LWG3876 Default constructor of std::layout_XX::mapping misses precondition

Author: burblebee

source/containers.tex

@@ -19315,6 +19315,12 @@
 \tcode{layout_left::mapping<E>} is a trivially copyable type
 that models \libconcept{regular} for each \tcode{E}.
 
+\pnum
+\mandates
+If \tcode{Extents::rank_dynamic() == 0} is \tcode{true},
+then the size of the multidimensional index space \tcode{Extents()}
+is representable as a value of type \tcode{typename Extents::index_type}.
+
 \rSec5[mdspan.layout.left.cons]{Constructors}
 
 \indexlibraryctor{layout_left::mapping}%
@@ -19567,6 +19573,12 @@
 \tcode{layout_right::mapping<E>} is a trivially copyable type
 that models \libconcept{regular} for each \tcode{E}.
 
+\pnum
+\mandates
+If \tcode{Extents::rank_dynamic() == 0} is \tcode{true},
+then the size of the multidimensional index space \tcode{Extents()}
+is representable as a value of type \tcode{typename Extents::index_type}.
+
 \rSec5[mdspan.layout.right.cons]{Constructors}
 
 \indexlibraryctor{layout_right::mapping}%
@@ -19821,6 +19833,12 @@
 \tcode{layout_stride::mapping<E>} is a trivially copyable type
 that models \libconcept{regular} for each \tcode{E}.
 
+\pnum
+\mandates
+If \tcode{Extents::rank_dynamic() == 0} is \tcode{true},
+then the size of the multidimensional index space \tcode{Extents()}
+is representable as a value of type \tcode{typename Extents::index_type}.
+
 \rSec5[mdspan.layout.stride.expo]{Exposition-only helpers}
 
 \pnum