swift234

[swiftc] Add 💥 case (😢 → 42, 😀 → 5090) triggered in swift::ArchetypeBuilder::enumerateRequirements(…)

Add crash case with stack trace:

```
swift: /path/to/swift/lib/AST/GenericSignature.cpp:283: auto swift::GenericSignature::getCanonicalManglingSignature(swift::ModuleDecl &)::(anonymous class)::operator()(swift::RequirementKind, ArchetypeBuilder::PotentialArchetype *, llvm::PointerUnion<Type, ArchetypeBuilder::PotentialArchetype *>, swift::RequirementSource) const: Assertion `constraintType->isExistentialType()' failed.
10 swift           0x0000000000fdd429 swift::ArchetypeBuilder::enumerateRequirements(llvm::function_ref<void (swift::RequirementKind, swift::ArchetypeBuilder::PotentialArchetype*, llvm::PointerUnion<swift::Type, swift::ArchetypeBuilder::PotentialArchetype*>, swift::RequirementSource)>) + 185
11 swift           0x00000000010d2395 swift::GenericSignature::getCanonicalManglingSignature(swift::ModuleDecl&) const + 405
12 swift           0x0000000000f29dd5 swift::constraints::ConstraintSystem::openFunctionType(swift::AnyFunctionType*, swift::constraints::ConstraintLocatorBuilder, llvm::DenseMap<swift::CanType, swift::TypeVariableType*, llvm::DenseMapInfo<swift::CanType>, llvm::detail::DenseMapPair<swift::CanType, swift::TypeVariableType*> >&, swift::DeclContext*, swift::DeclContext*, bool) + 133
13 swift           0x0000000000f2ad37 swift::constraints::ConstraintSystem::getTypeOfReference(swift::ValueDecl*, bool, bool, swift::constraints::ConstraintLocatorBuilder, swift::DeclRefExpr const*) + 1127
18 swift           0x0000000000ee7ea9 swift::TypeChecker::checkConformance(swift::NormalProtocolConformance*) + 2313
19 swift           0x0000000000ee8347 swift::TypeChecker::checkConformancesInContext(swift::DeclContext*, swift::IterableDeclContext*) + 471
22 swift           0x0000000000ea13c6 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) + 150
25 swift           0x0000000000f08544 swift::TypeChecker::typeCheckClosureBody(swift::ClosureExpr*) + 244
26 swift           0x0000000000f3428c swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool, bool) + 876
27 swift           0x0000000000e8f9e1 swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*) + 769
28 swift           0x0000000000e90af7 swift::TypeChecker::typeCheckBinding(swift::Pattern*&, swift::Expr*&, swift::DeclContext*) + 343
29 swift           0x0000000000e90d0b swift::TypeChecker::typeCheckPatternBinding(swift::PatternBindingDecl*, unsigned int) + 267
38 swift           0x0000000000ea13c6 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) + 150
39 swift           0x0000000000ec3572 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int) + 1026
40 swift           0x0000000000c590f9 swift::CompilerInstance::performSema() + 3289
42 swift           0x00000000007d72b9 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2857
43 swift           0x00000000007a32c8 main + 2872
Stack dump:
0.	Program arguments: /path/to/swift/bin/swift -frontend -c -primary-file validation-test/compiler_crashers/28320-swift-archetypebuilder-enumeraterequirements.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -module-name main -o /tmp/28320-swift-archetypebuilder-enumeraterequirements-3ae5c2.o
1.	While type-checking declaration 0x50d5c40 at validation-test/compiler_crashers/28320-swift-archetypebuilder-enumeraterequirements.swift:10:1
2.	While type-checking expression at [validation-test/compiler_crashers/28320-swift-archetypebuilder-enumeraterequirements.swift:10:37 - line:10:45] RangeText="{enum T{c"
3.	While type-checking 'T' at validation-test/compiler_crashers/28320-swift-archetypebuilder-enumeraterequirements.swift:10:38
<unknown>:0: error: unable to execute command: Aborted
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)
```