c++: explicit ctor and list-initialization [PR109159]

When I implemented explicit(bool) in r9-3735, I added this code to
add_template_candidate_real:
+  /* Now the explicit specifier might have been deduced; check if this
+     declaration is explicit.  If it is and we're ignoring non-converting
+     constructors, don't add this function to the set of candidates.  */
+  if ((flags & LOOKUP_ONLYCONVERTING) && DECL_NONCONVERTING_P (fn))
+    return NULL;
but as this test demonstrates, that's incorrect when we're initializing
from a {}: for list-initialization we consider explicit constructors and
complain if one is chosen.

	PR c++/109159

gcc/cp/ChangeLog:

	* call.cc (add_template_candidate_real): Add explicit decls to the
	set of candidates when the initializer is a braced-init-list.

libstdc++-v3/ChangeLog:

	* testsuite/20_util/pair/cons/explicit_construct.cc: Adjust dg-error.
	* testsuite/20_util/tuple/cons/explicit_construct.cc: Likewise.
	* testsuite/23_containers/span/explicit.cc: Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/explicit16.C: New test.

2 files changed, 21 insertions, 1 deletions

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index c01e7b8..c52a09b 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -3612,7 +3612,9 @@ add_template_candidate_real (struct z_candidate **candidates, tree tmpl,
   /* Now the explicit specifier might have been deduced; check if this
      declaration is explicit.  If it is and we're ignoring non-converting
      constructors, don't add this function to the set of candidates.  */
-  if ((flags & LOOKUP_ONLYCONVERTING) && DECL_NONCONVERTING_P (fn))
+  if (((flags & (LOOKUP_ONLYCONVERTING|LOOKUP_LIST_INIT_CTOR))
+       == LOOKUP_ONLYCONVERTING)
+      && DECL_NONCONVERTING_P (fn))
     return NULL;
 
   if (DECL_CONSTRUCTOR_P (fn) && nargs == 2)
diff --git a/gcc/testsuite/g++.dg/cpp0x/explicit16.C b/gcc/testsuite/g++.dg/cpp0x/explicit16.C
new file mode 100644
index 0000000..bb5a823
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/explicit16.C
@@ -0,0 +1,18 @@
+// PR c++/109159
+// { dg-do compile { target c++11 } }
+
+struct A {
+  A(float) {}
+  template<class U>
+  explicit A(U) {}
+};
+
+void f(A t)
+{
+  t = {1}; // { dg-error "explicit constructor" }
+  t = 1;
+  A a1{1};
+  A a2 = {1}; // { dg-error "explicit constructor" }
+  A a3 = 1;
+  A a4(1);
+}