diff --git a/include/swift/SIL/AbstractionPattern.h b/include/swift/SIL/AbstractionPattern.h
index e9771df716956..6f31004f6233e 100644
--- a/include/swift/SIL/AbstractionPattern.h
+++ b/include/swift/SIL/AbstractionPattern.h
@@ -783,7 +783,8 @@ class AbstractionPattern {
   /// Note that, for most purposes, you should lower a field's type against its
   /// *unsubstituted* interface type.
   AbstractionPattern
-  unsafeGetSubstFieldType(ValueDecl *member, CanType origMemberType) const;
+  unsafeGetSubstFieldType(ValueDecl *member, CanType origMemberType,
+                          SubstitutionMap subMap) const;
   
 private:
   /// Return an abstraction pattern for the curried type of an
diff --git a/lib/SIL/IR/AbstractionPattern.cpp b/lib/SIL/IR/AbstractionPattern.cpp
index 5ce151a7cf576..1896258930562 100644
--- a/lib/SIL/IR/AbstractionPattern.cpp
+++ b/lib/SIL/IR/AbstractionPattern.cpp
@@ -1376,6 +1376,26 @@ void AbstractionPattern::dump() const {
   llvm::errs() << "\n";
 }
 
+static void printGenerics(raw_ostream &out, const AbstractionPattern &pattern) {
+  if (auto sig = pattern.getGenericSignature()) {
+    sig->print(out);
+  }
+  // It'd be really nice if we could get these interleaved with the types.
+  if (auto subs = pattern.getGenericSubstitutions()) {
+    out << "@<";
+    bool first = false;
+    for (auto sub : subs.getReplacementTypes()) {
+      if (!first) {
+        out << ",";
+      } else {
+        first = true;
+      }
+      out << sub;
+    }
+    out << ">";
+  }
+}
+
 void AbstractionPattern::print(raw_ostream &out) const {
   switch (getKind()) {
   case Kind::Invalid:
@@ -1396,9 +1416,7 @@ void AbstractionPattern::print(raw_ostream &out) const {
               ? "AP::Type" :
             getKind() == Kind::Discard
               ? "AP::Discard" : "<<UNHANDLED CASE>>");
-    if (auto sig = getGenericSignature()) {
-      sig->print(out);
-    }
+    printGenerics(out, *this);
     out << '(';
     getType().dump(out);
     out << ')';
@@ -1425,9 +1443,7 @@ void AbstractionPattern::print(raw_ostream &out) const {
             getKind() == Kind::ObjCCompletionHandlerArgumentsType
               ? "AP::ObjCCompletionHandlerArgumentsType("
               : "AP::CFunctionAsMethodType(");
-    if (auto sig = getGenericSignature()) {
-      sig->print(out);
-    }
+    printGenerics(out, *this);
     getType().dump(out);
     out << ", ";
     // [TODO: Improve-Clang-type-printing]
@@ -1459,9 +1475,7 @@ void AbstractionPattern::print(raw_ostream &out) const {
             getKind() == Kind::CurriedCXXMethodType
               ? "AP::CurriedCXXMethodType("
               : "AP::PartialCurriedCXXMethodType");
-    if (auto sig = getGenericSignature()) {
-      sig->print(out);
-    }
+    printGenerics(out, *this);
     getType().dump(out);
     out << ", ";
     getCXXMethod()->dump();
@@ -1569,13 +1583,14 @@ bool AbstractionPattern::hasSameBasicTypeStructure(CanType l, CanType r) {
 
 AbstractionPattern
 AbstractionPattern::unsafeGetSubstFieldType(ValueDecl *member,
-                                            CanType origMemberInterfaceType)
+                                            CanType origMemberInterfaceType,
+                                            SubstitutionMap subMap)
 const {
   assert(origMemberInterfaceType);
   if (isTypeParameterOrOpaqueArchetype()) {
     // Fall back to the generic abstraction pattern for the member.
     auto sig = member->getDeclContext()->getGenericSignatureOfContext();
-    return AbstractionPattern(sig.getCanonicalSignature(),
+    return AbstractionPattern(subMap, sig.getCanonicalSignature(),
                               origMemberInterfaceType);
   }
 
@@ -1612,7 +1627,9 @@ const {
                                       member, origMemberInterfaceType)
                              ->getReducedType(getGenericSignature());
       
