SIL: Pass SubstFlags::PreservePackExpansionLevel in a few places

Fixes rdar://problem/111219086.

Author: slavapestov

include/swift/SIL/SILCloner.h

@@ -195,9 +195,9 @@ class SILCloner : protected SILInstructionVisitor<ImplClass> {
       if (Subs.hasLocalArchetypes()) {
         // If we found a type containing a local archetype, substitute
         // open existentials throughout the substitution map.
-        Subs = Subs.subst(QueryTypeSubstitutionMapOrIdentity{
-                            LocalArchetypeSubs},
-                          MakeAbstractConformanceForGenericType());
+        Subs = Subs.subst(QueryTypeSubstitutionMapOrIdentity{LocalArchetypeSubs},
+                          MakeAbstractConformanceForGenericType(),
+                          SubstFlags::PreservePackExpansionLevel);
       }
     }
 
@@ -220,7 +220,9 @@ class SILCloner : protected SILInstructionVisitor<ImplClass> {
     return Ty.subst(
       Builder.getModule(),
       QueryTypeSubstitutionMapOrIdentity{LocalArchetypeSubs},
-      MakeAbstractConformanceForGenericType());
+      MakeAbstractConformanceForGenericType(),
+      CanGenericSignature(),
+      SubstFlags::PreservePackExpansionLevel);
   }
   SILType getOpType(SILType Ty) {
     Ty = getTypeInClonedContext(Ty);
@@ -239,7 +241,8 @@ class SILCloner : protected SILInstructionVisitor<ImplClass> {
 
     return ty.subst(
       QueryTypeSubstitutionMapOrIdentity{LocalArchetypeSubs},
-      MakeAbstractConformanceForGenericType()
+      MakeAbstractConformanceForGenericType(),
+      SubstFlags::PreservePackExpansionLevel
     )->getCanonicalType();
   }
 
@@ -352,7 +355,8 @@ class SILCloner : protected SILInstructionVisitor<ImplClass> {
         conformance.subst(ty,
                           QueryTypeSubstitutionMapOrIdentity{
                                                         LocalArchetypeSubs},
-                          MakeAbstractConformanceForGenericType());
+                          MakeAbstractConformanceForGenericType(),
+                          SubstFlags::PreservePackExpansionLevel);
     }
 
     return asImpl().remapConformance(getASTTypeInClonedContext(ty),

test/SILOptimizer/variadic_generics_sil_cloner.swift

@@ -0,0 +1,18 @@
+// RUN: %target-swift-frontend -emit-sil -O %s | %FileCheck %s
+
+@_optimize(none)
+public func callee<T, each X>(_: T, _: repeat each X) {}
+
+@_transparent
+public func caller<each X>(_ x: repeat each X) {
+  repeat callee(each x, repeat each x)
+}
+
+public func outerCaller<each X>(_ x: repeat each X) {
+  caller(repeat each x)
+}
+
+// CHECK-LABEL: sil @$s28variadic_generics_sil_cloner11outerCalleryyxxQpRvzlF : $@convention(thin) <each X> (@pack_guaranteed Pack{repeat each X}) -> () {
+// CHECK: [[CALLEE:%.*]] = function_ref @$s28variadic_generics_sil_cloner6calleeyyx_q_q_QptRv_r0_lF : $@convention(thin) <τ_0_0, each τ_0_1> (@in_guaranteed τ_0_0, @pack_guaranteed Pack{repeat each τ_0_1}) -> ()
+// CHECK: apply [[CALLEE]]<@pack_element("{{.*}}") each X, Pack{repeat each X}>(
+// CHECK: // end sil function '$s28variadic_generics_sil_cloner11outerCalleryyxxQpRvzlF'