Sema: A couple of recursion-breaking hacks

lib/AST/GenericSignatureBuilder.cpp

@@ -1662,9 +1662,13 @@ PotentialArchetype *PotentialArchetype::getNestedArchetypeAnchor(
         assocType = dyn_cast<AssociatedTypeDecl>(member);
 
       // FIXME: Filter out type declarations that aren't in the protocol itself?
-      if (!concreteDecl && !isa<AssociatedTypeDecl>(member))
+      if (!concreteDecl && !isa<AssociatedTypeDecl>(member)) {
+        if (!member->hasInterfaceType())
+          builder.getLazyResolver()->resolveDeclSignature(member);
+        if (member->hasInterfaceType())
           concreteDecl = dyn_cast<TypeDecl>(member);
       }
+    }
 
     if (assocType &&
         (!bestAssocType ||
@@ -1781,9 +1785,13 @@ PotentialArchetype *PotentialArchetype::updateNestedTypeForConformance(
       assocType = dyn_cast<AssociatedTypeDecl>(member);
 
     // FIXME: Filter out concrete types that aren't in the protocol itself?
-    if (!concreteDecl && !isa<AssociatedTypeDecl>(member))
+    if (!concreteDecl && !isa<AssociatedTypeDecl>(member)) {
+      if (!member->hasInterfaceType())
+        proto->getASTContext().getLazyResolver()->resolveDeclSignature(member);
+      if (member->hasInterfaceType())
         concreteDecl = dyn_cast<TypeDecl>(member);
     }
+  }
 
   // There is no associated type or concrete type with this name in this
   // protocol

lib/AST/Module.cpp

@@ -599,6 +599,10 @@ ModuleDecl::lookupConformance(Type type, ProtocolDecl *protocol,
   // existential's list of conformances and the existential conforms to
   // itself.
   if (type->isExistentialType()) {
+    // FIXME: Recursion break.
+    if (!protocol->hasValidSignature())
+      return None;
+
     // If the existential type cannot be represented or the protocol does not
     // conform to itself, there's no point in looking further.
     if (!protocol->existentialConformsToSelf() ||

lib/Sema/TypeCheckProtocol.cpp

@@ -4200,7 +4200,13 @@ void ConformanceChecker::resolveTypeWitnesses() {
     }
 
     TC.validateDecl(assocType);
-    Type defaultType = assocType->getDefaultDefinitionLoc().getType().subst(
+    Type defaultType = assocType->getDefaultDefinitionLoc().getType();
+
+    // FIXME: Circularity
+    if (!defaultType)
+      return Type();
+
+    defaultType = defaultType.subst(
         QueryTypeSubstitutionMap{substitutions},
         LookUpConformanceInModule(DC->getParentModule()));
 

validation-test/compiler_crashers_fixed/28742-swift-type-subst-llvm-function-ref-swift-type-swift-substitutabletype-llvm-funct.swift

@@ -5,5 +5,5 @@
 // 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
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol P{{}typealias a:=A.a:struct A:P

validation-test/compiler_crashers_fixed/28743-swift-typechecker-substmembertypewithbase-swift-moduledecl-swift-typedecl-swift-.swift

@@ -5,5 +5,5 @@
 // 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
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol P}extension P{typealias a:Self.a{}func a:Self.a

validation-test/compiler_crashers_fixed/28752-hasinterfacetype-no-interface-type-was-set.swift

@@ -6,5 +6,5 @@
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
 // REQUIRES: asserts
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+// RUN: not %target-swift-frontend %s -emit-ir
 @objc protocol P{typealias e:P{}var a}{}extension P{typealias e:P