3 files changed, 25 insertions, 6 deletions

diff --git a/clang/include/clang/AST/ASTLambda.h b/clang/include/clang/AST/ASTLambda.h
index 358ac7131e4..9af016b13d4 100644
--- a/clang/include/clang/AST/ASTLambda.h
+++ b/clang/include/clang/AST/ASTLambda.h
@@ -36,9 +36,9 @@ inline bool isLambdaCallOperator(const DeclContext *DC) {
   return isLambdaCallOperator(cast<CXXMethodDecl>(DC));
 }
 
-inline bool isGenericLambdaCallOperatorSpecialization(CXXMethodDecl *MD) {
+inline bool isGenericLambdaCallOperatorSpecialization(const CXXMethodDecl *MD) {
   if (!MD) return false;
-  CXXRecordDecl *LambdaClass = MD->getParent();
+  const CXXRecordDecl *LambdaClass = MD->getParent();
   if (LambdaClass && LambdaClass->isGenericLambda())
     return isLambdaCallOperator(MD) && 
                     MD->isFunctionTemplateSpecialization();
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 13681ddf559..15410f0e9ba 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -13,6 +13,7 @@
 
 #include "clang/AST/Decl.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTLambda.h"
 #include "clang/AST/ASTMutationListener.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/DeclCXX.h"
@@ -2830,14 +2831,34 @@ FunctionDecl *FunctionDecl::getTemplateInstantiationPattern() const {
   // Handle class scope explicit specialization special case.
   if (getTemplateSpecializationKind() == TSK_ExplicitSpecialization)
     return getClassScopeSpecializationPattern();
-
+  
+  // If this is a generic lambda call operator specialization, its 
+  // instantiation pattern is always its primary template's pattern
+  // even if its primary template was instantiated from another 
+  // member template (which happens with nested generic lambdas).
+  // Since a lambda's call operator's body is transformed eagerly, 
+  // we don't have to go hunting for a prototype definition template 
+  // (i.e. instantiated-from-member-template) to use as an instantiation 
+  // pattern.
+
+  if (isGenericLambdaCallOperatorSpecialization(
+          dyn_cast<CXXMethodDecl>(this))) {
+    assert(getPrimaryTemplate() && "A generic lambda specialization must be "
+                                   "generated from a primary call operator "
+                                   "template");
+    assert(getPrimaryTemplate()->getTemplatedDecl()->getBody() &&
+           "A generic lambda call operator template must always have a body - "
+           "even if instantiated from a prototype (i.e. as written) member "
+           "template");
+    return getPrimaryTemplate()->getTemplatedDecl();
+  }
+  
   if (FunctionTemplateDecl *Primary = getPrimaryTemplate()) {
     while (Primary->getInstantiatedFromMemberTemplate()) {
       // If we have hit a point where the user provided a specialization of
       // this template, we're done looking.
       if (Primary->isMemberSpecialization())
         break;
-      
       Primary = Primary->getInstantiatedFromMemberTemplate();
     }
     
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 8616b492977..1ee3e4b23a8 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -837,8 +837,6 @@ namespace {
                               OldCallOperator->getDescribedFunctionTemplate();
         NewCallOperatorTemplate->setInstantiatedFromMemberTemplate(
                                                      OldCallOperatorTemplate);
-        // Mark the NewCallOperatorTemplate a specialization.  
-        NewCallOperatorTemplate->setMemberSpecialization();
       } else 
         // For a non-generic lambda we set the NewCallOperator to 
         // be an instantiation of the OldCallOperator.