Implement C++ DR1391 (wg21.link/cwg1391)

Check for implicit conversion sequences for non-dependent function
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside the
immediate context is much more common during substitution than during implicit
conversion sequence formation.

This re-commits r290808, reverted in r290811, with a fix for handling of
explicitly-specified template argument packs.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291410 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 2 deletions

diff --git a/test/SemaTemplate/temp_arg_nontype.cpp b/test/SemaTemplate/temp_arg_nontype.cpp
index 93f11b5657..27a0a03f84 100644
--- a/test/SemaTemplate/temp_arg_nontype.cpp
+++ b/test/SemaTemplate/temp_arg_nontype.cpp
@@ -173,12 +173,16 @@ namespace pr6249 {
 }
 
 namespace PR6723 {
-  template<unsigned char C> void f(int (&a)[C]); // expected-note {{candidate template ignored}} \
-  // expected-note{{substitution failure [with C = '\x00']}}
+  template<unsigned char C> void f(int (&a)[C]); // expected-note 3{{candidate template ignored: substitution failure [with C = '\x00']}}
+  // expected-note@-1 {{not viable: no known conversion from 'int [512]' to 'int (&)[0]'}}
   void g() {
     int arr512[512];
     f(arr512); // expected-error{{no matching function for call}}
     f<512>(arr512); // expected-error{{no matching function for call}}
+
+    int arr0[0];
+    f(arr0); // expected-error{{no matching function for call}}
+    f<0>(arr0); // expected-error{{no matching function for call}}
   }
 }