Serialization: Deserialize opaque type xrefs from the right extension module.

include/swift/AST/Decl.h

@@ -2853,6 +2853,11 @@ class OpaqueTypeDecl : public GenericTypeDecl {
 
   ValueDecl *getNamingDecl() const { return NamingDecl; }
 
+  void setNamingDecl(ValueDecl *D) {
+    assert(!NamingDecl && "already have naming decl");
+    NamingDecl = D;
+  }
+
   GenericSignature *getOpaqueInterfaceGenericSignature() const {
     return OpaqueInterfaceGenericSignature;
   }

lib/Serialization/Deserialization.cpp

@@ -1724,9 +1724,10 @@ ModuleFile::resolveCrossReference(ModuleID MID, uint32_t pathLen) {
 
       auto name = getIdentifier(DefiningDeclNameID);
       pathTrace.addOpaqueReturnType(name);
-
-      if (auto opaqueTy = baseModule->lookupOpaqueResultType(name.str(),
-                                                             nullptr)) {
+
+      auto lookupModule = M ? M : baseModule;
+      if (auto opaqueTy = lookupModule->lookupOpaqueResultType(name.str(),
+                                                               nullptr)) {
         values.push_back(opaqueTy);
       }
       break;
@@ -3134,7 +3135,6 @@ class swift::DeclDeserializer {
                                               interfaceTypeID, genericEnvID,
                                               underlyingTypeID);
 
-    auto namingDecl = cast<ValueDecl>(MF.getDecl(namingDeclID));
     auto declContext = MF.getDeclContext(contextID);
     auto sig = MF.getGenericSignature(interfaceSigID);
     auto interfaceType = MF.getType(interfaceTypeID)
@@ -3146,10 +3146,13 @@ class swift::DeclDeserializer {
 
     // Create the decl.
     auto opaqueDecl =
-      new (ctx) OpaqueTypeDecl(namingDecl, nullptr, declContext,
+      new (ctx) OpaqueTypeDecl(nullptr, nullptr, declContext,
                                sig, interfaceType);
     declOrOffset = opaqueDecl;
 
+    auto namingDecl = cast<ValueDecl>(MF.getDecl(namingDeclID));
+    opaqueDecl->setNamingDecl(namingDecl);
+
     if (auto genericParams = MF.maybeReadGenericParams(opaqueDecl))
       opaqueDecl->setGenericParams(genericParams);
 

test/SIL/Serialization/Inputs/OpaqueReturnTypeExporter.swift

@@ -2,3 +2,9 @@ public protocol Butt {}
 extension Int: Butt {}
 
 public func exportsOpaqueReturn() -> some Butt { return 0 }
+
+extension Int {
+  public func someButt() -> some Butt {
+    return self
+  }
+}

test/SIL/Serialization/opaque_return_type_serialize.sil

@@ -3,18 +3,27 @@
 // RUN: %target-sil-opt -I %t %s -emit-sib -module-name test -o %t/test.sib
 // RUN: %target-swift-frontend -disable-availability-checking -I %t -emit-ir %t/test.sib
 
+import Swift
 import OpaqueReturnTypeExporter
 
 typealias SomeButt = @_opaqueReturnTypeOf("$s24OpaqueReturnTypeExporter07exportsaB0QryF", 0) opaque
+typealias SomeButt2 = @_opaqueReturnTypeOf("$sSi24OpaqueReturnTypeExporterE8someButtQryF", 0) opaque
 
 sil @$s24OpaqueReturnTypeExporter07exportsaB0QryF : $@convention(thin) () -> @out SomeButt
+sil @$sSi24OpaqueReturnTypeExporterE8someButtQryF : $@convention(thin) (Int) -> @out SomeButt2
 
-sil @use_opaque_type : $@convention(thin) () -> () {
-entry:
+sil @use_opaque_type : $@convention(thin) (Int) -> () {
+entry(%a : $Int):
   %f = function_ref @$s24OpaqueReturnTypeExporter07exportsaB0QryF : $@convention(thin) () -> @out SomeButt
   %x = alloc_stack $SomeButt
   apply %f(%x) : $@convention(thin) () -> @out SomeButt
   destroy_addr %x : $*SomeButt
   dealloc_stack %x : $*SomeButt
+
+  %g = function_ref @$sSi24OpaqueReturnTypeExporterE8someButtQryF : $@convention(thin) (Int) -> @out SomeButt2
+  %y = alloc_stack $SomeButt2
+  apply %g(%y, %a) : $@convention(thin) (Int) -> @out SomeButt2
+  destroy_addr %y : $*SomeButt2
+  dealloc_stack %y : $*SomeButt2
   return undef : $()
 }