Statement: Fix TypeInfo

substrate/primitives/statement-store/src/lib.rs

@@ -24,7 +24,7 @@ extern crate alloc;
 
 use alloc::vec::Vec;
 use codec::{Decode, DecodeWithMemTracking, Encode};
-use scale_info::TypeInfo;
+use scale_info::{build::Fields, Path, Type, TypeInfo};
 use sp_application_crypto::RuntimeAppPublic;
 #[cfg(feature = "std")]
 use sp_core::Pair;
@@ -173,7 +173,7 @@ impl Field {
 }
 
 /// Statement structure.
-#[derive(DecodeWithMemTracking, TypeInfo, Debug, Clone, PartialEq, Eq, Default)]
+#[derive(DecodeWithMemTracking, Debug, Clone, PartialEq, Eq, Default)]
 pub struct Statement {
 	proof: Option<Proof>,
 	decryption_key: Option<DecryptionKey>,
@@ -184,6 +184,20 @@ pub struct Statement {
 	data: Option<Vec<u8>>,
 }
 
+/// Note: The `TypeInfo` implementation reflects the actual encoding format (`Vec<Field>`)
+/// rather than the struct fields, since `Statement` has custom `Encode`/`Decode` implementations.
+impl TypeInfo for Statement {
+	type Identity = Self;
+
+	fn type_info() -> Type {
+		// Statement encodes as Vec<Field>, so we report the same type info
+		Type::builder()
+			.path(Path::new("Statement", module_path!()))
+			.docs(&["Statement structure"])
+			.composite(Fields::unnamed().field(|f| f.ty::<Vec<Field>>()))
+	}
+}
+
 impl Decode for Statement {
 	fn decode<I: codec::Input>(input: &mut I) -> core::result::Result<Self, codec::Error> {
 		// Encoding matches that of Vec<Field>. Basically this just means accepting that there
@@ -543,6 +557,7 @@ impl Statement {
 mod test {
 	use crate::{hash_encoded, Field, Proof, SignatureVerificationResult, Statement};
 	use codec::{Decode, Encode};
+	use scale_info::{MetaType, TypeInfo};
 	use sp_application_crypto::Pair;
 
 	#[test]
@@ -659,4 +674,23 @@ mod test {
 		let decrypted = statement.decrypt_private(&pair).unwrap();
 		assert_eq!(decrypted, Some(plain));
 	}
+
+	#[test]
+	fn statement_type_info_matches_encoding() {
+		// Statement has custom Encode/Decode that encodes as Vec<Field>.
+		// Verify that TypeInfo reflects this by containing a reference to Vec<Field>.
+		let statement_type = Statement::type_info();
+		let vec_field_meta = MetaType::new::<Vec<Field>>();
+
+		// The Statement type should be a composite with one unnamed field of type Vec<Field>
+		match statement_type.type_def {
+			scale_info::TypeDef::Composite(composite) => {
+				assert_eq!(composite.fields.len(), 1, "Statement should have exactly one field");
+				let field = &composite.fields[0];
+				assert!(field.name.is_none(), "Field should be unnamed (newtype pattern)");
+				assert_eq!(field.ty, vec_field_meta, "Statement's inner type should be Vec<Field>");
+			},
+			_ => panic!("Statement TypeInfo should be a Composite"),
+		}
+	}
 }