[gcc r12-4077] libstdc++: Implement LWG 3522 for std::priority_queue

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:e5c093e515c4d1745ea3887da21a49d196475da6

commit r12-4077-ge5c093e515c4d1745ea3887da21a49d196475da6
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu May 13 14:30:26 2021 +0100

    libstdc++: Implement LWG 3522 for std::priority_queue
    
    The LWG 3522 issue constrains all constructors of container adaptors
    that have InputIterator parameters.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/stl_queue.h (priority_queue): Constrain
            constructors with InputIterator parameters (LWG 3522).
            * testsuite/23_containers/priority_queue/lwg3522.cc: New test.

Diff:
---
 libstdc++-v3/include/bits/stl_queue.h              |  8 ++++++--
 .../23_containers/priority_queue/lwg3522.cc        | 24 ++++++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h
index 41ffc50d380..5e7808c0247 100644
--- a/libstdc++-v3/include/bits/stl_queue.h
+++ b/libstdc++-v3/include/bits/stl_queue.h
@@ -594,7 +594,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  std::make_heap(c.begin(), c.end(), comp);
 	}
 #else
-      template<typename _InputIterator>
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 3522. Missing requirement on InputIterator template parameter
+      template<typename _InputIterator,
+	       typename = std::_RequireInputIter<_InputIterator>>
 	priority_queue(_InputIterator __first, _InputIterator __last,
 		       const _Compare& __x,
 		       const _Sequence& __s)
@@ -605,7 +608,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  std::make_heap(c.begin(), c.end(), comp);
 	}
 
-      template<typename _InputIterator>
+      template<typename _InputIterator,
+	       typename = std::_RequireInputIter<_InputIterator>>
 	priority_queue(_InputIterator __first, _InputIterator __last,
 		       const _Compare& __x = _Compare(),
 		       _Sequence&& __s = _Sequence())
diff --git a/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3522.cc b/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3522.cc
new file mode 100644
index 00000000000..c026438585b
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3522.cc
@@ -0,0 +1,24 @@
+// { dg-do compile { target c++11 } }
+
+#include <queue>
+
+// LWG 3522
+// Missing requirement on InputIterator template parameter for priority_queue
+// constructors
+std::priority_queue<int> x = {1, 2}; // { dg-error "could not convert" }
+
+using Q = std::priority_queue<int>;
+using Compare = Q::value_compare;
+using Sequence = Q::container_type;
+
+static_assert( ! std::is_constructible<Q, int, int>(),
+	       "priority_queue(InputIterator, InputIterator) is constrained" );
+
+static_assert( ! std::is_constructible<Q, int, int, Compare>(),
+	       "priority_queue(InputIterator, InputIterator, const Compare&) "
+	       " is constrained" );
+
+static_assert( ! std::is_constructible<Q, int, int, Compare, const Sequence&>(),
+	       "and with const Sequence lvalue argument" );
+static_assert( ! std::is_constructible<Q, int, int, Compare, Sequence>(),
+	       "and with Sequence rvalue argument" );