Compiler crashes with a particular combination of protocol conformance and a "dynamic" property modifier

[bewebste]

Description

I have encountered a reproducible crash in the Swift compiler with a particular setup involving a protocol implemented in one module and implemented by a class in another module. I have included a test project that will reproduce the crash. The code is set up as follows:

1. This is an Xcode project with an application and two frameworks, one called Operations, and one called Dependent
2. The Operations framework has a class named BWOperation which subclasses Operation.
3. The Operations framework also has a protocol named BWOperationProtocol, which requires implementors to subclass BWOperation
4. BWOperationProtocol requires var progress: Progress { get set }
5. BWOperation provides a progress property declared as @objc public dynamic var progress: Progress
6. The Dependent framework defines a OperationSubclass subclass of BWOperation which conforms to BWOperationProtocol

Attempting to build this project will result in a compiler crash. Making any of the following changes will prevent the crash:

• Remove the conformance to BWOperationProtocol on OperationSubclass
• Remove the dynamic keyword on the progress property in BWOperation
• Remove the requirement on BWOperationProtocol that implementors must subclass BWOperation

Declaring the same subclass inside the Operations framework does not cause a crash, only when the subclass is in another module.

Reproduction

Attached is an Xcode project that reproduces the problem. Build the "SwiftCrashTest" app to trigger the compiler crash.

The Operations framework declares the following:

open class BWOperation: Operation, ProgressReporting, @unchecked Sendable {
	@objc public dynamic var progress: Progress = Progress()
}

public protocol BWOperationProtocol: BWOperation {
	var progress: Progress { get set }
}

And the Dependent framework declares this subclass

import Operations

public class OperationSubclass: BWOperation, BWOperationProtocol, @unchecked Sendable {
}

SwiftCrashTest.zip

Stack dump

Showing All Errors Only
SwiftCompile normal arm64 Compiling\ Dependent.swift /Users/bwebster/Projects/Radar/SwiftCrashTest/Dependent/Dependent.swift (in target 'Dependent' from project 'SwiftCrashTest')