-    return AbstractionPattern(getGenericSignature(), memberTy);
+    return AbstractionPattern(getGenericSubstitutions(),
+                              getGenericSignature(),
+                              memberTy);
   }
   llvm_unreachable("invalid abstraction pattern kind");
 }
diff --git a/lib/SIL/IR/SILFunctionType.cpp b/lib/SIL/IR/SILFunctionType.cpp
index 4ed98fb82dcf6..28f21ac4f49da 100644
--- a/lib/SIL/IR/SILFunctionType.cpp
+++ b/lib/SIL/IR/SILFunctionType.cpp
@@ -4748,7 +4748,17 @@ class SILTypeSubstituter :
       return origType;
     }
 
-    AbstractionPattern abstraction(Sig, origType);
+    // We've looked through all the top-level structure in the orig
+    // type that's affected by type lowering.  If substitution has
+    // given us a type with top-level structure that's affected by
+    // type lowering, it must be because the orig type was a type
+    // variable of some sort, and we should lower using an opaque
+    // abstraction pattern.  If substitution hasn't given us such a
+    // type, it doesn't matter what abstraction pattern we use,
+    // lowering will just come back with substType.  So we can just
+    // use an opaque abstraction pattern here and not put any effort
+    // into computing a more "honest" abstraction pattern.
+    AbstractionPattern abstraction = AbstractionPattern::getOpaque();
     return TC.getLoweredRValueType(typeExpansionContext, abstraction,
                                    substType);
   }
diff --git a/lib/SIL/IR/SILType.cpp b/lib/SIL/IR/SILType.cpp
index e4ee158320678..a0cbcdb204453 100644
--- a/lib/SIL/IR/SILType.cpp
+++ b/lib/SIL/IR/SILType.cpp
@@ -301,9 +301,30 @@ bool SILType::canRefCast(SILType operTy, SILType resultTy, SILModule &M) {
     && toTy.isHeapObjectReferenceType();
 }
 
+static bool needsFieldSubstitutions(const AbstractionPattern &origType) {
+  if (origType.isTypeParameter()) return false;
+  auto type = origType.getType();
+  if (!type->hasTypeParameter()) return false;
+  return type.findIf([](CanType type) {
+    return isa<PackExpansionType>(type);
+  });
+}
+
+static void addFieldSubstitutionsIfNeeded(TypeConverter &TC, SILType ty,
+                                          ValueDecl *field,
+                                          AbstractionPattern &origType) {
+  if (needsFieldSubstitutions(origType)) {
+    auto subMap = ty.getASTType()->getContextSubstitutionMap(
+                    &TC.M, field->getDeclContext());
+    origType = origType.withSubstitutions(subMap);
+  }
+}
+
 SILType SILType::getFieldType(VarDecl *field, TypeConverter &TC,
                               TypeExpansionContext context) const {
   AbstractionPattern origFieldTy = TC.getAbstractionPattern(field);
+  addFieldSubstitutionsIfNeeded(TC, *this, field, origFieldTy);
+
   CanType substFieldTy;
   if (field->hasClangNode()) {
     substFieldTy = origFieldTy.getType();
@@ -372,6 +393,9 @@ SILType SILType::getEnumElementType(EnumElementDecl *elt, TypeConverter &TC,
                    getCategory());
   }
 
