Sema: Set the interface type of lazy properties during validation.

Otherwise, we end up treating the contextual type as the interface type in situations where the lazy property is seen from other files. Fixes SR-837.

Author: jckarter

lib/Sema/CodeSynthesis.cpp

@@ -1581,10 +1581,12 @@ void TypeChecker::completeLazyVarImplementation(VarDecl *VD) {
   NameBuf += ".storage";
   auto StorageName = Context.getIdentifier(NameBuf);
   auto StorageTy = OptionalType::get(VD->getType());
+  auto StorageInterfaceTy = OptionalType::get(VD->getInterfaceType());
 
   auto *Storage = new (Context) VarDecl(/*isStatic*/false, /*isLet*/false,
                                         VD->getLoc(), StorageName, StorageTy,
                                         VD->getDeclContext());
+  Storage->setInterfaceType(StorageInterfaceTy);
   Storage->setUserAccessible(false);
   addMemberToContextIfNeeded(Storage, VD->getDeclContext(), VD);
 

test/decl/var/Inputs/lazy_properties_multi_file_2.swift

@@ -0,0 +1,4 @@
+struct MyGenericStruct<T> {
+    lazy var prop2 = [AnotherGenericStruct<T>]()
+}
+struct AnotherGenericStruct<T> { }

test/decl/var/lazy_properties_multi_file.swift

@@ -0,0 +1,7 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: %target-swift-frontend %s -verify -O -primary-file %s %S/Inputs/lazy_properties_multi_file_2.swift -c -o %t/lazy_properties_multi_file.o
+
+class MyClass {
+    var myProperty = MyGenericStruct<Int>()
+}