[swiftc (32 vs. 5544)] Add crasher in swift::Expr::walk(...)

Add test case for crash triggered in `swift::Expr::walk(...)`.

Current number of unresolved compiler crashers: 32 (5544 resolved)

/cc @DougGregor - just wanted to let you know that this crasher caused an assertion failure for the assertion `ty->getNominalOrBoundGenericNominal() || ty->is<DynamicSelfType>() || ty->isExistentialType() || ty->is<ArchetypeType>()` added on 2014-02-25 by you in commit 6a532e0 :-)

Assertion failure in [`lib/Sema/CSApply.cpp (line 7121)`](https://github.com/apple/swift/blob/5c1859e98aca8d6292fb4f7563d47fd2856b7715/lib/Sema/CSApply.cpp#L7121):

```
Assertion `ty->getNominalOrBoundGenericNominal() || ty->is<DynamicSelfType>() || ty->isExistentialType() || ty->is<ArchetypeType>()' failed.

When executing: swift::Expr *(anonymous namespace)::ExprRewriter::finishApply(swift::ApplyExpr *, swift::Type, swift::constraints::ConstraintLocatorBuilder)
```

Assertion context:

```c++
  }

  // We're constructing a value of nominal type. Look for the constructor or
  // enum element to use.
  assert(ty->getNominalOrBoundGenericNominal() || ty->is<DynamicSelfType>() ||
         ty->isExistentialType() || ty->is<ArchetypeType>());
  auto ctorLocator = cs.getConstraintLocator(
                 locator.withPathElement(ConstraintLocator::ApplyFunction)
                        .withPathElement(ConstraintLocator::ConstructorMember));
  auto selected = getOverloadChoiceIfAvailable(ctorLocator);

```
Stack trace:

```
0 0x0000000003a5f2b8 llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/path/to/swift/bin/swift+0x3a5f2b8)
1 0x0000000003a5f9f6 SignalHandler(int) (/path/to/swift/bin/swift+0x3a5f9f6)
2 0x00007f45d9d9b390 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
3 0x00007f45d82c1428 gsignal /build/glibc-9tT8Do/glibc-2.23/signal/../sysdeps/unix/sysv/linux/raise.c:54:0
4 0x00007f45d82c302a abort /build/glibc-9tT8Do/glibc-2.23/stdlib/abort.c:91:0
5 0x00007f45d82b9bd7 __assert_fail_base /build/glibc-9tT8Do/glibc-2.23/assert/assert.c:92:0
6 0x00007f45d82b9c82 (/lib/x86_64-linux-gnu/libc.so.6+0x2dc82)
7 0x00000000013d899e (/path/to/swift/bin/swift+0x13d899e)
8 0x00000000013eeb93 (anonymous namespace)::ExprRewriter::visitApplyExpr(swift::ApplyExpr*) (/path/to/swift/bin/swift+0x13eeb93)
9 0x00000000013d4294 (anonymous namespace)::ExprRewriter::walkToExprPost(swift::Expr*) (/path/to/swift/bin/swift+0x13d4294)
10 0x00000000013d9a61 (anonymous namespace)::ExprWalker::walkToExprPost(swift::Expr*) (/path/to/swift/bin/swift+0x13d9a61)
11 0x000000000150b49c swift::Expr::walk(swift::ASTWalker&) (/path/to/swift/bin/swift+0x150b49c)
12 0x00000000013d125f swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool, bool) (/path/to/swift/bin/swift+0x13d125f)
13 0x000000000132a7bd swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) (/path/to/swift/bin/swift+0x132a7bd)
14 0x00000000014002fc (anonymous namespace)::FailureDiagnosis::typeCheckChildIndependently(swift::Expr*, swift::Type, swift::ContextualTypePurpose, swift::OptionSet<TCCFlags, unsigned int>, swift::ExprTypeCheckListener*, bool) (/path/to/swift/bin/swift+0x14002fc)
15 0x00000000013fd957 swift::ASTVisitor<(anonymous namespace)::FailureDiagnosis, bool, void, void, void, void, void>::visit(swift::Expr*) (/path/to/swift/bin/swift+0x13fd957)
16 0x00000000013f448b swift::constraints::ConstraintSystem::diagnoseFailureForExpr(swift::Expr*) (/path/to/swift/bin/swift+0x13f448b)
17 0x00000000013fa2c9 swift::constraints::ConstraintSystem::salvage(llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::Expr*) (/path/to/swift/bin/swift+0x13fa2c9)
18 0x0000000001326d88 swift::TypeChecker::solveForExpression(swift::Expr*&, swift::DeclContext*, swift::Type, swift::FreeTypeVariableBinding, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem&, llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>) (/path/to/swift/bin/swift+0x1326d88)
19 0x000000000132a6c2 swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) (/path/to/swift/bin/swift+0x132a6c2)
20 0x000000000132e814 swift::TypeChecker::typeCheckBinding(swift::Pattern*&, swift::Expr*&, swift::DeclContext*, bool) (/path/to/swift/bin/swift+0x132e814)
21 0x000000000132ea76 swift::TypeChecker::typeCheckPatternBinding(swift::PatternBindingDecl*, unsigned int, bool) (/path/to/swift/bin/swift+0x132ea76)
22 0x0000000001347158 validatePatternBindingEntries(swift::TypeChecker&, swift::PatternBindingDecl*) (/path/to/swift/bin/swift+0x1347158)
23 0x0000000001343428 swift::TypeChecker::validateDecl(swift::ValueDecl*) (/path/to/swift/bin/swift+0x1343428)
24 0x000000000143201a swift::createImplicitConstructor(swift::TypeChecker&, swift::NominalTypeDecl*, swift::ImplicitConstructorKind) (/path/to/swift/bin/swift+0x143201a)
25 0x000000000134887c swift::TypeChecker::addImplicitConstructors(swift::NominalTypeDecl*) (/path/to/swift/bin/swift+0x134887c)
26 0x0000000001351f0e (anonymous namespace)::DeclChecker::visitStructDecl(swift::StructDecl*) (/path/to/swift/bin/swift+0x1351f0e)
27 0x0000000001341414 (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x1341414)
28 0x000000000135316b (anonymous namespace)::DeclChecker::visitProtocolDecl(swift::ProtocolDecl*) (/path/to/swift/bin/swift+0x135316b)
29 0x0000000001341434 (anonymous namespace)::DeclChecker::visit(swift::Decl*) (/path/to/swift/bin/swift+0x1341434)
30 0x0000000001341333 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) (/path/to/swift/bin/swift+0x1341333)
31 0x00000000013cba85 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int) (/path/to/swift/bin/swift+0x13cba85)
32 0x0000000000f93106 swift::CompilerInstance::performSema() (/path/to/swift/bin/swift+0xf93106)
33 0x00000000004aaa09 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) (/path/to/swift/bin/swift+0x4aaa09)
34 0x00000000004a8f9c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) (/path/to/swift/bin/swift+0x4a8f9c)
35 0x00000000004655c7 main (/path/to/swift/bin/swift+0x4655c7)
36 0x00007f45d82ac830 __libc_start_main /build/glibc-9tT8Do/glibc-2.23/csu/../csu/libc-start.c:325:0
37 0x0000000000462c69 _start (/path/to/swift/bin/swift+0x462c69)
```

Author: practicalswift

validation-test/compiler_crashers/28767-ty-getnominalorboundgenericnominal-ty-is-dynamicselftype-ty-isexistentialtype-ty.swift

@@ -0,0 +1,10 @@
+// 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
+
+// REQUIRES: asserts
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+@objc protocol P{struct B{var f=_=a{}}class a{}typealias a