Merge pull request #11127 from slavapestov/protocol-typealias-validate-for-lookup-fun-4.0

Sema/AST: Fix a couple of protocol typealias validation order bugs [4.0]

Author: slavapestov

lib/AST/Decl.cpp

@@ -2421,14 +2421,19 @@ void TypeAliasDecl::setUnderlyingType(Type underlying) {
     underlying = mapTypeOutOfContext(underlying);
   UnderlyingTy.setType(underlying);
 
-  // Create a NameAliasType which will resolve to the underlying type.
-  ASTContext &Ctx = getASTContext();
-  auto aliasTy = new (Ctx, AllocationArena::Permanent) NameAliasType(this);
-  aliasTy->setRecursiveProperties(getUnderlyingTypeLoc().getType()
-      ->getRecursiveProperties());
-
-  // Set the interface type of this declaration.
-  setInterfaceType(MetatypeType::get(aliasTy, Ctx));
+  // FIXME -- if we already have an interface type, we're changing the
+  // underlying type. See the comment in the ProtocolDecl case of
+  // validateDecl().
+  if (!hasInterfaceType()) {
+    // Create a NameAliasType which will resolve to the underlying type.
+    ASTContext &Ctx = getASTContext();
+    auto aliasTy = new (Ctx, AllocationArena::Permanent) NameAliasType(this);
+    aliasTy->setRecursiveProperties(getUnderlyingTypeLoc().getType()
+        ->getRecursiveProperties());
+
+    // Set the interface type of this declaration.
+    setInterfaceType(MetatypeType::get(aliasTy, Ctx));
+  }
 }
 
 UnboundGenericType *TypeAliasDecl::getUnboundGenericType() const {

lib/Sema/TypeCheckType.cpp

@@ -3183,6 +3183,14 @@ Type TypeChecker::substMemberTypeWithBase(ModuleDecl *module,
   }
 
   if (auto *aliasDecl = dyn_cast<TypeAliasDecl>(member)) {
+    // FIXME: If this is a protocol typealias and we haven't built the
+    // protocol's generic environment yet, do so now, to ensure the
+    // typealias's underlying type has fully resoved dependent
+    // member types.
+    if (auto *protoDecl = dyn_cast<ProtocolDecl>(aliasDecl->getDeclContext()))
+      if (protoDecl->getGenericEnvironment() == nullptr)
+        validateDecl(protoDecl);
+
     if (aliasDecl->getGenericParams()) {
       return UnboundGenericType::get(
           aliasDecl, baseTy,

validation-test/compiler_crashers_2_fixed/0114-rdar33189068.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend %s -typecheck
+
+struct Bar : BarProtocol {
+    typealias Element = Int
+}
+
+struct Foo: FooProtocol {
+    typealias Things = Bar
+    func thing() -> Thing {}
+}
+
+protocol BarProtocol {
+    associatedtype Element
+}
+
+protocol FooProtocol {
+    associatedtype Things: BarProtocol
+    typealias Thing = Things.Element
+}