Add test for issue-61747

Author: JohnTitor

src/test/ui/const-generics/issues/issue-61747.rs

@@ -0,0 +1,16 @@
+// check-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+struct Const<const N: usize>;
+
+impl<const C: usize> Const<{C}> {
+    fn successor() -> Const<{C + 1}> {
+        Const
+    }
+}
+
+fn main() {
+    Const::<1>::successor();
+}

src/test/ui/const-generics/issues/issue-61747.stderr

@@ -0,0 +1,8 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/issue-61747.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+