CWG1696 Temporary lifetime and non-static data member initializers

Also fixes CWG1815.

source/declarators.tex

@@ -2980,6 +2980,23 @@
 \tcode{a} and \tcode{b} have the same value
 \exitexample
 
+\pnum
+If a reference member is initialized from its \grammarterm{brace-or-equal-initializer}
+and a potentially-evaluated subexpression thereof is an aggregate
+initialization that would use that \grammarterm{brace-or-equal-initializer},
+the program is ill-formed.
+\enterexample
+\begin{codeblock}
+  struct A;
+  extern A a;
+  struct A {
+    const A& a1 { A{a,a} };   // OK
+    const A& a2 { A{} };      // error
+  };
+  A a{a,a};                   // OK
+\end{codeblock}
+\exitexample
+
 \pnum
 If an aggregate class \tcode{C} contains a subaggregate member
 \tcode{m} that has no members for purposes of aggregate initialization,

source/special.tex

@@ -482,9 +482,7 @@
 persists for the lifetime of the reference except:
 
 \begin{itemize}
-\item A temporary bound to a reference member in a constructor's \grammarterm{ctor-initializer}~(\ref{class.base.init}) persists until the constructor exits.
-
-\item A temporary bound to a reference parameter in a function call~(\ref{expr.call})
+\item A temporary object bound to a reference parameter in a function call~(\ref{expr.call})
 persists until the completion of the full-expression containing the call.
 
 \item The lifetime of a temporary bound to the returned value in a function return statement~(\ref{stmt.return}) is not extended; the temporary is destroyed at the end of the full-expression in the return statement.
@@ -1691,6 +1689,18 @@
 a virtual base class is ignored during execution of a constructor of any class that is
 not the most derived class.
 
+\pnum
+A temporary expression bound to a reference member in a \grammarterm{mem-initializer}
+is ill-formed.
+\enterexample
+\begin{codeblock}
+  struct A {
+  A() : v(42) { }  // error
+    const int& v;
+  };
+\end{codeblock}
+\exitexample
+
 \pnum
 In a non-delegating constructor, if
 a given potentially constructed subobject is not designated by a
@@ -1781,6 +1791,21 @@
 will not take place.
 \exitexample
 
+\pnum
+A temporary expression bound to a reference member from a
+\grammarterm{brace-or-equal-initializer} is ill-formed.
+\enterexample Given
+\begin{codeblock}
+  struct A {
+    A() = default;          // OK
+    A(int v) : v(v) { }     // OK
+    const int& v = 42;      // OK
+  };
+  A a1;                     // error: ill-formed binding of temporary to reference
+  A a2(1);                  // OK, unfortunately
+\end{codeblock}
+\exitexample
+
 \pnum
 In a non-delegating constructor, the destructor for each potentially constructed
 subobject of class type is potentially invoked~(\ref{class.dtor}).