add a Copyable conformance for PackExpansionType

Author: kavon

lib/AST/Module.cpp

@@ -1724,6 +1724,16 @@ LookupConformanceInModuleRequest::evaluate(
     return getBuiltinBuiltinTypeConformance(type, builtinType, protocol);
   }
 
+  // Specific handling of Copyable for pack expansions.
+  if (auto packExpansion = type->getAs<PackExpansionType>()) {
+    if (protocol->isSpecificProtocol(KnownProtocolKind::Copyable)) {
+      auto patternType = packExpansion->getPatternType();
+      return (patternType->isTypeParameter()
+               ? ProtocolConformanceRef(protocol)
+               : mod->lookupConformance(patternType, protocol));
+    }
+  }
+
   auto nominal = type->getAnyNominal();
 
   // If we don't have a nominal type, there are no conformances.

test/type/pack_expansion.swift

@@ -74,3 +74,9 @@ func invalidPackRef(_: each Int) {}
 
 // expected-error@+1 {{pack reference 'T' can only appear in pack expansion or generic requirement}}
 func packRefOutsideExpansion<each T>(_: each T) {}
+
+// coverage to ensure a 'repeat each' type is considered Copyable
+func golden<Z>(_ z: Z) {}
+func hour<each T>(_ t: repeat each T)  {
+  _ = repeat golden(each t)
+}