extension BinaryInteger {
  init(bytes: [UInt8]) { fatalError() }

  init<S: Sequence>(bytes: S) where S.Iterator.Element == UInt8 {
    self.init(bytes

extension
} 

Application Specific Information:
Stack dump:
0.  Program arguments: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2018-10-03-a.xctoolchain/usr/bin/swift -frontend -c -primary-file /tmp/test.swift -target x86_64-apple-darwin18.0.0 -enable-objc-interop -color-diagnostics -module-name test -o /var/folders/jn/jqt21vpn01d0m1k3ygry46hh0000gn/T/test-19ece3.o 
1.  While type-checking 'init(bytes:)' at /tmp/test.swift:4:3
2.  While type-checking statement at [/tmp/test.swift:4:65 - line:8:1] RangeText="{
    self.init(bytes
 
extension
"
3.  While type-checking expression at [/tmp/test.swift:5:5 - line:5:15] RangeText="self.init("
 

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   swift                           0x000000010a12c04d swift::constraints::RequirementFailure::getRequirement() const + 13
1   swift                           0x000000010a12c859 swift::constraints::RequirementFailure::diagnoseAsNote() + 25
2   swift                           0x000000010a12b573 swift::constraints::MissingConformance::diagnose(swift::Expr*, bool) const + 195
3   swift                           0x000000010a15f0ef swift::constraints::ConstraintSystem::diagnoseAmbiguityWithFixes(swift::Expr*, llvm::ArrayRef<swift::constraints::Solution>) + 927
4   swift                           0x000000010a15e93a swift::constraints::ConstraintSystem::salvage(llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::Expr*) + 346
5   swift                           0x000000010a11b3e8 swift::constraints::ConstraintSystem::solve(swift::Expr*&, swift::Type, swift::ExprTypeCheckListener*, llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::FreeTypeVariableBinding) + 72
6   swift                           0x000000010a1b9e37 swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 951
7   swift                           0x000000010a2472c8 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 584
8   swift                           0x000000010a246578 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::BraceStmt>(swift::BraceStmt*&) + 136
9   swift                           0x000000010a245511 swift::TypeChecker::typeCheckConstructorBodyUntil(swift::ConstructorDecl*, swift::SourceLoc) + 721
10  swift                           0x000000010a245c4f swift::TypeChecker::typeCheckAbstractFunctionBody(swift::AbstractFunctionDecl*) + 271
11  swift                           0x000000010a266133 typeCheckFunctionsAndExternalDecls(swift::SourceFile&, swift::TypeChecker&) + 339
12  swift                           0x000000010a26728d swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 2061
13  swift                           0x0000000109f09d28 swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 472
14  swift                           0x0000000109f08973 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 435
15  swift                           0x0000000109f08038 swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 616
16  swift                           0x0000000109242067 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1335
17  swift                           0x0000000109240a9d swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3021
18  swift                           0x00000001091f2f0e main + 686
19  libdyld.dylib                   0x00007fff742fd085 start + 1