PR42104: Support instantiations of lambdas that implicitly capture

packs.

Two changes:
 * Track odr-use via FunctionParmPackExprs to properly handle dependent
   odr-uses of packs in generic lambdas.
 * Do not instantiate implicit captures; instead, regenerate them by
   instantiating the body of the lambda. This is necessary to
   distinguish between cases where only one element of a pack is
   captured and cases where the entire pack is captured.

This reinstates r362358 (reverted in r362375) with a fix for an
uninitialized variable use in UpdateMarkingForLValueToRValue.

llvm-svn: 362531

1 files changed, 9 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index ba54d5010ba..973f564d305 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1368,9 +1368,11 @@ TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
     Vars.push_back(D);
   }
 
-  return FunctionParmPackExpr::Create(getSema().Context, T,
-                                      E->getParameterPack(),
-                                      E->getParameterPackLocation(), Vars);
+  auto *PackExpr =
+      FunctionParmPackExpr::Create(getSema().Context, T, E->getParameterPack(),
+                                   E->getParameterPackLocation(), Vars);
+  getSema().MarkFunctionParmPackReferenced(PackExpr);
+  return PackExpr;
 }
 
 ExprResult
@@ -1389,8 +1391,10 @@ TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
       QualType T = TransformType(E->getType());
       if (T.isNull())
         return ExprError();
-      return FunctionParmPackExpr::Create(getSema().Context, T, PD,
-                                          E->getExprLoc(), *Pack);
+      auto *PackExpr = FunctionParmPackExpr::Create(getSema().Context, T, PD,
+                                                    E->getExprLoc(), *Pack);
+      getSema().MarkFunctionParmPackReferenced(PackExpr);
+      return PackExpr;
     }
 
     TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];