Macros with lazy var

tiagosousa · January 31, 2024, 2:33pm

Hi everyone,
I've been exploring Macros and was trying to create one that only returns a lazy var, using the following code:

public struct SubjectPublisherMacro: PeerMacro {

    public static func expansion(of node: AttributeSyntax,
                                 providingPeersOf declaration: some DeclSyntaxProtocol,
                                 in context: some MacroExpansionContext) throws -> [SwiftSyntax.DeclSyntax] {

        return [
            "lazy var state: AnyPublisher<String, Never> = { subject.eraseToAnyPublisher() }()"
        ]
    }
}

When applied to a Subject, like the following:

@SubjectPublisher
private var subject = PassthroughSubject<String, Never>()

If we expand the macro, the code generated is effectively:

lazy var state: AnyPublisher<String, Never> = {
    subject.eraseToAnyPublisher()
}()

However, when we compile, it gives an error, and we have the following Stack dump:


0.	Program arguments: /Applications/Xcode-15.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c -primary-file /Users/xpto/macros/FFMacros/Sources/FFMacrosClient/main.swift -emit-dependencies-path /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.d -emit-const-values-path /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.swiftconstvalues -emit-reference-dependencies-path /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.swiftdeps -serialize-diagnostics-path /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.dia -target arm64-apple-macos10.15 -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk -I /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Products/Debug -I /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib -F /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Products/Debug/PackageFrameworks -F /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Products/Debug -F /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -no-color-diagnostics -enable-testing -g -module-cache-path /Users/xpto/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -profile-generate -profile-coverage-mapping -swift-version 5 -enforce-exclusivity=checked -Onone -D SWIFT_PACKAGE -D DEBUG -D Xcode -serialize-debugging-options -load-plugin-executable /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Products/Debug/FFMacrosMacros#FFMacrosMacros -package-name ffmacros -const-gather-protocols-file /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/FFMacrosClient_const_extract_protocols.json -empty-abi-descriptor -validate-clang-modules-once -clang-build-session-file /Users/xpto/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/Session.modulevalidation -Xcc -working-directory -Xcc /Users/xpto/macros/FFMacros -resource-dir /Applications/Xcode-15.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -enable-anonymous-context-mangled-names -Xcc -ivfsstatcache -Xcc /Users/xpto/Library/Developer/Xcode/DerivedData/SDKStatCaches.noindex/macosx14.2-23C53-ddea79c7890ab41bba4a63928c655a96.sdkstatcache -Xcc -I/Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Products/Debug/include -Xcc -I/Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/DerivedSources-normal/arm64 -Xcc -I/Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/DerivedSources/arm64 -Xcc -I/Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/DerivedSources -Xcc -DSWIFT_PACKAGE -Xcc -DDEBUG=1 -module-name FFMacrosClient -frontend-parseable-output -disable-clang-spi -target-sdk-version 14.2 -target-sdk-name macosx14.2 -external-plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk/usr/lib/swift/host/plugins#/Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk/usr/local/lib/swift/host/plugins#/Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode-15.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Applications/Xcode-15.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/local/lib/swift/host/plugins -o /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Build/Intermediates.noindex/FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.o -index-unit-output-path /FFMacros.build/Debug/FFMacrosClient.build/Objects-normal/arm64/main.o -index-store-path /Users/xpto/Library/Developer/Xcode/DerivedData/FFMacros-byrxxptdunfedzeunapzrisyulor/Index.noindex/DataStore -index-system-modules
1.	Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
2.	Compiling with the current language version
3.	While evaluating request IRGenRequest(IR Generation for file "/Users/macros/FFMacros/Sources/FFMacrosClient/main.swift")
4.	While emitting IR SIL function "@$s14FFMacrosClient4TestC5state7Combine12AnyPublisherVySSs5NeverOGvg".
 for getter for state (at @__swiftmacro_14FFMacrosClient4TestC7subject33_32E41C858868D91DD4497E3BF955E2AFLL16SubjectPublisherfMp_.swift:1:10)
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           0x000000010728dabc llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000109ef3cb0 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000109c5d054 SignalHandler(int) + 352
3  libsystem_platform.dylib 0x0000000186829a24 _sigtramp + 56
4  swift-frontend           0x00000001098a52a4 swift::irgen::projectPhysicalClassMemberAddress(swift::irgen::IRGenFunction&, llvm::Value*, swift::SILType, swift::SILType, swift::VarDecl*, swift::GenericSignature) + 1036
5  swift-frontend           0x00000001098a52a4 swift::irgen::projectPhysicalClassMemberAddress(swift::irgen::IRGenFunction&, llvm::Value*, swift::SILType, swift::SILType, swift::VarDecl*, swift::GenericSignature) + 1036
6  swift-frontend           0x0000000106e90ee4 (anonymous namespace)::IRGenSILFunction::visitSILBasicBlock(swift::SILBasicBlock*) + 79544
7  swift-frontend           0x0000000109611fdc swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 11680
8  swift-frontend           0x00000001072109c8 swift::irgen::IRGenerator::emitGlobalTopLevel(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>,
std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>> const&) + 2516
9  swift-frontend           0x00000001058b59d0 swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 6532
10 swift-frontend           0x0000000105188adc swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenRequest const&, swift::Evaluator&) + 176
11 swift-frontend           0x0000000106b59f64 llvm::Expected<swift::IRGenRequest::OutputType> swift::Evaluator::getResultUncached<swift::IRGenRequest>(swift::IRGenRequest const&) + 1480
12 swift-frontend           0x0000000108e00fb8 swift::performIRGeneration(swift::FileUnit*, swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::GlobalVariable**) + 264
13 swift-frontend           0x00000001097cd99c generateIR(swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, llvm::GlobalVariable*&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>) + 156
14 swift-frontend           0x00000001097d56d4 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*) + 1596
15 swift-frontend           0x00000001097d0a08 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1748
16 swift-frontend           0x00000001097d4854 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 4568
17 swift-frontend           0x000000010983bd44 swift::mainEntry(int, char const**) + 4408
18 dyld                     0x00000001864790e0 start + 2360
LLVM Profile Error: Failed to write file "default.profraw": Operation not permitted