+  auto origEltType = TC.getAbstractionPattern(elt);
+  addFieldSubstitutionsIfNeeded(TC, *this, elt, origEltType);
+
   auto substEltTy = getASTType()->getTypeOfMember(
       &TC.M, elt, elt->getArgumentInterfaceType());
   auto loweredTy = TC.getLoweredRValueType(
diff --git a/lib/SIL/IR/TypeLowering.cpp b/lib/SIL/IR/TypeLowering.cpp
index fe71adc24b2d0..26bc61f04e11b 100644
--- a/lib/SIL/IR/TypeLowering.cpp
+++ b/lib/SIL/IR/TypeLowering.cpp
@@ -749,11 +749,12 @@ namespace {
     RetTy visitTupleType(CanTupleType type, AbstractionPattern origType,
                          IsTypeExpansionSensitive_t isSensitive) {
       RecursiveProperties props;
-      for (unsigned i = 0, e = type->getNumElements(); i < e; ++i) {
-        props.addSubobject(classifyType(origType.getTupleElementType(i),
-                                        type.getElementType(i),
-                                        TC, Expansion));
-      }
+      origType.forEachExpandedTupleElement(type,
+          [&](AbstractionPattern origEltType, CanType substEltType,
+              const TupleTypeElt &elt) {
+        props.addSubobject(
+          classifyType(origEltType, substEltType, TC, Expansion));
+      });
       props = mergeIsTypeExpansionSensitive(isSensitive, props);
       return asImpl().handleAggregateByProperties(type, props);
     }
@@ -2250,12 +2251,12 @@ namespace {
                                  AbstractionPattern origType,
                                  IsTypeExpansionSensitive_t isSensitive) {
       RecursiveProperties properties;
-      for (unsigned i = 0, e = tupleType->getNumElements(); i < e; ++i) {
-        auto eltType = tupleType.getElementType(i);
-        auto origEltType = origType.getTupleElementType(i);
-        auto &lowering = TC.getTypeLowering(origEltType, eltType, Expansion);
-        properties.addSubobject(lowering.getRecursiveProperties());
-      }
+      origType.forEachExpandedTupleElement(tupleType,
+          [&](AbstractionPattern origEltType, CanType substEltType,
+              const TupleTypeElt &elt) {
+        properties.addSubobject(
+          classifyType(origEltType, substEltType, TC, Expansion));
+      });
       properties = mergeIsTypeExpansionSensitive(isSensitive, properties);
 
       return handleAggregateByProperties<LoadableTupleTypeLowering>(tupleType,
@@ -2343,7 +2344,8 @@ namespace {
         auto sig = field->getDeclContext()->getGenericSignatureOfContext();
         auto interfaceTy = field->getInterfaceType()->getReducedType(sig);
         auto origFieldType = origType.unsafeGetSubstFieldType(field,
-                                                              interfaceTy);
+                                                              interfaceTy,
+                                                              subMap);
         
         properties.addSubobject(classifyType(origFieldType, substFieldType,
                                              TC, Expansion));
@@ -2422,7 +2424,8 @@ namespace {
         
         auto origEltType = origType.unsafeGetSubstFieldType(elt,
                               elt->getArgumentInterfaceType()
-                                 ->getReducedType(D->getGenericSignature()));
+                                 ->getReducedType(D->getGenericSignature()),
+                              subMap);
         properties.addSubobject(classifyType(origEltType, substEltType,
                                              TC, Expansion));
         properties =
@@ -2765,7 +2768,8 @@ bool TypeConverter::visitAggregateLeaves(
           auto interfaceTy =
               structField->getInterfaceType()->getReducedType(sig);
           auto origFieldType =
-              origTy.unsafeGetSubstFieldType(structField, interfaceTy);
+              origTy.unsafeGetSubstFieldType(structField, interfaceTy,
+                                             subMap);
           insertIntoWorklist(substFieldTy, origFieldType, structField,
                              llvm::None);
         }
@@ -2782,7 +2786,7 @@ bool TypeConverter::visitAggregateLeaves(
                                       ->getCanonicalType();
           auto origElementTy = origTy.unsafeGetSubstFieldType(
               element, element->getArgumentInterfaceType()->getReducedType(
-                           decl->getGenericSignature()));
+                           decl->getGenericSignature()), subMap);
 
           insertIntoWorklist(substElementType, origElementTy, element,
                              llvm::None);
diff --git a/lib/SILGen/SILGenApply.cpp b/lib/SILGen/SILGenApply.cpp
index 78eda39d4ce3d..5fc3d2caa5ed5 100644
--- a/lib/SILGen/SILGenApply.cpp
+++ b/lib/SILGen/SILGenApply.cpp
@@ -3389,10 +3389,23 @@ class ArgEmitter {
     // If the source expression is a tuple literal, we can break it
     // up directly.
     if (auto tuple = dyn_cast<TupleExpr>(e)) {
-      for (auto i : indices(tuple->getElements())) {
-        emit(tuple->getElement(i),
-             origParamType.getTupleElementType(i));
-      }
+      auto substTupleType =
+        cast<TupleType>(e->getType()->getCanonicalType());
+      origParamType.forEachTupleElement(substTupleType,
+          [&](unsigned origEltIndex, unsigned substEltIndex,
+              AbstractionPattern origEltType, CanType substEltType) {
+        emit(tuple->getElement(substEltIndex), origEltType);
+      },
+          [&](unsigned origEltIndex, unsigned substEltIndex,
+              AbstractionPattern origExpansionType,
+              CanTupleEltTypeArrayRef substEltTypes) {
+        SmallVector<ArgumentSource, 4> eltArgs;
+        eltArgs.reserve(substEltTypes.size());
+        for (auto i : range(substEltIndex, substEltTypes.size())) {
+          eltArgs.emplace_back(tuple->getElement(i));
+        }
+        emitPackArg(eltArgs, origExpansionType);
+      });
       return;
     }
 
