Add regression test for rust-lang#105742

Author: GuillaumeGomez

src/test/rustdoc-ui/issue-105742.rs

@@ -0,0 +1,40 @@
+// compile-flags: -Znormalize-docs
+
+use std::ops::Index;
+
+pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
+//~^ ERROR
+//~^^ ERROR
+//~^^^ ERROR
+    let _ = s;
+}
+
+pub trait SVec: Index<
+    <Self as SVec>::Item,
+//~^ ERROR
+//~^^ ERROR
+//~^^^ ERROR
+//~^^^^ ERROR
+    Output = <Index<<Self as SVec>::Item,
+//~^ ERROR
+//~^^ ERROR
+//~^^^ ERROR
+//~^^^^ ERROR
+    Output = <Self as SVec>::Item> as SVec>::Item,
+//~^ ERROR
+//~^^ ERROR
+//~^^^ ERROR
+//~^^^^ ERROR
+//~^^^^^ ERROR
+//~^^^^^^ ERROR
+//~^^^^^^^ ERROR
+//~^^^^^^^^ ERROR
+> {
+    type Item<'a, T>;
+
+    fn len(&self) -> <Self as SVec>::Item;
+    //~^ ERROR
+    //~^^ ERROR
+    //~^^^ ERROR
+    //~^^^^ ERROR
+}