diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -6935,6 +6935,14 @@
   llvm::ContextualFoldingSet<ConstraintSatisfaction, const ASTContext &>
       SatisfactionCache;
 
+  /// Introduce the instantiated function parameters into the local
+  /// instantiation scope, and set the parameter names to those used
+  /// in the template.
+  bool addInstantiatedParametersToScope(
+      FunctionDecl *Function, const FunctionDecl *PatternDecl,
+      LocalInstantiationScope &Scope,
+      const MultiLevelTemplateArgumentList &TemplateArgs);
+
 public:
   const NormalizedConstraint *
   getNormalizedAssociatedConstraints(
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4377,10 +4377,10 @@
 /// Introduce the instantiated function parameters into the local
 /// instantiation scope, and set the parameter names to those used
 /// in the template.
-static bool addInstantiatedParametersToScope(Sema &S, FunctionDecl *Function,
-                                             const FunctionDecl *PatternDecl,
-                                             LocalInstantiationScope &Scope,
-                           const MultiLevelTemplateArgumentList &TemplateArgs) {
+bool Sema::addInstantiatedParametersToScope(
+    FunctionDecl *Function, const FunctionDecl *PatternDecl,
+    LocalInstantiationScope &Scope,
+    const MultiLevelTemplateArgumentList &TemplateArgs) {
   unsigned FParamIdx = 0;
   for (unsigned I = 0, N = PatternDecl->getNumParams(); I != N; ++I) {
     const ParmVarDecl *PatternParam = PatternDecl->getParamDecl(I);
@@ -4396,9 +4396,9 @@
       // it's instantiation-dependent.
       // FIXME: Updating the type to work around this is at best fragile.
       if (!PatternDecl->getType()->isDependentType()) {
-        QualType T = S.SubstType(PatternParam->getType(), TemplateArgs,
-                                 FunctionParam->getLocation(),
-                                 FunctionParam->getDeclName());
+        QualType T = SubstType(PatternParam->getType(), TemplateArgs,
+                               FunctionParam->getLocation(),
+                               FunctionParam->getDeclName());
         if (T.isNull())
           return true;
         FunctionParam->setType(T);
@@ -4411,8 +4411,8 @@
 
     // Expand the parameter pack.
     Scope.MakeInstantiatedLocalArgPack(PatternParam);
-    Optional<unsigned> NumArgumentsInExpansion
-      = S.getNumArgumentsInExpansion(PatternParam->getType(), TemplateArgs);
+    Optional<unsigned> NumArgumentsInExpansion =
+        getNumArgumentsInExpansion(PatternParam->getType(), TemplateArgs);
     if (NumArgumentsInExpansion) {
       QualType PatternType =
           PatternParam->getType()->castAs<PackExpansionType>()->getPattern();
@@ -4420,10 +4420,10 @@
         ParmVarDecl *FunctionParam = Function->getParamDecl(FParamIdx);
         FunctionParam->setDeclName(PatternParam->getDeclName());
         if (!PatternDecl->getType()->isDependentType()) {
-          Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(S, Arg);
-          QualType T = S.SubstType(PatternType, TemplateArgs,
-                                   FunctionParam->getLocation(),
-                                   FunctionParam->getDeclName());
+          Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, Arg);
+          QualType T =
+              SubstType(PatternType, TemplateArgs, FunctionParam->getLocation(),
+                        FunctionParam->getDeclName());
           if (T.isNull())
             return true;
           FunctionParam->setType(T);
@@ -4487,8 +4487,7 @@
 
     FunctionDecl *Pattern = FD->getTemplateInstantiationPattern(
         /*ForDefinition*/ false);
-    if (addInstantiatedParametersToScope(*this, FD, Pattern, Local,
-                                         TemplateArgs))
+    if (addInstantiatedParametersToScope(FD, Pattern, Local, TemplateArgs))
       return true;
 
     runWithSufficientStackSpace(CallLoc, [&] {
@@ -4561,8 +4560,7 @@
   // we don't store enough information to map back to the friend declaration in
   // the template.
   FunctionDecl *Template = Proto->getExceptionSpecTemplate();
-  if (addInstantiatedParametersToScope(*this, Decl, Template, Scope,
-                                       TemplateArgs)) {
+  if (addInstantiatedParametersToScope(Decl, Template, Scope, TemplateArgs)) {
     UpdateExceptionSpec(Decl, EST_None);
     return;
   }
@@ -4603,8 +4601,7 @@
     MultiLevelTemplateArgumentList MLTAL(
         *Decl->getTemplateSpecializationArgs());
     if (addInstantiatedParametersToScope(
-            *this, Decl, Decl->getPrimaryTemplate()->getTemplatedDecl(),
-            Scope, MLTAL))
+            Decl, Decl->getPrimaryTemplate()->getTemplatedDecl(), Scope, MLTAL))
       return true;
   }
   Qualifiers ThisQuals;
@@ -5050,7 +5047,7 @@
     // PushDeclContext because we don't have a scope.
     Sema::ContextRAII savedContext(*this, Function);
 
-    if (addInstantiatedParametersToScope(*this, Function, PatternDecl, Scope,
+    if (addInstantiatedParametersToScope(Function, PatternDecl, Scope,
                                          TemplateArgs))
       return;