-- `+=xs v`, `mset m k v`, and `mdel m k` look like in-place mutation but
-- ilo's functional semantics return a NEW value. The source binding is
-- only updated when you write the rebind form: `xs=+=xs v`, `m=mset m k v`,
-- `m=mdel m k`. As a bare statement, the result is silently discarded on
-- every engine and the original binding is unchanged.
--
-- The verifier flags this with ILO-T033. This file pins the canonical
-- rebind shapes that fix it. `tests/examples_engines.rs` runs every
-- function under each engine and asserts the output matches.
-- Append: rebind back to `out` so the new list sticks across iterations.
build-list>L n;out=[];@i 0..3{out=+=out i};out
-- Map set: rebind back to `m` so each key-value pair sticks.
build-map>M t n;m=mmap;m=mset m "a" 1;m=mset m "b" 2;m
-- Map delete: rebind back to `m` so the deletion sticks.
trim-map>M t n;m=mset mmap "a" 1;m=mset m "b" 2;m=mdel m "a";m
-- Tail position in a function body is fine — `+=` as the function's
-- return value flows out to the caller, no warning, no discard.
-- Demonstrated here by appending inside a single-iteration loop and
-- returning the rebound list as the tail.
push-one>L n;xs=[1 2];@k [0]{xs=+=xs 99};xs
-- run: build-list
-- out: [0, 1, 2]
-- run: build-map
-- out: {a: 1; b: 2}
-- run: trim-map
-- out: {b: 2}
-- run: push-one
-- out: [1, 2, 99]