Auto merge of rust-lang#125456 - fmease:rollup-n8608gc, r=fmease

Rollup of 7 pull requests

Successful merges:

 - rust-lang#122382 (Detect unused structs which implement private traits)
 - rust-lang#124389 (Add a warning to proc_macro::Delimiter::None that rustc currently does not respect it.)
 - rust-lang#125224 (Migrate `run-make/issue-53964` to `rmake`)
 - rust-lang#125227 (Migrate `run-make/issue-30063` to `rmake`)
 - rust-lang#125336 (Add dedicated definition for intrinsics)
 - rust-lang#125401 (Migrate `run-make/rustdoc-scrape-examples-macros` to `rmake.rs`)
 - rust-lang#125454 (Improve the doc of query associated_item)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

proc_macro/src/lib.rs

@@ -815,6 +815,18 @@ pub enum Delimiter {
     /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
     /// `$var * 3` where `$var` is `1 + 2`.
     /// Invisible delimiters might not survive roundtrip of a token stream through a string.
+    ///
+    /// <div class="warning">
+    ///
+    /// Note: rustc currently can ignore the grouping of tokens delimited by `None` in the output
+    /// of a proc_macro. Only `None`-delimited groups created by a macro_rules macro in the input
+    /// of a proc_macro macro are preserved, and only in very specific circumstances.
+    /// Any `None`-delimited groups (re)created by a proc_macro will therefore not preserve
+    /// operator priorities as indicated above. The other `Delimiter` variants should be used
+    /// instead in this context. This is a rustc bug. For details, see
+    /// [rust-lang/rust#67062](https://github.com/rust-lang/rust/issues/67062).
+    ///
+    /// </div>
     #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     None,
 }