Add regression test for rust-lang#140026

Author: GuillaumeGomez

tests/rustdoc-ui/intra-doc/empty-associated-items.rs

@@ -0,0 +1,8 @@
+// This test ensures that an empty associated item will not crash rustdoc.
+// This is a regression test for <https://github.com/rust-lang/rust/issues/140026>.
+
+#[deny(rustdoc::broken_intra_doc_links)]
+
+/// [`String::`]
+//~^ ERROR
+pub struct Foo;

tests/rustdoc-ui/intra-doc/empty-associated-items.stderr

@@ -0,0 +1,14 @@
+error: unresolved link to `String::`
+  --> $DIR/empty-associated-items.rs:6:7
+   |
+LL | /// [`String::`]
+   |       ^^^^^^^^ the struct `String` has no field or associated item named ``
+   |
+note: the lint level is defined here
+  --> $DIR/empty-associated-items.rs:4:8
+   |
+LL | #[deny(rustdoc::broken_intra_doc_links)]
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+