user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/available/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/available">@available(*, unavailable) func f() { fatalError("Unreachable") } ``` The compiler currently produces: ```asm sub sp, sp, #0x20 stp x29, x30, [sp, #0x10] add x29, sp, #0x10 mov w8, #0x1 ; =1 str w8, [sp, #0x8] mov w8, #0xc ; =12 str x8, [sp] adrp x0, 0 add x0, x0, #0x6a8 ; "Fatal error" adrp x5, 0 add x5, x5, #0x690 ; "UnreachableTest/S.swift" mov x3, #0x6e55 ; =28245 movk x3, #0x6572, lsl #16 movk x3, #0x6361, lsl #32 movk x3, #0x6168, lsl #48 mov x4, #0x6c62 ; =27746 movk x4, #0x65, lsl #16 movk x4, #0xeb00, lsl #48 mov w1, #0xb ; =11 mov w2, #0x2 ; =2 mov w6, #0x17 ; =23 mov w7, #0x2 ; =2 bl 0x100000680 ; symbol stub for: Swift._assertionFailure(_: Swift.StaticString, _: Swift.String, file: Swift.StaticString, line: Swift.UInt, flags: Swift.UInt32) -> Swift.Never brk #0x1 ``` But with this change: ```swift @available(*, unavailable) func f() { swt_unreachable() } ``` It instead compiles to simply: ```asm brk #0x1 ```

Add an unreachable marker function.#1150grynspan merged 1 commit intomainswiftlang/swift-testing:mainfrom jgrynspan/unreachableswiftlang/swift-testing:jgrynspan/unreachableCopy head branch name to clipboard

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Commits on Jun 11, 2025

Add an unreachable marker function.

Add an unreachable marker function.#1150
grynspan merged 1 commit intomainfrom
jgrynspan/unreachable