Open Radar

 
The following code causes the most recent Swift compiler to crash:

protocol ExecutionContext {}
class ExecutionContextImpl: ExecutionContext {}
let defaultExecutionContext: ExecutionContext = ExecutionContextImpl()

class Future {
    func onSuccess() {
        onComplete(defaultExecutionContext)
    }
    func onComplete(_ executionContext: ExecutionContext = defaultExecutionContext) {}
}


The crash appears to be related to using a default function parameter that is a protocol.


Expected Results:
Should either compile or exit with a valid error message.

Actual Results:
Segmentation fault: 11

1. While emitting SIL for 'onSuccess' at /Users/pzh/Dev/crash/Concurrency/Future.swift:21:5

0  swift                    0x0000000106b65a08 llvm::sys::PrintStackTrace(__sFILE*) + 40
1  swift                    0x0000000106b65ee4 SignalHandler(int) + 452
2  libsystem_platform.dylib 0x00007fff8ac3ef1a _sigtramp + 26
3  libsystem_platform.dylib 0x00007fc67109e970 _sigtramp + 3863345776
4  swift                    0x00000001065fdf2e (anonymous namespace)::Transform::transform(swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::SGFContext) + 494
5  swift                    0x00000001065fe618 swift::Lowering::SILGenFunction::emitSubstToOrigValue(swift::SILLocation, swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::SGFContext) + 56
6  swift                    0x00000001065996ef swift::Lowering::ArgumentSource::forwardInto(swift::Lowering::SILGenFunction&, swift::Lowering::AbstractionPattern, swift::Lowering::Initialization*, swift::Lowering::TypeLowering const&) && + 559
7  swift                    0x000000010659947f swift::Lowering::ArgumentSource::materialize(swift::Lowering::SILGenFunction&, swift::Lowering::AbstractionPattern, swift::SILType) && + 415
8  swift                    0x00000001065ae633 (anonymous namespace)::ArgEmitter::emit(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 1315
9  swift                    0x00000001065b0097 (anonymous namespace)::ArgEmitter::emitShuffle(swift::Expr*, swift::Expr*, llvm::ArrayRef<swift::TupleTypeElt>, swift::ConcreteDeclRef, llvm::ArrayRef<swift::Expr*>, llvm::ArrayRef<int>, swift::Type, swift::Lowering::AbstractionPattern) + 2839
10 swift                    0x00000001065af373 (anonymous namespace)::ArgEmitter::emitExpanded(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 2387
...