set_extra(extra);
     }
+
+    fn as_package_interface(&self) -> &dyn crate::package::PackageInterface {
+        self
+    }
 }
 
 impl CompletePackageInterface for RootAliasPackage {
@@ -248,4 +252,8 @@ impl CompletePackageInterface for RootAliasPackage {
     fn set_archive_excludes(&mut self, excludes: Vec<String>) {
         self.inner.set_archive_excludes(excludes);
     }
+
+    fn as_package_interface(&self) -> &dyn crate::package::PackageInterface {
+        self
+    }
 }
diff --git a/crates/shirabe/src/package/root_package.rs b/crates/shirabe/src/package/root_package.rs
index fc04d25..9cdc6e2 100644
--- a/crates/shirabe/src/package/root_package.rs
+++ b/crates/shirabe/src/package/root_package.rs
@@ -129,6 +129,10 @@ impl RootPackageInterface for RootPackage {
     fn set_extra(&mut self, extra: IndexMap<String, PhpMixed>) {
         self.inner.inner.set_extra(extra);
     }
+
+    fn as_package_interface(&self) -> &dyn PackageInterface {
+        self
+    }
 }
 
 impl CompletePackageInterface for RootPackage {
@@ -231,6 +235,10 @@ impl CompletePackageInterface for RootPackage {
     fn set_archive_excludes(&mut self, excludes: Vec<String>) {
         CompletePackageInterface::set_archive_excludes(&mut self.inner, excludes)
     }
+
+    fn as_package_interface(&self) -> &dyn PackageInterface {
+        self
+    }
 }
 
 impl std::fmt::Display for RootPackage {
diff --git a/crates/shirabe/src/package/root_package_interface.rs b/crates/shirabe/src/package/root_package_interface.rs
index aa2534a..d597555 100644
--- a/crates/shirabe/src/package/root_package_interface.rs
+++ b/crates/shirabe/src/package/root_package_interface.rs
@@ -51,7 +51,5 @@ pub trait RootPackageInterface: CompletePackageInterface {
 
     fn set_extra(&mut self, extra: IndexMap<String, PhpMixed>);
 
-    fn as_package_interface(&self) -> &dyn PackageInterface {
-        todo!()
-    }
+    fn as_package_interface(&self) -> &dyn PackageInterface;
 }