toConstantSized does not work as expected

[turbolent]

Current Behavior

Reported by @sisyphusSmiling on Discord https://discord.com/channels/613813861610684416/1108479699732152503/1257730833352233131:

I ran into a really strange behaviour with the toConstantSized function. Take a look at this script:

access(all) fun main(): [UInt8;20] {
    let hexStr = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" // 20-byte hex string
    let res = hexStr.decodeHex().toConstantSized<[UInt8;20]>() ?? panic("toConstantSized failed")
    return res
}

This panics every time, even though the cast should work. But, if I rewrite it like this:

access(all) fun main(): [UInt8;20] {
    let hexStr = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    let res = hexStr.decodeHex().toConstantSized<[UInt8;20]>()
    let res2 = res ?? panic("toConstantSized failed")
    return res2
}

Expected Behavior

Both scripts succeed

Steps To Reproduce

Use flow-c1 cadence script.cdc for the first script and it panics

Environment

- Cadence version: Latest preview release (v1.0.0-preview.35)
- Network: N/A