update DefaultNoBound derive macro (#12723)

fix derive for empty enums

Update derive & ui tests

clean up

Apply suggestions from code review

Co-authored-by: Bastian Köcher <git@kchr.de>

rename variable

formatting & clippy

formatting

Co-authored-by: parity-processbot <>

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

@@ -110,10 +110,33 @@ fn test_struct_unnamed() {
 	assert!(b != a_1);
 }
 
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
+struct StructNoGenerics {
+	field1: u32,
+	field2: u64,
+}
+
+#[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
+enum EnumNoGenerics {
+	#[default]
+	VariantUnnamed(u32, u64),
+	VariantNamed {
+		a: u32,
+		b: u64,
+	},
+	VariantUnit,
+}
+
 #[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
 enum Enum<T: Config, U, V> {
+	#[default]
 	VariantUnnamed(u32, u64, T::C, core::marker::PhantomData<(U, V)>),
-	VariantNamed { a: u32, b: u64, c: T::C, phantom: core::marker::PhantomData<(U, V)> },
+	VariantNamed {
+		a: u32,
+		b: u64,
+		c: T::C,
+		phantom: core::marker::PhantomData<(U, V)>,
+	},
 	VariantUnit,
 	VariantUnit2,
 }
@@ -121,7 +144,12 @@ enum Enum<T: Config, U, V> {
 // 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 },
+	#[default]
+	VariantNamed {
+		a: u32,
+		b: u64,
+		c: T::C,
+	},
 	VariantUnnamed(u32, u64, T::C),
 	VariantUnit,
 	VariantUnit2,
@@ -130,8 +158,13 @@ enum Enum2<T: Config> {
 // enum that will have a unit default.
 #[derive(DebugNoBound, CloneNoBound, EqNoBound, PartialEqNoBound, DefaultNoBound)]
 enum Enum3<T: Config> {
+	#[default]
 	VariantUnit,
-	VariantNamed { a: u32, b: u64, c: T::C },
+	VariantNamed {
+		a: u32,
+		b: u64,
+		c: T::C,
+	},
 	VariantUnnamed(u32, u64, T::C),
 	VariantUnit2,
 }

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

@@ -0,0 +1,4 @@
+#[derive(frame_support::DefaultNoBound)]
+enum Empty {}
+
+fn main() {}

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

@@ -0,0 +1,5 @@
+error: cannot derive Default for an empty enum
+ --> tests/derive_no_bound_ui/default_empty_enum.rs:2:6
+  |
+2 | enum Empty {}
+  |      ^^^^^

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

@@ -0,0 +1,11 @@
+trait Config {
+	type C;
+}
+
+#[derive(frame_support::DefaultNoBound)]
+enum Foo<T: Config> {
+	Bar(T::C),
+	Baz,
+}
+
+fn main() {}

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

@@ -0,0 +1,5 @@
+error: no default declared, make a variant default by placing `#[default]` above it
+ --> tests/derive_no_bound_ui/default_no_attribute.rs:6:6
+  |
+6 | enum Foo<T: Config> {
+  |      ^^^

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

@@ -0,0 +1,13 @@
+trait Config {
+	type C;
+}
+
+#[derive(frame_support::DefaultNoBound)]
+enum Foo<T: Config> {
+	#[default]
+	Bar(T::C),
+	#[default]
+	Baz,
+}
+
+fn main() {}

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

@@ -0,0 +1,21 @@
+error: multiple declared defaults
+ --> tests/derive_no_bound_ui/default_too_many_attributes.rs:5:10
+  |
+5 | #[derive(frame_support::DefaultNoBound)]
+  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the derive macro `frame_support::DefaultNoBound` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: first default
+ --> tests/derive_no_bound_ui/default_too_many_attributes.rs:7:2
+  |
+7 | /     #[default]
+8 | |     Bar(T::C),
+  | |_____________^
+
+error: additional default
+  --> tests/derive_no_bound_ui/default_too_many_attributes.rs:9:2
+   |
+9  | /     #[default]
+10 | |     Baz,
+   | |_______^

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

@@ -0,0 +1,7 @@
+#[derive(frame_support::DefaultNoBound)]
+union Foo {
+	field1: u32,
+	field2: (),
+}
+
+fn main() {}

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

@@ -0,0 +1,5 @@
+error: Union type not supported by `derive(DefaultNoBound)`
+ --> tests/derive_no_bound_ui/default_union.rs:2:1
+  |
+2 | union Foo {
+  | ^^^^^