LWG3466 Specify the requirements for promise/future/shared_future consistently

Author: burblebee

source/threads.tex

@@ -6150,6 +6150,10 @@
 }
 \end{codeblock}
 
+\pnum
+For the primary template, \tcode{R} shall be an object type that
+meets the \oldconcept{Destructible} requirements.
+
 \pnum
 The implementation provides the template \tcode{promise} and two specializations,
 \tcode{promise<R\&>} and \tcode{promise<\brk{}void>}. These differ only in the argument type
@@ -6494,6 +6498,10 @@
 }
 \end{codeblock}
 
+\pnum
+For the primary template, \tcode{R} shall be an object type that
+meets the \oldconcept{Destructible} requirements.
+
 \pnum
 The implementation provides the template \tcode{future} and two specializations,
 \tcode{future<R\&>} and \tcode{future<\brk{}void>}. These differ only in the return type and return
@@ -6794,6 +6802,10 @@
 }
 \end{codeblock}
 
+\pnum
+For the primary template, \tcode{R} shall be an object type that
+meets the \oldconcept{Destructible} requirements.
+
 \pnum
 The implementation provides the template \tcode{shared_future} and two
 specializations, \tcode{shared_future<R\&>} and \tcode{shared_future<void>}. These