feat: add proc macro to reduce overseer mock boilerplate (#2949)

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-enum.rs

@@ -0,0 +1,13 @@
+#![allow(dead_code)]
+
+use polkadot_procmacro_overseer_subsystems_gen::AllSubsystemsGen;
+
+#[derive(Clone, AllSubsystemsGen)]
+enum AllSubsystems<A,B> {
+	A(A),
+	B(B),
+}
+
+fn main() {
+	let all = AllSubsystems::<u8,u16>::A(0u8);
+}

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-enum.stderr

@@ -0,0 +1,5 @@
+error: expected `struct`
+ --> $DIR/err-01-enum.rs:6:1
+  |
+6 | enum AllSubsystems<A,B> {
+  | ^^^^

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-generic-used-twice.rs

@@ -0,0 +1,17 @@
+#![allow(dead_code)]
+
+use polkadot_procmacro_overseer_subsystems_gen::AllSubsystemsGen;
+
+#[derive(Clone, AllSubsystemsGen)]
+struct AllSubsystems<X> {
+	a: X,
+	b: X,
+}
+
+fn main() {
+	let all = AllSubsystems::<u16> {
+		a: 0_u16,
+		b: 1_u16,
+	};
+	let _all = all.replace_a(77u8);
+}

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-generic-used-twice.stderr

@@ -0,0 +1,14 @@
+error: Generic type parameters may only be used for exactly one field, but is used more than once.
+ --> $DIR/err-01-generic-used-twice.rs:7:5
+  |
+7 |     a: X,
+  |        ^
+
+error[E0599]: no method named `replace_a` found for struct `AllSubsystems<u16>` in the current scope
+  --> $DIR/err-01-generic-used-twice.rs:16:17
+   |
+6  | struct AllSubsystems<X> {
+   | ----------------------- method `replace_a` not found for this
+...
+16 |     let _all = all.replace_a(77u8);
+   |                    ^^^^^^^^^ method not found in `AllSubsystems<u16>`

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-no-generic.rs

@@ -0,0 +1,17 @@
+#![allow(dead_code)]
+
+use polkadot_procmacro_overseer_subsystems_gen::AllSubsystemsGen;
+
+#[derive(Clone, AllSubsystemsGen)]
+struct AllSubsystems {
+	a: f32,
+	b: u16,
+}
+
+fn main() {
+	let all = AllSubsystems {
+		a: 0_f32,
+		b: 1_u16,
+	};
+	let _all = all.replace_a(77u8);
+}

polkadot/node/overseer/subsystems-gen/tests/ui/err-01-no-generics.stderr

@@ -0,0 +1,14 @@
+error: Generic type parameters may only be used once have at least one generic parameter.
+ --> $DIR/err-01-no-generics.rs:7:5
+  |
+7 |     a: X,
+  |        ^
+
+error[E0599]: no method named `replace_a` found for struct `AllSubsystems<u16>` in the current scope
+  --> $DIR/err-01-no-generics.rs:16:17
+   |
+6  | struct AllSubsystems<X> {
+   | ----------------------- method `replace_a` not found for this
+...
+16 |     let _all = all.replace_a(77u8);
+   |                    ^^^^^^^^^ method not found in `AllSubsystems<u16>`

polkadot/node/overseer/subsystems-gen/tests/ui/ok-01-w-generics.rs

@@ -0,0 +1,17 @@
+#![allow(dead_code)]
+
+use polkadot_procmacro_overseer_subsystems_gen::AllSubsystemsGen;
+
+#[derive(Clone, AllSubsystemsGen)]
+struct AllSubsystems<A, B> {
+    a: A,
+    b: B,
+}
+
+fn main() {
+    let all = AllSubsystems::<u8, u16> {
+        a: 0u8,
+        b: 1u16,
+    };
+    let _all: AllSubsystems<_,_> = all.replace_a::<u32>(777_777u32);
+}