add a Copyable catch-all for non-nominals

After filtering out aggregates when
determining if a type is Copyable, its safe
to say that a type is Copyable if its not
a nominal. The only types that are not
copyable at the moment are move-only
nominals and tuples containing such types.

Author: kavon

lib/AST/Module.cpp

@@ -1646,6 +1646,11 @@ LookupConformanceInModuleRequest::evaluate(
 
   auto nominal = type->getAnyNominal();
 
+  // If it's not a nominal, then it's safe to assume its copyable.
+  if (!nominal && protocol->isSpecificProtocol(KnownProtocolKind::Copyable)) {
+    return ProtocolConformanceRef(protocol);
+  }
+
   // If we don't have a nominal type, there are no conformances.
   if (!nominal || isa<ProtocolDecl>(nominal))
     return ProtocolConformanceRef::forMissingOrInvalid(type, protocol);

test/Parse/type_parameter_packs.swift

@@ -32,3 +32,9 @@ func quux<each T: P>(_ x: repeat each T) {}
 func foobar<T, U, each V>(x: T, y: U, z: repeat each V) { }
 func foobaz<T, each U, V>(x: T, y: repeat each U, z: V) { }
 func fooqux<each T, each U, each V>(x: repeat each T, y: repeat each U, z: repeat each V) { }
+
+// coverage to ensure a 'repeat each' type is considered Copyable
+func golden<Z>(_ z: Z) {}
+func hour<each T>(_ t: repeat each T)  {
+  golden(t)
+}