Swift Compiler Error: The enum case has a single tuple as an associated value, but there are several patterns here

I found you can also silence this error by treating the associated value more like a tuple by wrapping it in an extra set of brackets:

switch result {
case .error(let err):
    //
case .value((let staff, let locations)):  
    //
}

Ok, figured it out. Seems like enum with associated values, where the value type is a tuple, can no longer be matched on a switch statement like that:

// Works on Xcode 11.3.1, yields error on 11.4 (Swift 5.2)
switch result {
case .error(let err):
    //
case .value(let staff, let locations):  
    //
}

Solution

Values from tuple have to be manually extracted in Xcode 11.4 (Swift 5.2):

// Works on Xcode 11.4
switch result {
case .error(let err):
    //
case .value(let tuple):  
    let (staff, locations) = tuple
    // 
}

This is a known issue: https://developer.apple.com/documentation/xcode_release_notes/xcode_11_4_release_notes

Code that relies on the compiler automatically tupling a pattern may lead to a compiler error when upgrading to Xcode 11.4, even though the code compiled before. (58425942)

For example, leaving out parentheses when switching on an Optional of a tuple type causes a compiler error:

switch x { // error: switch must be exhaustive
case .some((let a, let b), let c): // warning: the enum case has a
     // single tuple as an associated value, but there are several
     // patterns here, implicitly tupling the patterns and trying
     // to match that instead
...

}

Workaround: Add extra parentheses to explicitly tuple the pattern:

switch x {
case .some(((let a, let b), let c)): // Notice the extra pair of parentheses.
...

}