rustdoc: add regression test for broken link due to double backticks

tests/rustdoc-ui/unescaped_backticks.rs

@@ -340,3 +340,15 @@ id! {
     /// level changes.
     pub mod tracing_macro {}
 }
+
+/// Regression test for <https://github.com/rust-lang/rust/issues/111117>
+pub mod trillium_server_common {
+    /// One-indexed, because the first CloneCounter is included. If you don't
+    /// want the original to count, construct a [``CloneCounterObserver`]
+    /// instead and use [`CloneCounterObserver::counter`] to increment.
+    //~^ ERROR unescaped backtick
+    pub struct CloneCounter;
+
+    /// This is used by the above.
+    pub struct CloneCounterObserver;
+}

tests/rustdoc-ui/unescaped_backticks.stderr

@@ -341,6 +341,18 @@ LL | |     /// level changes.
             change: [`rebuild_interest_cache`][rebuild] is called after the value of the max
            to this: [`rebuild_interest_cache\`][rebuild] is called after the value of the max
 
+error: unescaped backtick
+  --> $DIR/unescaped_backticks.rs:348:56
+   |
+LL |     /// instead and use [`CloneCounterObserver::counter`] to increment.
+   |                                                        ^
+   |
+   = help: the opening or closing backtick of an inline code may be missing
+help: if you meant to use a literal backtick, escape it
+   |
+LL |     /// instead and use [`CloneCounterObserver::counter\`] to increment.
+   |                                                        +
+
 error: unescaped backtick
   --> $DIR/unescaped_backticks.rs:11:5
    |
@@ -955,5 +967,5 @@ help: if you meant to use a literal backtick, escape it
 LL | /// | table`( | )\`body |
    |                  +
 
-error: aborting due to 63 previous errors
+error: aborting due to 64 previous errors