AST: Fix compareDependentTypes() for protocol typealiases

lib/AST/ASTContext.cpp

@@ -2926,6 +2926,8 @@ getGenericFunctionRecursiveProperties(Type Input, Type Result) {
   RecursiveTypeProperties properties;
   if (Result->getRecursiveProperties().hasDynamicSelf())
     properties |= RecursiveTypeProperties::HasDynamicSelf;
+  if (Result->getRecursiveProperties().hasError())
+    properties |= RecursiveTypeProperties::HasError;
   return properties;
 }
 
@@ -3127,17 +3129,23 @@ SILFunctionType::SILFunctionType(GenericSignature *genericSig, ExtInfo ext,
 
     for (auto param : getParameters()) {
       (void)param;
+      assert(!param.getType()->hasError()
+             && "interface type of parameter should not contain error types");
       assert(!param.getType()->hasArchetype()
-             && "interface type of generic type should not contain context archetypes");
+             && "interface type of parameter should not contain context archetypes");
     }
     for (auto result : getResults()) {
       (void)result;
+      assert(!result.getType()->hasError()
+             && "interface type of result should not contain error types");
       assert(!result.getType()->hasArchetype()
-             && "interface type of generic type should not contain context archetypes");
+             && "interface type of result should not contain context archetypes");
     }
     if (hasErrorResult()) {
+      assert(!getErrorResult().getType()->hasError()
+             && "interface type of result should not contain error types");
       assert(!getErrorResult().getType()->hasArchetype()
-             && "interface type of generic type should not contain context archetypes");
+             && "interface type of result should not contain context archetypes");
     }
   }
 #endif

lib/AST/ArchetypeBuilder.cpp

@@ -373,6 +373,12 @@ static int compareDependentTypes(
   if (a->isGenericParam() != b->isGenericParam())
     return a->isGenericParam() ? -1 : +1;
 
+  // Typealiases must be ordered *after* everything else, to ensure they
+  // don't become representatives in the case where a typealias is equated
+  // with an associated type.
+  if (!!a->getTypeAliasDecl() != !!b->getTypeAliasDecl())
+    return a->getTypeAliasDecl() ? +1 : -1;
+
   // - Dependent members
   auto ppa = a->getParent();
   auto ppb = b->getParent();
@@ -411,27 +417,22 @@ static int compareDependentTypes(
   // Make sure typealiases are properly ordered, to avoid crashers.
   // FIXME: Ideally we would eliminate typealiases earlier.
   if (auto *aa = a->getTypeAliasDecl()) {
-    if (auto *ab = b->getTypeAliasDecl()) {
-      // - by protocol, so t_n_m.`P.T` < t_n_m.`Q.T` (given P < Q)
-      auto protoa =
-        aa->getDeclContext()->getAsProtocolOrProtocolExtensionContext();
-      auto protob =
-        ab->getDeclContext()->getAsProtocolOrProtocolExtensionContext();
+    auto *ab = b->getTypeAliasDecl();
+    assert(ab != nullptr && "Should have handled this case above");
 
-      if (int compareProtocols
-            = ProtocolType::compareProtocols(&protoa, &protob))
-        return compareProtocols;
+    // - by protocol, so t_n_m.`P.T` < t_n_m.`Q.T` (given P < Q)
+    auto protoa =
+      aa->getDeclContext()->getAsProtocolOrProtocolExtensionContext();
+    auto protob =
+      ab->getDeclContext()->getAsProtocolOrProtocolExtensionContext();
 
-      // FIXME: Arbitrarily break the result here.
-      if (aa != ab)
-        return aa < ab ? -1 : +1;
-    } else {
-      // A resolved archetype is always ordered before an unresolved one.
-      return -1;
-    }
-  } else if (b->getTypeAliasDecl()) {
-    // A resolved archetype is always ordered before an unresolved one.
-    return +1;
+    if (int compareProtocols
+          = ProtocolType::compareProtocols(&protoa, &protob))
+      return compareProtocols;
+
+    // FIXME: Arbitrarily break the result here.
+    if (aa != ab)
+      return aa < ab ? -1 : +1;
   }
 
   // Along the error path where one or both of the potential archetypes was
@@ -533,8 +534,6 @@ auto ArchetypeBuilder::PotentialArchetype::getNestedType(
           continue;
 
         auto type = alias->getDeclaredInterfaceType();
-        SmallVector<Identifier, 4> identifiers;
-
         if (auto existingPA = builder.resolveArchetype(type)) {
           builder.addSameTypeRequirementBetweenArchetypes(pa, existingPA,
                                                           redundantSource);

test/SILGen/same_type_abstraction.swift

@@ -38,3 +38,20 @@ extension MyProtocol where Data == (ReadData, ReadData) {
     return (readData(), readData())
   }
 }
+
+// Problem with protocol typealiases, which are modeled as same-type
+// constraints
+
+protocol Refined : Associated {
+  associatedtype Key
+  typealias Assoc = Key
+
+  init()
+}
+
+extension Refined {
+  // CHECK-LABEL: sil hidden @_T021same_type_abstraction7RefinedPAAEx3KeyQz12withElements_tcfC : $@convention(method) <Self where Self : Refined> (@in Self.Key, @thick Self.Type) -> @out Self
+  init(withElements newElements: Key) {
+    self.init()
+  }
+}

validation-test/compiler_crashers_2_fixed/0066-sr3687.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend %s -emit-ir
+
+public protocol QHash : Collection, ExpressibleByArrayLiteral {
+  associatedtype Key
+  typealias Element = Key
+
+  init()
+}
+
+extension QHash {
+  init(withElements newElements: Key...) {
+    self.init()
+  }
+}