add test for borrow checker ICE with nested generic closures

Author: Aditya-PS-05

tests/ui/issues/issue-143821.rs

@@ -0,0 +1,39 @@
+//@ check-pass
+// Regression test for issue https://github.com/rust-lang/rust/issues/143821
+// Tests that we don't ICE when borrow-checking nested closures with generic type parameters
+// and late-bound lifetime parameters.
+
+fn data_<T: 'static>(_: &()) -> &T {
+    loop {}
+}
+
+fn register<T, F>(f: F) -> IfaceToken<T>
+where
+    T: 'static,
+    F: FnOnce(&()),
+{
+    loop {}
+}
+
+fn method_with_cr_async<CB>(cb: CB)
+where
+    CB: Fn(),
+{
+    loop {}
+}
+
+struct IfaceToken<T: 'static>(T);
+
+fn foo<T>() -> IfaceToken<T> {
+    register::<T, _>(|b: &()| {
+        method_with_cr_async(|| {
+            data_::<T>(&());
+        });
+    })
+}
+
+struct A();
+
+fn main() {
+    foo::<A>();
+}