{code: title=$ swift /tmp/test.swift}
/tmp/test.swift:12:1: error: expected '}' at end of brace statement

^
/tmp/test.swift:10:42: note: to match this opening '{'
    public var errorDescription: String? {
                                         ^
/tmp/test.swift:12:1: error: expected '}' at end of extension

^
/tmp/test.swift:9:35: note: to match this opening '{'
extension AFError: LocalizedError {
                                  ^
/tmp/test.swift:9:1: error: declaration is only valid at file scope
extension AFError: LocalizedError {
^
/tmp/test.swift:12:1: error: expected '}' at end of brace statement

^
/tmp/test.swift:7:40: note: to match this opening '{'
    public var isInvalidURLError: Bool {
                                       ^
/tmp/test.swift:12:1: error: expected '}' at end of extension

^
/tmp/test.swift:6:19: note: to match this opening '{'
extension AFError {
                  ^
Assertion failed: (getDeclContext()->getSelfProtocolDecl() || isOperator() || result == checkAccessUsingAccessScopes(useDC, this, access)), function isAccessibleFrom, file /Users/nhawes/github/swift/lib/AST/Decl.cpp, line 2646.
Stack dump:
0.  Program arguments: /Users/nhawes/github/build/Ninja-RelWithDebInfoAssert/swift-macosx-x86_64/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/wq/tdzgm3g56_98b0h3fv0mn61w0000gn/T/test-0d9f41.o 
0  swift                    0x0000000103f21138 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x0000000103f203b5 llvm::sys::RunSignalHandlers() + 85
2  swift                    0x0000000103f21742 SignalHandler(int) + 258
3  libsystem_platform.dylib 0x00007fff5a953b3d _sigtramp + 29
4  libsystem_platform.dylib 0x0000000000003e58 _sigtramp + 2775253816
5  libsystem_c.dylib        0x00007fff5a8121c9 abort + 127
6  libsystem_c.dylib        0x00007fff5a7da868 basename_r + 0
7  swift                    0x00000001016639e9 swift::ValueDecl::isAccessibleFrom(swift::DeclContext const*, bool) const + 249
8  swift                    0x0000000101397a2e swift::WitnessChecker::checkWitnessAccess(swift::AccessScope&, swift::ValueDecl*, swift::ValueDecl*, bool*) + 222
9  swift                    0x0000000101397c5a swift::WitnessChecker::checkWitness(swift::AccessScope, swift::ValueDecl*, swift::RequirementMatch const&) + 122
10 swift                    0x000000010139e72c swift::ConformanceChecker::resolveWitnessViaLookup(swift::ValueDecl*) + 1196
11 swift                    0x000000010139af79 swift::ConformanceChecker::checkConformance(swift::MissingWitnessDiagnosisKind) + 729
12 swift                    0x0000000101399abc swift::MultiConformanceChecker::checkIndividualConformance(swift::NormalProtocolConformance*, bool) + 6156
13 swift                    0x00000001013980e2 swift::MultiConformanceChecker::checkAllConformances() + 114
14 swift                    0x00000001013a2b87 swift::TypeChecker::checkConformancesInContext(swift::DeclContext*, swift::IterableDeclContext*) + 3063
15 swift                    0x00000001013ed9fe typeCheckFunctionsAndExternalDecls(swift::SourceFile&, swift::TypeChecker&) + 174
16 swift                    0x00000001013eec4b swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 2139
17 swift                    0x0000000101090698 swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 472
18 swift                    0x000000010108f2d7 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 439
19 swift                    0x000000010108e993 swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 627
20 swift                    0x00000001003e39b6 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1334
21 swift                    0x00000001003e23ed swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3021
22 swift                    0x000000010039456e main + 686
23 libdyld.dylib            0x00007fff5a76a085 start + 1
<unknown>:0: error: unable to execute command: Abort trap: 6