#require does not always fail correctly with if let

[davidbarry-kr]

Description

In Swift 6.1 using #require with an if let syntax produces an incorrect warning about redundant usage:

'#require(_:_:)' is redundant because 'container.text' never equals 'nil' (from macro 'require')

This is displayed when the function/property in question is indeed optional. Additionally in this case with an if let if the expression in the #require yields a nil value no failure is recorded. This is a regression from Swift 6.0 where a failure would still be recorded despite the use of try? along with #require.

Another wrinkle with this: if the expression inside the require is awaited (if let value = try? #require(await getSomeValue())) the warning will still appear, but it will correctly record a test failure when the value is nil.

Reproduction

This is a simplified example to show a compact reproduction of the problem. This test will pass despite the value being nil.

struct Container {
    var text: String? = nil
}

@Test
func example() {
    let container = Container()

    if let text = try? #require(container.text) {
        #expect(text == "some value")
    }
}

This does not demonstrate a good reason to use an if let with #require, but simply reproduces the problem. I've attached a package with more thorough examples of the problem as well as an example of when you may want to use if let with a #require.
The package also includes an example of identical code but an awaited expression which produces the same warning but which fails correctly when the test is run.

SwiftTestingRegression.zip

Expected behavior

• The #require in the above example should generate a test failure.
• The '#require(_:_:)' is redundant because 'container.text' never equals 'nil' (from macro 'require') warning should not be present.

Environment

Testing Library Version: 124

swift-driver version: 1.120.5 Apple Swift version 6.1 (swiftlang-6.1.0.110.21 clang-1700.0.13.3)
Target: arm64-apple-macosx15.0

Darwin OF060LKFWC4L02U 24.4.0 Darwin Kernel Version 24.4.0: Wed Mar 19 21:17:35 PDT 2025; root:xnu-11417.101.15~1/RELEASE_ARM64_T6041 arm64

Additional information

This warning and behavior appeared in Swift 6.1. The tests in the attached package will fail as expected and not generate warnings, in Swift 6.0.

[grynspan]

Known type inference bug, @stmontgomery to find original.

Thanks for filing!

[stmontgomery]

Duplicate of #80633

As I commented in that original, it may be a duplicate of another bug, #79202, although the compiler team should confirm.