Bad diagnostic for type mismatch in `switch` expression when optional promotion is involved

[tridiak]

Description

No response

Reproduction

enum SpellFieldDBv4 {
	case spellid
	case name
	case school

}

struct SpellFieldsv4 {
	var spellid : Int
	var name : String
	var school : String?

      func stringVal(idx: SpellFieldDBv4) -> String? {
		return switch idx {
			case .name: name
			case .school: school    (1)
     }

}

(1) Value of optional type 'String?' must be unwrapped to a value of type 'String'
Minimal XC project attached.

Expected behavior

No compiler error for that line.

Environment

Apple Swift version 6.2.1 (swiftlang-6.2.1.4.8 clang-1700.4.4.1)
Target: arm64-apple-macosx26.0

XC 26.1

Additional information

Work around is to drop 'return switch ...'
and use

switch idx {
    case .school: return school
}

[hamishknight]

Does not reproduce for me in Xcode 26.1, instead I get error: switch must be exhaustive (after removing the (1)). @tridiak is it possible you've reduced the example too much?

[tridiak]

Oops.

struct SpellFieldsv4 {
	var spellid : Int
	var name : String
	var school : String?

      func stringVal(idx: SpellFieldDBv4) -> String? {
		return switch idx {
			case .name: name
			case .school: school    (1)
            case .spellid: spellid

     }

}

[hamishknight]

I see, so the issue here is a bad diagnostic, not that the code should be valid (since spellid is Int)

[hamishknight]

Reduced a bit:

enum E {
  case a
  case b
}

func foo(_ e: E, optStr: String?, i: Int) -> String? {
  switch e {
  case .a: optStr // error: value of optional type 'String?' must be unwrapped to a value of type 'String'
  case .b: i
  }
}