CWG2485 Bit-fields in integral promotions

Author: burblebee

source/expressions.tex

@@ -829,29 +829,22 @@
 
 \rSec2[conv.prom]{Integral promotions}
 
+\pnum
+For the purposes of \ref{conv.prom},
+a \defnadj{converted}{bit-field} is a prvalue that is the result of
+an lvalue-to-rvalue conversion\iref{conv.lval} applied to
+a bit-field\iref{class.bit}.
+
 \pnum
 \indextext{promotion!integral}%
-A prvalue of an integer type other than \keyword{bool}, \keyword{char8_t}, \keyword{char16_t},
+A prvalue that is not a converted bit-field and has an integer type other than
+\keyword{bool}, \keyword{char8_t}, \keyword{char16_t},
 \keyword{char32_t}, or \keyword{wchar_t} whose integer conversion
 rank\iref{conv.rank} is less than the rank of \keyword{int} can be
 converted to a prvalue of type \keyword{int} if \keyword{int} can represent
 all the values of the source type; otherwise, the source prvalue can be
 converted to a prvalue of type \tcode{\keyword{unsigned} \keyword{int}}.
 
-\pnum
-\indextext{type!underlying!\idxcode{wchar_t}}%
-\indextext{type!underlying!\idxcode{char16_t}}%
-\indextext{type!underlying!\idxcode{char32_t}}%
-A prvalue of type \keyword{char8_t}, \keyword{char16_t}, \keyword{char32_t}, or
-\keyword{wchar_t}\iref{basic.fundamental} can be converted to a prvalue
-of the first of the following types that can represent all the values of
-its underlying type: \keyword{int}, \tcode{\keyword{unsigned} \keyword{int}}, \tcode{\keyword{long} \keyword{int}},
-\tcode{\keyword{unsigned} \keyword{long} \keyword{int}}, \tcode{\keyword{long} \keyword{long} \keyword{int}},
-or \tcode{\keyword{unsigned} \keyword{long} \keyword{long} \keyword{int}}. If none of the types in that list can
-represent all the values of its underlying type, a prvalue of type
-\keyword{char8_t}, \keyword{char16_t}, \keyword{char32_t}, or \keyword{wchar_t} can be converted
-to a prvalue of its underlying type.
-
 \pnum
 \indextext{type!underlying!enumeration}%
 A prvalue of an unscoped enumeration type whose underlying type is not
@@ -871,15 +864,38 @@
 if integral promotion can be applied to its underlying type, a prvalue of an unscoped
 enumeration type whose underlying type is fixed can also be converted to a prvalue of
 the promoted underlying type.
+\begin{note}
+A converted bit-field of enumeration type is treated as
+any other value of that type for promotion purposes.
+\end{note}
 
 \pnum
-A prvalue for an integral bit-field\iref{class.bit} can be converted
+A converted bit-field of integral type can be converted
 to a prvalue of type \keyword{int} if \keyword{int} can represent all the
 values of the bit-field; otherwise, it can be converted to
 \tcode{\keyword{unsigned} \keyword{int}} if \tcode{\keyword{unsigned} \keyword{int}} can represent all the
-values of the bit-field. If the bit-field is larger yet, no integral
-promotion applies to it. If the bit-field has enumeration type, it is
-treated as any other value of that type for promotion purposes.
+values of the bit-field.
+
+\pnum
+\indextext{type!underlying!\idxcode{wchar_t}}%
+\indextext{type!underlying!\idxcode{char16_t}}%
+\indextext{type!underlying!\idxcode{char32_t}}%
+A prvalue of type
+\keyword{char8_t}, \keyword{char16_t}, \keyword{char32_t}, or
+\keyword{wchar_t}\iref{basic.fundamental}
+(including a converted bit-field that was not
+already promoted to \keyword{int} or \tcode{\keyword{unsigned} \keyword{int}}
+according to the rules above)
+can be converted to a prvalue
+of the first of the following types that can represent all the values of
+its underlying type:
+\keyword{int},
+\tcode{\keyword{unsigned} \keyword{int}},
+\tcode{\keyword{long} \keyword{int}},
+\tcode{\keyword{unsigned} \keyword{long} \keyword{int}},
+\tcode{\keyword{long} \keyword{long} \keyword{int}},
+\tcode{\keyword{unsigned} \keyword{long} \keyword{long} \keyword{int}}, or
+its underlying type.
 
 \pnum
 \indextext{promotion!bool to int}%