extension Decodable {
    public static func decode(from data: Data) throws -> Self {
        let decoder = JSONDecoder()
        return try decoder.decode(self, from: data)
    }
}

public protocol TestDecodable: Decodable {}

public final class TestJSONDecoder: JSONDecoder {
    public override func decode<T: TestDecodable>(_ type: T.Type, from data: Data) throws -> T {
        return try super.decode(T.self, from: data)
    }
}

Assertion failed: (!substType->hasError() && "Error types should not appear in type-checked AST"), function getLoweredRValueType, file /Users/buildnode/jenkins/workspace/oss-swift-package-osx/swift/lib/SIL/TypeLowering.cpp, line 1566.
0  swift                    0x00000001112d2718 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x00000001112d1666 llvm::sys::RunSignalHandlers() + 86
2  swift                    0x00000001112d2cde SignalHandler(int) + 366
3  libsystem_platform.dylib 0x00007fff553ccf5a _sigtramp + 26
4  libsystem_platform.dylib 0x00000000000034f0 _sigtramp + 2864932272
5  libsystem_c.dylib        0x00007fff551f7312 abort + 127
6  libsystem_c.dylib        0x00007fff551bf368 basename_r + 0
7  swift                    0x000000010eabe0a5 swift::Lowering::TypeConverter::getLoweredRValueType(swift::Lowering::AbstractionPattern, swift::CanType) + 3077
8  swift                    0x000000010eabd043 swift::Lowering::TypeConverter::getTypeLowering(swift::Lowering::AbstractionPattern, swift::Type) + 435
9  swift                    0x000000010ea180b6 (anonymous namespace)::SILTypeSubstituter::visitType(swift::CanType) + 310
10 swift                    0x000000010ea17a2f swift::CanType swift::CanTypeVisitor<(anonymous namespace)::SILTypeSubstituter, swift::CanType>::visit<>(swift::CanType) + 95
11 swift                    0x000000010ea124d1 (anonymous namespace)::SILTypeSubstituter::substSILFunctionType(swift::CanTypeWrapper<swift::SILFunctionType>) + 257
12 swift                    0x000000010ea12387 swift::SILFunctionType::substGenericArgs(swift::SILModule&, llvm::function_ref<swift::Type (swift::SubstitutableType*)>, llvm::function_ref<llvm::Optional<swift::ProtocolConformanceRef> (swift::CanType, swift::Type, swift::ProtocolType*)>) + 71
13 swift                    0x000000010ea122f8 swift::SILFunctionType::substGenericArgs(swift::SILModule&, swift::SubstitutionMap const&) + 56
14 swift                    0x000000010ea12246 swift::SILFunctionType::substGenericArgs(swift::SILModule&, llvm::ArrayRef<swift::Substitution>) + 54
15 swift                    0x000000010e66af5e swift::devirtualizeClassMethod(swift::FullApplySite, swift::SILValue, swift::OptRemark::Emitter*) + 1566
16 swift                    0x000000010e81c52f speculateMonomorphicTarget(swift::FullApplySite, swift::SILType, swift::CheckedCastBranchInst*&) + 2127
17 swift                    0x000000010e81ad0a (anonymous namespace)::SpeculativeDevirtualization::run() + 3114
18 swift                    0x000000010e6ee529 swift::SILPassManager::runPassOnFunction(swift::SILFunctionTransform*, swift::SILFunction*) + 4041
19 swift                    0x000000010e6ef6c4 swift::SILPassManager::runFunctionPasses(llvm::ArrayRef<swift::SILFunctionTransform*>) + 1092
20 swift                    0x000000010e6f0b74 swift::SILPassManager::runOneIteration() + 964
21 swift                    0x000000010dfaabfb swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 187
22 swift                    0x000000010e6f93a5 swift::runSILOptimizationPasses(swift::SILModule&) + 117
23 swift                    0x000000010de58b7b performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 13723
24 swift                    0x000000010de545da swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3210
25 swift                    0x000000010de15470 main + 3360
26 libdyld.dylib            0x00007fff5514b115 start + 1

1.  While running pass #&#8203;6059 SILFunctionTransform "Speculative Devirtualization via Guarded Calls" on SILFunction "@_T0s9DecodableP7testPPPE6decodex10Foundation4DataV4from_tKFZ".
 for 'decode(from:)'