Index: clang/lib/Sema/SemaTemplate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplate.cpp
+++ clang/lib/Sema/SemaTemplate.cpp
@@ -1947,16 +1947,35 @@
 /// constructor to a deduction guide.
 class ExtractTypeForDeductionGuide
   : public TreeTransform<ExtractTypeForDeductionGuide> {
+  llvm::SmallVectorImpl<TypedefDecl *> &MaterializedTypedefs;
+
 public:
   typedef TreeTransform<ExtractTypeForDeductionGuide> Base;
-  ExtractTypeForDeductionGuide(Sema &SemaRef) : Base(SemaRef) {}
+  ExtractTypeForDeductionGuide(
+      Sema &SemaRef, llvm::SmallVectorImpl<TypedefDecl *> &MaterializedTypedefs)
+      : Base(SemaRef), MaterializedTypedefs(MaterializedTypedefs) {}
 
   TypeSourceInfo *transform(TypeSourceInfo *TSI) { return TransformType(TSI); }
 
   QualType TransformTypedefType(TypeLocBuilder &TLB, TypedefTypeLoc TL) {
-    return TransformType(
-        TLB,
-        TL.getTypedefNameDecl()->getTypeSourceInfo()->getTypeLoc());
+    ASTContext &Context = SemaRef.getASTContext();
+    TypeLocBuilder InnerTLB;
+    QualType Transformed = TransformType(
+        InnerTLB, TL.getTypedefNameDecl()->getTypeSourceInfo()->getTypeLoc());
+    TypeSourceInfo *TSI = Context.getTrivialTypeSourceInfo(Transformed);
+
+    auto *Decl = TypedefDecl::Create(
+        SemaRef.getASTContext(),
+        SemaRef.getASTContext().getTranslationUnitDecl(), SourceLocation(),
+        SourceLocation(), TL.getTypedefNameDecl()->getIdentifier(), TSI);
+    MaterializedTypedefs.push_back(Decl);
+
+    QualType TDTy = Context.getTypedefType(Decl);
+    TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(TDTy);
+    TypedefTL.setNameLoc(TL.getNameLoc());
+
+    return TDTy;
+
   }
 };
 
@@ -2041,14 +2060,16 @@
     // new ones.
     TypeLocBuilder TLB;
     SmallVector<ParmVarDecl*, 8> Params;
-    QualType NewType = transformFunctionProtoType(TLB, FPTL, Params, Args);
+    SmallVector<TypedefDecl*, 4> MaterializedTypedefs;
+    QualType NewType = transformFunctionProtoType(TLB, FPTL, Params, Args,
+                                                  MaterializedTypedefs);
     if (NewType.isNull())
       return nullptr;
     TypeSourceInfo *NewTInfo = TLB.getTypeSourceInfo(SemaRef.Context, NewType);
 
-    return buildDeductionGuide(TemplateParams, CD->getExplicitSpecifier(),
-                               NewTInfo, CD->getBeginLoc(), CD->getLocation(),
-                               CD->getEndLoc());
+    return buildDeductionGuide(
+        TemplateParams, CD->getExplicitSpecifier(), NewTInfo, CD->getBeginLoc(),
+        CD->getLocation(), CD->getEndLoc(), MaterializedTypedefs);
   }
 
   /// Build a deduction guide with the specified parameter types.
@@ -2143,16 +2164,18 @@
     return NewParam;
   }
 
-  QualType transformFunctionProtoType(TypeLocBuilder &TLB,
-                                      FunctionProtoTypeLoc TL,
-                                      SmallVectorImpl<ParmVarDecl*> &Params,
-                                      MultiLevelTemplateArgumentList &Args) {
+  QualType transformFunctionProtoType(
+      TypeLocBuilder &TLB, FunctionProtoTypeLoc TL,
+      SmallVectorImpl<ParmVarDecl *> &Params,
+      MultiLevelTemplateArgumentList &Args,
+      SmallVectorImpl<TypedefDecl *> &MaterializedTypedefs) {
     SmallVector<QualType, 4> ParamTypes;
     const FunctionProtoType *T = TL.getTypePtr();
 
