16-spread-dot

16 — Spread-dot (*->)

Borrowed from Groovy's spread-dot operator.

$coll*->method(args) calls method on every element of a collection and collects the results into an array. $coll*->prop does the same for a property read. It turns a loop into a single expression:

$users*->getName();       // [ $u->getName() for each $u ]
$users*->name;            // [ $u->name    for each $u ]
$orders*->total(withTax: true);

Behaviour

• Maps over the collection. The result is an array of one result per element.

• Keys are preserved — ["x" => $a, "y" => $b]*->name yields ["x" => …, "y" => …].

• Chains. Each stage returns an array, which the next *-> maps again:

  $boxes*->inc()*->get();   // inc() on each, then get() on each

• Left to right, once per element. For $coll*->m(), m() runs on each element in order.

• The left operand may be any expression: (getUsers())*->name.

How it works

A new *-> token and a pure parser desugar — no new opcode, no compiler or VM changes. $coll*->m(args) is rewritten to a plain array_map over an arrow function:

$coll*->m(a, b)   ==>   array_map(fn($__each) => $__each->m(a, b), $coll)
$coll*->prop      ==>   array_map(fn($__each) => $__each->prop,     $coll)

array_map is resolved in the global namespace, so it works unchanged from inside a namespace. Ordinary *, ** and *= are untouched — *-> is only recognised as a single token when the * is immediately followed by ->. See feature.patch and the RFC.

Scope of this experiment (v1)

• Array collections. Because it lowers to array_map, the left operand must be an array; a non-array raises array_map()'s TypeError. For a Traversable, wrap it with iterator_to_array(...) first. (A future version could target a helper that also accepts iterables.)
• Arguments are evaluated per element (they live inside the mapped closure), so keep side-effecting argument expressions in mind — $coll*->m(next()) calls next() once per element.
• There is no null-safe form (*?->); elements are expected to be objects.

Try it

scripts/setup.sh 16-spread-dot && scripts/build.sh
features/16-spread-dot/smoke.sh