add test for opaque type with non-universal region substs #101852

Fixes #101852

Author: matthiaskrgr

tests/ui/impl-trait/recursive-ice-101862.rs

@@ -0,0 +1,12 @@
+// issue: rust-lang/rust#101852
+// ICE opaque type with non-universal region substs
+
+pub fn ice(x: impl AsRef<str>) -> impl IntoIterator<Item = ()> {
+//~^ WARN function cannot return without recursing
+    vec![].append(&mut ice(x.as_ref()));
+    //~^ ERROR expected generic type parameter, found `&str`
+
+    Vec::new()
+}
+
+fn main() {}

tests/ui/impl-trait/recursive-ice-101862.stderr

@@ -0,0 +1,24 @@
+warning: function cannot return without recursing
+  --> $DIR/recursive-ice-101862.rs:4:1
+   |
+LL | pub fn ice(x: impl AsRef<str>) -> impl IntoIterator<Item = ()> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
+LL |
+LL |     vec![].append(&mut ice(x.as_ref()));
+   |                        --------------- recursive call site
+   |
+   = help: a `loop` may express intention better if this is on purpose
+   = note: `#[warn(unconditional_recursion)]` on by default
+
+error[E0792]: expected generic type parameter, found `&str`
+  --> $DIR/recursive-ice-101862.rs:6:5
+   |
+LL | pub fn ice(x: impl AsRef<str>) -> impl IntoIterator<Item = ()> {
+   |               --------------- this generic parameter must be used with a generic type parameter
+LL |
+LL |     vec![].append(&mut ice(x.as_ref()));
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0792`.