Compiler crash when a protocol containing an associatedType has an attached extension macro and multiple extensions containing freestanding macros

[DavidSkrundz]

Description

I'm trying to use a macro to help write default implementations for functions on a protocol, but the compiler is crashing. I found multiple possible causes but I'm not sure how they all interact: the attached extension macro on the protocol, the associated type, or the exact number of other extensions on the protocol.

I reduced the example as much as I could and made it available at https://github.com/DavidSkrundz/MacroICE/tree/declare_funcs_in_extensions (also pasted below)

Reproduction

Library Target:

@attached(extension, names: arbitrary)
public macro DeclExtension() = #externalMacro(module: "Macros", type: "DeclExtensionMacro")

@freestanding(declaration, names: arbitrary)
public macro DeclStructFunc(_ struct: Any.Type) = #externalMacro(module: "Macros", type: "DeclStructFuncMacro")

// A) Comment out the attached macro to prevent the crash
@DeclExtension
public protocol SyntaxVisitor {
    // B) Comment out the associatedtype to prevent the crash
    associatedtype Context
}

struct StructOne {}
extension SyntaxVisitor {
    #DeclStructFunc(StructOne)
}

struct StructTwo {}
extension SyntaxVisitor {
    #DeclStructFunc(StructTwo)
}

struct StructThree {}
extension SyntaxVisitor {
    #DeclStructFunc(StructThree)
}

// C) Comment out any of the four extensions to prevent the crash
struct StructFour {}
extension SyntaxVisitor {
    #DeclStructFunc(StructFour)
}

// D) Uncomment this extension to prevent the crash
//struct StructFive {}
//extension SyntaxVisitor {
//    #DeclStructFunc(StructFive)
//}

Macro Target:

import SwiftCompilerPlugin
import SwiftSyntaxMacros

@main
struct SupermanPlugin: CompilerPlugin {
    let providingMacros: [Macro.Type] = [
        DeclExtensionMacro.self,
        DeclStructFuncMacro.self,
    ]
}

import SwiftSyntax

public struct DeclExtensionMacro: ExtensionMacro {
    public static func expansion(of node: AttributeSyntax,
                                 attachedTo declaration: some DeclGroupSyntax,
                                 providingExtensionsOf type: some TypeSyntaxProtocol,
                                 conformingTo protocols: [TypeSyntax],
                                 in context: some MacroExpansionContext) throws -> [ExtensionDeclSyntax] {
        return [
            ExtensionDeclSyntax(
                extendedType: type,
                memberBlock: MemberBlockSyntax(members: [])
            ),
        ]
    }
}

struct DeclStructFuncMacro: DeclarationMacro {
    static func expansion(of node: some FreestandingMacroExpansionSyntax,
                          in context: some MacroExpansionContext) throws -> [DeclSyntax] {
        let type = node.arguments.first!.expression.as(DeclReferenceExprSyntax.self)!.baseName
        return ["func Gen\(raw: type)() {}"]
    }
}

