P0138R2 Construction Rules for enum class Values

Author: Dawn Perchik

source/declarators.tex

@@ -3738,6 +3738,34 @@
 \end{codeblock}
 \exitexample
 
+\item Otherwise, if \tcode{T} is an enumeration
+with a fixed underlying type~(\ref{dcl.enum}),
+the \grammarterm{initializer-list} has a single element \tcode{v}, and
+the initialization is direct-list-initialization,
+the object is initialized with the value \tcode{T(v)}~(\ref{expr.type.conv});
+if a narrowing conversion is required to convert \tcode{v}
+to the underlying type of \tcode{T}, the program is ill-formed.
+
+\enterexample
+\begin{codeblock}
+enum byte : unsigned char { };
+byte b { 42 };                      // OK
+byte c = { 42 };                    // error
+byte d = byte{ 42 };                // OK; same value as \tcode{b}
+byte e { -1 };                      // error
+
+struct A { byte b; };
+A a1 = { { 42 } };                  // error
+A a2 = { byte{ 42 } };              // OK
+
+void f(byte);
+f({ 42 });                          // error
+
+enum class Handle : uint32_t { Invalid = 0 };
+Handle h { 42 };                    // OK
+\end{codeblock}
+\exitexample
+
 \item Otherwise, if the initializer list has no elements, the object is
 value-initialized.