Svelte 5: `.length` does not work on arrays being set with `bind:this` directive

[Not-Jayden]

Describe the bug

When using bind:this to set a reference to an element at an index of an array, while it does correctly create the proxied state, accessinglength directly on the array always returns 0 instead of the length of the proxied array value.

I believe this is actually consistent with how proxies ordinarily work, though it seems in other cases the proxy handler allows length to be read to directly.

Reproduction

REPL

Logs

N/A

System Info

REPL Chrome

Severity

annoyance

[Not-Jayden]

I've also just noticed another weird probably related bug. When trying to use $inspect on the elements array.

Uncaught DOMException: Failed to read the 'cookie' property from 'Document': The document is sandboxed and lacks the 'allow-same-origin' flag.
    at deep_read (playground:output:1130:20)
    at deep_read (playground:output:1130:5)
    at deep_read (playground:output:1130:5)
    at deep_read (playground:output:1130:5)
    at deep_read (playground:output:1130:5)
    at deep_read (playground:output:1130:5)
    at deep_read (playground:output:1130:5)
    at eval (playground:output:1168:4)
    at eval (playground:output:975:17)
    at execute_signal_fn (playground:output:311:40)