BUG: Should not be able to statically access the fields of a optionally casted reference

[joshuahannan]

Problem

When creating a reference to an object stored in a dictionary using as?, the checker does not report a static error when trying to access a field of the optional reference.

Steps to Reproduce

1. Copy this contract

pub contract TestCollection {
    pub resource IDRes {
        pub let id: UInt32
        init() {
            self.id = 0
        }
    }

    pub resource Collection {
        access(self) var idResources: @{String: IDRes}
        init() {
            self.idResources <- {}
        }

        destroy() {
            destroy self.idResources
        }

        pub fun borrowID(_ key: String, _ id: UInt32): UInt32 {
            let idref = &self.idResources[key] as? &IDRes

            let id = idref.id

            return id
        }
    }

    init() {
        let col <- create Collection()

        let del = col.borrowID("hello", 1)

        destroy col
    }
}

2. Deploy the contract and see this error:

WARN[0004] ERR [08e509] Execution failed:
error: dereference failed
  --> 01cf0e2f2f715450.TestCollection:23:21
   |
23 |             let id = idref.id

Acceptance Criteria

It should cause a static error because it is trying to access the field of an optional, right?

[joshuahannan]

Or maybe I am misinterpreting what the result of the cast should be if the key doesn't exist in the dictionary. It seems like it should be nil, but it looks like it is still giving me an &IDRes even though it doesn't point to anything. I get the same thing when doing a force cast also.