swift234

[swiftc] Add test case for crash triggered in swift::TypeChecker::typeCheckPattern(swift::Pattern*, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*)

Stack trace:

```
swift: /path/to/swift/include/swift/AST/Pattern.h:111: swift::Type swift::Pattern::getType() const: Assertion `hasType()' failed.
8  swift           0x0000000000ebebae swift::TypeChecker::typeCheckPattern(swift::Pattern*, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*) + 1198
9  swift           0x0000000000e720ed swift::TypeChecker::typeCheckStmtCondition(llvm::MutableArrayRef<swift::StmtConditionElement>&, swift::DeclContext*, swift::Diag<>) + 189
13 swift           0x0000000000ee251a swift::TypeChecker::typeCheckClosureBody(swift::ClosureExpr*) + 218
14 swift           0x0000000000f0c66c swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool, bool) + 812
15 swift           0x0000000000e703ca swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::Type, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*) + 746
17 swift           0x0000000000ee2666 swift::TypeChecker::typeCheckTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 134
18 swift           0x0000000000ea523d swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int) + 1117
19 swift           0x0000000000cdbaef swift::CompilerInstance::performSema() + 3279
21 swift           0x000000000079001c frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2492
22 swift           0x000000000078aa95 main + 2837
Stack dump:
0.	Program arguments: /path/to/swift/bin/swift -frontend -c -primary-file validation-test/compiler_crashers/28285-swift-typechecker-typecheckpattern.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -module-name main -o /tmp/28285-swift-typechecker-typecheckpattern-437ef8.o
1.	While type-checking expression at [validation-test/compiler_crashers/28285-swift-typechecker-typecheckpattern.swift:10:10 - line:10:25] RangeText="{if let f as a:{"
<unknown>:0: error: unable to execute command: Aborted
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)
```