Detect conflicting module names in construct_runtime! (#7968)

substrate/frame/support/test/tests/construct_runtime_ui/conflicting_module_name.rs

@@ -0,0 +1,15 @@
+use frame_support::construct_runtime;
+
+construct_runtime! {
+	pub enum Runtime where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic
+	{
+		System: system::{Module},
+		Balance: balances::{Module},
+		Balance: balances::{Module},
+	}
+}
+
+fn main() {}

substrate/frame/support/test/tests/construct_runtime_ui/conflicting_module_name.stderr

@@ -0,0 +1,11 @@
+error: Two modules with the same name!
+  --> $DIR/conflicting_module_name.rs:10:3
+   |
+10 |         Balance: balances::{Module},
+   |         ^^^^^^^
+
+error: Two modules with the same name!
+  --> $DIR/conflicting_module_name.rs:11:3
+   |
+11 |         Balance: balances::{Module},
+   |         ^^^^^^^