If we modify our macro to return a computed var instead of a lazy var, we can compile successfully. However, our goal was to return the lazy var. Does anyone have an idea of what the issue might be?

Thanks for your help!

daniel-b · September 5, 2024, 3:20pm

I see something similar, and generating lazy vars for dependency management is what I want to use SwiftMacros for the most. Backtrace on Xcode 16.1-beta1:

1.	Apple Swift version 6.0 (swiftlang-6.0.0.7.6 clang-1600.0.24.1)
2.	Compiling with effective version 5.10
3.	While evaluating request IRGenRequest(IR Generation for file "/Users/danielbeard/Dev/GenVarsSwiftMacro/Sources/GenVarsSwiftMacroClient/main.swift")
4.	While emitting IR SIL function "@$s23GenVarsSwiftMacroClient1AC12themeManager33_0E3B81B0FDC98D18539F28AD09635FF8LLAA05ThemeG4Type_pvg".
 for getter for themeManager (at @__swiftmacro_23GenVarsSwiftMacroClient1AC12Dependencies0aB0fMp_.swift:3:22)
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           0x0000000105f95194 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000105f933e8 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000105f95760 SignalHandler(int) + 292
3  libsystem_platform.dylib 0x000000018051e584 _sigtramp + 56
4  swift-frontend           0x00000001010275c4 swift::irgen::ElementLayout::project(swift::irgen::IRGenFunction&, swift::irgen::Address, std::__1::optional<swift::irgen::NonFixedOffsetsImpl*>, llvm::Twine const&) const + 816
5  swift-frontend           0x0000000100da0520 swift::irgen::projectPhysicalClassMemberAddress(swift::irgen::IRGenFunction&, llvm::Value*, swift::SILType, swift::SILType, swift::VarDecl*, swift::GenericSignature) + 1040
6  swift-frontend           0x0000000100f926dc (anonymous namespace)::IRGenSILFunction::visitSILBasicBlock(swift::SILBasicBlock*) + 49820
7  swift-frontend           0x0000000100f85124 (anonymous namespace)::IRGenSILFunction::emitSILFunction() + 13220
8  swift-frontend           0x0000000100f818dc swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 2088
9  swift-frontend           0x0000000100dcd8b4 swift::irgen::IRGenerator::emitGlobalTopLevel(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>> const&) + 3364
10 swift-frontend           0x0000000100f39118 swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 4700
11 swift-frontend           0x0000000100f80e28 swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenRequest const&, swift::Evaluator&) + 176
12 swift-frontend           0x0000000100f42010 swift::IRGenRequest::OutputType swift::Evaluator::getResultUncached<swift::IRGenRequest, swift::IRGenRequest::OutputType swift::evaluateOrFatal<swift::IRGenRequest>(swift::Evaluator&, swift::IRGenRequest)::'lambda'()>(swift::IRGenRequest const&, swift::IRGenRequest::OutputType swift::evaluateOrFatal<swift::IRGenRequest>(swift::Evaluator&, swift::IRGenRequest)::'lambda'()) + 784
13 swift-frontend           0x0000000100f3ba48 swift::performIRGeneration(swift::FileUnit*, swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::GlobalVariable**) + 180
14 swift-frontend           0x000000010094cd5c generateIR(swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, llvm::GlobalVariable*&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>) + 156
15 swift-frontend           0x0000000100948588 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*) + 2176
16 swift-frontend           0x0000000100947474 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 984
17 swift-frontend           0x000000010094a728 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1680
18 swift-frontend           0x0000000100949458 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3572
19 swift-frontend           0x00000001008d050c swift::mainEntry(int, char const**) + 3680
20 dyld                     0x0000000180163154 start + 2476