Fix PR18498: Support explicit template arguments with variadic generic lambdas

http://llvm.org/bugs/show_bug.cgi?id=18498

This code was resulting in a crash:

auto L = [](auto ... v) { };
L.operator()<int>(3);

The reason is that the partially-substituted-pack is incorrectly retained within the current-instantiation-scope during template-argument-finalization, and because lambda's are local, there parent instantiation scopes are merged, which leads to the expansion-pattern being retained in the finalized specialization.

This patch ensures that once we have finalized deduction of a parameter-pack, we remove the partially-substituted-pack so that it doesn't cause CheckParameterPacksForExpansion to incorrectly inform the caller that it needs to retain the expansion pattern.


Thanks to Richard Smith for the review!

http://reviews.llvm.org/D2135


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209992 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 1 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 7d9cec141a..f941a0992c 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -2816,9 +2816,19 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
         // argument, because it was explicitly-specified. Just record the
         // presence of this argument.
         Builder.push_back(Deduced[I]);
+        // We may have had explicitly-specified template arguments for a
+        // template parameter pack (that may or may not have been extended
+        // via additional deduced arguments).
+        if (Param->isParameterPack() && CurrentInstantiationScope) {
+          if (CurrentInstantiationScope->getPartiallySubstitutedPack() ==
+              Param) {
+            // Forget the partially-substituted pack; its substitution is now
+            // complete.
+            CurrentInstantiationScope->ResetPartiallySubstitutedPack();
+          }
+        }
         continue;
       }
-
       // We have deduced this argument, so it still needs to be
       // checked and converted.