quest: plan a reference to a closure as a string pattern

quest/m3/README.md

@@ -53,3 +53,4 @@ generic std gap is planned here even when moq never calls it.
 - [A box's clone_from, and a vector's AsRef and AsMut](/quest/m3/ts-box-vec-conversions.md) - `clone_from` of a `Box<String>` and `AsRef<[T]>` of a `Vec` translate
 - [A std map with a crate's own BuildHasher](/quest/m3/ts-map-own-hasher.md) - std's and hashbrown's maps built with a crate's own hasher translate for keys that are JS objects
 - [A crate's own hasher that JS copies](/quest/m3/ts-copied-hasher.md) - an enum `Hasher`, whose `&mut` is a place, hashes as a struct one does
+- [A reference to a closure as a string pattern](/quest/m3/ts-closure-patterns.md) - `s.contains(&f)` and `s.split(&mut f)` translate, leaving the closure to its owner to drop

quest/m3/ts-closure-patterns.md

@@ -0,0 +1,24 @@
+# [S] A reference to a closure as a string pattern
+
+## Goal
+
+[rust2-ts](/ts/README.md) translates a `str` search given a reference to a closure as its
+pattern, `s.contains(&f)` or `s.split(&mut f)`. The search calls the closure as std's does
+and never drops it, which leaves the drop to its owner. Differential tests against native
+Rust prove it, covering closures that own a value that drops and searches that return a
+value and an iterator.
+
+## Plan
+
+Found in [#471](https://github.com/moq-dev/rust2/pull/471), which made a search drop a
+closure it owns. A reference to one is refused as a pattern other than a `char`, a
+`&str`, a predicate, or chars, as the README's list of what is refused says. std takes
+`&F` for an `F: Fn` and `&mut F` for an `F: FnMut`, as each implements `FnMut`.
+
+The closure drop logic that #471 extended already tells a lent closure from an owned one,
+and wraps a lent one in `rt.lent` for an iterator that would drop what it holds. A
+`&mut` to a function JS copies is that function's place. Watch that a lent closure is
+neither dropped by the search nor by the iterator it returns, and drop the refusal from the
+README once it translates.
+
+Public API: the translator's output.