Stack dump

Building for debugging...
 error: emit-module command failed due to signal 11 (use -v to see invocation)
 Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
 Stack dump:
 0.	Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -emit-module -experimental-skip-non-inlinable-function-bodies-without-types /Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift -target arm64-apple-macosx10.15 -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -I /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Modules -I /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib -F /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -color-diagnostics -enable-testing -g -debug-info-format=dwarf -dwarf-version=4 -module-cache-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/ModuleCache -swift-version 6 -Onone -D SWIFT_PACKAGE -D DEBUG -new-driver-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-driver -load-plugin-executable /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Macros-tool#Macros -empty-abi-descriptor -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -enable-anonymous-context-mangled-names -file-compilation-dir /Volumes/Data/Development/skrundz/MacroICE -Xcc -fmodule-map-file=/Volumes/Data/Development/skrundz/MacroICE/.build/checkouts/swift-syntax/Sources/_SwiftSyntaxCShims/include/module.modulemap -Xcc -I -Xcc /Volumes/Data/Development/skrundz/MacroICE/.build/checkouts/swift-syntax/Sources/_SwiftSyntaxCShims/include -Xcc -isysroot -Xcc /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -Xcc -F -Xcc /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -Xcc -fPIC -Xcc -g -module-name MacroCrash -package-name macroice -disable-clang-spi -target-sdk-version 15.2 -target-sdk-name macosx15.2 -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/local/lib/swift/host/plugins -emit-module-doc-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Modules/MacroCrash.swiftdoc -emit-module-source-info-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Modules/MacroCrash.swiftsourceinfo -emit-objc-header-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/MacroCrash.build/MacroCrash-Swift.h -emit-dependencies-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/MacroCrash.build/MacroCrash.emit-module.d -parse-as-library -o /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Modules/MacroCrash.swiftmodule -emit-abi-descriptor-path /Volumes/Data/Development/skrundz/MacroICE/.build/arm64-apple-macosx/debug/Modules/MacroCrash.abi.json
 1.	Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
 2.	Compiling with the current language version
 3.	While evaluating request TypeCheckSourceFileRequest(source_file "/Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift")
 4.	While type-checking 'SyntaxVisitor' (at /Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift:18:8)
 5.	While type-checking 'Context' (at /Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift:20:2)
 6.	While evaluating request CheckRedeclarationRequest(MacroCrash.(file).SyntaxVisitor.Context@/Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift:20:17, MacroCrash.(file).SyntaxVisitor@/Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift:18:17)
 7.	While evaluating request DirectLookupRequest(directly looking up 'Context' on MacroCrash.(file).SyntaxVisitor@/Volumes/Data/Development/skrundz/MacroICE/Sources/MacroCrash/MacroCrash.swift:18:17 with options {  })
 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           0x00000001063aea9c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
 1  swift-frontend           0x00000001063accf0 llvm::sys::RunSignalHandlers() + 112
 2  swift-frontend           0x00000001063af068 SignalHandler(int) + 292
 3  libsystem_platform.dylib 0x0000000182420184 _sigtramp + 56
 4  swift-frontend           0x00000001026b9c8c swift::DirectLookupRequest::evaluate(swift::Evaluator&, swift::DirectLookupDescriptor) const + 6912
 5  swift-frontend           0x00000001026d3824 swift::SimpleRequest<swift::DirectLookupRequest, llvm::TinyPtrVector<swift::ValueDecl*> (swift::DirectLookupDescriptor), (swift::RequestFlags)17>::evaluateRequest(swift::DirectLookupRequest const&, swift::Evaluator&) + 36
 6  swift-frontend           0x00000001026ca60c swift::DirectLookupRequest::OutputType swift::Evaluator::getResultUncached<swift::DirectLookupRequest, swift::DirectLookupRequest::OutputType swift::evaluateOrDefault<swift::DirectLookupRequest>(swift::Evaluator&, swift::DirectLookupRequest, swift::DirectLookupRequest::OutputType)::'lambda'()>(swift::DirectLookupRequest const&, swift::DirectLookupRequest::OutputType swift::evaluateOrDefault<swift::DirectLookupRequest>(swift::Evaluator&, swift::DirectLookupRequest, swift::DirectLookupRequest::OutputType)::'lambda'()) + 552
 7  swift-frontend           0x00000001026b8148 swift::DirectLookupRequest::OutputType swift::evaluateOrDefault<swift::DirectLookupRequest>(swift::Evaluator&, swift::DirectLookupRequest, swift::DirectLookupRequest::OutputType) + 196
 8  swift-frontend           0x00000001026b8040 swift::NominalTypeDecl::lookupDirect(swift::DeclName, swift::SourceLoc, swift::optionset::OptionSet<swift::NominalTypeDecl::LookupDirectFlags, unsigned int>) + 264
 9  swift-frontend           0x0000000102123150 swift::CheckRedeclarationRequest::evaluate(swift::Evaluator&, swift::ValueDecl*, swift::NominalTypeDecl*) const + 376
 10 swift-frontend           0x0000000102129494 (anonymous namespace)::DeclChecker::visit(swift::Decl*) + 5856
 11 swift-frontend           0x0000000102128448 (anonymous namespace)::DeclChecker::visit(swift::Decl*) + 1684
 12 swift-frontend           0x0000000102127da4 swift::TypeChecker::typeCheckDecl(swift::Decl*) + 152
 13 swift-frontend           0x000000010220f01c swift::TypeCheckSourceFileRequest::evaluate(swift::Evaluator&, swift::SourceFile*) const + 660
 14 swift-frontend           0x0000000102216680 swift::TypeCheckSourceFileRequest::OutputType swift::Evaluator::getResultUncached<swift::TypeCheckSourceFileRequest, swift::TypeCheckSourceFileRequest::OutputType swift::evaluateOrDefault<swift::TypeCheckSourceFileRequest>(swift::Evaluator&, swift::TypeCheckSourceFileRequest, swift::TypeCheckSourceFileRequest::OutputType)::'lambda'()>(swift::TypeCheckSourceFileRequest const&, swift::TypeCheckSourceFileRequest::OutputType swift::evaluateOrDefault<swift::TypeCheckSourceFileRequest>(swift::Evaluator&, swift::TypeCheckSourceFileRequest, swift::TypeCheckSourceFileRequest::OutputType)::'lambda'()) + 620
 15 swift-frontend           0x000000010220ed6c swift::performTypeChecking(swift::SourceFile&) + 328
 16 swift-frontend           0x000000010112be48 swift::CompilerInstance::performSema() + 332
 17 swift-frontend           0x0000000100d58df0 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1532
 18 swift-frontend           0x0000000100d57bb4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3572
 19 swift-frontend           0x0000000100cdea5c swift::mainEntry(int, char const**) + 3680
 20 dyld                     0x0000000182068274 start + 2840

Expected behavior

The compiler should not crash.

Environment

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0

Additional information

No response