Incorrect warning with #require in optional assignment

[macguru]

Description

When using try #require inside an optional assignment, an incorrect warning ist being produced:

'#require(_:_:)' is redundant because 'x' never equals 'nil' (from macro 'require')

Reproduction

import Testing

struct A {
	var value: Int?
}

@Test func run() throws {
	let one = A()
	var two = A()
	
	two.value = try #require(one.value)
	// warning: '#require(_:_:)' is redundant because 'one.value' never equals 'nil' (from macro 'require')
}

Expected behavior

There should be no warning, the code is correct, as one.value can indeed become nil. Changing the code as follows does not have the warning:

@Test func run() throws {
	let one = A()
	let two = try #require(one.value)
}

Environment

Swift 6.1, Xcode Version 16.3 (16E140)

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

Additional information

This was not an issue with Swift 6.0 and previous Xcode releases.

[stmontgomery]

I suspect this could be a duplicate of #79202

We added a workaround to Swift Testing (in swiftlang/swift-testing#949) to suppress this warning when certain syntax (such as ?) are seen in the expression, taking it as a hint there may be optionality. But in this issue there is no such syntax to hint on.

Also, the potential original issue I linked above involved a reference (class) type and, and there was a suspicion that was relevant to the bug. But this report is about a simpler value type.

[macguru]

Yes, I've since found out this is also happening with primitive types:

@Test func run() throws {
	let a: String?
	var b: String?
	
	b = try #require(a)
	// warning: '#require(_:_:)' is redundant because 'a' never equals 'nil' (from macro 'require')
	
	_ = b // silence unused declaration warning
}

[grynspan]

Yes, this is a duplicate. It's not clear to me what the root cause is, but I imagine the core compiler team will know where to look.