func foo() -> () -> (@escaping ()) -> Void { { {} } }

Assertion failed: (Loc.isValid()), function getLineNumber, file /Users/hamishknight/Desktop/swift-dev/swift/include/swift/Basic/SourceManager.h, line 209.
Stack dump:
0.  Program arguments: ./swift -frontend -typecheck /Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
1.  Swift version 5.1-dev (LLVM 606965a6c8, Swift cae2eba999)
2.  While type-checking 'foo()' (at /Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:204:1)
3.  While type-checking statement at [/Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:204:51 - line:204:60] RangeText="{ { {} } "
4.  While type-checking statement at [/Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:204:53 - line:204:58] RangeText="{ {} "
5.  While type-checking expression at [/Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:204:53 - line:204:58] RangeText="{ {} "
0  swift                    0x000000010de83e75 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift                    0x000000010de82e78 llvm::sys::RunSignalHandlers() + 248
2  swift                    0x000000010de84478 SignalHandler(int) + 264
3  libsystem_platform.dylib 0x00007fff5e9e4b5d _sigtramp + 29
4  libsystem_platform.dylib 0x00000001116e8938 _sigtramp + 2999991800
5  libsystem_c.dylib        0x00007fff5e8a46a6 abort + 127
6  libsystem_c.dylib        0x00007fff5e86d20d basename_r + 0
7  swift                    0x000000010e18e7f3 swift::constraints::ClosureParamDestructuringFailure::diagnoseAsError() (.cold.3) + 35
8  swift                    0x000000010aa88c02 swift::constraints::ClosureParamDestructuringFailure::diagnoseAsError() + 4082
9  swift                    0x000000010aa7a830 swift::constraints::AllowClosureParamDestructuring::diagnose(swift::Expr*, bool) const + 112
10 swift                    0x000000010a9e5cbb swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&)::$_12::operator()(swift::Expr*) const + 203
11 swift                    0x000000010aa04161 swift::Expr* llvm::function_ref<swift::Expr* (swift::Expr*)>::callback_fn<swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&)::$_13>(long, swift::Expr*) + 33
12 swift                    0x000000010ae907be swift::Expr::forEachChildExpr(llvm::function_ref<swift::Expr* (swift::Expr*)>)::ChildWalker::walkToExprPre(swift::Expr*) + 14
13 swift                    0x000000010ae1687c swift::ASTVisitor<(anonymous namespace)::Traversal, swift::Expr*, swift::Stmt*, bool, swift::Pattern*, bool, void>::visit(swift::Expr*) + 7340
14 swift                    0x000000010ae14641 swift::Expr::walk(swift::ASTWalker&) + 81
15 swift                    0x000000010ae87013 swift::Expr::forEachChildExpr(llvm::function_ref<swift::Expr* (swift::Expr*)>) + 51
16 swift                    0x000000010a9e5b24 swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&) + 532
17 swift                    0x000000010a9e5ded swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool) + 141
18 swift                    0x000000010ab2081f swift::TypeChecker::typeCheckExpressionImpl(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener&, swift::constraints::ConstraintSystem*) + 1071
19 swift                    0x000000010ab203df swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 63
20 swift                    0x000000010abbaf0e swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 10542
21 swift                    0x000000010abbbb48 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::Stmt>(swift::Stmt*&) + 136
22 swift                    0x000000010abb86e9 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 265
23 swift                    0x000000010abb7968 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::BraceStmt>(swift::BraceStmt*&) + 136
24 swift                    0x000000010abb659d swift::TypeChecker::typeCheckFunctionBodyUntil(swift::FuncDecl*, swift::SourceLoc) + 493
25 swift                    0x000000010abb70ae swift::TypeChecker::typeCheckAbstractFunctionBody(swift::AbstractFunctionDecl*) + 334
26 swift                    0x000000010abd7547 typeCheckFunctionsAndExternalDecls(swift::SourceFile&, swift::TypeChecker&) + 247
27 swift                    0x000000010abd7ced swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 1005
28 swift                    0x000000010a390846 swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 502
29 swift                    0x000000010a38f656 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 342
30 swift                    0x000000010a38effa swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 618
31 swift                    0x000000010a17ed72 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1730
32 swift                    0x000000010a17d6d1 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3025
33 swift                    0x000000010a126c49 main + 729
34 libdyld.dylib            0x00007fff5e7ff3d5 start + 1
fish: './swift -frontend -typecheck /U…' terminated by signal SIGABRT (Abort)