Assertion failed: ((!hasSharedVisibility(F->getLinkage()) || F->hasForeignBody()) && "cannot deserialize shared function"), function deserializeAndPushToWorklist at Linker.cpp:88.
(to display assertion configuration options: -Xllvm -assert-help)
Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c -primary-file /Users/bwebster/Projects/Radar/SwiftCrashTest/Dependent/Dependent.swift -emit-dependencies-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.d -emit-const-values-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.swiftconstvalues -emit-reference-dependencies-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.swiftdeps -serialize-diagnostics-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.dia -emit-localized-strings -emit-localized-strings-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64 -target arm64-apple-macos26.0 -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libFoundationMacros.dylib#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server#FoundationMacros -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libObservationMacros.dylib#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server#ObservationMacros -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libSwiftMacros.dylib#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server#SwiftMacros -disable-implicit-swift-modules -Xcc -fno-implicit-modules -Xcc -fno-implicit-module-maps -explicit-swift-module-map-file /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent-dependencies-57.json -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk -I /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug -F /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug -no-color-diagnostics -Xcc -fno-color-diagnostics -enable-library-evolution -enable-testing -g -debug-info-format=dwarf -dwarf-version=5 -module-cache-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules -swift-version 5 -enforce-exclusivity=checked -Onone -D DEBUG -serialize-debugging-options -const-gather-protocols-file /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent_const_extract_protocols.json -enable-upcoming-feature DisableOutwardActorInference -enable-upcoming-feature InferSendableFromCaptures -enable-upcoming-feature GlobalActorIsolatedTypesUsability -enable-upcoming-feature MemberImportVisibility -enable-upcoming-feature InferIsolatedConformances -enable-upcoming-feature NonisolatedNonsendingByDefault -enable-experimental-feature DebugDescriptionMacro -enable-bare-slash-regex -validate-clang-modules-once -clang-build-session-file /Users/bwebster/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/Session.modulevalidation -Xcc -working-directory -Xcc /Users/bwebster/Projects/Radar/SwiftCrashTest -enable-anonymous-context-mangled-names -file-compilation-dir /Users/bwebster/Projects/Radar/SwiftCrashTest -Xcc -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG -Xcc -ivfsstatcache -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SDKStatCaches.noindex/macosx26.0-25A5344a-bf0ffbe9ae4a19f9acfa348bfdda0e8c.sdkstatcache -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-generated-files.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-own-target-headers.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-all-target-headers.hmap -Xcc -iquote -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-project-headers.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug/include -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources-normal/arm64 -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources/arm64 -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources -Xcc -DDEBUG=1 -no-auto-bridging-header-chaining -module-name Dependent -frontend-parseable-output -disable-clang-spi -target-sdk-version 26.0 -target-sdk-name macosx26.0 -clang-target arm64-apple-macos26.0 -in-process-plugin-server-path /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/libSwiftInProcPluginServer.dylib -parse-as-library -o /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.o -index-unit-output-path /SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.o -index-store-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Index.noindex/DataStore -index-system-modules
1.	Apple Swift version 6.2 (swiftlang-6.2.0.19.9 clang-1700.3.19.1)
2.	Compiling with effective version 5.10
3.	While evaluating request ExecuteSILPipelineRequest(Run pipelines { Mandatory Diagnostic Passes + Enabling Optimization Passes } on SIL for Dependent)
4.	While running pass #207 SILModuleTransform "MandatorySILLinker".
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x000000010688dbcc llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x000000010688b55c llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x000000010688e1f8 SignalHandler(int, __siginfo*, void*) + 344
3  libsystem_platform.dylib 0x000000018f5a0704 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000018f596848 pthread_kill + 296
5  libsystem_c.dylib        0x000000018f49c808 abort + 124
6  swift-frontend           0x00000001021523c0 ASSERT_failure(char const*, char const*, int, char const*) + 1720
7  swift-frontend           0x0000000100d9e32c swift::SILLinkerVisitor::process() + 380
8  swift-frontend           0x0000000100d9e13c swift::SILLinkerVisitor::processFunction(swift::SILFunction*) + 152
9  swift-frontend           0x0000000101541b30 (anonymous namespace)::SILLinker::run() + 196
10 swift-frontend           0x0000000101414778 swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 13328
11 swift-frontend           0x00000001014370a0 swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::__1::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) + 52
12 swift-frontend           0x000000010141ae5c swift::ExecuteSILPipelineRequest::OutputType swift::Evaluator::getResultUncached<swift::ExecuteSILPipelineRequest, swift::ExecuteSILPipelineRequest::OutputType swift::evaluateOrFatal<swift::ExecuteSILPipelineRequest>(swift::Evaluator&, swift::ExecuteSILPipelineRequest)::'lambda'()>(swift::ExecuteSILPipelineRequest const&, swift::ExecuteSILPipelineRequest::OutputType swift::evaluateOrFatal<swift::ExecuteSILPipelineRequest>(swift::Evaluator&, swift::ExecuteSILPipelineRequest)::'lambda'()) + 412
