Add DefaultNoBound (#8542)

* Add DefaultNoBound

* Add tests

* Fix

substrate/frame/support/test/tests/derive_no_bound.rs

@@ -15,9 +15,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//! Tests for DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, and RuntimeDebugNoBound
+//! Tests for DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound, and
+//! RuntimeDebugNoBound
 
-use frame_support::{DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound};
+use frame_support::{
+	DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound, DefaultNoBound,
+};
 
 #[derive(RuntimeDebugNoBound)]
 struct Unnamed(u64);
@@ -29,7 +32,7 @@ fn runtime_debug_no_bound_display_correctly() {
 }
 
 trait Config {
-	type C: std::fmt::Debug + Clone + Eq + PartialEq;
+	type C: std::fmt::Debug + Clone + Eq + PartialEq + Default;
 }
 
 struct Runtime;
@@ -39,7 +42,7 @@ impl Config for Runtime {
 	type C = u32;
 }
 
-#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound)]
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
 struct StructNamed<T: Config, U, V> {
 	a: u32,
 	b: u64,
@@ -56,6 +59,12 @@ fn test_struct_named() {
 		phantom: Default::default(),
 	};
 
+	let a_default: StructNamed::<Runtime, ImplNone, ImplNone> = Default::default();
+	assert_eq!(a_default.a, 0);
+	assert_eq!(a_default.b, 0);
+	assert_eq!(a_default.c, 0);
+	assert_eq!(a_default.phantom, Default::default());
+
 	let a_2 = a_1.clone();
 	assert_eq!(a_2.a, 1);
 	assert_eq!(a_2.b, 2);
@@ -76,7 +85,7 @@ fn test_struct_named() {
 	assert!(b != a_1);
 }
 
-#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound)]
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
 struct StructUnnamed<T: Config, U, V>(u32, u64, T::C, core::marker::PhantomData<(U, V)>);
 
 #[test]
@@ -88,6 +97,12 @@ fn test_struct_unnamed() {
 		Default::default(),
 	);
 
+	let a_default: StructUnnamed::<Runtime, ImplNone, ImplNone> = Default::default();
+	assert_eq!(a_default.0, 0);
+	assert_eq!(a_default.1, 0);
+	assert_eq!(a_default.2, 0);
+	assert_eq!(a_default.3, Default::default());
+
 	let a_2 = a_1.clone();
 	assert_eq!(a_2.0, 1);
 	assert_eq!(a_2.1, 2);
@@ -108,7 +123,7 @@ fn test_struct_unnamed() {
 	assert!(b != a_1);
 }
 
-#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound)]
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
 enum Enum<T: Config, U, V> {
 	VariantUnnamed(u32, u64, T::C, core::marker::PhantomData<(U, V)>),
 	VariantNamed {
@@ -121,6 +136,32 @@ enum Enum<T: Config, U, V> {
 	VariantUnit2,
 }
 
+// enum that will have a named default.
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
+enum Enum2<T: Config> {
+	VariantNamed {
+		a: u32,
+		b: u64,
+		c: T::C,
+	},
+	VariantUnnamed(u32, u64, T::C),
+	VariantUnit,
+	VariantUnit2,
+}
+
+// enum that will have a unit default.
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
+enum Enum3<T: Config> {
+	VariantUnit,
+	VariantNamed {
+		a: u32,
+		b: u64,
+		c: T::C,
+	},
+	VariantUnnamed(u32, u64, T::C),
+	VariantUnit2,
+}
+
 #[test]
 fn test_enum() {
 	type TestEnum = Enum::<Runtime, ImplNone, ImplNone>;
@@ -131,6 +172,22 @@ fn test_enum() {
 	let variant_2 = TestEnum::VariantUnit;
 	let variant_3 = TestEnum::VariantUnit2;
 
+	let default: TestEnum = Default::default();
+	assert_eq!(
+		default,
+		// first variant is default.
+		TestEnum::VariantUnnamed(0, 0, 0, Default::default())
+	);
+
+	assert_eq!(
+		Enum2::<Runtime>::default(),
+		Enum2::<Runtime>::VariantNamed { a: 0, b: 0, c: 0},
+	);
+	assert_eq!(
+		Enum3::<Runtime>::default(),
+		Enum3::<Runtime>::VariantUnit,
+	);
+
 	assert!(variant_0 != variant_0_bis);
 	assert!(variant_1 != variant_1_bis);
 	assert!(variant_0 != variant_1);

substrate/frame/support/test/tests/derive_no_bound_ui/default.rs

@@ -0,0 +1,10 @@
+trait Config {
+	type C;
+}
+
+#[derive(frame_support::DefaultNoBound)]
+struct Foo<T: Config> {
+	c: T::C,
+}
+
+fn main() {}

substrate/frame/support/test/tests/derive_no_bound_ui/default.stderr

@@ -0,0 +1,7 @@
+error[E0277]: the trait bound `<T as Config>::C: std::default::Default` is not satisfied
+ --> $DIR/default.rs:7:2
+  |
+7 |     c: T::C,
+  |     ^ the trait `std::default::Default` is not implemented for `<T as Config>::C`
+  |
+  = note: required by `std::default::Default::default`