-mm=rc: { s: p.child } takes no reference; overwriting p.child frees what the literal holds #460

Under -mm=rc, an object literal whose field is read out of another object's field takes no reference. Overwriting the source field frees the value the literal still holds.

class Node {
    name = "";
}

class P {
    child: Node = new Node();
}

function main() {
    const p = new P();
    p.child.name = "first" + 1;
    const o = { s: p.child };
    p.child = new Node();
    let keep: string[] = [];
    for (let i = 0; i < 1000; i++) keep.push("k" + i);
    print(o.s.name);
}

Expected: first1.

Actual, tslang --emit=jit --no-default-lib, main 8b9d631:

• gc and none: first1.
• rc: k15. The node and its string were freed, and the keep loop reused the memory.

Under -mm=own the program is rejected (borrows a field and cannot be stored), which is correct. Found by the review of Shared<T> (own phase 8). A Shared<T> field read into an object literal crashes under rc the same way.

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