13 swift-frontend           0x000000010141d438 swift::runSILDiagnosticPasses(swift::SILModule&) + 416
14 swift-frontend           0x00000001008c3c68 swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 656
15 swift-frontend           0x00000001004c8460 performCompileStepsPostSILGen(swift::CompilerInstance&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 1360
16 swift-frontend           0x00000001004c774c swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1032
17 swift-frontend           0x00000001004caa7c performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1764
18 swift-frontend           0x00000001004c968c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3580
19 swift-frontend           0x000000010044ac6c swift::mainEntry(int, char const**) + 5412
20 dyld                     0x000000018f1d9924 start + 6400
Failed frontend command:
/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c -primary-file /Users/bwebster/Projects/Radar/SwiftCrashTest/Dependent/Dependent.swift -emit-dependencies-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.d -emit-const-values-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.swiftconstvalues -emit-reference-dependencies-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.swiftdeps -serialize-diagnostics-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.dia -emit-localized-strings -emit-localized-strings-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64 -target arm64-apple-macos26.0 -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libFoundationMacros.dylib\#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server\#FoundationMacros -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libObservationMacros.dylib\#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server\#ObservationMacros -load-resolved-plugin /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins/libSwiftMacros.dylib\#/Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server\#SwiftMacros -disable-implicit-swift-modules -Xcc -fno-implicit-modules -Xcc -fno-implicit-module-maps -explicit-swift-module-map-file /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent-dependencies-57.json -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk -I /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug -F /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug -no-color-diagnostics -Xcc -fno-color-diagnostics -enable-library-evolution -enable-testing -g -debug-info-format\=dwarf -dwarf-version\=5 -module-cache-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftExplicitPrecompiledModules -swift-version 5 -enforce-exclusivity\=checked -Onone -D DEBUG -serialize-debugging-options -const-gather-protocols-file /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent_const_extract_protocols.json -enable-upcoming-feature DisableOutwardActorInference -enable-upcoming-feature InferSendableFromCaptures -enable-upcoming-feature GlobalActorIsolatedTypesUsability -enable-upcoming-feature MemberImportVisibility -enable-upcoming-feature InferIsolatedConformances -enable-upcoming-feature NonisolatedNonsendingByDefault -enable-experimental-feature DebugDescriptionMacro -enable-bare-slash-regex -validate-clang-modules-once -clang-build-session-file /Users/bwebster/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/Session.modulevalidation -Xcc -working-directory -Xcc /Users/bwebster/Projects/Radar/SwiftCrashTest -enable-anonymous-context-mangled-names -file-compilation-dir /Users/bwebster/Projects/Radar/SwiftCrashTest -Xcc -D_LIBCPP_HARDENING_MODE\=_LIBCPP_HARDENING_MODE_DEBUG -Xcc -ivfsstatcache -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SDKStatCaches.noindex/macosx26.0-25A5344a-bf0ffbe9ae4a19f9acfa348bfdda0e8c.sdkstatcache -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-generated-files.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-own-target-headers.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-all-target-headers.hmap -Xcc -iquote -Xcc /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Dependent-project-headers.hmap -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Products/Debug/include -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources-normal/arm64 -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources/arm64 -Xcc -I/Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/DerivedSources -Xcc -DDEBUG\=1 -no-auto-bridging-header-chaining -module-name Dependent -frontend-parseable-output -disable-clang-spi -target-sdk-version 26.0 -target-sdk-name macosx26.0 -clang-target arm64-apple-macos26.0 -in-process-plugin-server-path /Applications/Xcode-26.0.0-beta.7.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/libSwiftInProcPluginServer.dylib -parse-as-library -o /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Build/Intermediates.noindex/SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.o -index-unit-output-path /SwiftCrashTest.build/Debug/Dependent.build/Objects-normal/arm64/Dependent.o -index-store-path /Users/bwebster/Library/Developer/Xcode/DerivedData/SwiftCrashTest-fyyvpdmmdagefhfemmvfumbyaluu/Index.noindex/DataStore -index-system-modules

SwiftCompile normal arm64 /Users/bwebster/Projects/Radar/SwiftCrashTest/Dependent/Dependent.swift (in target 'Dependent' from project 'SwiftCrashTest')
    cd /Users/bwebster/Projects/Radar/SwiftCrashTest
    

Command SwiftCompile failed with a nonzero exit code

Command SwiftCompile failed with a nonzero exit code

Expected behavior

The project should build and link successfully.

Environment

This crash reproduces using Apple Swift version 6.2 (swiftlang-6.2.0.19.9 clang-1700.3.19.1), part of Xcode 26 beta 7 (17A5305k).

Compliing with Xcode 16.4 (16F6) does not crash the compiler.

Additional information

No response