is duplicated by:

• SR-4688 Compiler crash using variable before its declaration
• SR-4840 Segmentation fault because of weird order of variables
• SR-5840 Compiler crash
• SR-6099 Segmentation Fault 11, emanating from SIL generation
• SR-6121 Internal error on shadowing let in a guard
• SR-4918 Compiler crash related to Optionals

relates to:

• SR-4082 Compiler Crash on multi-statement if with shadowed variable

Issue Description:

Hey,

these couple of lines of invalid code result in a segfault instead of the expected compiler error:

struct Person {
    let name: String?
}

struct Company {
    let owner: Person?
}

func test() {
    let example: Company? = Company(owner: Person(name: "Owner"))
    if let person = aCompany.owner,
        let aCompany = example {
        print("\(person)")
    }
}

The error is that aCompany is happening after let person = aCompany.owner that would provide it. Instead of pointing out to the user, that the variable `aCompany` doesn't exist, the compiler crashes.