Fix TypeLowering: BitwiseCopyable archetypes are trivial

Author: atrick

include/swift/SIL/SILTypeProperties.h

@@ -241,6 +241,7 @@ class SILTypeProperties {
     return HasRawLayout_t((Flags & HasRawLayoutFlag) != 0);
   }
 
+  void setTrivial() { Flags &= ~NonTrivialFlag; }
   void setNonTrivial() { Flags |= NonTrivialFlag; }
   void setIsOrContainsRawPointer() { Flags |= HasRawPointerFlag; }
 

lib/SIL/IR/TypeLowering.cpp

@@ -772,8 +772,18 @@ namespace {
               type, getReferenceSILTypeProperties(isSensitive));
         }
       }
-      return asImpl().handleAddressOnly(
-          type, getOpaqueSILTypeProperties(isSensitive));
+      auto props = getOpaqueSILTypeProperties(isSensitive);
+      if (ProtocolDecl *bitwiseCopyable =
+          TC.Context.getProtocol(KnownProtocolKind::BitwiseCopyable)) {
+        // If a context is available, then the caller will have mapped into it.
+        // Opaque function type results still have interface types here.
+        if (auto conformance =
+            checkConformanceWithoutContext(type, bitwiseCopyable)) {
+          if (!conformance->isInvalid())
+            props.setTrivial();
+        }
+      }
+      return asImpl().handleAddressOnly(type, props);
     }
 
     RetTy visitExistentialType(CanType type,