[gcc r12-8759] c++: cast to array of unknown bound [PR93259]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:8f37a44483870e0db8cd6437ae9716cbe28b7f59

commit r12-8759-g8f37a44483870e0db8cd6437ae9716cbe28b7f59
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Sep 12 14:14:24 2022 -0400

    c++: cast to array of unknown bound [PR93259]
    
    We already know to treat a variable of array-of-unknown-bound type as
    dependent, we should do the same for arr{}.
    
            PR c++/93259
    
    gcc/cp/ChangeLog:
    
            * pt.cc (type_dependent_expression_p): Treat a compound
            literal of array-of-unknown-bound type like a variable.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/initlist-array17.C: New test.

Diff:
---
 gcc/cp/pt.cc                                  |  6 ++---
 gcc/testsuite/g++.dg/cpp0x/initlist-array17.C | 37 +++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index bef31416fb7..2f3cbf4895d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27952,11 +27952,11 @@ type_dependent_expression_p (tree expression)
      If the array has no length and has an initializer, it must be that
      we couldn't determine its length in cp_complete_array_type because
      it is dependent.  */
-  if (VAR_P (expression)
+  if (((VAR_P (expression) && DECL_INITIAL (expression))
+       || COMPOUND_LITERAL_P (expression))
       && TREE_TYPE (expression) != NULL_TREE
       && TREE_CODE (TREE_TYPE (expression)) == ARRAY_TYPE
-      && !TYPE_DOMAIN (TREE_TYPE (expression))
-      && DECL_INITIAL (expression))
+      && !TYPE_DOMAIN (TREE_TYPE (expression)))
    return true;
 
   /* Pull a FUNCTION_DECL out of a BASELINK if we can.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-array17.C b/gcc/testsuite/g++.dg/cpp0x/initlist-array17.C
new file mode 100644
index 00000000000..c4284a7b391
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-array17.C
@@ -0,0 +1,37 @@
+// PR c++/93259
+// { dg-do compile { target c++11 } }
+
+template <class T, class U> struct is_same;
+template <class T> struct is_same<T,T> { };
+
+using Array = int[];
+
+template <typename ...Ts>
+void bar1(Ts ...)
+{
+  auto && array = Array{ 1, 2, 3 };
+
+  is_same<int (&&)[3], decltype(array)>{}; // this fails, deduces array as int (&&) []
+}
+
+template <typename T>
+void bar2()
+{
+  auto && array = Array{ 1, 2, 3 };
+
+  is_same<int (&&)[3], decltype(array)>{};  // this fails, deduces array as int (&&) []
+}
+
+void bar3()
+{
+  auto && array = Array{ 1, 2, 3 };
+
+  is_same<int (&&)[3], decltype(array)>{}; // OK
+}
+
+int main()
+{
+  bar1<int>(1, 2, 3);
+  bar2<int>();
+  bar3();
+}