Open Radar

 
Summary:
I was astonished that this compiles, but subsequently bemused that it crashes while merging the module.


Steps to Reproduce:
1. A module compiled from code:
protocol P {
	typealias T
}

enum E<F : P where F.T == E<F>> {
	indirect case Roll(F.T)
}


Expected Results:
should not crash swiftc


Actual Results:
but totally does:

rob@Resonance ~/Desktop> swiftc -emit-module boom.swift; and ./boom
0  swift                    0x0000000111967bbb llvm::sys::PrintStackTrace(__sFILE*) + 43
1  swift                    0x00000001119682fb SignalHandler(int) + 379
2  libsystem_platform.dylib 0x00007fff992d8eaa _sigtramp + 26
3  libsystem_platform.dylib 000000000000000000 _sigtramp + 1725067632
4  swift                    0x00000001100d539e swift::GenericParamList::addNestedArchetypes(swift::ArchetypeType*, llvm::SmallPtrSetImpl<swift::ArchetypeType*>&, llvm::SmallVectorImpl<swift::ArchetypeType*>&) + 30
5  swift                    0x00000001100d5663 swift::GenericParamList::deriveAllArchetypes(llvm::ArrayRef<swift::GenericTypeParamDecl*>, llvm::SmallVectorImpl<swift::ArchetypeType*>&) + 355
6  swift                    0x000000010fd11a21 swift::ModuleFile::maybeReadGenericParams(swift::DeclContext*, llvm::BitstreamCursor&, swift::GenericParamList*) + 561
7  swift                    0x000000010fd0b86d swift::ModuleFile::getDecl(llvm::Fixnum<31u, unsigned int>, llvm::Optional<swift::DeclContext*>) + 14605
8  swift                    0x000000010fd05d72 swift::ModuleFile::getType(llvm::Fixnum<31u, unsigned int>) + 3026
9  swift                    0x000000010fd0795b swift::ModuleFile::getType(llvm::Fixnum<31u, unsigned int>) + 10171
10 swift                    0x000000010fd0c70f swift::ModuleFile::getDecl(llvm::Fixnum<31u, unsigned int>, llvm::Optional<swift::DeclContext*>) + 18351
11 swift                    0x000000010fd11ddd swift::ModuleFile::maybeReadGenericParams(swift::DeclContext*, llvm::BitstreamCursor&, swift::GenericParamList*) + 1517
12 swift                    0x000000010fd0b86d swift::ModuleFile::getDecl(llvm::Fixnum<31u, unsigned int>, llvm::Optional<swift::DeclContext*>) + 14605
13 swift                    0x000000010fd3771a swift::ModuleFile::getTopLevelDecls(llvm::SmallVectorImpl<swift::Decl*>&) + 666
14 swift                    0x000000010fd4d7f8 swift::serialization::Serializer::writeAST(llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>) + 648
15 swift                    0x000000010fd507a7 swift::serialization::Serializer::writeToStream(llvm::raw_ostream&, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::SILModule const*, swift::SerializationOptions const&) + 135
16 swift                    0x000000010fd51282 withOutputFile(swift::ASTContext&, llvm::StringRef, llvm::function_ref<void (llvm::raw_ostream&)>) + 226
17 swift                    0x000000010fd510b5 swift::serialize(llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::SerializationOptions const&, swift::SILModule const*) + 149
18 swift                    0x000000010f92b899 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&) + 13945
19 swift                    0x000000010f927fc8 frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2728
20 swift                    0x000000010f92402f main + 2015
21 libdyld.dylib            0x00007fff97a025ad start + 1
Stack dump:
0.	Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -emit-module /var/folders/9y/f7n4rvx901nctm_5d16c1wm40000gn/T/boom-b39a27.swiftmodule -parse-as-library -target x86_64-apple-darwin15.0.0 -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -emit-module-doc-path boom.swiftdoc -color-diagnostics -module-name boom -o boom.swiftmodule 
1.	While reading from /var/folders/9y/f7n4rvx901nctm_5d16c1wm40000gn/T/boom-b39a27.swiftmodule
2.	While deserializing decl #4 (ENUM_DECL)
3.	While deserializing 'F' (GenericTypeParamDecl #10) 
4.	While deserializing decl #4 (ENUM_DECL)
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: merge-module command failed due to signal (use -v to see invocation)


Regression:
This apparently compiles just fine if you don’t put it in a module, i.e. if you omit the `-emit-modules` flag to swiftc.


Notes:
N/A