3 files changed, 24 insertions, 8 deletions
diff --git a/mingling_core/src/lib.rs b/mingling_core/src/lib.rs
index 2cb24b9..31476c9 100644
--- a/mingling_core/src/lib.rs
+++ b/mingling_core/src/lib.rs
@@ -90,8 +90,14 @@ pub mod setup {
 /// Private API — not intended for direct use.
 #[doc(hidden)]
 pub mod __private {
+    use crate::ProgramCollect;
+
     /// Sealed trait for `StructuralData` — only implementable via derive macro.
-    pub trait StructuralDataSealed {}
+    pub trait StructuralDataSealed<C>
+    where
+        C: ProgramCollect<Enum = C>,
+    {
+    }
 
     /// Re-export so the derive macro can reference the trait without
     /// conflicting with the derive macro name at `::mingling::StructuralData`.
diff --git a/mingling_core/src/renderer/structural.rs b/mingling_core/src/renderer/structural.rs
index 30255aa..0449e72 100644
--- a/mingling_core/src/renderer/structural.rs
+++ b/mingling_core/src/renderer/structural.rs
@@ -1,5 +1,5 @@
 use crate::{
-    RenderResult, StructuralRendererSetting,
+    ProgramCollect, RenderResult, StructuralRendererSetting,
     renderer::structural::error::StructuralRendererSerializeError,
 };
 use serde::Serialize;
@@ -24,11 +24,15 @@ impl StructuralRenderer {
     ///
     /// Returns `Err(StructuralRendererSerializeError)` if serialization fails.
     #[allow(unused_variables)]
-    pub fn render<T: StructuralData + Send>(
+    pub fn render<T, C>(
         data: &T,
         setting: &StructuralRendererSetting,
         r: &mut RenderResult,
-    ) -> Result<(), StructuralRendererSerializeError> {
+    ) -> Result<(), StructuralRendererSerializeError>
+    where
+        T: StructuralData<C> + Send,
+        C: ProgramCollect<Enum = C>,
+    {
         match setting {
             StructuralRendererSetting::Disable => Ok(()),
             #[cfg(feature = "json_serde_fmt")]
@@ -148,7 +152,7 @@ impl StructuralRenderer {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::RenderResult;
+    use crate::{MockProgramCollect, RenderResult};
     use serde::Serialize;
 
     #[derive(Debug, Clone, PartialEq, Serialize)]
@@ -157,8 +161,8 @@ mod tests {
         value: i32,
     }
 
-    impl crate::__private::StructuralDataSealed for TestData {}
-    impl StructuralData for TestData {}
+    impl crate::__private::StructuralDataSealed<MockProgramCollect> for TestData {}
+    impl StructuralData<MockProgramCollect> for TestData {}
 
     fn test_data() -> TestData {
         TestData {
diff --git a/mingling_core/src/renderer/structural/structural_data.rs b/mingling_core/src/renderer/structural/structural_data.rs
index 1cafac3..583808c 100644
--- a/mingling_core/src/renderer/structural/structural_data.rs
+++ b/mingling_core/src/renderer/structural/structural_data.rs
@@ -1,5 +1,7 @@
 use serde::Serialize;
 
+use crate::ProgramCollect;
+
 /// Marker trait for types that support structured output (JSON / YAML / TOML / RON).
 ///
 /// This trait is a **supertrait** of `serde::Serialize` and is sealed via
@@ -12,4 +14,8 @@ use serde::Serialize;
 /// These entry points also register the type in the global `STRUCTURED_TYPES`
 /// registry, which is required for the `structural_render` match arm to be generated.
 #[doc(hidden)]
-pub trait StructuralData: Serialize + crate::__private::StructuralDataSealed {}
+pub trait StructuralData<C>: Serialize + crate::__private::StructuralDataSealed<C>
+where
+    C: ProgramCollect<Enum = C>,
+{
+}