public protocol QueryableModel {}


protocol _DocumentKeyConvertible {
    func makeDocumentKey() -> String
}


typealias DocumentKeyConvertible<M> = _DocumentKeyConvertible & PartialKeyPath<M>


extension KeyPath: _DocumentKeyConvertible where Root: QueryableModel, Value: Codable {
    func makeDocumentKey() -> String {
        return ""
    }
}


func somethingWithDocumentKeyConvertible<M>(_ something: DocumentKeyConvertible<M>) {
    print(something.makeDocumentKey())
}


struct SomeModel: QueryableModel {
    var someProperty: Int
}


somethingWithDocumentKeyConvertible(\SomeModel.someProperty)

Compile Swift Module 'StoredValueTypeDoesNotMatchPointerOperandTypeError' (1 sources)
Stored value type does not match pointer operand type!
  store %Ts14PartialKeyPathCy041StoredValueTypeDoesNotMatchPointerOperandF5Error9SomeModelVG* %7, %Ts14PartialKeyPathC** %3, align 8
 %Ts14PartialKeyPathC*<unknown>:0: error: fatal error encountered during compilation; please file a bug report with your project and the crash log
<unknown>:0: note: Broken function found, compilation aborted!
0  swift                    0x000000010d43464a PrintStackTraceSignalHandler(void*) + 42
1  swift                    0x000000010d433dfe SignalHandler(int) + 302
2  libsystem_platform.dylib 0x00007fff61069b3d _sigtramp + 29
3  libsystem_platform.dylib 000000000000000000 _sigtramp + 2667144416
4  libsystem_c.dylib        0x00007fff60f281c9 abort + 127
5  swift                    0x00000001096bbaf7 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*)::$_1::__invoke(void*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool) + 519
6  swift                    0x000000010d3e8278 llvm::report_fatal_error(llvm::Twine const&, bool) + 280
7  swift                    0x000000010d3e815b llvm::report_fatal_error(char const*, bool) + 43
8  swift                    0x000000010d3af7e6 (anonymous namespace)::VerifierLegacyPass::runOnFunction(llvm::Function&) + 54
9  swift                    0x000000010d35604e llvm::FPPassManager::runOnFunction(llvm::Function&) + 446
10 swift                    0x000000010d35e363 llvm::legacy::FunctionPassManagerImpl::run(llvm::Function&) + 115
11 swift                    0x000000010d35e258 llvm::legacy::FunctionPassManager::run(llvm::Function&) + 392
12 swift                    0x0000000109882228 swift::performLLVM(swift::IRGenOptions&, swift::DiagnosticEngine*, llvm::sys::SmartMutex<false>*, llvm::GlobalVariable*, llvm::Module*, llvm::TargetMachine*, swift::version::Version const&, llvm::StringRef, swift::UnifiedStatsReporter*) + 4504
13 swift                    0x0000000109886e0e ThreadEntryPoint(swift::irgen::IRGenerator*, llvm::sys::SmartMutex<false>*, int) + 206
14 swift                    0x0000000109885d1e swift::performIRGeneration(swift::IRGenOptions&, swift::ModuleDecl*, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::LLVMContext&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >, llvm::GlobalVariable**) + 7598
15 swift                    0x00000001096c7982 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 46786
16 swift                    0x00000001096b8dc5 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7717
17 swift                    0x000000010965ea35 main + 1349
18 libdyld.dylib            0x00007fff60e80085 start + 1
Stack dump:
0.  Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/Sources/StoredValueTypeDoesNotMatchPointerOperandTypeError/main.swift -emit-module-path /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release/StoredValueTypeDoesNotMatchPointerOperandTypeError.swiftmodule -emit-module-doc-path /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release/StoredValueTypeDoesNotMatchPointerOperandTypeError.swiftdoc -emit-dependencies-path /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release/StoredValueTypeDoesNotMatchPointerOperandTypeError.build/StoredValueTypeDoesNotMatchPointerOperandTypeError.d -target x86_64-apple-macosx10.10 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -I /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release -F /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -module-cache-path /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release/ModuleCache -swift-version 4.2 -O -D SWIFT_PACKAGE -color-diagnostics -module-name StoredValueTypeDoesNotMatchPointerOperandTypeError -num-threads 4 -o /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/x86_64-apple-macosx10.10/release/StoredValueTypeDoesNotMatchPointerOperandTypeError.build/main.swift.o 
1.  Running pass 'Module Verifier' on function '@main'
<unknown>:0: error: unable to execute command: Abort trap: 6
<unknown>:0: error: compile command failed due to signal 6 (use -v to see invocation)
error: terminated(1): /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-build-tool -f /Users/robbertbrandsma/Workingcopies/Speelsels/StoredValueTypeDoesNotMatchPointerOperandTypeError/.build/release.yaml main output: