Open Radar

 
Summary:
Trying to work around rdar://22064783, swiftc died another death instead.

Steps to Reproduce:
This code:
protocol A: _A {
	typealias O : B
}

protocol _A {
	typealias O
	init(_ : O)
	var out: O { get }
}

protocol B {
	typealias O : _A
}

enum Expr<T>: B {
	typealias O = T
	case Null
	func map<U>(transform: T -> U) -> Expr<U> { return .Null }
}

func out<Fix: A>(v: Fix) -> Fix.O { return v.out }

func cata<T, Fix: A where Fix.O == Expr<Fix>>(f: Expr<T> -> T)(_ term: Fix) -> T {
	return f({ $0.map(cata(f)) }(out(term)))
}


Expected Results:
should not crash swiftc

Actual Results:
but totally does:
rob@Resonance ~/Desktop> swiftc -v boom.swift
Apple Swift version 2.0 (swiftlang-700.0.47.4 clang-700.0.59.1)
Target: x86_64-apple-darwin14.4.0
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file boom.swift -target x86_64-apple-darwin14.4.0 -enable-objc-interop -color-diagnostics -module-name boom -o /var/folders/9y/f7n4rvx901nctm_5d16c1wm40000gn/T/boom-57cfd6.o
boom.swift:23:33: error: same-type constraint type '<<error type>>' does not conform to required protocol '_A'
func cata<T, Fix: A where Fix.O == Expr<Fix>>(f: Expr<T> -> T)(_ term: Fix) -> T {
                                ^
boom.swift:23:33: error: same-type constraint type '<<error type>>' does not conform to required protocol '_A'
func cata<T, Fix: A where Fix.O == Expr<Fix>>(f: Expr<T> -> T)(_ term: Fix) -> T {
                                ^
boom.swift:15:6: error: type 'Expr<T>' does not conform to protocol 'B'
enum Expr<T>: B {
     ^
boom.swift:12:12: note: protocol requires nested type 'O'
        typealias O : _A
                  ^
boom.swift:16:12: note: possibly intended match 'O' does not conform to '_A'
        typealias O = T
                  ^
Assertion failed: ((conforms || firstArchetype->getIsRecursive() || isOpenedAnyObject(replacement) || replacement->is<GenericTypeParamType>()) && "Constraint system missed a conformance?"), function computeSubstitutions, file /Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-700.0.47.4/src/swift/lib/Sema/CSApply.cpp, line 145.
0  swift                    0x000000010b876b8b llvm::sys::PrintStackTrace(__sFILE*) + 43
1  swift                    0x000000010b8772cb SignalHandler(int) + 379
2  libsystem_platform.dylib 0x00007fff86e08f1a _sigtramp + 26
3  libc++.1.dylib           0x00007fff8b20043e operator new(unsigned long) + 30
4  libsystem_c.dylib        0x00007fff905e3b53 abort + 129
5  libsystem_c.dylib        0x00007fff905abc39 basename + 0
6  swift                    0x0000000109e567e5 swift::constraints::Solution::computeSubstitutions(swift::Type, swift::DeclContext*, swift::Type, swift::constraints::ConstraintLocator*, llvm::SmallVectorImpl<swift::Substitution>&) const + 2117
7  swift                    0x0000000109e6c7fd (anonymous namespace)::ExprRewriter::buildDeclRef(swift::ValueDecl*, swift::SourceLoc, swift::Type, swift::constraints::ConstraintLocatorBuilder, bool, bool, swift::AccessSemantics) + 557
8  swift                    0x0000000109e68839 swift::ASTVisitor<(anonymous namespace)::ExprRewriter, swift::Expr*, void, void, void, void, void>::visit(swift::Expr*) + 11129
9  swift                    0x0000000109e628c6 (anonymous namespace)::ExprWalker::walkToExprPost(swift::Expr*) + 22
10 swift                    0x0000000109fa96bc (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 76
11 swift                    0x0000000109fa78eb (anonymous namespace)::Traversal::visit(swift::Expr*) + 219
12 swift                    0x0000000109fa7890 (anonymous namespace)::Traversal::visit(swift::Expr*) + 128
13 swift                    0x0000000109fa96f0 (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 128
14 swift                    0x0000000109fa78eb (anonymous namespace)::Traversal::visit(swift::Expr*) + 219
15 swift                    0x0000000109fa7890 (anonymous namespace)::Traversal::visit(swift::Expr*) + 128
16 swift                    0x0000000109fa96f0 (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 128
17 swift                    0x0000000109fa78eb (anonymous namespace)::Traversal::visit(swift::Expr*) + 219
18 swift                    0x0000000109fa6cd5 swift::Expr::walk(swift::ASTWalker&) + 53
19 swift                    0x0000000109e56d94 swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool) + 484
20 swift                    0x0000000109ee40af swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::Type, swift::Type, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::FreeTypeVariableBinding, swift::ExprTypeCheckListener*) + 399
21 swift                    0x0000000109f492f2 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 4242
22 swift                    0x0000000109f48399 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 313
23 swift                    0x0000000109f47769 (anonymous namespace)::StmtChecker::typeCheckBody(swift::BraceStmt*&) + 25
24 swift                    0x0000000109f4682f swift::TypeChecker::typeCheckFunctionBodyUntil(swift::FuncDecl*, swift::SourceLoc) + 415
25 swift                    0x0000000109f46641 swift::TypeChecker::typeCheckAbstractFunctionBodyUntil(swift::AbstractFunctionDecl*, swift::SourceLoc) + 49
26 swift                    0x0000000109f4736a swift::TypeChecker::typeCheckAbstractFunctionBody(swift::AbstractFunctionDecl*) + 138
27 swift                    0x0000000109ecc258 typeCheckFunctionsAndExternalDecls(swift::TypeChecker&) + 200
28 swift                    0x0000000109eccf53 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int) + 1731
29 swift                    0x0000000109cd66d5 swift::CompilerInstance::performSema() + 4149
30 swift                    0x000000010985a9d5 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&) + 725
31 swift                    0x000000010985a4e3 frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2627
32 swift                    0x00000001098565af main + 2015
33 libdyld.dylib            0x00007fff86cb45c9 start + 1
34 libdyld.dylib            0x000000000000000d start + 2033498693
Stack dump:
0.	Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file boom.swift -target x86_64-apple-darwin14.4.0 -enable-objc-interop -color-diagnostics -module-name boom -o /var/folders/9y/f7n4rvx901nctm_5d16c1wm40000gn/T/boom-57cfd6.o 
1.	While type-checking 'cata' at boom.swift:23:1
2.	While type-checking expression at [boom.swift:24:9 - line:24:41] RangeText="f({ $0.map(cata(f)) }(out(term)))"
<unknown>:0: error: unable to execute command: Abort trap: 6
<unknown>:0: error: swift frontend command failed due to signal (use -v to see invocation)


Regression:
N/A

Notes:
N/A