3 files changed, 67 insertions, 11 deletions

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 4dc8a7bedd..371a4e39eb 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -9831,7 +9831,7 @@ bool Sema::canCaptureVariable(VarDecl *Var, SourceLocation Loc, bool Explicit,
 // Check if the variable needs to be captured; if so, try to perform
 // the capture.
 void Sema::TryCaptureVar(VarDecl *var, SourceLocation loc,
-                         TryCaptureKind Kind) {
+                         TryCaptureKind Kind, SourceLocation EllipsisLoc) {
   QualType type;
   unsigned functionScopesIndex;
   bool Nested;
@@ -9909,7 +9909,8 @@ void Sema::TryCaptureVar(VarDecl *var, SourceLocation loc,
       }
     }
 
-    CSI->AddCapture(var, hasBlocksAttr, byRef, Nested, loc, copyExpr);
+    CSI->AddCapture(var, hasBlocksAttr, byRef, Nested, loc, EllipsisLoc, 
+                    copyExpr);
 
     Nested = true;
     if (shouldAddConstForScope(CSI, var))
diff --git a/lib/Sema/SemaLambda.cpp b/lib/Sema/SemaLambda.cpp
index 0ce1c74163..c75c3c5b7d 100644
--- a/lib/Sema/SemaLambda.cpp
+++ b/lib/Sema/SemaLambda.cpp
@@ -291,9 +291,26 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
       continue;
     }
 
+    // C++11 [expr.prim.lambda]p23:
+    //   A capture followed by an ellipsis is a pack expansion (14.5.3).
+    SourceLocation EllipsisLoc;
+    if (C->EllipsisLoc.isValid()) {
+      if (Var->isParameterPack()) {
+        EllipsisLoc = C->EllipsisLoc;
+      } else {
+        Diag(C->EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
+          << SourceRange(C->Loc);
+        
+        // Just ignore the ellipsis.
+      }
+    } else if (Var->isParameterPack()) {
+      Diag(C->Loc, diag::err_lambda_unexpanded_pack);
+      continue;
+    }
+    
     TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
                                                  TryCapture_ExplicitByVal;
-    TryCaptureVar(Var, C->Loc, Kind);
+    TryCaptureVar(Var, C->Loc, Kind, EllipsisLoc);
   }
   finishLambdaExplicitCaptures(LSI);
 
@@ -380,10 +397,9 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
       }
 
       VarDecl *Var = From.getVariable();
-      // FIXME: Handle pack expansions.
       LambdaCaptureKind Kind = From.isCopyCapture()? LCK_ByCopy : LCK_ByRef;
       Captures.push_back(LambdaExpr::Capture(From.getLocation(), IsImplicit, 
-                                             Kind, Var));
+                                             Kind, Var, From.getEllipsisLoc()));
       CaptureInits.push_back(From.getCopyExpr());
     }
 
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index a63b9c804a..71037b6b3e 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -7706,6 +7706,49 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
       continue;
     }
     
+    // Determine the capture kind for Sema.
+    Sema::TryCaptureKind Kind
+      = C->isImplicit()? Sema::TryCapture_Implicit
+                       : C->getCaptureKind() == LCK_ByCopy
+                           ? Sema::TryCapture_ExplicitByVal
+                           : Sema::TryCapture_ExplicitByRef;
+    SourceLocation EllipsisLoc;
+    if (C->isPackExpansion()) {
+      UnexpandedParameterPack Unexpanded(C->getCapturedVar(), C->getLocation());
+      bool ShouldExpand = false;
+      bool RetainExpansion = false;
+      llvm::Optional<unsigned> NumExpansions;
+      if (getDerived().TryExpandParameterPacks(C->getEllipsisLoc(), 
+                                               C->getLocation(), 
+                                               Unexpanded,
+                                               ShouldExpand, RetainExpansion,
+                                               NumExpansions))
+        return ExprError();
+      
+      if (ShouldExpand) {
+        // The transform has determined that we should perform an expansion;
+        // transform and capture each of the arguments.
+        // expansion of the pattern. Do so.
+        VarDecl *Pack = C->getCapturedVar();
+        for (unsigned I = 0; I != *NumExpansions; ++I) {
+          Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), I);
+          VarDecl *CapturedVar
+            = cast_or_null<VarDecl>(getDerived().TransformDecl(C->getLocation(), 
+                                                               Pack));
+          if (!CapturedVar) {
+            Invalid = true;
+            continue;
+          }
+          
+          // Capture the transformed variable.
+          getSema().TryCaptureVar(CapturedVar, C->getLocation(), Kind);          
+        }          
+        continue;
+      }
+      
+      EllipsisLoc = C->getEllipsisLoc();
+    }
+    
     // Transform the captured variable.
     VarDecl *CapturedVar
       = cast_or_null<VarDecl>(getDerived().TransformDecl(C->getLocation(), 
@@ -7714,13 +7757,9 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
       Invalid = true;
       continue;
     }
-    
+  
     // Capture the transformed variable.
-    getSema().TryCaptureVar(CapturedVar, C->getLocation(),
-                            C->isImplicit()? Sema::TryCapture_Implicit
-                                           : C->getCaptureKind() == LCK_ByCopy
-                                             ? Sema::TryCapture_ExplicitByVal
-                                             : Sema::TryCapture_ExplicitByRef);
+    getSema().TryCaptureVar(CapturedVar, C->getLocation(), Kind);
   }
   if (!FinishedExplicitCaptures)
     getSema().finishLambdaExplicitCaptures(LSI);