[5.9] Switch expression won't compile when assigning value to already defined variable.

[kr1sc]

Description

Function foo1will not compile but function foo2 will. Compilator error is Cannot find 'val' in scope. The difference is only with declaration and initialization of bar variable.

func foo1() {
    let value: Int? = nil
    
    var bar: Int = 1
    bar = switch value {
    case let val?: val
    default: 0
    }
}

func foo2() {
    let value: Int? = nil
    
    var bar: Int = switch value {
    case let val?: val
    default: 0
    }
}

Steps to reproduce

Try to compile above code in Xcode 15.0 beta.

Expected behavior

Both functions compile.

Environment

• Swift compiler version info

swift-driver version: 1.82.2 Apple Swift version 5.9 (swiftlang-5.9.0.114.6 clang-1500.0.27.1)
Target: arm64-apple-macosx13.0

• Xcode version info

Version 15.0 beta (15A5160n)

• Deployment target:

iOS 17.0

[hamishknight]

This is a known issue, and is noted in the Xcode 15 release notes:

An if or switch expression that introduces a new variable may produce a spurious “cannot find ‘’ in scope” error when that if or switch is used in an assignment. (109192116)

Was recently fixed by #65893