From 4f9dee7511473c86b8e22f76dfc6ed569314e017 Mon Sep 17 00:00:00 2001
From: Meador Inge <meadori@codesourcery.com>
Date: Fri, 26 Jun 2015 00:09:55 +0000
Subject: [PATCH] [Sema] Maintain ellipsis location when transforming lambda
 captures

This patch fixes a crash caused by the following case:

  template<typename T>
  auto f(T x) {
    auto g = [](auto ... args) {
      auto h = [args...]() -> int {
        return 0;
      };
      return h;
    };
    return g;
  }

  auto x = f(0)();

When the templated function 'f' is instantiated and the inner-most
lambda is transformed the ellipsis location on the captured variable
is lost.  Then the lambda returned by 'f' is instantiated and the
tree transformer chokes on the invalid ellipsis location.  The
problem is fixed by making a minor change to properly track the
ellipsis location.

This fixes PR23716.

Differential Revision: http://reviews.llvm.org/D10590

llvm-svn: 240740
---
 clang/lib/Sema/TreeTransform.h               |  3 ++-
 clang/test/SemaCXX/cxx1y-generic-lambdas.cpp | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 3b2a17c..5d9c35f 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -9399,7 +9399,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
     }
 
     // Capture the transformed variable.
-    getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind);
+    getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind,
+                                 EllipsisLoc);
   }
   if (!FinishedExplicitCaptures)
     getSema().finishLambdaExplicitCaptures(LSI);
diff --git a/clang/test/SemaCXX/cxx1y-generic-lambdas.cpp b/clang/test/SemaCXX/cxx1y-generic-lambdas.cpp
index f4c67fb..b49a641 100644
--- a/clang/test/SemaCXX/cxx1y-generic-lambdas.cpp
+++ b/clang/test/SemaCXX/cxx1y-generic-lambdas.cpp
@@ -933,3 +933,18 @@ namespace PR22117 {
     };
   }(0)(0);
 }
+
+namespace PR23716 {
+template<typename T>
+auto f(T x) {
+  auto g = [](auto&&... args) {
+    auto h = [args...]() -> int {
+      return 0;
+    };
+    return h;
+  };
+  return g;
+}
+
+auto x = f(0)();
+}
-- 
2.7.4