From 44ea0c47103850873c00f4f60a74e18fd25dc640 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Wed, 4 Jan 2017 02:59:16 +0000
Subject: [PATCH] Fix deduction of pack elements after a braced-init-list.

Previously, if the arguments for a parameter pack contained a braced-init-list,
we would abort deduction (keeping the pack deductions from prior arguments) at
the point when we reached the braced-init-list, resulting in wrong deductions
and rejects-valids. We now just leave a "hole" in the pack for such an argument,
which needs to be filled by another deduction of the same pack.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290933 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateDeduction.cpp                 |  8 ++------
 .../cxx0x-initializer-stdinitializerlist.cpp       | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 7923e7d7e6..6dae37be27 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -3468,12 +3468,8 @@ Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
       if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg)) {
         TemplateDeductionResult Result;
         if (!DeduceFromInitializerList(*this, TemplateParams, ParamType, ILE,
-                                       Info, Deduced, TDF, Result)) {
-          // FIXME: Bailing out here is wrong; we could still need to deduce
-          // from later pack elements.
-          ++ArgIdx;
-          break;
-        }
+                                       Info, Deduced, TDF, Result))
+          continue;
 
         if (Result)
           return Result;
diff --git a/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp b/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
index 060a0f236b..c8595d2e36 100644
--- a/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
+++ b/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
@@ -103,6 +103,12 @@ T deduce(std::initializer_list<T>); // expected-note {{conflicting types for par
 template <typename T>
 T deduce_ref(const std::initializer_list<T>&); // expected-note {{conflicting types for parameter 'T' ('int' vs. 'double')}}
 
+template<typename T, typename U> struct pair { pair(...); };
+template<typename T> void deduce_pairs(std::initializer_list<pair<T, typename T::type>>);
+struct WithIntType { typedef int type; };
+
+template<typename ...T> void deduce_after_init_list_in_pack(void (*)(T...), T...); // expected-note {{<int, int> vs. <(no value), double>}}
+
 void argument_deduction() {
   static_assert(same_type<decltype(deduce({1, 2, 3})), int>::value, "bad deduction");
   static_assert(same_type<decltype(deduce({1.0, 2.0, 3.0})), double>::value, "bad deduction");
@@ -113,6 +119,14 @@ void argument_deduction() {
   static_assert(same_type<decltype(deduce_ref({1.0, 2.0, 3.0})), double>::value, "bad deduction");
 
   deduce_ref({1, 2.0}); // expected-error {{no matching function}}
+
+  pair<WithIntType, int> pi;
+  pair<WithIntType, float> pf;
+  deduce_pairs({pi, pi, pi}); // ok
+  deduce_pairs({pi, pf, pi}); // FIXME: This should be rejected, as we fail to produce a type that exactly matches the argument type.
+
+  deduce_after_init_list_in_pack((void(*)(int,int))0, {}, 0);
+  deduce_after_init_list_in_pack((void(*)(int,int))0, {}, 0.0); // expected-error {{no matching function}}
 }
 
 void auto_deduction() {
-- 
2.40.0