4 files changed, 40 insertions, 7 deletions
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 716ffd131b..6a83518bc0 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -111,7 +111,7 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
                                        &Context);
 
   ExprEvalContexts.push_back(
-        ExpressionEvaluationContextRecord(PotentiallyEvaluated, 0, false));
+        ExpressionEvaluationContextRecord(PotentiallyEvaluated, 0, false, 0));
 
   FunctionScopes.push_back(new FunctionScopeInfo(Diags));
 }
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 3f1fabcaa3..1008a3ab43 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -9275,11 +9275,13 @@ ExprResult Sema::TranformToPotentiallyEvaluated(Expr *E) {
 }
 
 void
-Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext) {
+Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
+                                      Decl *LambdaContextDecl) {
   ExprEvalContexts.push_back(
              ExpressionEvaluationContextRecord(NewContext,
                                                ExprCleanupObjects.size(),
-                                               ExprNeedsCleanups));
+                                               ExprNeedsCleanups,
+                                               LambdaContextDecl));
   ExprNeedsCleanups = false;
   if (!MaybeODRUseExprs.empty())
     std::swap(MaybeODRUseExprs, ExprEvalContexts.back().SavedMaybeODRUseExprs);
diff --git a/lib/Sema/SemaLambda.cpp b/lib/Sema/SemaLambda.cpp
index 6d54d403aa..047a28436f 100644
--- a/lib/Sema/SemaLambda.cpp
+++ b/lib/Sema/SemaLambda.cpp
@@ -485,6 +485,7 @@ static void addBlockPointerConversion(Sema &S,
 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body, 
                                  Scope *CurScope, 
                                  llvm::Optional<unsigned> ManglingNumber,
+                                 Decl *ContextDecl,
                                  bool IsInstantiation) {
   // Leave the expression-evaluation context.
   DiscardCleanupsInEvaluationContext();
@@ -638,8 +639,34 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
   // If we don't already have a mangling number for this lambda expression,
   // allocate one now.
   if (!ManglingNumber) {
-    // FIXME: Default arguments, data member initializers are special.
-    ManglingNumber = Context.getLambdaManglingNumber(CallOperator);
+    ContextDecl = ExprEvalContexts.back().LambdaContextDecl;
+    
+    // FIXME: Data member initializers.
+    enum ContextKind {
+      Normal,
+      DefaultArgument
+    } Kind = Normal;
+
+    // Default arguments of member function parameters that appear in a class
+    // definition receive special treatment. Identify them.
+    if (ParmVarDecl *Param = dyn_cast_or_null<ParmVarDecl>(ContextDecl)) {
+      if (const DeclContext *LexicalDC
+            = Param->getDeclContext()->getLexicalParent())
+        if (LexicalDC->isRecord())
+          Kind = DefaultArgument;
+    }
+    
+    switch (Kind) {
+    case Normal:
+      ManglingNumber = Context.getLambdaManglingNumber(CallOperator);
+      ContextDecl = 0;
+      break;
+      
+    case DefaultArgument:
+      ManglingNumber = ExprEvalContexts.back().getLambdaMangleContext()
+                         .getManglingNumber(CallOperator);
+      break;
+    }
   }
   
   LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange, 
@@ -647,7 +674,7 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
                                           ExplicitParams, ExplicitResultType,
                                           CaptureInits, ArrayIndexVars, 
                                           ArrayIndexStarts, Body->getLocEnd(),
-                                          *ManglingNumber);
+                                          *ManglingNumber, ContextDecl);
 
   // C++11 [expr.prim.lambda]p2:
   //   A lambda-expression shall not appear in an unevaluated operand
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 7e095f7336..7e775f55e0 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -7768,10 +7768,14 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
                                /*IsInstantiation=*/true);
     return ExprError();    
   }
-  
+
+  // Note: Once a lambda mangling number and context declaration have been
+  // assigned, they never change.
   unsigned ManglingNumber = E->getLambdaClass()->getLambdaManglingNumber();
+  Decl *ContextDecl = E->getLambdaClass()->getLambdaContextDecl();
   return getSema().ActOnLambdaExpr(E->getLocStart(), Body.take(), 
                                    /*CurScope=*/0, ManglingNumber,
+                                   ContextDecl,
                                    /*IsInstantiation=*/true);
 }