add tests

Author: lcnr

tests/ui/traits/next-solver/opaques/overflow-hr-fn-trait-sized-1.rs

@@ -0,0 +1,25 @@
+//@ ignore-compare-mode-next-solver
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+// Regression test for trait-system-refactor-initiative#220. Builtin `Fn`-trait
+// candidates required `for<'latebound> Output<'latebound>: Sized` which ended
+// up resulting in overflow if the return type is an opaque in the defining scope.
+//
+// We now eagerly instantiate the binder of the function definition which avoids
+// that overflow by relating the lifetime of the opaque to something from the
+// input.
+fn flat_map<T, F, I, G>(_: F, _: G)
+where
+    F: FnOnce(T) -> I,
+    I: Iterator,
+    G: Fn(<I as Iterator>::Item) -> usize,
+{
+}
+
+fn rarw<'a>(_: &'a ()) -> impl Iterator<Item = &'a str> {
+    flat_map(rarw, |x| x.len());
+    std::iter::empty()
+}
+
+fn main() {}

tests/ui/traits/next-solver/opaques/overflow-hr-fn-trait-sized-2.rs

@@ -0,0 +1,14 @@
+//@ ignore-compare-mode-next-solver
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+// Regression test for trait-system-refactor-initiative#204, see
+// the sibling test for more details.
+
+fn constrain<'a, F: FnOnce(&'a ())>(_: F) {}
+fn foo<'a>(_: &'a ()) -> impl Sized + use<'a> {
+    constrain(foo);
+    ()
+}
+
+fn main() {}