C++ PATCH for c++/83227, C++17 ICE with list derived-to-base conversion

[Jason Merrill]

The code to avoid doing an extra copy of a list-initialized temporary
was incorrectly being used even when we actually want a
derived-to-base conversion.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit b2413566649273c0b7e172213ebf41c6269c947c
Author: Jason Merrill <ja...@redhat.com>
Date:   Thu Feb 15 17:22:35 2018 -0500

            PR c++/83227 - C++17 ICE with init-list derived-to-base conversion.
    
            * call.c (convert_like_real): Don't use the copy-list-initialization
            shortcut for ck_base.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 7176e4afa15..5698ff60a4d 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -6938,6 +6938,11 @@ convert_like_real (conversion *convs, tree expr, tree 
fn, int argnum,
          && DECL_INHERITED_CTOR (current_function_decl))
        return expr;
 
+      if (TREE_CODE (expr) == TARGET_EXPR
+         && TARGET_EXPR_LIST_INIT_P (expr))
+       /* Copy-list-initialization doesn't actually involve a copy.  */
+       return expr;
+
       /* Fall through.  */
     case ck_base:
       if (convs->kind == ck_base && !convs->need_temporary_p)
@@ -6964,10 +6969,6 @@ convert_like_real (conversion *convs, tree expr, tree 
fn, int argnum,
       if (convs->rvaluedness_matches_p)
        /* standard_conversion got LOOKUP_PREFER_RVALUE.  */
        flags |= LOOKUP_PREFER_RVALUE;
-      if (TREE_CODE (expr) == TARGET_EXPR
-         && TARGET_EXPR_LIST_INIT_P (expr))
-       /* Copy-list-initialization doesn't actually involve a copy.  */
-       return expr;
       expr = build_temp (expr, totype, flags, &diag_kind, complain);
       if (diag_kind && complain)
        {
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist98.C 
b/gcc/testsuite/g++.dg/cpp0x/initlist98.C
new file mode 100644
index 00000000000..4f2fcd20219
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist98.C
@@ -0,0 +1,17 @@
+// PR c++/83227
+// { dg-do compile { target c++11 } }
+
+#include <initializer_list>
+
+template <typename d> struct f {
+  f(std::initializer_list<d>) {}
+};
+
+struct h {};
+struct i : h {
+  i();
+};
+void foo(f<h>);
+int main() {
+  foo({i{}});
+}