     //    -- The types of the function parameters are those of the constructor.
     for (auto *OldParam : TL.getParams()) {
-      ParmVarDecl *NewParam = transformFunctionTypeParam(OldParam, Args);
+      ParmVarDecl *NewParam =
+          transformFunctionTypeParam(OldParam, Args, MaterializedTypedefs);
       if (!NewParam)
         return QualType();
       ParamTypes.push_back(NewParam->getType());
@@ -2194,9 +2217,9 @@
     return Result;
   }
 
-  ParmVarDecl *
-  transformFunctionTypeParam(ParmVarDecl *OldParam,
-                             MultiLevelTemplateArgumentList &Args) {
+  ParmVarDecl *transformFunctionTypeParam(
+      ParmVarDecl *OldParam, MultiLevelTemplateArgumentList &Args,
+      llvm::SmallVectorImpl<TypedefDecl *> &MaterializedTypedefs) {
     TypeSourceInfo *OldDI = OldParam->getTypeSourceInfo();
     TypeSourceInfo *NewDI;
     if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
@@ -2219,7 +2242,8 @@
     // 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);
+    NewDI = ExtractTypeForDeductionGuide(SemaRef, MaterializedTypedefs)
+                .transform(NewDI);
 
     // Resolving a wording defect, we also inherit default arguments from the
     // constructor.
@@ -2250,10 +2274,12 @@
     return NewParam;
   }
 
-  NamedDecl *buildDeductionGuide(TemplateParameterList *TemplateParams,
-                                 ExplicitSpecifier ES, TypeSourceInfo *TInfo,
-                                 SourceLocation LocStart, SourceLocation Loc,
-                                 SourceLocation LocEnd) {
+  FunctionTemplateDecl *
+  buildDeductionGuide(TemplateParameterList *TemplateParams,
+                      ExplicitSpecifier ES, TypeSourceInfo *TInfo,
+                      SourceLocation LocStart, SourceLocation Loc,
+                      SourceLocation LocEnd,
+                      llvm::ArrayRef<TypedefDecl *> MaterializedTypedefs = {}) {
     DeclarationNameInfo Name(DeductionGuideName, Loc);
     ArrayRef<ParmVarDecl *> Params =
         TInfo->getTypeLoc().castAs<FunctionProtoTypeLoc>().getParams();
@@ -2267,6 +2293,8 @@
 
     for (auto *Param : Params)
       Param->setDeclContext(Guide);
+    for (auto *TD : MaterializedTypedefs)
+      TD->setDeclContext(Guide);
 
     auto *GuideTemplate = FunctionTemplateDecl::Create(
         SemaRef.Context, DC, Loc, DeductionGuideName, TemplateParams, Guide);
Index: clang/test/AST/deduction-guides.cpp
===================================================================
--- /dev/null
+++ clang/test/AST/deduction-guides.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -fsyntax-only %s -ast-dump -std=c++17 | FileCheck %s
+
+namespace PR46111 {
+template <typename>
+struct S;
+
+template <typename T>
+struct HasDeductionGuide {
+  typedef PR46111::S<T> STy;
+  HasDeductionGuide(typename STy::Child);
+  };
+
+// This causes deduction guides to be generated for all constructors.
+HasDeductionGuide() ->HasDeductionGuide<int>;
+
+// The parameter to this one shouldn't be an elaborated type.
+// CHECK: CXXDeductionGuideDecl {{.*}} implicit <deduction guide for HasDeductionGuide> 'auto (typename STy::Child) -> HasDeductionGuide<T>'
+// CHECK: CXXDeductionGuideDecl {{.*}} implicit <deduction guide for HasDeductionGuide> 'auto (HasDeductionGuide<T>) -> HasDeductionGuide<T>'
+// CHECK: CXXDeductionGuideDecl {{.*}} <deduction guide for HasDeductionGuide> 'auto () -> HasDeductionGuide<int>'
+} // namespace PR46111