diff --git a/test/SILGen/variadic-generic-tuples.swift b/test/SILGen/variadic-generic-tuples.swift
index a0fe0fad7bb03..fbcfbe6ec51e7 100644
--- a/test/SILGen/variadic-generic-tuples.swift
+++ b/test/SILGen/variadic-generic-tuples.swift
@@ -204,3 +204,52 @@ func projectTupleElements<each T>(_ value: repeat Wrapper<each T>) {
 
   let tuple = (repeat (each value).value)
 }
+
+func takesVariadicTuple<each T>(tuple: (repeat each T)) {}
+
+// CHECK-LABEL: sil{{.*}} @$s4main28testConcreteVariadicTupleArg1i1sySi_SStF :
+// CHECK:       [[PACK:%.*]] = alloc_pack $Pack{Int, String}
+// CHECK-NEXT:  [[I_COPY:%.*]] = alloc_stack $Int
+// CHECK-NEXT:  store %0 to [trivial] [[I_COPY]] : $*Int
+// CHECK-NEXT:  [[I_INDEX:%.*]] = scalar_pack_index 0 of $Pack{Int, String}
+// CHECK-NEXT:  pack_element_set [[I_COPY]] : $*Int into [[I_INDEX]] of [[PACK]] :
+// CHECK-NEXT:  [[S_COPY:%.*]] = alloc_stack $String
+// CHECK-NEXT:  [[T0:%.*]] = copy_value %1 : $String
+// CHECK-NEXT:  store [[T0]] to [init] [[S_COPY]] : $*String
+// CHECK-NEXT:  [[S_INDEX:%.*]] = scalar_pack_index 1 of $Pack{Int, String}
+// CHECK-NEXT:  pack_element_set [[S_COPY]] : $*String into [[S_INDEX]] of [[PACK]] :
+// CHECK-NEXT:  // function_ref
+// CHECK-NEXT:  [[FN:%.*]] = function_ref @$s4main18takesVariadicTuple5tupleyxxQp_t_tRvzlF : $@convention(thin) <each τ_0_0> (@pack_guaranteed Pack{repeat each τ_0_0}) -> ()
+// CHECK-NEXT:  apply [[FN]]<Pack{Int, String}>([[PACK]])
+// CHECK-NEXT:  destroy_addr [[S_COPY]] :
+// CHECK-NEXT:  dealloc_stack [[S_COPY]] :
+// CHECK-NEXT:  dealloc_stack [[I_COPY]] :
+// CHECK-NEXT:  dealloc_pack [[PACK]] :
+func testConcreteVariadicTupleArg(i: Int, s: String) {
+  takesVariadicTuple(tuple: (i, s))
+}
+
+struct TupleHolder<each T> {
+  var content: (repeat each T)
+
+  // Suppress the memberwise initializer
+  init(values: repeat each T) {
+    content = (repeat each values)
+  }
+}
+
+// CHECK-LABEL: sil{{.*}} @$s4main31takesConcreteTupleHolderFactory7factoryyAA0dE0VySi_SSQPGyXE_tF :
+// CHECK-SAME:    $@convention(thin) (@guaranteed @noescape @callee_guaranteed () -> @owned TupleHolder<Int, String>) -> ()
+// CHECK:       [[T0:%.*]] = copy_value %0 :
+// CHECK:       [[T1:%.*]] = begin_borrow [[T0]]
+// CHECK:       [[RESULT:%.*]] = apply [[T1]]() :
+// CHECK:       destroy_value [[RESULT]]
+func takesConcreteTupleHolderFactory(factory: () -> TupleHolder<Int, String>) {
+  let holder = factory()
+}
+
+/* We still crash with memberwise initializers
+func generateConcreteMemberTuple() -> TupleHolder<Int, String> {
+  return HasMemberTuple(content: (0, "hello"))
+}
+ */