[swiftc (56 vs. 5600)] Add crasher in swift::TypeChecker::resolveIdentifierType

Add test case for crash triggered in `swift::TypeChecker::resolveIdentifierType`.

Current number of unresolved compiler crashers: 56 (5600 resolved)

Stack trace:

```
0 0x0000000003ea2314 PrintStackTraceSignalHandler(void*) (/path/to/swift/bin/swift+0x3ea2314)
1 0x0000000003ea2656 SignalHandler(int) (/path/to/swift/bin/swift+0x3ea2656)
2 0x00007fa080f3e390 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
3 0x00007fa07f463428 gsignal /build/glibc-bfm8X4/glibc-2.23/signal/../sysdeps/unix/sysv/linux/raise.c:54:0
4 0x00007fa07f46502a abort /build/glibc-bfm8X4/glibc-2.23/stdlib/abort.c:91:0
5 0x0000000003e38c5d llvm::llvm_unreachable_internal(char const*, char const*, unsigned int) (/path/to/swift/bin/swift+0x3e38c5d)
6 0x00000000012d0c4a (/path/to/swift/bin/swift+0x12d0c4a)
7 0x00000000013230f2 resolveIdentTypeComponent(swift::TypeChecker&, swift::DeclContext*, llvm::ArrayRef<swift::ComponentIdentTypeRepr*>, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, bool, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) (/path/to/swift/bin/swift+0x13230f2)
8 0x0000000001322a5a swift::TypeChecker::resolveIdentifierType(swift::DeclContext*, swift::IdentTypeRepr*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, bool, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) (/path/to/swift/bin/swift+0x1322a5a)
9 0x00000000013237f0 (anonymous namespace)::TypeResolver::resolveType(swift::TypeRepr*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>) (/path/to/swift/bin/swift+0x13237f0)
10 0x00000000013236fc swift::TypeChecker::resolveType(swift::TypeRepr*, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) (/path/to/swift/bin/swift+0x13236fc)
11 0x0000000001321ff5 swift::TypeChecker::validateType(swift::TypeLoc&, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) (/path/to/swift/bin/swift+0x1321ff5)
12 0x00000000012d1c66 checkGenericFuncSignature(swift::TypeChecker&, swift::GenericSignatureBuilder*, swift::AbstractFunctionDecl*, swift::GenericTypeResolver&) (/path/to/swift/bin/swift+0x12d1c66)
13 0x00000000012d1a33 swift::TypeChecker::validateGenericFuncSignature(swift::AbstractFunctionDecl*) (/path/to/swift/bin/swift+0x12d1a33)
14 0x00000000012b658f (anonymous namespace)::DeclChecker::visitFuncDecl(swift::FuncDecl*) (/path/to/swift/bin/swift+0x12b658f)
15 0x00000000012a094f (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x12a094f)
16 0x00000000012b3e0b (anonymous namespace)::DeclChecker::visitProtocolDecl(swift::ProtocolDecl*) (/path/to/swift/bin/swift+0x12b3e0b)
17 0x00000000012a092f (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x12a092f)
18 0x00000000012b2acb (anonymous namespace)::DeclChecker::visitClassDecl(swift::ClassDecl*) (/path/to/swift/bin/swift+0x12b2acb)
19 0x00000000012a0a1e (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x12a0a1e)
20 0x00000000012b3e0b (anonymous namespace)::DeclChecker::visitProtocolDecl(swift::ProtocolDecl*) (/path/to/swift/bin/swift+0x12b3e0b)
21 0x00000000012a092f (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x12a092f)
22 0x00000000012a07c3 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) (/path/to/swift/bin/swift+0x12a07c3)
23 0x0000000001331325 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int) (/path/to/swift/bin/swift+0x1331325)
24 0x0000000001054ae4 swift::CompilerInstance::parseAndTypeCheckMainFile(swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) (/path/to/swift/bin/swift+0x1054ae4)
25 0x0000000001053ba7 swift::CompilerInstance::parseAndCheckTypes(swift::CompilerInstance::ImplicitImports const&) (/path/to/swift/bin/swift+0x1053ba7)
26 0x00000000010534ca swift::CompilerInstance::performSema() (/path/to/swift/bin/swift+0x10534ca)
27 0x00000000004bdb56 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) (/path/to/swift/bin/swift+0x4bdb56)
28 0x00000000004bc919 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) (/path/to/swift/bin/swift+0x4bc919)
29 0x0000000000474c14 main (/path/to/swift/bin/swift+0x474c14)
30 0x00007fa07f44e830 __libc_start_main /build/glibc-bfm8X4/glibc-2.23/csu/../csu/libc-start.c:325:0
31 0x00000000004724c9 _start (/path/to/swift/bin/swift+0x4724c9)
```

Author: practicalswift

validation-test/compiler_crashers/28850-unreachable-executed-at-swift-lib-sema-typecheckgeneric-cpp-220.swift

@@ -0,0 +1,9 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+protocol P{class a{protocol a:P{func a:a.a{}typealias a