Index: lib/Sema/SemaTemplate.cpp
===================================================================
--- lib/Sema/SemaTemplate.cpp
+++ lib/Sema/SemaTemplate.cpp
@@ -1659,6 +1659,23 @@
 }
 
 namespace {
+/// Tree transform to "extract" a transformed type from a class template's
+/// constructor to a deduction guide.
+class ExtractTypeForDeductionGuide
+  : public TreeTransform<ExtractTypeForDeductionGuide> {
+public:
+  typedef TreeTransform<ExtractTypeForDeductionGuide> Base;
+  ExtractTypeForDeductionGuide(Sema &SemaRef) : Base(SemaRef) {}
+
+  TypeSourceInfo *transform(TypeSourceInfo *TSI) { return TransformType(TSI); }
+
+  QualType TransformTypedefType(TypeLocBuilder &TLB, TypedefTypeLoc TL) {
+    return TransformType(
+        TLB,
+        TL.getTypedefNameDecl()->getTypeSourceInfo()->getTypeLoc());
+  }
+};
+
 /// Transform to convert portions of a constructor declaration into the
 /// corresponding deduction guide, per C++1z [over.match.class.deduct]p1.
 struct ConvertConstructorToDeductionGuideTransform {
@@ -1880,9 +1897,7 @@
                              MultiLevelTemplateArgumentList &Args) {
     TypeSourceInfo *OldDI = OldParam->getTypeSourceInfo();
     TypeSourceInfo *NewDI;
-    if (!Args.getNumLevels())
-      NewDI = OldDI;
-    else if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
+    if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
       // Expand out the one and only element in each inner pack.
       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(SemaRef, 0);
       NewDI =
@@ -1898,23 +1913,17 @@
     if (!NewDI)
       return nullptr;
 
-    // Canonicalize the type. This (for instance) replaces references to
-    // typedef members of the current instantiations with the definitions of
-    // those typedefs, avoiding triggering instantiation of the deduced type
-    // during deduction.
-    // FIXME: It would be preferable to retain type sugar and source
-    // information here (and handle this in substitution instead).
-    NewDI = SemaRef.Context.getTrivialTypeSourceInfo(
-        SemaRef.Context.getCanonicalType(NewDI->getType()),
-        OldParam->getLocation());
+    // Extract the type. This (for instance) replaces references to typedef
+    // members of the current instantiations with the definitions of those
+    // typedefs, avoiding triggering instantiation of the deduced type during
+    // deduction.
+    NewDI = ExtractTypeForDeductionGuide(SemaRef).transform(NewDI);
 
     // Resolving a wording defect, we also inherit default arguments from the
     // constructor.
     ExprResult NewDefArg;
     if (OldParam->hasDefaultArg()) {
-      NewDefArg = Args.getNumLevels()
-                      ? SemaRef.SubstExpr(OldParam->getDefaultArg(), Args)
-                      : OldParam->getDefaultArg();
+      NewDefArg = SemaRef.SubstExpr(OldParam->getDefaultArg(), Args);
       if (NewDefArg.isInvalid())
         return nullptr;
     }
@@ -1929,6 +1938,7 @@
                                                 NewDefArg.get());
     NewParam->setScopeInfo(OldParam->getFunctionScopeDepth(),
                            OldParam->getFunctionScopeIndex());
+    SemaRef.CurrentInstantiationScope->InstantiatedLocal(OldParam, NewParam);
     return NewParam;
   }
 
Index: test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
===================================================================
--- test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -373,6 +373,35 @@
 }
 }
 
+namespace rdar41330135 {
+template <int> struct A {};
+template <class T>
+struct S {
+  template <class U>
+  S(T a, U t, A<sizeof(t)>);
+};
+template <class T> struct D {
+  D(T t, A<sizeof(t)>);
+};
+int f() {
+  S s(0, 0, A<sizeof(int)>());
+  D d(0, A<sizeof(int)>());
+}
+
+namespace test_dupls {
+template<unsigned long> struct X {};
+template<typename T> struct A {
+  A(T t, X<sizeof(t)>);
+};
+A a(0, {});
+template<typename U> struct B {
+  B(U u, X<sizeof(u)>);
+};
+B b(0, {});
+}
+
+}
+
 #else
 
 // expected-no-diagnostics