chore(quest): plan the fresh-write shapes #394 left refused

quest/m3/README.md

@@ -41,3 +41,4 @@ generic std gap is planned here even when moq never calls it.
 - [Type errors at the Rust that made them](/quest/m3/ts-span-precision.md) - a `tsc` error on output names the tail expression or call argument that made it
 - [An empty iterator of mutable references](/quest/m3/ts-empty-places.md) - `iter::empty::<&mut T>()` given to `zip` or `chain` translates
 - [An Option of numbers in the result slot](/quest/m3/ts-option-slot.md) - `varint_opt`'s `Option` comes back through the slot with no object per call
+- [Fresh writes through a zip, a copy, and a repeat](/quest/m3/ts-fresh-shapes.md) - zipping a `Vec<[T; N]>`, reading a `T` out of `Zip::next`, and `copied` or `vec![x; n]` over a `Copy` type translate

quest/m3/ts-fresh-shapes.md

@@ -0,0 +1,30 @@
+# [M] Fresh writes through a zip, a copy, and a repeat
+
+## Goal
+
+[rust2-ts](/ts/README.md) translates three shapes it refuses for concrete types and type
+parameters alike, proven by differential tests against native Rust:
+
+- zipping a slot with a `Vec<[T; N]>`, as `[u8; N]`;
+- reading a `T` back out of `Zip::next`'s result;
+- `iter().copied()` and `vec![x; n]` over a `Copy` type, a crate's own or a `T: Copy`.
+
+## Plan
+
+Found by [#394](https://github.com/moq-dev/rust2/pull/394), which made a whole write into
+fresh memory count as fresh in a function generic over a type. These three stay refused for
+reasons that have nothing to do with type parameters:
+
+- `vec::IntoIter` points at a type the slot holds in place, so zipping with it refuses.
+- Reading a `T` out of `Zip::next`'s result makes it a holder. A concrete control
+  (`Vec<Option<u8>>`) is refused as well.
+- `Copy`'s supertrait `Clone` selects a parameter candidate, so `copied` and `vec![x; n]`
+  count as running the crate's `Clone`. The two differ: `copied` copies and calls no
+  `clone`, while `vec![x; n]` calls `clone` `n - 1` times, and a `Copy` type's hand-written
+  `Clone` may have effects or panic. Treat `copied` as running no crate code; keep
+  `vec![x; n]` calling the crate's `clone`, judged fresh only where that `clone` writes
+  nothing the slot holds. Cover both with differential tests whose `Clone` logs and panics.
+
+Reproduce each first and fix the one that is a single cause before the others.
+
+Public API: the translator's output.