[PATCH] Fix some blockers of PR c++/24666 (arrays decay to pointers too early)

[Patrick Palka]

This patch just makes convert_for_initialization() to avoid eagerly
decaying an array, function, etc if the type we're converting to is a
class type, so that the correct conversion constructor could be later be
selected in perform_implicit_conversion_flags().

Bootstrap + regtest in progress on x86_64-pc-linux-gnu, OK to commit if
no new regressions?

gcc/cp/ChangeLog:

        PR c++/16333
        PR c++/41426
        PR c++/59878
        PR c++/66895
        * typeck.c (convert_for_initialization): Don't perform an early
        decaying conversion if converting to a class type.

gcc/testsuite/ChangeLog:

        PR c++/16333
        PR c++/41426
        PR c++/59878
        PR c++/66895
        * g++.dg/conversion/pr16333.C: New test.
        * g++.dg/conversion/pr41426.C: New test.
        * g++.dg/conversion/pr59878.C: New test.
        * g++.dg/conversion/pr66895.C: New test.
---
 gcc/cp/typeck.c                           | 16 +++++++++-------
 gcc/testsuite/g++.dg/conversion/pr16333.C |  8 ++++++++
 gcc/testsuite/g++.dg/conversion/pr41426.C | 28 ++++++++++++++++++++++++++++
 gcc/testsuite/g++.dg/conversion/pr59878.C | 19 +++++++++++++++++++
 gcc/testsuite/g++.dg/conversion/pr66895.C | 11 +++++++++++
 5 files changed, 75 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/conversion/pr16333.C
 create mode 100644 gcc/testsuite/g++.dg/conversion/pr41426.C
 create mode 100644 gcc/testsuite/g++.dg/conversion/pr59878.C
 create mode 100644 gcc/testsuite/g++.dg/conversion/pr66895.C

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 39c1af2..1059b26 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8479,13 +8479,15 @@ convert_for_initialization (tree exp, tree type, tree 
rhs, int flags,
       || (TREE_CODE (rhs) == TREE_LIST && TREE_VALUE (rhs) == error_mark_node))
     return error_mark_node;
 
-  if ((TREE_CODE (TREE_TYPE (rhs)) == ARRAY_TYPE
-       && TREE_CODE (type) != ARRAY_TYPE
-       && (TREE_CODE (type) != REFERENCE_TYPE
-          || TREE_CODE (TREE_TYPE (type)) != ARRAY_TYPE))
-      || (TREE_CODE (TREE_TYPE (rhs)) == FUNCTION_TYPE
-         && !TYPE_REFFN_P (type))
-      || TREE_CODE (TREE_TYPE (rhs)) == METHOD_TYPE)
+  if (MAYBE_CLASS_TYPE_P (type))
+    ;
+  else if ((TREE_CODE (TREE_TYPE (rhs)) == ARRAY_TYPE
+           && TREE_CODE (type) != ARRAY_TYPE
+           && (TREE_CODE (type) != REFERENCE_TYPE
+               || TREE_CODE (TREE_TYPE (type)) != ARRAY_TYPE))
+          || (TREE_CODE (TREE_TYPE (rhs)) == FUNCTION_TYPE
+              && !TYPE_REFFN_P (type))
+          || TREE_CODE (TREE_TYPE (rhs)) == METHOD_TYPE)
     rhs = decay_conversion (rhs, complain);
 
   rhstype = TREE_TYPE (rhs);
diff --git a/gcc/testsuite/g++.dg/conversion/pr16333.C 
b/gcc/testsuite/g++.dg/conversion/pr16333.C
new file mode 100644
index 0000000..979e0ac
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr16333.C
@@ -0,0 +1,8 @@
+// PR c++/16333
+
+struct X {
+   X (const int (&)[3]);
+};
+
+int a[3];
+X foo () { return a; }
diff --git a/gcc/testsuite/g++.dg/conversion/pr41426.C 
b/gcc/testsuite/g++.dg/conversion/pr41426.C
new file mode 100644
index 0000000..cc86dd5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr41426.C
@@ -0,0 +1,28 @@
+// PR c++/41426
+
+template <typename _T>
+struct A
+{
+   template <int _N>
+       A(_T (&V)[_N]);
+   A();
+};
+
+A<float> g1()
+{
+   float f[] = {1.1f, 2.3f};
+   return f;
+}
+
+struct B
+{
+   B (int (&v)[10]);
+   B();
+};
+
+B g2()
+{
+   int c[10];
+   return c;
+}
+
diff --git a/gcc/testsuite/g++.dg/conversion/pr59878.C 
b/gcc/testsuite/g++.dg/conversion/pr59878.C
new file mode 100644
index 0000000..15f3a37
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr59878.C
@@ -0,0 +1,19 @@
+struct Test {
+ template <int N>
+ Test(const char (&array)[N]) {}
+};
+
+Test test() {
+ return "test1";
+}
+
+void test2(Test arg = "test12") {}
+
+template <typename T>
+void test3(T arg = "test123") {}
+
+int main() {
+ test();
+ test2();
+ test3<Test>();
+}
diff --git a/gcc/testsuite/g++.dg/conversion/pr66895.C 
b/gcc/testsuite/g++.dg/conversion/pr66895.C
new file mode 100644
index 0000000..a4bf651
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/pr66895.C
@@ -0,0 +1,11 @@
+// { dg-do compile { target c++11 } }
+
+#include <cstddef>
+#include <initializer_list>
+
+struct S {
+    template<std::size_t N> S(char const (&)[N]);
+};
+struct T { S s; };
+void f(std::initializer_list<T>);
+void g() { f({{""}}); }
-- 
2.7.0.rc0.50.g1470d8f.dirty